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(1659, 1, '2021-08-30 19:13:32', '2021-08-30 13:43:32', '<!-- wp:paragraph -->\n<p>Water held in soil is termed groundwater. It may be in saturated or unsaturated form.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The water table is the line showing the change of water level in the soil. Below the water table, the soil is saturated with water.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Water held in the soil acts as a lubricant. It increases the tendency of soil to slip or slide. This property is dangerous and causes difficulties when excavations to be done during construction works.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Construction of foundation below the subsoil water level creates problems due to waterlogging. Therefore, it is necessary to dewater the area of excavation and keep it dry.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Several operations have to be carried out within the excavation. For example, laying bed concrete, laying of RCC raft slab, construction of masonry works are a few of them. Work can be carried out efficiently when the excavation area is kept dry.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Reducing Water Level below the Excavation Bottom</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>For keeping the area of excavation in dry condition, the water table should be maintained at least 0.5 m below the bottom of the excavation.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The following two methods are frequently used for lowering the water table during construction.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Dewatering for Shallow Foundations</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The simplest and easiest method is to excavate drains along the edges of the excavation, collect water to sumps and remove using pumps. This method is suitable for fairly dense soil and shallow excavations. This is an economical method and is possible of being performed with unskilled labour and simple equipment.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1648,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2021/08/image-11.png\" alt=\"\" class=\"wp-image-1648\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:image {\"id\":1649,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2021/08/image-12.png\" alt=\"\" class=\"wp-image-1649\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Dewatering for Large Excavations and Deep&nbsp;Foundations</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Wellpoint system</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Wellpoint systems are used when dewatering to be done in large excavations such as<strong> </strong>for raft foundations. In this method, the flow of groundwater into the excavation is cut off using pipe wells driven deeper than the excavation around the perimeter.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1650,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2021/08/image-13.png\" alt=\"\" class=\"wp-image-1650\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A wellpoint comprises a 120 cm long and 4 cm diameter perforated pipe, with a valve which is used to regulate the flow and a screen preventing entry of mud, etc.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These wellpoints are installed along the outside edges of the excavation at the required depth, normally deeper than the bottom level of excavation. The spacing of the wellpoint is to be decided on the type of soil, normally around 1 meter.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1651,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2021/08/image-14.png\" alt=\"\" class=\"wp-image-1651\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>The wellpoint tube is connected to a pipe known as riser pipe having <em>5 </em>to 7.5 cm. These are sunk into the ground by jetting. Then, these riser pipes are connected to a header pipe which is connected to a high capacity suction pump.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The groundwater is drawn out by the operation of the pump and is discharged away from the excavation area.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>When installing well points using the process of jetting, water is forced down through the<strong> </strong>wellpoint at the rate of 20 to 25 liters per second. The high-pressure water jet displaces the surrounding soil, enabling the well point to be sunk to the required depth.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>After the wellpoint has been driven into the required depth, the water jet is allowed to run for some time. It ensures washing all sand or silt out of the hole, till the return water from the hole is clean. Then, the water jet is stopped and the annular space formed around the wellpoint due to the jetting action of water is filled with coarse sand and gravel. It forms a filter zone around the wellpoint. Entering of fine particles from the surrounding soil into the wellpoint is prevented due to the filter zone. And also it prevents clogging of the wellpoint screen. Normally, the filter sand should be filled up to the water table. The depth of the hole above the water table up to the ground level can be filled with tamped clay. This acts as a clay seal reducing air getting into the wellpoint through the sand filter.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>After installing and connecting all the wellpoint, the suction pump is operated.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Due to the suction, the ball valve in the wellpoint gets closed; the groundwater is drawn in through the wellpoint screen and is sucked up through the riser pipes, flows through the header pipe, and is discharged away from the excavation area.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This method can be successfully adopted for a modest depth of excavation, normally up to 18 m.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, the suction pump is normally not used to lift water above 6 m depth. Therefore, in deep excavations, a multi-stage system of wellpoint can be used.&nbsp;&nbsp;</p>\n<!-- /wp:paragraph -->', 'Techniques used to control groundwater', 'For keeping the area of excavation in dry condition, the water table should be maintained at least 0.5 m below the bottom of the excavation.', 'inherit', 'closed', 'closed', '', '1647-revision-v1', '', '', '2021-08-30 19:13:32', '2021-08-30 13:43:32', '', 1647, 'https://civilengineeringlectures.com/?p=1659', 0, 'revision', '', 0),
(1814, 1, '2023-02-25 22:51:40', '2023-02-25 17:21:40', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer to remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate), with small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone). This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process and recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly, dragging up a cylindrical ribbon of glass 13 m high, the diameter of the cylinder being maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass blocks</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C, followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity but not insulation. Fire stop blocks (F-30) manufactured from 26 mm rather than 8 mm glass offer increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Standard float glass sizes</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Traditional blown and drawn glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Curved sheet glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Self-cleaning glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Clear white glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Embossed pattern glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern but also upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Screen printed glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Decorative etched and sandblasted glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Georgian wired glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat, but ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Toughened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Heat-strengthened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening, but with a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Laminated glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film and for fire protection</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Insulating glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material, preventing the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Fire-resistant glass with intumescent material laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong>SPECIAL GLASSES</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>One-way observation glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area and wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Mirror glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Alarm glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>&nbsp;</strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system, which is activated when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Electrically-heatable laminated safety glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Electromagnetic radiation-shielding glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>X-ray protection glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Variable transmission (smart) glasses</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Electro-optic laminates</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Intelligent glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Intelligent glass facades</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions, thus reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions and also in reducing operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>STRUCTURAL GLASS</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. 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(1665, 1, '2021-09-01 19:27:10', '2021-09-01 13:57:10', '<!-- wp:heading {\"level\":4} -->\n<h4><strong><em>The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.</em></strong></h4>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In the traditional method, the employer first selects a suitably qualified Engineer / Architect to prepare designs and to do all other pre-contract activities needed for the project. Normally, it is done long before the selection of the contractor. He is paid under a separate contract with the employer. He is considered as the employer’s agent for the project.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, when carrying out other tasks as the contract administrator, for example, when certifying payments or recommending time extensions, during the post-contract period, their actions must be impartial and fair between the employer and the contractor. They are required to make impartial decisions in these circumstances.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These dual roles sometimes may end up giving rise to difficult situations.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is well established that if the employer applies pressure on the contract administrator when carrying out his tasks resulting in the administrator’s judgments being influenced, his decision may be held invalid and set aside. A failure to act or certify payments independently by the contract administrator may result in disqualification.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Hickman &amp; Co v Roberts </em></strong><strong>(1913)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Hickman &amp; Co. v Roberts (1913)</em></strong>, the contract had the provision that the decision of the architect as to payment due to the contractor was to be final. It also mentioned that the architect’s certificate is needed for any payment to be made to the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The employer crossed the line and refused to allow the certificate to be issued by the contract administrator.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The contractor requested that he was owed certain sums but the architect had failed to issue a payment certificate in his favour. When challenged by the contractor the architect openly admitted to the contractor that the employer would not allow him to issue a certificate. It clearly showed that the architect’s impartiality had been seriously compromised.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The architect replied that his clients, the owners, would not allow it:&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>“Had you better call and see my clients, because in the face of their instructions to me I cannot issue a certificate, whatever my own private opinion in the matter.”</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The House of Lords held that the contract administrator had improperly allowed the owners to influence him: the owners could not rely on the absence of a certificate as a reason not to pay the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Therefore, the Engineer / Architect / Contract Administrator should exercise his judgment rather than taking the employer’s instructions in the certification of works.</p>\n<!-- /wp:paragraph -->', 'Case Law – if the Contract Administrator is not acting impartially', 'The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.', 'publish', 'open', 'open', '', 'case-law-2', '', '', '2021-09-01 21:22:07', '2021-09-01 15:52:07', '', 0, 'https://civilengineeringlectures.com/?p=1665', 0, 'post', '', 0),
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(1667, 1, '2021-09-01 19:27:10', '2021-09-01 13:57:10', '<!-- wp:heading {\"level\":4} -->\n<h4><strong><em>The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.</em></strong></h4>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In the traditional method, the employer first selects a suitably qualified Engineer / Architect to prepare designs and to do all other pre-contract activities needed for the project. Normally, it is done long before the selection of the contractor. He is paid under a separate contract with the employer. He is considered as the employer’s agent for the project.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, when carrying out other tasks as the contract administrator, for example, when certifying payments or recommending time extensions, their actions must be impartial and fair between the employer and the contractor. They are required to make impartial decisions in these circumstances.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These dual roles sometimes may end up giving rise to difficult situations.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is well established that if the employer applies pressure on the contract administrator when carrying out his tasks resulting in the administrator’s judgments being influenced, his decision may be held invalid and set aside. A failure to act or certify payments independently by the contract administrator may result in disqualification.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Hickman &amp; Co v Roberts </em></strong><strong>(1913)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Hickman &amp; Co. v Roberts (1913)</em></strong>, the contract had the provision that the decision of the architect as to payment due to the contractor was to be final. It also mentioned that the architect’s certificate is needed for any payment to be made to the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The employer crossed the line and refused to allow the certificate to be issued by the contract administrator.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The contractor requested that he was owed certain sums but the architect had failed to issue a payment certificate in his favour. When challenged by the contractor the architect openly admitted to the contractor that the employer would not allow him to issue a certificate. It clearly showed that the architect’s impartiality had been seriously compromised.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The architect replied that his clients, the owners, would not allow it:&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>“Had you better call and see my clients, because in the face of their instructions to me I cannot issue a certificate, whatever my own private opinion in the matter.”</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The House of Lords held that the contract administrator had improperly allowed the owners to influence him: the owners could not rely on the absence of a certificate as a reason not to pay the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Therefore, the Engineer / Architect / Contract Administrator should exercise his judgment rather than taking the employer’s instructions in the certification of works.</p>\n<!-- /wp:paragraph -->', 'Case Law – if the Contract Administrator is not acting impartially', 'The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.', 'inherit', 'closed', 'closed', '', '1665-revision-v1', '', '', '2021-09-01 19:27:10', '2021-09-01 13:57:10', '', 1665, 'https://civilengineeringlectures.com/?p=1667', 0, 'revision', '', 0),
(1796, 1, '2022-07-10 23:58:36', '2022-07-10 18:28:36', '<!-- wp:heading -->\n<h2>Rosalie T. Ruegg &amp; Harold E. Marshall</h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Download the free e-book here</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:buttons -->\n<div class=\"wp-block-buttons\"><!-- wp:button -->\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link\" href=\"https://drive.google.com/uc?export=download&amp;id=1rmDnGb_L5In-Ni_T0NrEEjZa0c10YSxF\">Download the free e-book</a></div>\n<!-- /wp:button --></div>\n<!-- /wp:buttons -->', 'Building Economics - Theory & Practice', '', 'draft', 'open', 'open', '', 'building-economics-theory-practice', '', '', '2023-02-25 23:40:50', '2023-02-25 18:10:50', '', 0, 'https://civilengineeringlectures.com/?p=1796', 0, 'post', '', 0),
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(1798, 1, '2022-07-10 23:58:36', '2022-07-10 18:28:36', '<!-- wp:paragraph -->\n<p>Rosalie T. Ruegg &amp; Harold E. Marshall</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Download the free e-book here</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:buttons -->\n<div class=\"wp-block-buttons\"><!-- wp:button -->\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link\" href=\"https://drive.google.com/uc?export=download&amp;id=1rmDnGb_L5In-Ni_T0NrEEjZa0c10YSxF\">Download the free e-book</a></div>\n<!-- /wp:button --></div>\n<!-- /wp:buttons -->', 'Building Economics - Theory & Practice', '', 'inherit', 'closed', 'closed', '', '1796-revision-v1', '', '', '2022-07-10 23:58:36', '2022-07-10 18:28:36', '', 1796, 'https://civilengineeringlectures.com/?p=1798', 0, 'revision', '', 0),
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(1800, 1, '2022-07-10 23:59:24', '2022-07-10 18:29:24', '<!-- wp:paragraph -->\n<p>You can download the following e-books completely free</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:list {\"ordered\":true} -->\n<ol><li><strong><a href=\"https://civilengineeringlectures.com/construction-contracts-law-and-management/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction contracts - Law and management</a></strong> - Third edition: John Murdoch &amp; Will Hughes</li><li><a href=\"https://civilengineeringlectures.com/construction-cost-management/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Construction Cost Management</strong></a> - Learning from case studies, Second edition: Second Edition: Keith Potts and Nii Ankrah</li><li><strong><a href=\"https://civilengineeringlectures.com/building-cost-planning-for-the-design-team/\" target=\"_blank\" rel=\"noreferrer noopener\">Building cost planning for the design team</a></strong> - Second edition: Jim Smith and David Jaggar</li><li><strong><a href=\"https://civilengineeringlectures.com/construction-economics-a-new-approach/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction Economics - A new approach</a></strong> - Second edition: Danny Myers</li><li><a href=\"https://civilengineeringlectures.com/200-contractual-problems-their-solutions/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>200 Contractual Problems &amp; Their Solutions</strong></a> - Third Edition - Roger Knowles</li><li><strong><a href=\"https://civilengineeringlectures.com/advanced-building-measurements/\">Advanced Building Measurements</a></strong> - Second Edition - Ivor H. Seeley</li><li><strong><a href=\"https://civilengineeringlectures.com/alternative-project-delivery-procurement-and-contracting-methods-for-highways/\" target=\"_blank\" rel=\"noreferrer noopener\">Alternative Project Delivery, Procurement, and Contracting Methods for Highways</a></strong> - Keith Molenaar, Ph.D. &amp; Gerald Yakowenko, P.E.</li><li><strong><a href=\"https://civilengineeringlectures.com/analysis-of-concurrent-delay-on-construction-claims/\" target=\"_blank\" rel=\"noreferrer noopener\">Analysis of Concurrent Delay on Construction Claims</a></strong> - Richard J. Long, P.E.</li><li><strong><a href=\"https://civilengineeringlectures.com/bim-and-construction-management-proven-tools-methods-and-workflows/\">BIM and Construction Management - Proven tools, methods, and workflows</a></strong> - Second Edition - Brad Hardin &amp; Dave McCool</li><li><strong><a href=\"https://civilengineeringlectures.com/building-contract-claims/\" target=\"_blank\" rel=\"noreferrer noopener\">Building Contract Claims</a></strong> - David Chappell</li><li><strong><a href=\"https://civilengineeringlectures.com/building-economics/\" target=\"_blank\" rel=\"noreferrer noopener\">Building Economics</a></strong> - Fourth Edition - Ivor H. Seeley</li><li><strong><a href=\"https://civilengineeringlectures.com/building-economics-theory-practice/\" target=\"_blank\" rel=\"noreferrer noopener\">Building Economics - Theory &amp; Practice</a></strong> - Rosalie T. Ruegg &amp; Harold E. Marshall</li></ol>\n<!-- /wp:list -->', 'Quantity Surveying e-books', '', 'inherit', 'closed', 'closed', '', '1727-revision-v1', '', '', '2022-07-10 23:59:24', '2022-07-10 18:29:24', '', 1727, 'https://civilengineeringlectures.com/?p=1800', 0, 'revision', '', 0),
(1669, 1, '2023-05-27 05:13:01', '2021-09-01 13:58:06', ' ', '', '', 'publish', 'closed', 'closed', '', '1669', '', '', '2023-05-27 05:13:01', '2023-05-26 23:43:01', '', 0, 'https://civilengineeringlectures.com/1669/', 20, 'nav_menu_item', '', 0),
(1674, 1, '2021-09-01 21:13:52', '2021-09-01 15:43:52', '<!-- wp:heading {\"level\":4} -->\n<h4><strong><em>The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.</em></strong></h4>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In the traditional method, the employer first selects a suitably qualified Engineer / Architect to prepare designs and to do all other pre-contract activities needed for the project. Normally, it is done long before the selection of the contractor. He is paid under a separate contract with the employer. He is considered as the employer’s agent for the project.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, when carrying out other tasks as the contract administrator, for example, when certifying payments or recommending time extensions, during the post-contract period, their actions must be impartial and fair between the employer and the contractor. They are required to make impartial decisions in these circumstances.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These dual roles sometimes may end up giving rise to difficult situations.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is well established that if the employer applies pressure on the contract administrator when carrying out his tasks resulting in the administrator’s judgments being influenced, his decision may be held invalid and set aside. A failure to act or certify payments independently by the contract administrator may result in disqualification.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Hickman &amp; Co v Roberts </em></strong><strong>(1913)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Hickman &amp; Co. v Roberts (1913)</em></strong>, the contract had the provision that the decision of the architect as to payment due to the contractor was to be final. It also mentioned that the architect’s certificate is needed for any payment to be made to the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The employer crossed the line and refused to allow the certificate to be issued by the contract administrator.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The contractor requested that he was owed certain sums but the architect had failed to issue a payment certificate in his favour. When challenged by the contractor the architect openly admitted to the contractor that the employer would not allow him to issue a certificate. It clearly showed that the architect’s impartiality had been seriously compromised.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The architect replied that his clients, the owners, would not allow it:&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>“Had you better call and see my clients, because in the face of their instructions to me I cannot issue a certificate, whatever my own private opinion in the matter.”</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The House of Lords held that the contract administrator had improperly allowed the owners to influence him: the owners could not rely on the absence of a certificate as a reason not to pay the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Therefore, the Engineer / Architect / Contract Administrator should exercise his judgment rather than taking the employer’s instructions in the certification of works.</p>\n<!-- /wp:paragraph -->', 'Case Law – if the Contract Administrator is not acting impartially', 'The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.', 'inherit', 'closed', 'closed', '', '1665-revision-v1', '', '', '2021-09-01 21:13:52', '2021-09-01 15:43:52', '', 1665, 'https://civilengineeringlectures.com/?p=1674', 0, 'revision', '', 0),
(1673, 1, '2021-09-01 21:13:21', '2021-09-01 15:43:21', '<!-- wp:heading {\"level\":4} -->\n<h4><strong><em>The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.</em></strong></h4>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In the traditional method, the employer first selects a suitably qualified Engineer / Architect to prepare designs and to do all other pre-contract activities needed for the project. Normally, it is done long before the selection of the contractor. He is paid under a separate contract with the employer. He is considered as the employer’s agent for the project.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, when carrying out other tasks as the contract administrator, for example, when certifying payments or recommending time extensions, during the post-contract period, their actions must be impartial and fair between the employer and the contractor. They are required to make impartial decisions in these circumstances.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These dual roles sometimes may end up giving rise to difficult situations.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is well established that if the employer applies pressure on the contract administrator when carrying out his tasks resulting in the administrator’s judgments being influenced, his decision may be held invalid and set aside. A failure to act or certify payments independently by the contract administrator may result in disqualification.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Hickman &amp; Co v Roberts </em></strong><strong>(1913)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Hickman &amp; Co. v Roberts (1913)</em></strong>, the contract had the provision that the decision of the architect as to payment due to the contractor was to be final. It also mentioned that the architect’s certificate is needed for any payment to be made to the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The employer crossed the line and refused to allow the certificate to be issued by the contract administrator.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The contractor requested that he was owed certain sums but the architect had failed to issue a payment certificate in his favour. When challenged by the contractor the architect openly admitted to the contractor that the employer would not allow him to issue a certificate. It clearly showed that the architect’s impartiality had been seriously compromised.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The architect replied that his clients, the owners, would not allow it:&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>“Had you better call and see my clients, because in the face of their instructions to me I cannot issue a certificate, whatever my own private opinion in the matter.”</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The House of Lords held that the contract administrator had improperly allowed the owners to influence him: the owners could not rely on the absence of a certificate as a reason not to pay the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Therefore, the Engineer / Architect / Contract Administrator should exercise his judgment rather than taking the employer’s instructions in the certification of works.</p>\n<!-- /wp:paragraph -->', 'Case Law – if the Contract Administrator is not acting impartially', 'The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.', 'inherit', 'closed', 'closed', '', '1665-revision-v1', '', '', '2021-09-01 21:13:21', '2021-09-01 15:43:21', '', 1665, 'https://civilengineeringlectures.com/?p=1673', 0, 'revision', '', 0),
(1671, 1, '2021-09-01 21:11:34', '2021-09-01 15:41:34', '<!-- wp:paragraph -->\n<p>Construction projects are generally long-term engagements that require a lot of capital. Therefore, different funding arrangements are required for contractors to control their cash flow. If contractors do not receive interim payments during the construction for what they have already constructed, they need higher capital to finish the contract. Then, the cost of money for the required capital will be reflected in the tender sum. Therefore, it is a usual practice to include a clause in any Condition of Contracts enabling interim payments to contractors. This will help to relieve the contractor of the burden of financing the whole of the work.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Any certificate of payment issued by the Engineer before the Final Payment Certificate is defined as an interim Payment.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is how the contractors receive progress payments during the construction. Interim certificates are normally issued monthly. However, on very large contracts, a shorter period also may be specified.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An interim valuation involves a re-valuation of the whole work up to the time of measurement. It is not the valuation of work done since the last payment was issued. When preparing an interim valuation, it should be treated as a mini final account, because it largely reflects all the elements which appear in a final account.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Another important matter is an interim valuation needs the same scrutiny as final accounts. It must be a genuine valuation of work done up to the time of measurement. If the valuation is lower, it creates unreasonable financial problems for a contractor. Similarly, a high valuation makes a risk to the employer of paying added amounts without having any benefit.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Anyhow, an interim certificate is not definite about anything. It says nothing about the quality of materials or workmanship. Also, it does not indicate satisfaction with the work done to date. Anything included in an interim certificate may be changed, if necessary, with a later certificate. It is only the final certificate that is ever conclusive. Therefore, the only commitment covered from an interim certificate is an obligation on the employer to make a payment within the stated time in Condition of Contract. Failure to pay within the stipulated time is a breach of contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Almost any standard form of contract mentions an entitlement on the part of the contractor to receive interim payments. These payments assist in the contractor’s cash flow. However, the actual determination of the contractor’s entitlement is made when preparing the final certificate. Therefore, interim payments are sums paid on account of whatever the contractor might ultimately be entitled to receive from the Employer. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Most standard forms make the issue of a certificate a condition precedent to the contractor’s right to payment.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>CIDA (ICTAD)/ SBD / 01 – in Sri Lanka</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>As per the <strong>CIDA</strong> (<strong>ICTAD)/ SBD / 01, (Clause 42.1),</strong> the Contractor can submit to the Engineer monthly statements of the estimated value of work done less the cumulative value certified previously. Interim valuations are always carried out on a cumulative basis; the quantity surveyor will value the whole of the work executed up to the valuation date and then sums previously certified will be deducted.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>(Clause 42.2),</strong> The Engineer has to check the statement, certify the amount to be paid to the contractor and submit it to the Employer within 21 days of receipt of the bill. The amount certified after appropriate deductions must be greater than the minimum amount for interim payment certificate as stated in the Contract Data.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>After adjusting for deductions for advance payments <strong>(Clause 51.3)</strong> and retention <strong>(Clause 48.1),</strong> the Employer has to pay the Contractor within 14 days of receipt of the bill, <strong>(Clause 43.1).</strong>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Engineer can make any corrections or modifications to any previous payment certificate in light of the latter information <strong>(Clause 42.6).</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>The Interim Bill may contain;</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>1. The Value of the permanent works executed up to last measurement date for any item in the B.O.Q, including for contractor’s equipment, temporary works, nominated subcontractors’ / nominated suppliers’ works, and the like, <strong>(Clause 42.4),</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. The value of work executed under variations, <strong>(Clause 42.5),</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. The 80 percent invoice value of materials delivered by the Contractor onto the site for incorporation in the permanent works but not yet incorporated in such works, <strong>(Clause 42.5),</strong>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. Adjustments for price variations, <strong>(Clause 47.1),</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>5. Value of compensation events, <strong>(Clause 42.5),</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Note:</strong> The Practical Completion Bill also can be considered as an Interim payment.</p>\n<!-- /wp:paragraph -->', 'Interim Payment Certificates', 'Any certificate of payment issued by the Engineer before the Final Payment Certificate is defined as an interim Payment. ', 'inherit', 'closed', 'closed', '', '1660-revision-v1', '', '', '2021-09-01 21:11:34', '2021-09-01 15:41:34', '', 1660, 'https://civilengineeringlectures.com/?p=1671', 0, 'revision', '', 0),
(1675, 1, '2021-09-01 21:22:04', '2021-09-01 15:52:04', '<!-- wp:heading {\"level\":4} -->\n<h4><strong><em>The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.</em></strong></h4>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In the traditional method, the employer first selects a suitably qualified Engineer / Architect to prepare designs and to do all other pre-contract activities needed for the project. Normally, it is done long before the selection of the contractor. He is paid under a separate contract with the employer. He is considered as the employer’s agent for the project.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, when carrying out other tasks as the contract administrator, for example, when certifying payments or recommending time extensions, during the post-contract period, their actions must be impartial and fair between the employer and the contractor. They are required to make impartial decisions in these circumstances.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These dual roles sometimes may end up giving rise to difficult situations.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is well established that if the employer applies pressure on the contract administrator when carrying out his tasks resulting in the administrator’s judgments being influenced, his decision may be held invalid and set aside. A failure to act or certify payments independently by the contract administrator may result in disqualification.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Hickman &amp; Co v Roberts </em></strong><strong>(1913)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Hickman &amp; Co. v Roberts (1913)</em></strong>, the contract had the provision that the decision of the architect as to payment due to the contractor was to be final. It also mentioned that the architect’s certificate is needed for any payment to be made to the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The employer crossed the line and refused to allow the certificate to be issued by the contract administrator.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The contractor requested that he was owed certain sums but the architect had failed to issue a payment certificate in his favour. When challenged by the contractor the architect openly admitted to the contractor that the employer would not allow him to issue a certificate. It clearly showed that the architect’s impartiality had been seriously compromised.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The architect replied that his clients, the owners, would not allow it:&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>“Had you better call and see my clients, because in the face of their instructions to me I cannot issue a certificate, whatever my own private opinion in the matter.”</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The House of Lords held that the contract administrator had improperly allowed the owners to influence him: the owners could not rely on the absence of a certificate as a reason not to pay the contractor.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Therefore, the Engineer / Architect / Contract Administrator should exercise his judgment rather than taking the employer’s instructions in the certification of works.</p>\n<!-- /wp:paragraph -->', 'Case Law – if the Contract Administrator is not acting impartially', 'The Engineer/Architect/Contract Administrator is not acting impartially if he allows the employer to interfere with his independent judgment when issuing certificates.', 'inherit', 'closed', 'closed', '', '1665-revision-v1', '', '', '2021-09-01 21:22:04', '2021-09-01 15:52:04', '', 1665, 'https://civilengineeringlectures.com/?p=1675', 0, 'revision', '', 0),
(1677, 1, '2021-09-05 19:23:55', '2021-09-05 13:53:55', '<!-- wp:heading -->\n<h2><strong>Why do we need Contract Law?</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It is because our promises should be binding. The law enforces certain types of promises to be binding, especially if there are some forms of exchange.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>If you do not give anything back in a promise, it is called a gratuitous promise. It is not usually enforceable in law. <em>However, if it is put in the formal document called a deed, it is an exception.</em>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the kind of society we live in at present, we make lots of promises which involve exchange. For example, we buy and sell freely, on small scales as well as larger scales. We engage in the construction of larger projects like the construction of railway lines or multi-storied buildings.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, it is impossible to run a society if promises are not binding. For example, what happens when you order something from a manufacturer and withdraw the order when they are ready to deliver? What happens if the client refuses to pay the contractor after the construction is over?&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>So, society will run smoothly if the members of the society can rely on promises made to them. The contract law looks after whether the parties to the contract fulfill their contractual promises. If one party defaults, the law tries to compensate the innocent party financially, attempting to put them in the position they would have been in if the contract had been performed as agreed. So, any party who fails to fulfill their obligations cannot simply go away with their breach.&nbsp;&nbsp;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Contract law tries to enforce obligations which the parties have voluntarily assumed.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, all contracts do not have to be in writing. Even when they are in written form, important points may be left out. Therefore, it is important to find out what the parties agreed.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This was explained in <strong><em>Smith v Hughes (1871).</em></strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Smith v Hughes (1871)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In this case, the complainant, Mr. Smith, was a farmer. The defendant, Mr. Hughes, was a racehorse trainer. Mr. Smith brought Mr. Hughes a sample of his oats. After seeing the sample, Mr. Hughes ordered 40-50 quarters of oats from Mr. Smith. The price was 34 shillings per quarter.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Accordingly, to begin with, 16 quarters of oats were sent to Mr. Hughes. When it arrived, Mr. Hughes said that the oats were not the quality what he had thought they were. Since he was a racehorse trainer, he needed old oats. Mr. Hughes said old oats are the type of oats the horses had for their diet. The oats that were brought by Mr. Smith were green. But, it was the same type as the initial sample. However, Mr. Hughes refused to pay Mr. Smith for the delivery and the remaining order.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Mr. Smith argued that Mr. Hughes had breached the terms of the contract as he had not paid for the delivery and future oats to be delivered.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The issue, in this case, was whether the contract could be avoided by Mr. Hughes, as Mr. Smith had not delivered the type of oats he had expected.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It was held that there was a legally acceptable contract between Mr. Smith and Mr. Hughes. Therefore, it would not be avoided. However, there had been no discussion between the parties regarding the delivery of old oats. An objective test revealed that a reasonable person would expect the sale of good quality oats in a similar contract since there was no express discussion of old oats. The sample submitted by Mr. Smith gave Mr. Hughes the chance to inspect the oats.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>This is an example of caveat emptor (buyer beware).</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>‘If, whatever a man’s real intention maybe, he so conducts himself that a reasonable man would believe he was assenting to the terms proposed by the other party, and that another party upon that belief enters into the contract with him, the man thus conducting himself would be equally bound as if he had intended to agree to the other party’s terms.’</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In some cases, the basis for this approach is obvious. When you get into a hiring car and tell your destination, it is sensible for the driver to think you are agreeing to pay for the trip. It is not right to tell at the end of the trip that you had no such intention as to pay in your mind, and so you are not obliged to pay. It is true even your behavior might have suggested that.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>L’Estrange v F Graucob Ltd (1934)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong><em>In this case, it was affirmed that the clauses of a written contract are binding on the signatories, even where a party is unaware of the contract’s full contents.</em></strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The claimant, L’Estrange, contracted with the defendant, Graucob to purchase a slot machine for cigarettes.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>There was an express clause in the agreement which stated;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>“This agreement contains all the terms and conditions under which I agree to purchase the machine specified above and any express or implied condition, statement, or warranty, statutory or otherwise not stated herein is hereby excluded”.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, when put in to use after the purchase, the machine was found to be faulty. As a result, the claimant brought an action against the defendant. The claimant alleged that the machine breached the Sale of Goods Act by not being of merchantable quality.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The defendant emphasized that the statute was made irrelevant by the inclusion of the express clause mentioned above. Therefore, he was not in breach of the agreement between the parties. The claimant responded saying she had been unaware of the clause because she had not properly read the agreement and therefore it should not apply.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The issue here was whether the clause which excluded all terms not stated in the contract should be deemed effective and binding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Court of Appeal determined that the express provisions of the contract were binding. It effectively excluded the relevance of statutory sales provisions. Besides, the fact that the claimant had not properly read the contract did not impact its validity. When signing the contract she consented to be bound by its contents.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This case emphasizes the Court’s respect for the sanctity of contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong><em>When a person signs a contractual document, he is bound by it, even though he may not have understood or even read it.</em></strong></p>\n<!-- /wp:paragraph -->', 'Law of contract – The Necessity of the Law', 'Contract law tries to enforce obligations which the parties have voluntarily assumed. However, all contracts do not have to be in writing.', 'publish', 'open', 'open', '', 'contract-law', '', '', '2021-09-06 10:24:33', '2021-09-06 04:54:33', '', 0, 'https://civilengineeringlectures.com/?p=1677', 0, 'post', '', 0),
(1678, 1, '2021-09-05 19:23:03', '2021-09-05 13:53:03', '', 'business-signature-contract-962355', '', 'inherit', 'open', 'closed', '', 'business-signature-contract-962355', '', '', '2021-09-05 19:23:03', '2021-09-05 13:53:03', '', 0, 'https://civilengineeringlectures.com/wp-content/uploads/2021/09/business-signature-contract-962355.jpg', 0, 'attachment', 'image/jpeg', 0),
(1679, 1, '2021-09-05 19:23:55', '2021-09-05 13:53:55', '<!-- wp:heading -->\n<h2><strong>Why do we need Contract Law?</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It is because our promises should be binding. The law enforces certain types of promises to be binding, especially if there are some forms of exchange.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>If you do not give anything back in a promise, it is called a gratuitous promise. It is not usually enforceable in law. <em>However, if it is put in the formal document called a deed, it is an exception.</em>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the kind of society we live in at present, we make lots of promises which involve exchange. For example, we buy and sell freely, on small scales as well as larger scales. We engage in the construction of larger projects like the construction of railway lines or multi-storied buildings.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, it is impossible to run a society if promises are not binding. For example, what happens when you order something from a manufacturer and withdraw the order when they are ready to deliver? What happens if the client refuses to pay the contractor after the construction is over?&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>So, society will run smoothly if the members of the society can rely on promises made to them. The contract law looks after whether the parties to the contract fulfill their contractual promises. If one party defaults, the law tries to compensate the innocent party financially, attempting to put them in the position they would have been in if the contract had been performed as agreed. So, any party who fails to fulfill their obligations cannot simply go away with their breach.&nbsp;&nbsp;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Contract law tries to enforce obligations which the parties have voluntarily assumed.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, all contracts do not have to be in writing. Even when they are in written form, important points may be left out. Therefore, it is important to find out what the parties agreed.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This was explained in <strong><em>Smith v Hughes (1871).</em></strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Smith v Hughes (1871)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In this case, the complainant, Mr. Smith, was a farmer. The defendant, Mr. Hughes, was a racehorse trainer. Mr. Smith brought Mr. Hughes a sample of his oats. After seeing the sample, Mr. Hughes ordered 40-50 quarters of oats from Mr. Smith. The price was 34 shillings per quarter.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Accordingly, to begin with, 16 quarters of oats were sent to Mr. Hughes. When it arrived, Mr. Hughes said that the oats were not the quality what he had thought they were. Since he was a racehorse trainer, he needed old oats. Mr. Hughes said old oats are the type of oats the horses had for their diet. The oats that were brought by Mr. Smith were green. But, it was the same type as the initial sample. However, Mr. Hughes refused to pay Mr. Smith for the delivery and the remaining order.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Mr. Smith argued that Mr. Hughes had breached the terms of the contract as he had not paid for the delivery and future oats to be delivered.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The issue, in this case, was whether the contract could be avoided by Mr. Hughes, as Mr. Smith had not delivered the type of oats he had expected.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It was held that there was a legally acceptable contract between Mr. Smith and Mr. Hughes. Therefore, it would not be avoided. However, there had been no discussion between the parties regarding the delivery of old oats. An objective test revealed that a reasonable person would expect the sale of good quality oats in a similar contract since there was no express discussion of old oats. The sample submitted by Mr. Smith gave Mr. Hughes the chance to inspect the oats.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>This is an example of caveat emptor (buyer beware).</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>‘If, whatever a man’s real intention maybe, he so conducts himself that a reasonable man would believe he was assenting to the terms proposed by the other party, and that another party upon that belief enters into the contract with him, the man thus conducting himself would be equally bound as if he had intended to agree to the other party’s terms.’</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In some cases, the basis for this approach is obvious. When you get into a hiring car and tell your destination, it is sensible for the driver to think you are agreeing to pay for the trip. It is not right to tell at the end of the trip that you had no such intention as to pay in your mind, and so you are not obliged to pay. It is true even your behavior might have suggested that.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>L’Estrange v F Graucob Ltd (1934)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong><em>In this case, it was affirmed that the clauses of a written contract are binding on the signatories, even where a party is unaware of the contract’s full contents.</em></strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The claimant, L’Estrange, contracted with the defendant, Graucob to purchase a slot machine for cigarettes.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>There was an express clause in the agreement which stated;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>“This agreement contains all the terms and conditions under which I agree to purchase the machine specified above and any express or implied condition, statement, or warranty, statutory or otherwise not stated herein is hereby excluded”.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, when put in to use after the purchase, the machine was found to be faulty. As a result, the claimant brought an action against the defendant. The claimant alleged that the machine breached the Sale of Goods Act by not being of merchantable quality. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The defendant emphasized that the statute was made irrelevant by the inclusion of the express clause mentioned above. Therefore, he was not in breach of the agreement between the parties. The claimant responded saying she had been unaware of the clause because she had not properly read the agreement and therefore it should not apply.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The issue here was whether the clause which excluded all terms not stated in the contract should be deemed effective and binding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Court of Appeal determined that the express provisions of the contract were binding. It effectively excluded the relevance of statutory sales provisions. Besides, the fact that the claimant had not properly read the contract did not impact its validity. When signing the contract she consented to be bound by its contents.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This case emphasizes the Court’s respect for the sanctity of contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong><em>When a person signs a contractual document, he is bound by it, even though he may not have understood or even read it.</em></strong></p>\n<!-- /wp:paragraph -->', 'Law of contract – The Necessity of the Law', 'Contract law tries to enforce obligations which the parties have voluntarily assumed. However, all contracts do not have to be in writing.', 'inherit', 'closed', 'closed', '', '1677-revision-v1', '', '', '2021-09-05 19:23:55', '2021-09-05 13:53:55', '', 1677, 'https://civilengineeringlectures.com/?p=1679', 0, 'revision', '', 0),
(1810, 1, '2023-02-25 22:41:27', '2023-02-25 17:11:27', '', 'Glass', '', 'inherit', 'open', 'closed', '', 'glass', '', '', '2023-02-25 22:41:27', '2023-02-25 17:11:27', '', 1809, 'https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png', 0, 'attachment', 'image/png', 0),
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(1812, 1, '2023-02-25 22:48:19', '2023-02-25 17:18:19', '', 'Profiled-sections', '', 'inherit', 'open', 'closed', '', 'profiled-sections', '', '', '2023-02-25 22:48:19', '2023-02-25 17:18:19', '', 1809, 'https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg', 0, 'attachment', 'image/jpeg', 0);
INSERT INTO `wpba_posts` (`ID`, `post_author`, `post_date`, `post_date_gmt`, `post_content`, `post_title`, `post_excerpt`, `post_status`, `comment_status`, `ping_status`, `post_password`, `post_name`, `to_ping`, `pinged`, `post_modified`, `post_modified_gmt`, `post_content_filtered`, `post_parent`, `guid`, `menu_order`, `post_type`, `post_mime_type`, `comment_count`) VALUES
(1813, 1, '2023-02-25 22:48:38', '2023-02-25 17:18:38', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer to remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate), with small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone). This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process and recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly, dragging up a cylindrical ribbon of glass 13 m high, the diameter of the cylinder being maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Glass blocks</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C, followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity but not insulation. Fire stop blocks (F-30) manufactured from 26 mm rather than 8 mm glass offer increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>SHEET PRODUCTS</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Standard float glass sizes</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Traditional blown and drawn glasses</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Curved sheet glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Self-cleaning glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Clear white glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Embossed pattern glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern but also upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Screen printed glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Decorative etched and sandblasted glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Georgian wired glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat, but ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Toughened glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Heat-strengthened glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening, but with a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Laminated glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film and for fire protection</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Insulating glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material, preventing the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Fire-resistant glass with intumescent material laminates</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>SPECIAL GLASSES</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>One-way observation glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area and wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Mirror glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Alarm glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>&nbsp;</strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system, which is activated when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Electrically-heatable laminated safety glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Electromagnetic radiation-shielding glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>X-ray protection glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Variable transmission (smart) glasses</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Electro-optic laminates</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Intelligent glass</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>Intelligent glass facades</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions, thus reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions and also in reducing operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong>STRUCTURAL GLASS</strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. Glass is strong in compression and therefore an appropriate material for load-bearing columns and walls, providing that the design ensures sufficient strength, stiffness, and stability. <strong></strong></p>\n<!-- /wp:paragraph -->', 'Glass - as construction material', '', 'inherit', 'closed', 'closed', '', '1809-revision-v1', '', '', '2023-02-25 22:48:38', '2023-02-25 17:18:38', '', 1809, 'https://civilengineeringlectures.com/?p=1813', 0, 'revision', '', 0),
(1681, 1, '2023-05-27 05:13:01', '2021-09-05 13:56:05', ' ', '', '', 'publish', 'closed', 'closed', '', '1681', '', '', '2023-05-27 05:13:01', '2023-05-26 23:43:01', '', 0, 'https://civilengineeringlectures.com/1681/', 21, 'nav_menu_item', '', 0),
(1682, 1, '2021-09-06 10:21:27', '2021-09-06 04:51:27', '<!-- wp:heading -->\n<h2><strong>Why do we need Contract Law?</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It is because our promises should be binding. The law enforces certain types of promises to be binding, especially if there are some forms of exchange.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>If you do not give anything back in a promise, it is called a gratuitous promise. It is not usually enforceable in law. <em>However, if it is put in the formal document called a deed, it is an exception.</em>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the kind of society we live in at present, we make lots of promises which involve exchange. For example, we buy and sell freely, on small scales as well as larger scales. We engage in the construction of larger projects like the construction of railway lines or multi-storied buildings.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, it is impossible to run a society if promises are not binding. For example, what happens when you order something from a manufacturer and withdraw the order when they are ready to deliver? What happens if the client refuses to pay the contractor after the construction is over?&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>So, society will run smoothly if the members of the society can rely on promises made to them. The contract law looks after whether the parties to the contract fulfill their contractual promises. If one party defaults, the law tries to compensate the innocent party financially, attempting to put them in the position they would have been in if the contract had been performed as agreed. So, any party who fails to fulfill their obligations cannot simply go away with their breach.&nbsp;&nbsp;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Contract law tries to enforce obligations which the parties have voluntarily assumed.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, all contracts do not have to be in writing. Even when they are in written form, important points may be left out. Therefore, it is important to find out what the parties agreed.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This was explained in <strong><em>Smith v Hughes (1871).</em></strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Smith v Hughes (1871)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In this case, the complainant, Mr. Smith, was a farmer. The defendant, Mr. Hughes, was a racehorse trainer. Mr. Smith brought Mr. Hughes a sample of his oats. After seeing the sample, Mr. Hughes ordered 40-50 quarters of oats from Mr. Smith. The price was 34 shillings per quarter.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Accordingly, to begin with, 16 quarters of oats were sent to Mr. Hughes. When it arrived, Mr. Hughes said that the oats were not the quality what he had thought they were. Since he was a racehorse trainer, he needed old oats. Mr. Hughes said old oats are the type of oats the horses had for their diet. The oats that were brought by Mr. Smith were green. But, it was the same type as the initial sample. However, Mr. Hughes refused to pay Mr. Smith for the delivery and the remaining order.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Mr. Smith argued that Mr. Hughes had breached the terms of the contract as he had not paid for the delivery and future oats to be delivered.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The issue, in this case, was whether the contract could be avoided by Mr. Hughes, as Mr. Smith had not delivered the type of oats he had expected.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It was held that there was a legally acceptable contract between Mr. Smith and Mr. Hughes. Therefore, it would not be avoided. However, there had been no discussion between the parties regarding the delivery of old oats. An objective test revealed that a reasonable person would expect the sale of good quality oats in a similar contract since there was no express discussion of old oats. The sample submitted by Mr. Smith gave Mr. Hughes the chance to inspect the oats.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>This is an example of caveat emptor (buyer beware).</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>‘If, whatever a man’s real intention maybe, he so conducts himself that a reasonable man would believe he was assenting to the terms proposed by the other party, and that another party upon that belief enters into the contract with him, the man thus conducting himself would be equally bound as if he had intended to agree to the other party’s terms.’</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In some cases, the basis for this approach is obvious. When you get into a hiring car and tell your destination, it is sensible for the driver to think you are agreeing to pay for the trip. It is not right to tell at the end of the trip that you had no such intention as to pay in your mind, and so you are not obliged to pay. It is true even your behavior might have suggested that.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>L’Estrange v F Graucob Ltd (1934)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong><em>In this case, it was affirmed that the clauses of a written contract are binding on the signatories, even where a party is unaware of the contract’s full contents.</em></strong></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The claimant, L’Estrange, contracted with the defendant, Graucob to purchase a slot machine for cigarettes.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>There was an express clause in the agreement which stated;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>“This agreement contains all the terms and conditions under which I agree to purchase the machine specified above and any express or implied condition, statement, or warranty, statutory or otherwise not stated herein is hereby excluded”.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, when put in to use after the purchase, the machine was found to be faulty. As a result, the claimant brought an action against the defendant. The claimant alleged that the machine breached the Sale of Goods Act by not being of merchantable quality.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The defendant emphasized that the statute was made irrelevant by the inclusion of the express clause mentioned above. Therefore, he was not in breach of the agreement between the parties. The claimant responded saying she had been unaware of the clause because she had not properly read the agreement and therefore it should not apply.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The issue here was whether the clause which excluded all terms not stated in the contract should be deemed effective and binding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Court of Appeal determined that the express provisions of the contract were binding. It effectively excluded the relevance of statutory sales provisions. Besides, the fact that the claimant had not properly read the contract did not impact its validity. When signing the contract she consented to be bound by its contents.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>This case emphasizes the Court’s respect for the sanctity of contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong><em>When a person signs a contractual document, he is bound by it, even though he may not have understood or even read it.</em></strong></p>\n<!-- /wp:paragraph -->', 'Law of contract – The Necessity of the Law', 'Contract law tries to enforce obligations which the parties have voluntarily assumed. However, all contracts do not have to be in writing.', 'inherit', 'closed', 'closed', '', '1677-revision-v1', '', '', '2021-09-06 10:21:27', '2021-09-06 04:51:27', '', 1677, 'https://civilengineeringlectures.com/?p=1682', 0, 'revision', '', 0),
(1684, 1, '2021-09-12 00:00:30', '2021-09-11 18:30:30', '', 'laptop-office-hand-3196481', '', 'inherit', 'open', 'closed', '', 'laptop-office-hand-3196481', '', '', '2021-09-12 00:00:30', '2021-09-11 18:30:30', '', 0, 'https://civilengineeringlectures.com/wp-content/uploads/2021/09/laptop-office-hand-3196481.jpg', 0, 'attachment', 'image/jpeg', 0),
(1685, 1, '2021-09-12 00:01:13', '2021-09-11 18:31:13', '<!-- wp:paragraph -->\n<p>The basis of the law of contract is the legal enforceability of promises.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A contract may be defined as an agreement that the law can enforce if any party breach terms of the contract.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In breach of contract, the innocent party has several legal remedies. The first thing the innocent party can do is sue the party who breached terms and ask for damages. Or else, the innocent party can ask the court to order the other party to perform the contract.&nbsp;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: Kamal has agreed to sell land that belongs to him to Nimal for an agreed price. Nimal later hears that Kamal is planning to sell the same land to another person. Nimal can ask the court to order Kamal to sell the land to Nimal as agreed, and also for an order (injunction) to prevent Kamal from selling the land to another party.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Law of Contract is mostly based on judicial decisions instead of a single statute or code. However, in some areas that affecting contract law, the legislation also plays a major role.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>(For example, Sale of Goods Ordinance and more recently Consumer Protection Act in Sri Lanka).&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Most business agreements are simple contracts. A contract may be in writing or maybe done verbally. In some situations, the conduct of the parties may create a contract. No formalities are required for simple contracts. However, in some situations, specific formalities and documents are required by legislation.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The legal rules discussed below apply to simple contracts.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Definition and requirements of a contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A contract is an agreement between two or more parties that can be enforced by the law.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Requirements for a valid contract&nbsp;</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>1. There must be an agreement between two or more parties.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. The intention of the parties to the contract must be to have a legal relationship.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. The contract must conform to any required statutory formalities.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. In English law, there is a necessity that the agreement must be supported by consideration.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>However, the Roman-Dutch law, which applies in Sri Lanka and some other countries, does not require consideration. In Roman-Dutch law, any good or valid reason which is expressed by the Latin term </em><strong><em>justa causa</em></strong><em> will be sufficient for a contract.</em>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>5. The parties to the agreement must have the legal capacity to contract.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>For example, a contract with a minor is not considered a valid contract</em><em>.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>6. The agreement must be genuine. It must not be affected by factors such as mistake, misrepresentation, fraud, undue influence, and duress.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>7. The agreement must be for a purpose of an object which is not illegal. It must not conflict with public policy.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Intention to create legal relations</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong>&nbsp;</strong>An agreement only will not create a contract binding in law. A critical element in the formation of a contract is the need for an <strong><em>intention by the parties to create legally binding obligations</em></strong>. Unless the parties aim to create an agreement enforceable at law, there will be no contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Domestic or social agreements are generally not considered valid contracts</strong>.&nbsp;</h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>Example: If Sunil agrees to lend his motor car to his friend Namal, and later refuses or fails to do so, then Namal will not be able to sue Sunil for a breach of contract. This is because Sunil’s promise was of a social nature, a promise by a friend to another friend. Neither Sunil nor Namal would have expected legal action when Sunil promised to lend the motor car.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: If a husband does not honour his promise to buy his wife a birthday present, it is clear that the wife cannot sue the husband for not honouring his promises. This is because promises of these kinds are considered as domestic or social nature which the courts of law will not enforce if broken.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>There are several well-known judicial decisions to illustrate the above views.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Balfour v Balfour </em></strong><strong>[1919]</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Balfour v Balfour [1919]</em></strong> - a husband – the defendant - who was a British civil servant working in Sri Lanka came to England with his wife – the plaintiff - on a holiday. The husband has returned after the holiday, the wife staying in England due to health problems. The defendant promised to pay the plaintiff £30 per month for maintenance. However, the defendant failed to keep up the payments, and subsequently, the couple decided to separate. The wife sued the husband for the allowance after the husband had stopped paying. The English Court of Appeal held that the husband was not liable to pay it because;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>a) the wife had&nbsp;provided no consideration for the promise to pay £30; and&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>b) agreements&nbsp;between husbands and wives are not contracts, because the parties do not intend&nbsp;them to be legally binding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, every agreement between a husband and wife is not considered a social agreement.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The following is an example.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><a href=\"https://www.lawteacher.net/cases/merritt-v-merritt.php\"><strong><em>Merrit v Merrit</em></strong></a><strong><em>&nbsp;(1970)</em></strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Mr. and Mrs. Merritt married in 1941. They held their matrimonial home in joint names. In 1966, Mr. Merritt left the wife to live with another woman. After that, they met for making arrangements for the future. The&nbsp;husband agreed to pay £40 per month for maintenance. However, from this maintenance, the wife had to pay the mortgage of the house. At the wife’s request, Mr. Merritt signed a document confirming that after repaying the balance on the mortgage by her, he would hand over the matrimonial home into the wife’s name. Mrs. Merritt paid the mortgage fully and acquired a declaration that the house belonged to her. However, Mr. Merritt opposed saying that the agreement was a domestic arrangement between a husband and wife, and there was no intention to create a legal relationship. Therefore, it was not an enforceable contract. He also argued the alleged contract was insufficiently certain to be enforceable by the court because Mrs. Merritt failed to provide consideration for his promise. Mrs. Merritt argued that they were in the process of separating. Therefore, the presumption of no intention to create legal relations did not apply. She demanded that there was every intention of creating legal relations. She further argued that paying off all the expenses on the home and finishing off the mortgage payments amounted to consideration.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Court held that Mr. Merritt’s appeal was unsuccessful. When parties are in the process of separating or are separated, the presumption of there being no intention to create legal relations does not apply. The arrangement was sufficiently certain to be enforceable, and the paying of the mortgage was sufficient consideration for Mr. Merritt’s promise. Therefore, Mrs. Merritt was entitled to the matrimonial home entirely.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Agreements between business people are recognized as contracts</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>When business people or commercial bodies enter into agreements, there is a presumption that such agreements result in legally enforceable contracts.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: Gamini and Srimal are two businessmen. They are also good friends. Gamini agrees to sell a business property to Srimal for an agreed price and executes a notarial document to that effect. Gamini then tells Srimal, “although I agreed to sell that business property to you, I have now changed my mind and I have decided to sell it to another party”. Despite their close friendship, Srimal can take legal action against Gamini to enforce the written agreement since it is a commercial transaction.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Agreement between two or more persons</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The beginning of a contract is an agreement between two or more parties. The minds of both parties must agree about the subject matter of the contract.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong><em>Consensus ad idem</em></strong> is the legal term used to describe this as the meeting of two minds.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The courts have accepted the process of ‘offer and acceptance’ to see whether there has been an agreement between the parties.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: If Shiran wishes to buy a car from Reynold, they must agree about the price and other terms of delivery, etc. Shiran, the buyer, will be the offeror and Reynold will be the offeree. Shiran’s offer to Reynold is “I will buy your car for Rs. 1,000,000/-.” Reynold, the seller, has to accept this offer, for there to be a contract.&nbsp;</em></p>\n<!-- /wp:paragraph -->', 'Law of Contract – the basics', 'The basis of the law of contract is the legal enforceability of promises. In breach of contract, the innocent party has several legal remedy.', 'inherit', 'closed', 'closed', '', '1683-revision-v1', '', '', '2021-09-12 00:01:13', '2021-09-11 18:31:13', '', 1683, 'https://civilengineeringlectures.com/?p=1685', 0, 'revision', '', 0);
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(1761, 1, '2022-06-24 15:34:10', '2022-06-24 10:04:10', '<!-- wp:paragraph -->\n<p>You can download the following e-books completely free</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:list {\"ordered\":true} -->\n<ol><li><strong><a href=\"https://civilengineeringlectures.com/construction-contracts-law-and-management/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction contracts - Law and management</a></strong> - Third edition: John Murdoch &amp; Will Hughes</li><li><a href=\"https://civilengineeringlectures.com/construction-cost-management/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Construction Cost Management</strong></a> - Learning from case studies, Second edition: Second Edition: Keith Potts and Nii Ankrah</li><li><strong><a href=\"https://civilengineeringlectures.com/building-cost-planning-for-the-design-team/\" target=\"_blank\" rel=\"noreferrer noopener\">Building cost planning for the design team</a></strong> - Second edition: Jim Smith and David Jaggar</li><li><strong><a href=\"https://civilengineeringlectures.com/construction-economics-a-new-approach/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction Economics - A new approach</a></strong> - Second edition: Danny Myers</li><li><a href=\"https://civilengineeringlectures.com/200-contractual-problems-their-solutions/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>200 Contractual Problems &amp; Their Solutions</strong></a> - Third Edition - Roger Knowles</li></ol>\n<!-- /wp:list -->', 'Quantity Surveying e-books', '', 'inherit', 'closed', 'closed', '', '1727-revision-v1', '', '', '2022-06-24 15:34:10', '2022-06-24 10:04:10', '', 1727, 'https://civilengineeringlectures.com/?p=1761', 0, 'revision', '', 0),
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(1771, 1, '2022-07-10 23:19:00', '2022-07-10 17:49:00', '<!-- wp:heading -->\n<h2>Keith Molenaar, Ph.D. &amp; Gerald Yakowenko, P.E.</h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Download the free e-book here</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:buttons -->\n<div class=\"wp-block-buttons\"><!-- wp:button -->\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link\" href=\"https://drive.google.com/uc?export=download&amp;id=1axjfEDiLGyt4N6PfqvufZPy5KdELfW47\">Download Free e-book</a></div>\n<!-- /wp:button --></div>\n<!-- /wp:buttons -->', 'Alternative Project Delivery, Procurement, and Contracting Methods for Highways', 'Edited by Keith Molenaar, Ph.D. & Gerald Yakowenko, P.E. Downloadn the free e-book', 'inherit', 'closed', 'closed', '', '1769-revision-v1', '', '', '2022-07-10 23:19:00', '2022-07-10 17:49:00', '', 1769, 'https://civilengineeringlectures.com/?p=1771', 0, 'revision', '', 0),
(1766, 1, '2022-06-24 16:00:13', '2022-06-24 10:30:13', '<!-- wp:paragraph -->\n<p>You can download the following e-books completely free</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:list {\"ordered\":true} -->\n<ol><li><strong><a href=\"https://civilengineeringlectures.com/construction-contracts-law-and-management/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction contracts - Law and management</a></strong> - Third edition: John Murdoch &amp; Will Hughes</li><li><a href=\"https://civilengineeringlectures.com/construction-cost-management/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Construction Cost Management</strong></a> - Learning from case studies, Second edition: Second Edition: Keith Potts and Nii Ankrah</li><li><strong><a href=\"https://civilengineeringlectures.com/building-cost-planning-for-the-design-team/\" target=\"_blank\" rel=\"noreferrer noopener\">Building cost planning for the design team</a></strong> - Second edition: Jim Smith and David Jaggar</li><li><strong><a href=\"https://civilengineeringlectures.com/construction-economics-a-new-approach/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction Economics - A new approach</a></strong> - Second edition: Danny Myers</li><li><a href=\"https://civilengineeringlectures.com/200-contractual-problems-their-solutions/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>200 Contractual Problems &amp; Their Solutions</strong></a> - Third Edition - Roger Knowles</li><li><strong><a href=\"https://civilengineeringlectures.com/advanced-building-measurements/\">Advanced Building Measurements</a></strong> - Second Edition - Ivor H. Seeley</li></ol>\n<!-- /wp:list -->', 'Quantity Surveying e-books', '', 'inherit', 'closed', 'closed', '', '1727-revision-v1', '', '', '2022-06-24 16:00:13', '2022-06-24 10:30:13', '', 1727, 'https://civilengineeringlectures.com/?p=1766', 0, 'revision', '', 0),
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(1773, 1, '2022-07-10 23:20:55', '2022-07-10 17:50:55', '<!-- wp:paragraph -->\n<p>You can download the following e-books completely free</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:list {\"ordered\":true} -->\n<ol><li><strong><a href=\"https://civilengineeringlectures.com/construction-contracts-law-and-management/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction contracts - Law and management</a></strong> - Third edition: John Murdoch &amp; Will Hughes</li><li><a href=\"https://civilengineeringlectures.com/construction-cost-management/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Construction Cost Management</strong></a> - Learning from case studies, Second edition: Second Edition: Keith Potts and Nii Ankrah</li><li><strong><a href=\"https://civilengineeringlectures.com/building-cost-planning-for-the-design-team/\" target=\"_blank\" rel=\"noreferrer noopener\">Building cost planning for the design team</a></strong> - Second edition: Jim Smith and David Jaggar</li><li><strong><a href=\"https://civilengineeringlectures.com/construction-economics-a-new-approach/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction Economics - A new approach</a></strong> - Second edition: Danny Myers</li><li><a href=\"https://civilengineeringlectures.com/200-contractual-problems-their-solutions/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>200 Contractual Problems &amp; Their Solutions</strong></a> - Third Edition - Roger Knowles</li><li><strong><a href=\"https://civilengineeringlectures.com/advanced-building-measurements/\">Advanced Building Measurements</a></strong> - Second Edition - Ivor H. Seeley</li><li><strong><a href=\"https://civilengineeringlectures.com/alternative-project-delivery-procurement-and-contracting-methods-for-highways/\" target=\"_blank\" rel=\"noreferrer noopener\">Alternative Project Delivery, Procurement, and Contracting Methods for Highways</a></strong> - Keith Molenaar, Ph.D. &amp; Gerald Yakowenko, P.E.</li></ol>\n<!-- /wp:list -->', 'Quantity Surveying e-books', '', 'inherit', 'closed', 'closed', '', '1727-revision-v1', '', '', '2022-07-10 23:20:55', '2022-07-10 17:50:55', '', 1727, 'https://civilengineeringlectures.com/?p=1773', 0, 'revision', '', 0),
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(1792, 1, '2022-07-10 23:45:35', '2022-07-10 18:15:35', '<!-- wp:heading -->\n<h2>David Chappell</h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Download the free e-book here</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:buttons -->\n<div class=\"wp-block-buttons\"><!-- wp:button -->\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link\" href=\"https://drive.google.com/uc?export=download&amp;id=1AuL1BBWIAHMox773Jw9YlggSbCwI9NLx\">Download the free e-book</a></div>\n<!-- /wp:button --></div>\n<!-- /wp:buttons -->', 'Building Contract Claims', 'by David Chappell. Download the free e-book here', 'inherit', 'closed', 'closed', '', '1786-revision-v1', '', '', '2022-07-10 23:45:35', '2022-07-10 18:15:35', '', 1786, 'https://civilengineeringlectures.com/?p=1792', 0, 'revision', '', 0),
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(1794, 1, '2022-07-10 23:52:58', '2022-07-10 18:22:58', '<!-- wp:heading -->\n<h2>Fourth Edition - Ivor H. Seeley</h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Download the free e-book here</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:buttons -->\n<div class=\"wp-block-buttons\"><!-- wp:button -->\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link\" href=\"https://drive.google.com/file/d/1x9sZcszsEn1yyFQVik_wqZ1ERbD5aaJs/view?usp=sharing\">Download the free e-book</a></div>\n<!-- /wp:button --></div>\n<!-- /wp:buttons -->', 'Building Economics', '', 'inherit', 'closed', 'closed', '', '1791-revision-v1', '', '', '2022-07-10 23:52:58', '2022-07-10 18:22:58', '', 1791, 'https://civilengineeringlectures.com/?p=1794', 0, 'revision', '', 0),
(1790, 1, '2022-07-10 23:43:57', '2022-07-10 18:13:57', '<!-- wp:paragraph -->\n<p>You can download the following e-books completely free</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:list {\"ordered\":true} -->\n<ol><li><strong><a href=\"https://civilengineeringlectures.com/construction-contracts-law-and-management/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction contracts - Law and management</a></strong> - Third edition: John Murdoch &amp; Will Hughes</li><li><a href=\"https://civilengineeringlectures.com/construction-cost-management/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Construction Cost Management</strong></a> - Learning from case studies, Second edition: Second Edition: Keith Potts and Nii Ankrah</li><li><strong><a href=\"https://civilengineeringlectures.com/building-cost-planning-for-the-design-team/\" target=\"_blank\" rel=\"noreferrer noopener\">Building cost planning for the design team</a></strong> - Second edition: Jim Smith and David Jaggar</li><li><strong><a href=\"https://civilengineeringlectures.com/construction-economics-a-new-approach/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction Economics - A new approach</a></strong> - Second edition: Danny Myers</li><li><a href=\"https://civilengineeringlectures.com/200-contractual-problems-their-solutions/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>200 Contractual Problems &amp; Their Solutions</strong></a> - Third Edition - Roger Knowles</li><li><strong><a href=\"https://civilengineeringlectures.com/advanced-building-measurements/\">Advanced Building Measurements</a></strong> - Second Edition - Ivor H. Seeley</li><li><strong><a href=\"https://civilengineeringlectures.com/alternative-project-delivery-procurement-and-contracting-methods-for-highways/\" target=\"_blank\" rel=\"noreferrer noopener\">Alternative Project Delivery, Procurement, and Contracting Methods for Highways</a></strong> - Keith Molenaar, Ph.D. &amp; Gerald Yakowenko, P.E.</li><li><strong><a href=\"https://civilengineeringlectures.com/analysis-of-concurrent-delay-on-construction-claims/\" target=\"_blank\" rel=\"noreferrer noopener\">Analysis of Concurrent Delay on Construction Claims</a></strong> - Richard J. Long, P.E.</li><li><strong><a href=\"https://civilengineeringlectures.com/bim-and-construction-management-proven-tools-methods-and-workflows/\">BIM and Construction Management - Proven tools, methods, and workflows</a></strong> - Second Edition - Brad Hardin &amp; Dave McCool</li><li><strong><a href=\"https://civilengineeringlectures.com/building-contract-claims/\" target=\"_blank\" rel=\"noreferrer noopener\">Building Contract Claims</a></strong> - David Chappell</li></ol>\n<!-- /wp:list -->', 'Quantity Surveying e-books', '', 'inherit', 'closed', 'closed', '', '1727-revision-v1', '', '', '2022-07-10 23:43:57', '2022-07-10 18:13:57', '', 1727, 'https://civilengineeringlectures.com/?p=1790', 0, 'revision', '', 0),
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(1688, 1, '2021-09-12 00:08:14', '2021-09-11 18:38:14', '<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Offer</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The legal test to be applied for determining whether an agreement has been made between parties is that of offer and acceptance.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>For the formation of a contract, one party must make an offer. The other party must accept it. After the acceptance takes effect, a contract will be formed binding on both parties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A contractual offer consists of a firm and definite promise (or several promises).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Unilateral and bilateral contracts</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example - Kamal offers to sell his computer to Amal.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>(Although contracts with mutual obligations are called bilateral contracts, actually there may be more than two parties to a contract.)</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>By contrast, a unilateral contract arises where only one party assumes an obligation under the contract – promise in return for action.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Examples might be promising to pay Rs: 1,000 rewards to anyone who finds your lost purse</em>.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The person who makes an offer is called the offeror. The person to whom the offer is made is called the offeree.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Offers to the public at large</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In most cases, an offer will be made to a definite person – as when Kamal offers to sell his computer to Amal.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, offers can be addressed to a group of people. Or, the offer may be addressed even to the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>For example, a final year university student may offer to sell his old textbooks to any student in the year below – i.e. specific group. The owner of a lost dog may offer a reward to anyone who finds it – an offer addressed to the general public.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Offers addressed to the general public are accepted when the offer is acted upon by a member of the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Advertisements for unilateral contracts are generally treated as offers.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Carlill v Carbolic Smoke Ball Co </em></strong><strong>(1893)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>In </em><strong><em>Carlill </em></strong><em>v </em><strong><em>Carbolic Smoke Ball Co </em></strong><em>(1893), the defendants were the manufacturers of ‘smoke balls’ which they claimed could prevent flu. The defendants published an advertisement which stated that, after using their smoke balls for a specified time, if anyone caught flu, they would pay that person £100.&nbsp; To prove they were serious about the claim, they had deposited £1,000 with their bankers.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Mrs. Carlill bought and used a smoke ball as specified in the advertisement. But unfortunately, she ended up with the flu. Then, she claimed £100, and the company refused to pay. Carbolic Smoke Ball Co argued that their advertisement could not give rise to a contract, because it was impossible to make a contract with the whole world. Therefore, they were not legally bound to pay the money. The Court rejected this argument and held that the advertisement did constitute an offer to the world at large. It formed a contract when it was accepted by Mrs. Carlill using the smoke ball and getting flu. Therefore, she was entitled to the £100 reward.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Bowerman v Association of British Travel Agents Ltd </em></strong><strong>(1996)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>A school had booked a skiing holiday with a tour operator. The tour operator was a member of the Association of British Travel Agents (ABTA). All members of this association display a notice provided by ABTA. It states: Where holidays or other travel arrangements have not yet commenced at the time of failure [of the tour operator], ABTA arranges for you to be reimbursed the money you have paid in respect of your holiday arrangements.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>The tour operator became insolvent and canceled the skiing holiday tour. The school was refunded the money they had paid for the holiday. However, the cost of the wasted travel insurance was not refunded. The plaintiff – Bowerman - brought an action against ABTA and asked for reimbursement of the cost of the travel insurance. The Court of Appeal agreed with the plaintiff and held the ABTA notice constituted an offer which the customer accepted by contracting with an ABTA member. It was a contract arising from an offer to the public at large and hence a unilateral contract.</em></p>\n<!-- /wp:paragraph -->', 'Law of Contract - Unilateral and bilateral contracts', 'Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.', 'publish', 'open', 'open', '', 'unilateral-and-bilateral-contracts', '', '', '2021-09-12 21:17:55', '2021-09-12 15:47:55', '', 0, 'https://civilengineeringlectures.com/?p=1688', 0, 'post', '', 0),
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(1690, 1, '2021-09-12 00:08:14', '2021-09-11 18:38:14', '<!-- wp:heading -->\n<h2><strong>Offer</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The legal test to be applied for determining whether an agreement has been made between parties is that of offer and acceptance.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>For the formation of a contract, one party must make an offer. The other party must accept it. After the acceptance takes effect, a contract will be formed binding on both parties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A contractual offer consists of a firm and definite promise (or several promises).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Unilateral and bilateral contracts</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example - Kamal offers to sell his computer to Amal.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>(Although contracts with mutual obligations are called bilateral contracts, actually there may be more than two parties to a contract.)</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>By contrast, a unilateral contract arises where only one party assumes an obligation under the contract – promise in return for action.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Examples might be promising to pay Rs: 1,000 rewards to anyone who finds your lost purse</em>. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The person who makes an offer is called the offeror. The person to whom the offer is made is called the offeree.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Offers to the public at large</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In most cases, an offer will be made to a definite person – as when Kamal offers to sell his computer to Amal.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, offers can be addressed to a group of people. Or, the offer may be addressed even to the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>For example, a final year university student may offer to sell his old textbooks to any student in the year below – i.e. specific group. The owner of a lost dog may offer a reward to anyone who finds it – an offer addressed to the general public.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Offers addressed to the general public are accepted when the offer is acted upon by a member of the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Advertisements for unilateral contracts are generally treated as offers.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Carlill v Carbolic Smoke Ball Co </em></strong><strong>(1893)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>In </em><strong><em>Carlill </em></strong><em>v </em><strong><em>Carbolic Smoke Ball Co </em></strong><em>(1893), the defendants were the manufacturers of ‘smoke balls’ which they claimed could prevent flu. The defendants published an advertisement which stated that, after using their smoke balls for a specified time, if anyone caught flu, they would pay that person £100.&nbsp; To prove they were serious about the claim, they had deposited £1,000 with their bankers.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Mrs. Carlill bought and used a smoke ball as specified in the advertisement. But unfortunately, she ended up with the flu. Then, she claimed £100, and the company refused to pay. Carbolic Smoke Ball Co argued that their advertisement could not give rise to a contract, because it was impossible to make a contract with the whole world. Therefore, they were not legally bound to pay the money. The Court rejected this argument and held that the advertisement did constitute an offer to the world at large. It formed a contract when it was accepted by Mrs. Carlill using the smoke ball and getting flu. Therefore, she was entitled to the £100 reward.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Bowerman v Association of British Travel Agents Ltd </em></strong><strong>(1996)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>A school had booked a skiing holiday with a tour operator. The tour operator was a member of the Association of British Travel Agents (ABTA). All members of this association display a notice provided by ABTA. It states: Where holidays or other travel arrangements have not yet commenced at the time of failure [of the tour operator], ABTA arranges for you to be reimbursed the money you have paid in respect of your holiday arrangements.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>The tour operator became insolvent and canceled the skiing holiday tour. The school was refunded the money they had paid for the holiday. However, the cost of the wasted travel insurance was not refunded. The plaintiff – Bowerman - brought an action against ABTA and asked for reimbursement of the cost of the travel insurance. The Court of Appeal agreed with the plaintiff and held the ABTA notice constituted an offer which the customer accepted by contracting with an ABTA member. It was a contract arising from an offer to the public at large and hence a unilateral contract.</em></p>\n<!-- /wp:paragraph -->', 'Law of Contract - Unilateral and bilateral contracts', 'Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.', 'inherit', 'closed', 'closed', '', '1688-revision-v1', '', '', '2021-09-12 00:08:14', '2021-09-11 18:38:14', '', 1688, 'https://civilengineeringlectures.com/?p=1690', 0, 'revision', '', 0),
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(1926, 1, '2023-05-14 12:36:28', '2023-05-14 07:06:28', '<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Definition of a Contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term contract can be defined as an agreement that is enforceable by law.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Works contracts are different from other contracts.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Some of the special features of civil engineering works are:-</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>1. One-off projects – never the same, e.g. location, time.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. Labour is transient and recruited on an ad-hoc basis.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. Management team is freshly set up.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. Dispersed in big geographical areas.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>5. A tangible product results at the end of the contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>6. It takes a longer period to complete the work.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>7. It is performed in the open with exposure to the weather.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>8. People with many specialties participate in its performance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>9. Payment is done in many stages.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The conditions of contract for works contracts should address the peculiarities like the above ones.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>The main parts of a works contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Contract Agreement</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Letter of Acceptance</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Memorandum of Understanding (if any)</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Form of Bid</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Contract Data / Conditions of Particular Applications</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Conditions of Contract</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Specifications</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Drawings</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Bill of Quantities</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Conditions of Contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>These are a set of rules, agreed by the parties to the contract which govern their conduct.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These conditions:-</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Define the relationship between the employer and the contractor.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>State explicitly what to do if the relationship is disturbed.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Define the apportionment of risk between the parties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Define the rules under which one party is remunerated for the work done by it.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>To prepare a set of conditions of contract one should think of all probable risks which can affect the execution of the works and write clauses to address them by apportioning these risks. It is a time-consuming exercise and many risks may be missed or they may be apportioned erroneously. The remedies suggested for these risks may not be commensurate with the level of risks. To overcome these difficulties, standard conditions of contracts are available. They contain the experience of many individuals who have participated in contract management.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>While apportioning risks in works contract two principles are adhered to, namely;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Responsibility for risk is given to the party which can best manage that risk.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>All other risks are given to the client since he is the initiator of the project.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Standard Conditions of Contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>There are many standard forms of contracts to tackle the performance of work contracts such as;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>FIDIC</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>CIDA / ICTAD</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>NEC</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>ICE</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the acquisition of experience, the standard conditions of contracts have seen many revisions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>It is possible to disturb the balance found in the standard conditions of contract, by tinkering with them. But it is advisable not to disturb the balance in them, since this can result in the following:-</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>1. Higher bid prices</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. Disruption of the project implementation</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. Non-participation in the bidding process by genuinely serious contractors</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. Award of contract to a bidder who has not understood his responsibilities properly</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>5. Poor quality of work</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>6. Delayed completion</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>7. Unsatisfactory relationship between the Client and the Contractor</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>8. Frivolous claim by the Contractor</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>9. Frequent disputes</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>10. Termination of the Contract by non-performance</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Since most of the works contracts performed in Sri Lanka are based on the CIDA / ICTAD conditions of the contract, we will look into them more deeply:-</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>There are four versions of Standard Conditions of Contract available under CIDA / ICTAD. They are for;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>1. Major Works – Large scale contracts - recommended for contracts over LKR 100 million.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. Works for Medium scale contracts - recommended for contracts between LKR 10 million to 100 million.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. Works for Minor contracts – recommended for contracts up to LKR 10 million.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. Design and Build Contracts – where the contractor is responsible for the design and construction of the work.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>We will look into the Conditions of Contract for Major Works only. (CIDA / ICTAD - SBD2).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Some important features of the ICTAD/SBD2 Standard Conditions of Contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>1. It caters to the scenario where the bulk of the design is done by the Employer or a consultant appointed by the Employer. In both cases, the Employer is responsible for the design. The Contractor also can be given a small portion of the design for which the Contractor takes responsibility. All the</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Temporary Works are designed by the Contractor and he takes responsibility for them.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. Presence of an entity that is not a party to the Contract, but who has wide powers in the day-to-day running of the Contract is recognized in the Conditions of Contract. In a works contract the contract is between two parties, namely the Employer and the Contractor. But the conditions of contract for work contracts extensively talk of the responsibilities of three persons. In addition to the parties to the contract, the conditions of the contract talk a lot about a person called the Engineer. This Engineer is there to supervise the work and certify the payment statements.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Even though the Engineer is employed by the Employer, the Engineer is expected to be fair and reasonable in his dealings with the parties to the contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. This has two parts, namely General Conditions of Contract and Contract Data.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The General Conditions of the Contract contain general clauses. The Contract Data has project-specific data. The user is not expected to change anything in the General Conditions of Contract. Whatever he wants to change he can change in the Contract Data. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. The risk allocation between the parties is well-balanced. The risks which can be best managed by the Contractor are made his responsibility and all the other risks are given to the Employer.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Applicable Law</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Applicable Law will determine to what extent the Parties are bound to carry out their contractual obligations. In Sri Lanka, the applicable law is always the Sri Lankan law.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Liquidated Damages</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The Contractor is expected to complete the works before the Time for Completion. If he delays the work the Employer is entitled to recover his damages by way of Liquidated Damages from the Contractor. The damage per day is predetermined and stated in the Contract Data. A maximum limit for the cumulative Liquidated Damages is also stated in the Contract Data. Even when the maximum Liquidated Damages are imposed on the Contractor, he is expected to fulfill his obligations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The estimate of the damage shall be a genuine estimate at the time of forming the Contract. The Employer cannot get undue benefit by fixing the daily rate of this damage very high. If he does so, he may lose his right to impose the Liquidated Damages.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Liquidated Damages can be imposed in most breaches of contract. But in ICTAD/SBD/02 it is imposed on delayed completion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Usually, Contractors prevent the imposition of Liquidated Damages by requesting an extension of Time for Completion, whenever an opportunity presents itself.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Extension of Time for Completion</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Variations, exceptionally adverse weather conditions, unforeseeable shortages of goods and personnel, and delays attributable to the Employer are some of the reasons which give an entitlement to the Contractor for the extension of Time for Completion. The Contractor should claim for an extension of Time for Completion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Granting of extension of Time for Completion may sometimes result in the payment of prolongation costs to the Contractor.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Refusing to grant an extension of Time for Completion may result in the arbitrator/court deciding that the Employer cannot impose the Liquidated Damages.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Definitions</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Under this Clause, the contractual terms are defined.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Unless the key contractual terms are properly defined, the tendency for disputes increases. Each party will try to interpret the meaning of words to its advantage.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Cost is defined as the expenditure incurred by the Contractor and includes overheads but excludes profit.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>If the Contractor incurs additional expenditure by the failure of the Employer to give access to the Site, he can get the extra cost and reasonable profit. But if he incurs additional expenditure due to the presence of some unforeseeable physical condition he is entitled only to additional cost.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The defined words are generally distinguished by having their first letter written in upper case letters. Therefore if the same word is used with the first letter in upper case in some places and lower case in some other places, the difference is that the first case is that of a defined word and the other one is an undefined word. The words contractor / Contractor and cost / Cost are words with different meanings depending on the case of their first letter.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>The Engineer</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The Engineer is appointed by the Employer and his authority is specified in the Contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Engineer\'s authority can be curtailed by suitable adjustments in the Contract Data. The Contractor can assume that all the authorizations have been obtained by the Engineer. Examples of curtailment are the Engineer is not allowed to give variation orders above a certain amount. Each variation order is given a limit and above a cumulative limit he is not allowed to give any variation. In each case, he is expected to get the Employer\'s permission before giving a variation order.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Engineer</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Approves</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Checks</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Certifies</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Consents</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Examines</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Inspects</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Instructs</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Notices</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Proposes</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Requests</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Tests</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Engage in similar acts if needed.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Sub-Clause 3.5 says that the Engineer shall exercise his discretion impartially.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Variation</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Only the simplest of works is completed as planned in the beginning. Changes have to be made to the original plans. The changes can be due to natural reasons, due to a change of mind of the Employer or the Contractor proposes it. When changes are ordered, it has to be addressed contractually without both parties being affected unreasonably.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Engineer can initiate a Variation at any time before issuing a Taking over Certificate. He cannot issue any Variation Order during the Defects Notification Period. He can issue either a Variation Order directly or request a proposal from the Contractor for an intended variation order. The proposals are requested to assess the cost and time implications. The Contractor has the right to inform the Engineer that the Goods required to carry out the Variation Order are not readily available.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A Variation may include:-</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Changes in quantities</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Change in quality or other characteristics</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Change in levels, positions, and dimensions</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Omission of some items (such items cannot be executed by anybody else other than the Contractor subsequently)</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Additional work</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Change in the sequence of the work</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>If the Contractor proposes any change the benefit of that change is divided between the Contractor and the Employer.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2 class=\"wp-block-heading\"><strong>Dispute Resolution</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Any activity which has an element of interaction between human beings has a possibility of disputes. 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(1732, 1, '2022-06-21 13:36:38', '2022-06-21 08:06:38', '<!-- wp:paragraph -->\n<p>You can download the following e-books completely free</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:list {\"ordered\":true} -->\n<ol><li><strong><a href=\"https://civilengineeringlectures.com/construction-contracts-law-and-management/\" target=\"_blank\" rel=\"noreferrer noopener\">Construction contracts - Law and management</a></strong> - Third edition: John Murdoch &amp; Will Hughes</li></ol>\n<!-- /wp:list -->', 'Quantity Surveying e-books', '', 'inherit', 'closed', 'closed', '', '1727-revision-v1', '', '', '2022-06-21 13:36:38', '2022-06-21 08:06:38', '', 1727, 'https://civilengineeringlectures.com/?p=1732', 0, 'revision', '', 0);
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(1809, 1, '2023-02-25 23:19:49', '2023-02-25 17:49:49', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer. These remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate). Small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone) are also used. This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process. It also recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with small quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly. It drags up a cylindrical ribbon of glass 13 m high. The diameter of the cylinder is maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass blocks</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C. The process is then followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity. But, it will not give insulation. Fire stop blocks (F-30) are manufactured from 26 mm rather than 8 mm glass. It offers increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Standard float glass sizes</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Traditional blown and drawn glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Curved sheet glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Self-cleaning glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass and also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Clear white glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Embossed pattern glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern. It also depend upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Screen printed glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Decorative etched and sandblasted glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Georgian wired glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1821,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Georgian-wired-glass.jpg\" alt=\"\" class=\"wp-image-1821\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat. But, ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Toughened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1819,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Toughned-glass.jpg\" alt=\"\" class=\"wp-image-1819\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Heat-strengthened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening. But, it is done at a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Laminated glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1817,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass-2-585x1024.png\" alt=\"Anti bandit glass\" class=\"wp-image-1817\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Insulating glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material. It prevents the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1816,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass.png\" alt=\"Laminated glass\" class=\"wp-image-1816\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Fire-resistant glass with intumescent material laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading -->\n<h2><strong>SPECIAL GLASSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>One-way observation glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area. Also, he should wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Mirror glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alarm glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong> </strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system. It is set to activate when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electrically-heatable laminated safety glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electromagnetic radiation-shielding glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>X-ray protection glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Variable transmission (smart) glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electro-optic laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass facades</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions. It results in reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions. It also reduces the operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>STRUCTURAL GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. 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INSERT INTO `wpba_posts` (`ID`, `post_author`, `post_date`, `post_date_gmt`, `post_content`, `post_title`, `post_excerpt`, `post_status`, `comment_status`, `ping_status`, `post_password`, `post_name`, `to_ping`, `pinged`, `post_modified`, `post_modified_gmt`, `post_content_filtered`, `post_parent`, `guid`, `menu_order`, `post_type`, `post_mime_type`, `comment_count`) VALUES
(1695, 1, '2021-09-12 21:16:44', '2021-09-12 15:46:44', '<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Offer</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The legal test to be applied for determining whether an agreement has been made between parties is that of offer and acceptance.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>For the formation of a contract, one party must make an offer. The other party must accept it. After the acceptance takes effect, a contract will be formed binding on both parties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A contractual offer consists of a firm and definite promise (or several promises).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Unilateral and bilateral contracts</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example - Kamal offers to sell his computer to Amal.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>(Although contracts with mutual obligations are called bilateral contracts, actually there may be more than two parties to a contract.)</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>By contrast, a unilateral contract arises where only one party assumes an obligation under the contract – promise in return for action.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Examples might be promising to pay Rs: 1,000 rewards to anyone who finds your lost purse</em>.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The person who makes an offer is called the offeror. The person to whom the offer is made is called the offeree.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Offers to the public at large</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In most cases, an offer will be made to a definite person – as when Kamal offers to sell his computer to Amal.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, offers can be addressed to a group of people. Or, the offer may be addressed even to the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>For example, a final year university student may offer to sell his old textbooks to any student in the year below – i.e. specific group. The owner of a lost dog may offer a reward to anyone who finds it – an offer addressed to the general public.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Offers addressed to the general public are accepted when the offer is acted upon by a member of the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Advertisements for unilateral contracts are generally treated as offers.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Carlill v Carbolic Smoke Ball Co </em></strong><strong>(1893)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>In </em><strong><em>Carlill </em></strong><em>v </em><strong><em>Carbolic Smoke Ball Co </em></strong><em>(1893), the defendants were the manufacturers of ‘smoke balls’ which they claimed could prevent flu. The defendants published an advertisement which stated that, after using their smoke balls for a specified time, if anyone caught flu, they would pay that person £100.&nbsp; To prove they were serious about the claim, they had deposited £1,000 with their bankers.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Mrs. Carlill bought and used a smoke ball as specified in the advertisement. But unfortunately, she ended up with the flu. Then, she claimed £100, and the company refused to pay. Carbolic Smoke Ball Co argued that their advertisement could not give rise to a contract, because it was impossible to make a contract with the whole world. Therefore, they were not legally bound to pay the money. The Court rejected this argument and held that the advertisement did constitute an offer to the world at large. It formed a contract when it was accepted by Mrs. Carlill using the smoke ball and getting flu. Therefore, she was entitled to the £100 reward.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Bowerman v Association of British Travel Agents Ltd </em></strong><strong>(1996)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>A school had booked a skiing holiday with a tour operator. The tour operator was a member of the Association of British Travel Agents (ABTA). All members of this association display a notice provided by ABTA. It states: Where holidays or other travel arrangements have not yet commenced at the time of failure [of the tour operator], ABTA arranges for you to be reimbursed the money you have paid in respect of your holiday arrangements.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>The tour operator became insolvent and canceled the skiing holiday tour. The school was refunded the money they had paid for the holiday. However, the cost of the wasted travel insurance was not refunded. The plaintiff – Bowerman - brought an action against ABTA and asked for reimbursement of the cost of the travel insurance. The Court of Appeal agreed with the plaintiff and held the ABTA notice constituted an offer which the customer accepted by contracting with an ABTA member. It was a contract arising from an offer to the public at large and hence a unilateral contract.</em></p>\n<!-- /wp:paragraph -->', 'Law of Contract - Unilateral and bilateral contracts', 'Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.', 'inherit', 'closed', 'closed', '', '1688-revision-v1', '', '', '2021-09-12 21:16:44', '2021-09-12 15:46:44', '', 1688, 'https://civilengineeringlectures.com/?p=1695', 0, 'revision', '', 0),
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(1824, 1, '2023-02-25 23:17:33', '2023-02-25 17:47:33', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer to remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate), with small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone). This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process and recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly, dragging up a cylindrical ribbon of glass 13 m high, the diameter of the cylinder being maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass blocks</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C, followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity but not insulation. Fire stop blocks (F-30) manufactured from 26 mm rather than 8 mm glass offer increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Standard float glass sizes</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Traditional blown and drawn glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Curved sheet glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Self-cleaning glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Clear white glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Embossed pattern glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern but also upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Screen printed glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Decorative etched and sandblasted glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Georgian wired glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1821,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Georgian-wired-glass.jpg\" alt=\"\" class=\"wp-image-1821\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat, but ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Toughened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1819,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Toughned-glass.jpg\" alt=\"\" class=\"wp-image-1819\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Heat-strengthened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening, but with a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Laminated glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1817,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass-2-585x1024.png\" alt=\"Anti bandit glass\" class=\"wp-image-1817\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film and for fire protection</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Insulating glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material, preventing the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1816,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass.png\" alt=\"Laminated glass\" class=\"wp-image-1816\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Fire-resistant glass with intumescent material laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading -->\n<h2><strong>SPECIAL GLASSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>One-way observation glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area and wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Mirror glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alarm glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong>&nbsp;</strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system, which is activated when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electrically-heatable laminated safety glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electromagnetic radiation-shielding glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>X-ray protection glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Variable transmission (smart) glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electro-optic laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass facades</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions, thus reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions and also in reducing operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>STRUCTURAL GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. Glass is strong in compression and therefore an appropriate material for load-bearing columns and walls, providing that the design ensures sufficient strength, stiffness, and stability. <strong></strong></p>\n<!-- /wp:paragraph -->', 'Glass - as construction material', 'The term glass refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency', 'inherit', 'closed', 'closed', '', '1809-revision-v1', '', '', '2023-02-25 23:17:33', '2023-02-25 17:47:33', '', 1809, 'https://civilengineeringlectures.com/?p=1824', 0, 'revision', '', 0),
(1694, 1, '2021-09-12 21:15:47', '2021-09-12 15:45:47', '<!-- wp:paragraph -->\n<p>The basis of the law of contract is the legal enforceability of promises.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A contract may be defined as an agreement that the law can enforce if any party breach terms of the contract.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In breach of contract, the innocent party has several legal remedies. The first thing the innocent party can do is sue the party who breached terms and ask for damages. Or else, the innocent party can ask the court to order the other party to perform the contract.&nbsp;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: Kamal has agreed to sell land that belongs to him to Nimal for an agreed price. Nimal later hears that Kamal is planning to sell the same land to another person. Nimal can ask the court to order Kamal to sell the land to Nimal as agreed, and also for an order (injunction) to prevent Kamal from selling the land to another party.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Law of Contract is mostly based on judicial decisions instead of a single statute or code. However, in some areas that affecting contract law, the legislation also plays a major role.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>(For example, Sale of Goods Ordinance and more recently Consumer Protection Act in Sri Lanka).&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Most business agreements are simple contracts. A contract may be in writing or maybe done verbally. In some situations, the conduct of the parties may create a contract. No formalities are required for simple contracts. However, in some situations, specific formalities and documents are required by legislation.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The legal rules discussed below apply to simple contracts.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Definition and requirements of a contract</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A contract is an agreement between two or more parties that can be enforced by the law.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Requirements for a valid contract&nbsp;</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>1. There must be an agreement between two or more parties.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>2. The intention of the parties to the contract must be to have a legal relationship.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>3. The contract must conform to any required statutory formalities.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>4. In English law, there is a necessity that the agreement must be supported by consideration.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>However, the Roman-Dutch law, which applies in Sri Lanka and some other countries, does not require consideration. In Roman-Dutch law, any good or valid reason which is expressed by the Latin term </em><strong><em>justa causa</em></strong><em> will be sufficient for a contract.</em>&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>5. The parties to the agreement must have the legal capacity to contract.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>For example, a contract with a minor is not considered a valid contract</em><em>.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>6. The agreement must be genuine. It must not be affected by factors such as mistake, misrepresentation, fraud, undue influence, and duress.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>7. The agreement must be for a purpose of an object which is not illegal. It must not conflict with public policy.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Intention to create legal relations</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong>&nbsp;</strong>An agreement only will not create a contract binding in law. A critical element in the formation of a contract is the need for an <strong><em>intention by the parties to create legally binding obligations</em></strong>. Unless the parties aim to create an agreement enforceable at law, there will be no contract.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Domestic or social agreements are generally not considered valid contracts</strong> </h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>Example: If Sunil agrees to lend his motor car to his friend Namal, and later refuses or fails to do so, then Namal will not be able to sue Sunil for a breach of contract. This is because Sunil’s promise was of a social nature, a promise by a friend to another friend. Neither Sunil nor Namal would have expected legal action when Sunil promised to lend the motor car.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: If a husband does not honour his promise to buy his wife a birthday present, it is clear that the wife cannot sue the husband for not honouring his promises. This is because promises of these kinds are considered as domestic or social nature which the courts of law will not enforce if broken.&nbsp;</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>There are several well-known judicial decisions to illustrate the above views.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong><em>Balfour v Balfour </em></strong><strong>[1919]</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In <strong><em>Balfour v Balfour [1919]</em></strong> - a husband – the defendant - who was a British civil servant working in Sri Lanka came to England with his wife – the plaintiff - on a holiday. The husband has returned after the holiday, the wife staying in England due to health problems. The defendant promised to pay the plaintiff £30 per month for maintenance. However, the defendant failed to keep up the payments, and subsequently, the couple decided to separate. The wife sued the husband for the allowance after the husband had stopped paying. The English Court of Appeal held that the husband was not liable to pay it because;&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>a) the wife had&nbsp;provided no consideration for the promise to pay £30; and&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>b) agreements&nbsp;between husbands and wives are not contracts, because the parties do not intend&nbsp;them to be legally binding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>However, every agreement between a husband and wife is not considered a social agreement.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The following is an example.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Merritt v Merritt </em>[1970]</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Mr. and Mrs. Merritt married in 1941. They held their matrimonial home in joint names. In 1966, Mr. Merritt left the wife to live with another woman. After that, they met for making arrangements for the future. The&nbsp;husband agreed to pay £40 per month for maintenance. However, from this maintenance, the wife had to pay the mortgage of the house. At the wife’s request, Mr. Merritt signed a document confirming that after repaying the balance on the mortgage by her, he would hand over the matrimonial home into the wife’s name. Mrs. Merritt paid the mortgage fully and acquired a declaration that the house belonged to her. However, Mr. Merritt opposed saying that the agreement was a domestic arrangement between a husband and wife, and there was no intention to create a legal relationship. Therefore, it was not an enforceable contract. He also argued the alleged contract was insufficiently certain to be enforceable by the court because Mrs. Merritt failed to provide consideration for his promise. Mrs. Merritt argued that they were in the process of separating. Therefore, the presumption of no intention to create legal relations did not apply. She demanded that there was every intention of creating legal relations. She further argued that paying off all the expenses on the home and finishing off the mortgage payments amounted to consideration.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The Court held that Mr. Merritt’s appeal was unsuccessful. When parties are in the process of separating or are separated, the presumption of there being no intention to create legal relations does not apply. The arrangement was sufficiently certain to be enforceable, and the paying of the mortgage was sufficient consideration for Mr. Merritt’s promise. Therefore, Mrs. Merritt was entitled to the matrimonial home entirely.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Agreements between business people are recognized as contracts</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>When business people or commercial bodies enter into agreements, there is a presumption that such agreements result in legally enforceable contracts.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: Gamini and Srimal are two businessmen. They are also good friends. Gamini agrees to sell a business property to Srimal for an agreed price and executes a notarial document to that effect. Gamini then tells Srimal, “although I agreed to sell that business property to you, I have now changed my mind and I have decided to sell it to another party”. Despite their close friendship, Srimal can take legal action against Gamini to enforce the written agreement since it is a commercial transaction.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>Agreement between two or more persons</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The beginning of a contract is an agreement between two or more parties. The minds of both parties must agree about the subject matter of the contract.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><strong><em>Consensus ad idem</em></strong> is the legal term used to describe this as the meeting of two minds.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The courts have accepted the process of ‘offer and acceptance’ to see whether there has been an agreement between the parties.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example: If Shiran wishes to buy a car from Reynold, they must agree about the price and other terms of delivery, etc. Shiran, the buyer, will be the offeror and Reynold will be the offeree. Shiran’s offer to Reynold is “I will buy your car for Rs. 1,000,000/-.” Reynold, the seller, has to accept this offer, for there to be a contract.&nbsp;</em></p>\n<!-- /wp:paragraph -->', 'Law of Contract – the basics', 'The basis of the law of contract is the legal enforceability of promises. In breach of contract, the innocent party has several legal remedy.', 'inherit', 'closed', 'closed', '', '1683-revision-v1', '', '', '2021-09-12 21:15:47', '2021-09-12 15:45:47', '', 1683, 'https://civilengineeringlectures.com/?p=1694', 0, 'revision', '', 0);
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(1697, 1, '2021-09-12 21:17:29', '2021-09-12 15:47:29', '<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Offer</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The legal test to be applied for determining whether an agreement has been made between parties is that of offer and acceptance.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>For the formation of a contract, one party must make an offer. The other party must accept it. After the acceptance takes effect, a contract will be formed binding on both parties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>A contractual offer consists of a firm and definite promise (or several promises).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Unilateral and bilateral contracts</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Example - Kamal offers to sell his computer to Amal.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>(Although contracts with mutual obligations are called bilateral contracts, actually there may be more than two parties to a contract.)</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>By contrast, a unilateral contract arises where only one party assumes an obligation under the contract – promise in return for action.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Examples might be promising to pay Rs: 1,000 rewards to anyone who finds your lost purse</em>.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The person who makes an offer is called the offeror. The person to whom the offer is made is called the offeree.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong>Offers to the public at large</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>In most cases, an offer will be made to a definite person – as when Kamal offers to sell his computer to Amal.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>But, offers can be addressed to a group of people. Or, the offer may be addressed even to the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>For example, a final year university student may offer to sell his old textbooks to any student in the year below – i.e. specific group. The owner of a lost dog may offer a reward to anyone who finds it – an offer addressed to the general public.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Offers addressed to the general public are accepted when the offer is acted upon by a member of the general public.&nbsp;</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Advertisements for unilateral contracts are generally treated as offers.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Carlill v Carbolic Smoke Ball Co </em></strong><strong>(1893)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>In </em><strong><em>Carlill </em></strong><em>v </em><strong><em>Carbolic Smoke Ball Co </em></strong><em>(1893), the defendants were the manufacturers of ‘smoke balls’ which they claimed could prevent flu. The defendants published an advertisement which stated that, after using their smoke balls for a specified time, if anyone caught flu, they would pay that person £100.&nbsp; To prove they were serious about the claim, they had deposited £1,000 with their bankers.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>Mrs. Carlill bought and used a smoke ball as specified in the advertisement. But unfortunately, she ended up with the flu. Then, she claimed £100, and the company refused to pay. Carbolic Smoke Ball Co argued that their advertisement could not give rise to a contract, because it was impossible to make a contract with the whole world. Therefore, they were not legally bound to pay the money. The Court rejected this argument and held that the advertisement did constitute an offer to the world at large. It formed a contract when it was accepted by Mrs. Carlill using the smoke ball and getting flu. Therefore, she was entitled to the £100 reward.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"textAlign\":\"center\"} -->\n<h2 class=\"has-text-align-center\"><strong><em>Bowerman v Association of British Travel Agents Ltd </em></strong><strong>(1996)</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><em>A school had booked a skiing holiday with a tour operator. The tour operator was a member of the Association of British Travel Agents (ABTA). All members of this association display a notice provided by ABTA. It states: Where holidays or other travel arrangements have not yet commenced at the time of failure [of the tour operator], ABTA arranges for you to be reimbursed the money you have paid in respect of your holiday arrangements.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p><em>The tour operator became insolvent and canceled the skiing holiday tour. The school was refunded the money they had paid for the holiday. However, the cost of the wasted travel insurance was not refunded. The plaintiff – Bowerman - brought an action against ABTA and asked for reimbursement of the cost of the travel insurance. The Court of Appeal agreed with the plaintiff and held the ABTA notice constituted an offer which the customer accepted by contracting with an ABTA member. It was a contract arising from an offer to the public at large and hence a unilateral contract.</em></p>\n<!-- /wp:paragraph -->', 'Law of Contract - Unilateral and bilateral contracts', 'Most contracts are bilateral. This means that each party takes on an obligation, usually by promising the other something – promise in return for a promise.', 'inherit', 'closed', 'closed', '', '1688-revision-v1', '', '', '2021-09-12 21:17:29', '2021-09-12 15:47:29', '', 1688, 'https://civilengineeringlectures.com/?p=1697', 0, 'revision', '', 0),
(1826, 1, '2024-06-26 19:37:34', '2023-02-25 17:55:53', ' ', '', '', 'publish', 'closed', 'closed', '', '1826', '', '', '2024-06-26 19:37:34', '2024-06-26 14:07:34', '', 0, 'https://civilengineeringlectures.com/1826/', 76, 'nav_menu_item', '', 0),
(1837, 1, '2023-02-27 13:29:40', '2023-02-27 07:59:40', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer to remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate), with small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone). This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process and recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly, dragging up a cylindrical ribbon of glass 13 m high, the diameter of the cylinder being maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass blocks</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C, followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity but not insulation. Fire stop blocks (F-30) manufactured from 26 mm rather than 8 mm glass offer increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Standard float glass sizes</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Traditional blown and drawn glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Curved sheet glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Self-cleaning glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Clear white glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Embossed pattern glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern but also upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Screen printed glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Decorative etched and sandblasted glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Georgian wired glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1821,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Georgian-wired-glass.jpg\" alt=\"\" class=\"wp-image-1821\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat, but ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Toughened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1819,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Toughned-glass.jpg\" alt=\"\" class=\"wp-image-1819\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Heat-strengthened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening, but with a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Laminated glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1817,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass-2-585x1024.png\" alt=\"Anti bandit glass\" class=\"wp-image-1817\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Insulating glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material. It prevents the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1816,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass.png\" alt=\"Laminated glass\" class=\"wp-image-1816\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Fire-resistant glass with intumescent material laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading -->\n<h2><strong>SPECIAL GLASSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>One-way observation glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area. Also, he should wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Mirror glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alarm glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong> </strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system. It is set to activate when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electrically-heatable laminated safety glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electromagnetic radiation-shielding glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>X-ray protection glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Variable transmission (smart) glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electro-optic laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass facades</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions. It results in reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions. It also reduces the operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>STRUCTURAL GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. Glass is strong in compression and therefore an appropriate material for load-bearing columns and walls, providing that the design ensures sufficient strength, stiffness, and stability. <strong></strong></p>\n<!-- /wp:paragraph -->', 'Glass - as construction material', 'The term glass refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency', 'inherit', 'closed', 'closed', '', '1809-revision-v1', '', '', '2023-02-27 13:29:40', '2023-02-27 07:59:40', '', 1809, 'https://civilengineeringlectures.com/?p=1837', 0, 'revision', '', 0);
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(1834, 1, '2023-02-27 13:27:16', '2023-02-27 07:57:16', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer to remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate), with small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone). This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process and recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly, dragging up a cylindrical ribbon of glass 13 m high, the diameter of the cylinder being maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass blocks</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C, followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity but not insulation. Fire stop blocks (F-30) manufactured from 26 mm rather than 8 mm glass offer increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Standard float glass sizes</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Traditional blown and drawn glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Curved sheet glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Self-cleaning glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Clear white glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Embossed pattern glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern but also upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Screen printed glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Decorative etched and sandblasted glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Georgian wired glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1821,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Georgian-wired-glass.jpg\" alt=\"\" class=\"wp-image-1821\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat, but ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Toughened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1819,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Toughned-glass.jpg\" alt=\"\" class=\"wp-image-1819\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Heat-strengthened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening, but with a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Laminated glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1817,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass-2-585x1024.png\" alt=\"Anti bandit glass\" class=\"wp-image-1817\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film and for fire protection</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Insulating glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material, preventing the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1816,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass.png\" alt=\"Laminated glass\" class=\"wp-image-1816\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Fire-resistant glass with intumescent material laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading -->\n<h2><strong>SPECIAL GLASSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>One-way observation glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area. Also, he should wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Mirror glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alarm glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong> </strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system. It is set to activate when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electrically-heatable laminated safety glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electromagnetic radiation-shielding glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>X-ray protection glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Variable transmission (smart) glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electro-optic laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass facades</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions. It results in reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions. It also reduces the operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>STRUCTURAL GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. Glass is strong in compression and therefore an appropriate material for load-bearing columns and walls, providing that the design ensures sufficient strength, stiffness, and stability. <strong></strong></p>\n<!-- /wp:paragraph -->', 'Glass - as construction material', 'The term glass refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency', 'inherit', 'closed', 'closed', '', '1809-revision-v1', '', '', '2023-02-27 13:27:16', '2023-02-27 07:57:16', '', 1809, 'https://civilengineeringlectures.com/?p=1834', 0, 'revision', '', 0);
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(1829, 1, '2023-02-27 13:21:33', '2023-02-27 07:51:33', '<!-- wp:heading -->\n<h2><strong>GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The term <em>glass </em>refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1810,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Glass.png\" alt=\"Glass\" class=\"wp-image-1810\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Glass made from sand, lime, and soda ash has been known in Egypt for 5000 years. For many centuries glass was worked by drawing the molten material from a furnace. The glass was then rolled out or pressed into appropriate moulds and finally shaped by cutting and grinding.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Adding different metallic compounds to the melt, various coloured glasses can be manufactured. The blue colour was obtained by the addition of cobalt. Copper gives blue or red and iron or chromium produced green. In the fifteenth century, white opaque glass was produced by the addition of tin or arsenic. In the seventeenth century, ruby-red glass was made with the addition of gold chloride. Clear glass could be obtained by using antimony or manganese as a de-colourizer to remove the green colouration caused by iron impurities within the sand.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>In the late twentieth century, with the advent of fully glazed facades, the construction industry has become a major consumer of new glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>MANUFACTURE</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Soda lime silicate glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Modern glass is manufactured from sand (silica), soda ash (sodium carbonate), and limestone (calcium carbonate), with small additions of salt cake (calcium sulfate) and dolomite (magnesium limestone). This gives a final composition of typically 70–74% silica, 12–16% sodium oxide, 5–12% calcium oxide, and 2–5% magnesium oxide with small quantities of aluminium, iron, and potassium oxides. The addition of 25% broken glass or <em>cullet </em>to the furnace mix accelerates the melting process and recycles the production waste. The production process is relatively energy intensive at 15,000 kWh/m<sup>3</sup>.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alkaline earth silicate, borosilicate, and ceramic glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Alkaline earth silicate and borosilicate glasses are also used in the construction field. These have considerably different chemical compositions, and, give their particular physical properties. The composition of alkaline earth silicate glass is typically 55–70% silica, 5–14% potassium oxide, 3–12% calcium oxide, and 0–15% aluminium oxide, with quantities of zirconium, strontium, and barium oxides.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Borosilicate glass is typically 70–87% silica, 0–8% sodium oxide, 0–8% potassium oxide, 7–15% boron oxide, and 0–8% aluminium oxide, with small quantities of other oxides. A particular characteristic of borosilicate glass is that it has a coefficient of expansion of one-third that of standard soda lime silicate glass. This property makes it considerably more resistant to thermal shock in case of fire.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass-ceramics have a zero coefficient of expansion. It makes them highly resistant to thermal shock. The composition of glass ceramics is complex comprising typically 50–80% silica, and 15–27% alumina, with small quantities of sodium oxide, potassium oxide, barium oxide, calcium oxide, magnesium oxide, titanium oxide, zirconium oxide, zinc oxide, lithium oxide, and other minor constituents.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The glass is initially produced by a standard float or rolling technique, but subsequent heat treatment converts part of the normal glassy phase into a fine-grained crystalline form, giving rise to particular physical properties.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FORMING PROCESSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Early methods</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Initially, crown glass was formed by spinning a 4 kg cylindrical gob of molten glass on the end of a blowpipe. The solid glass was blown, flattened out, and then transferred to a solid iron rod<em>. </em>After reheating it was spun until it opened out into a 1.5 m diameter disc. The process involved considerable wastage including the bullion in the center.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>An alternative process involved the blowing of a glass cylinder which was then split open and flattened out in a kiln. Subsequently, in a major development, circular metal bait was lowered into a pot of molten glass and withdrawn slowly, dragging up a cylindrical ribbon of glass 13 m high, the diameter of the cylinder being maintained with compressed air. The completed cylinder was then detached, opened up, and flattened out to produce flat window glass.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>With the development of the Fourcault process in Belgium and the Colburn process in America that it became possible to produce flat glass directly. A straight bait was drawn vertically out of the molten glass to produce a ribbon of glass, which was then drawn directly up a tower, or in the Colburn process turned horizontally, through a series of rollers; finally, appropriate lengths were cut off. However, such drawn sheet glass suffered from manufacturing distortions. This problem was overcome by the production of plate glass, which involved horizontal casting and rolling, followed by grinding to remove distortions and polishing to give a clear, transparent but expensive product. The plate glass manufacturing process is now practically obsolete. It has been replaced by the <em>float process.</em></p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>FLOAT GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:image {\"id\":1811,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/FLOAT-GLASS-1024x339.jpg\" alt=\"\" class=\"wp-image-1811\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A furnace produces a continuous supply of molten glass at approximately 1100°C, which flows across the surface of a large shallow bath of molten tin contained within an atmosphere of hydrogen and nitrogen (this prevents oxidation of the surface of the molten metal). The glass ribbon moves across the molten metal, initially at a sufficiently high temperature for the irregularities on both surfaces to become evened out leaving a flat and parallel ribbon of glass. The temperature of the glass is gradually reduced as it moves forward until, at the end of the molten tin, it is sufficiently solid at 600°C not to be distorted when supported on rollers. Thickness is controlled by the speed at which the glass is drawn from the bath. Any residual stresses are removed as the glass passes through the 200 m annealing lehr or furnace, leaving a fire-polished material. Then, the glass is washed, and substandard material is discarded for recycling. The computer-controlled cutting, firstly across the ribbon, then the removal of the edges, is followed by stacking, warehousing, and dispatch.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Float glass for the construction industry is made within the thickness range of 2–25 mm, although 0.5 mm is available for the electronics industry. Many surface-modified glasses are produced by incorporating metal ions into the glass within the float process. Body-tinted glass, which is of uniform colour, is manufactured by blending additional metal oxides into the standard melt.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>NON-SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass fibres</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Continuous filament</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Continuous glass fibres are manufactured by constantly feeding molten glass from a furnace into a forehearth fitted with 1600 accurately manufactured holes. Molten glass is drawn through these holes, at a rate of several thousand metres per second. The fibres are as small as 9 microns in diameter. They pass over a size applicator and are gathered together as a bundle before to being wound up on a collet. The material may then be used as rovings, chopped strand, or woven strand mats for the production of glass-fibre reinforced materials such as GRP (glass-fibre reinforced polyester), GRC (glass-fibre reinforced cement), or GRG (glass-fibre reinforced gypsum).</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass wool</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass wool is used as an insulation material.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Cast glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass may be cast and pressed into shape for glass blocks and extruded sections.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Profiled sections</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Profile trough sections in clear or colored 6 or 7 mm cast glass are manufactured in sizes ranging from 232 to 498 mm wide, 41 and 60 mm deep, and up to 7 m long, with or without stainless steel longitudinal wires. The system can be used horizontally or vertically, as single or double glazing, and as a roofing system spanning up to 3 m.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1812,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Profiled-sections.jpg\" alt=\"\" class=\"wp-image-1812\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>A large radius curve is possible as well as the normal straight butt jointed system. The joints are sealed with a one-part translucent silicone.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Amber or blue-tinted versions are available for solar control or aesthetic reasons. The double-glazed system produces a sound reduction within the 100–3200 Hz range of typically 40 dB.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>The incorporation of 16-mm-thick translucent aerogel-insulated polycarbonate panels into profiled trough sections significantly increases the thermal insulating properties of the units. Airborne sound insulation is enhanced. Light transmission through the translucent aerogel panels is approximately 50%.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Glass blocks</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks for non-load-bearing walls and partitions are manufactured by casting two half blocks at 1050°C, joining them together at 800°C, followed by annealing at 560°C. The void space is partially evacuated. The standard blocks are 115, 190, 240, and 300 mm square with thicknesses of 80 and 100 mm, although rectangular and circular blocks are also available. The variety of patterns offering differing degrees of privacy includes clear, frosted, and crystal designs with colours from blue, green, and grey to pink and gold. For exterior and fire-retarding applications natural or coloured mortar (2 parts Portland cement, 1 part lime, 8 parts sand) is used for the jointing. Walls may be straight or curved. Bullet-proof blocks are available for higher security situations. For interior use, blocks can be laid with sealant rather than mortar.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>Glass blocks jointed with mortar give a fire resistance of 30 or 60 minutes of stability and integrity but not insulation. Fire stop blocks (F-30) manufactured from 26 mm rather than 8 mm glass offer increased fire protection of two hours’ integrity and 30 minutes’ thermal insulation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>SHEET PRODUCTS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Standard float glass sizes</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>The standard thicknesses for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19, and 25 mm to maximum sheet sizes of 3 to 12 m. Thicker grades are available in smaller sheet sizes.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Traditional blown and drawn glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Traditional blown and drawn glasses are available commercially both clear and in a wide range of colours. Drawn glass up to 1600 - 1200 mm is optically clear but varies in thickness from 3 to 5 mm. It is normally used for conservation work where old glass requires replacement. The blown glass contains variable quantities of air bubbles. Also, it has significant variations in thickness giving an antique appearance.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Curved sheet glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Curved glass can be manufactured by heating annealed glass to approximately 600°C when it softens and sag-bends to the shape of the supporting mould. Sheets up to 3 m - 4 m can be bent with curvature in either one or two directions. Bent glass can subsequently be sandblasted, toughened, or laminated, even incorporating coloured interlayers if required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Self-cleaning glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Self-cleaning glass has an invisible hard coating of 15 microns thick. These coatings include two special features. The surface incorporating titanium dioxide is photocatalytic. It absorbs ultraviolet light, which with oxygen from the air breaks down or loosens any organic dirt on the surface. Furthermore, the surface is hydrophilic. It causes rainwater to spread evenly over the surface, rather than running down in droplets. Therefore, the surface is uniformly washed and prevents any unsightly streaks or spots from appearing when the surface dries. Self-cleaning glass has a somewhat greater mirror effect than ordinary float glass, with a faint blue tint. It is available as normal annealed glass also in toughened or laminated form. The surface coating, which reduces the transmittance of the glass by about 5%, is tough but as with any glass can be damaged by scratching. A blue solar control version reduces the solar heat gain by approximately 60% depending upon the thickness of the glass used and its combination in a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Clear white glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard float glass is somewhat greener due to the effect of iron oxide impurities in the key raw material sand. However, clear white glass can be produced, at a greater cost, by using purified ingredients. The light transmittance of clear white glass is approximately 2% greater than standard glass for 4 and 6 mm glazing.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Embossed pattern glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>A wide range of 3, 4, 6, 8, and 10 mm patterned glass is commercially available. The degree of privacy afforded by the various glasses is not only dependent upon the pattern but also upon the relative lighting levels on either side and the proximity of any object to the glass. Patterned glasses may be toughened, laminated, or incorporated into double-glazing units for thermal, acoustic, or safety considerations.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Screen printed glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>White or coloured ceramic frit is screen printed onto clear or tinted float glass. It is then toughened and heat soaked, causing the ceramic enamel to fuse permanently into the glass surface. Standard patterns or individual designs may be created, giving the required level of solar transmission and privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Decorative etched and sandblasted glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Acid etched glass, 4 mm and 6 mm in thickness, is available to a maximum sheet size of 2140 – 1320 mm with a small range of patterns. Etched glasses need to be handled carefully on-site, as oil, grease, and finger marks are difficult to remove completely. Similar visual effects can be achieved by sandblasting techniques, but it gives the surface finish less smooth. Patterns may be clear on a frosted background or the reverse, depending upon the aesthetic effect and level of privacy required.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Georgian wired glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Georgian wired glass is produced by rolling a sandwich of a 13 mm electrically welded steel wire mesh between two ribbons of molten glass. This produces the standard cast 7 mm sheet, suitable when obscuration is required. Wired glass is not stronger than the equivalent thickness of annealed glass. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1821,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Georgian-wired-glass.jpg\" alt=\"\" class=\"wp-image-1821\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>However, when cracked, the pieces remain held together. On exposure to fire, the wire mesh dissipates some heat, but ultimately Georgian glass will crack, particularly if sprayed with water when hot. Accidental damage may cause the breakage of the glass. But again it is retained in position by the mesh, at least until the wires are affected by corrosion.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Toughened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass is up to four or five times stronger than standard annealed glass of the same thickness. It is produced by subjecting preheated annealed glass at 650°C to rapid surface cooling by the application of jets of air. This causes the outer faces to be set in compression with balancing tension forces within the centre of the glass. As cracking within glass commences with tensile failure at the surface, much greater force can be withstood before this critical point is reached. Toughened glass cannot be cut or worked. Therefore all necessary cutting, drilling of holes, and grinding or polishing of edges must be completed in advance of the toughening process.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1819,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Toughned-glass.jpg\" alt=\"\" class=\"wp-image-1819\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>Toughened glass will withstand considerable extremes of temperature and sudden shock temperatures. When broken, it shatters into small granules. This is not likely to cause serious injuries related to the accidental breakage of annealed glass. Any standard float, coated, roughcast, and patterned glasses can be toughened.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Heat-strengthened glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Heat-strengthened glass is manufactured by a similar process to toughening, but with a slower rate of cooling which produces only half the strength of toughened glass. On severe impact, heat-strengthened glass breaks into large pieces like annealed glass. Therefore it cannot be considered a safety glass. Heat-strengthened glass is frequently used in laminated glass where the residual strength after fracture gives some integrity to the laminate. Typical applications include locations where resistance to wind pressure is necessary, such as the upper storeys and corners of high buildings.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Laminated glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer of polyvinyl butyral (PVB) sheet or a polymethyl methacrylate low-viscosity resin. </p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1817,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-large\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass-2-585x1024.png\" alt=\"Anti bandit glass\" class=\"wp-image-1817\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:paragraph -->\n<p>The lamination process increases the impact resistance compared to annealed glass of the same thickness. Furthermore on impact, whilst the glass laminations crack, they do so without splintering or disintegration, being held together by the interlayer. Therefore, laminated glass can be defined as <em>safety glass</em>. The impact resistance of laminated glass may be increased using thicker interlayers or increasing the number of laminates or the inclusion of polycarbonate sheets. Typically, anti-bandit glass has two or three glass laminates while, depending on the anticipated caliber and muzzle velocity,</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:paragraph -->\n<p>bullet-resistant glass has four or more glass laminates. To prevent spalling, the rear face of bullet-resistant glass may be sealed with a scratch-resistant polyester film and for fire protection</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Insulating glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Insulating glasses are manufactured from float glass laminated with either intumescent or gel materials. Intumescent laminated glass has clear interlayers. When exposed to fire, intumescent or gel materials expand to a white opaque material, preventing the passage of conductive and radiant heat. The glass layers adjacent to the fire crack but retain integrity owing to their adhesion with the interlayers. The fire resistance, ranging between 30 and 120 minutes for insulation and integrity, depends on the number of laminations, usually between 3 and 5.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:image {\"id\":1816,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><img src=\"https://civilengineeringlectures.com/wp-content/uploads/2023/02/Laminated-glass.png\" alt=\"Laminated glass\" class=\"wp-image-1816\"/></figure>\n<!-- /wp:image -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Fire-resistant glass with intumescent material laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:heading -->\n<h2><strong>SPECIAL GLASSES</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>One-way observation glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Where unobserved surveillance is required, one-way observation mirror glass can be installed. To maintain privacy, the observer must be at an illumination level no greater than one-seventh that of the observed area and wear dark clothing. From the observed area, the one-way observation glass has the appearance of a normal mirror. One-way observation glass is available in annealed, toughened, or laminated.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Mirror glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Standard mirror glass is manufactured by the chemical deposition onto float glass of a thin film of silver, from aqueous silver and copper salt solutions. The film is then protected with two coats of paint or a plastic layer. Mirror glass is produced by the online application of a three-layer coating of silicon-silica-silicon, which acts by optical interference to give the mirror effect.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Alarm glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p><strong>&nbsp;</strong>Glass containing either a ceramic loop or a series of straight wires can be incorporated into an intruder alarm system, which is activated when the glass is broken. Usually, straight-wired alarm glass is incorporated into a laminated system, while a ceramic loop circuit would be fixed to the inner face of the toughened outer pane within a double-glazing system.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electrically-heatable laminated safety glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It incorporates fine electrically conducting wires which may be switched on when there is a risk of condensation. Typical applications are in areas of high humidity, such as swimming pools, kitchens, and glass roofs, particularly when there are significant differences between the internal and external temperatures.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electromagnetic radiation-shielding glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Itcan be used to protect building zones containing magnetically stored data from accidental or deliberate corruption by external electric fields. For maximum security, the conducting laminates within the composite glass should be in full peripheral electrical contact with the metal window frames and the surrounding wall surface screening.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>X-ray protection glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>It contains 70% lead oxide, which produces significant shielding against ionizing radiation. The glass is amber in colour due to the high lead content. A 6 mm sheet of this lead glass has the equivalent shielding effect of a 2 mm lead sheet against radiation.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Variable transmission (smart) glasses</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Variable transmission or <em>smart </em>glasses change their optical and thermal characteristics under the influence of light (photochromic), heat (thermochromic), or electric potential (electrochromic). These glasses offer the potential of highly responsive dynamic climate control to building facades. These smart materials including thermotropic products are also available as plastic laminates for incorporation into laminated glass systems.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Electro-optic laminates</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Electrically operated vision-control glass consists of a laminated system of glass and polyvinyl butyral layers containing a polymer-dispersed liquid crystal layer, which can be electrically switched from transparent to white/translucent for privacy.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Conventional glass coatings reduce both light and heat transmission. However, a coating based on tungsten-modified vanadium dioxide allows visible light through at all times but reflects infrared radiation at temperatures above 29°C. Thus, at this temperature, further heat penetration through the glass is blocked. Therefore the intelligent glass, which has a slight yellow/green colour, admits useful solar gain in cooler conditions but cuts out excessive infrared solar gain under hot conditions.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading {\"level\":3} -->\n<h3><strong>Intelligent glass facades</strong></h3>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>An intelligent glass building facade changes its physical properties, in response to sensors detecting the external light and weather conditions. It results in reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions and also in reducing operational building costs to clients and users.</p>\n<!-- /wp:paragraph -->\n\n<!-- wp:heading -->\n<h2><strong>STRUCTURAL GLASS</strong></h2>\n<!-- /wp:heading -->\n\n<!-- wp:paragraph -->\n<p>Glass columns are frequently used as fins to restrain excessive deflection caused by wind and other lateral loads to glass facades. The fixings between the façade glazing and fin units are usually stainless steel clamps bolted through preformed holes in the toughened or laminated glass, although silicone adhesives can also be used. A soft interlayer between the metal fixing and the glass is incorporated to prevent stress concentrations on the glass surface and to allow for differential thermal movement between the glass and metal. Glass is strong in compression and therefore an appropriate material for load-bearing columns and walls, providing that the design ensures sufficient strength, stiffness, and stability. <strong></strong></p>\n<!-- /wp:paragraph -->', 'Glass - as construction material', 'The term glass refers to materials, usually blends of metallic oxides, mainly silica, which do not crystallize when cooled from the liquid to the solid state. It is the non-crystalline or amorphous structure of glass that gives rise to its transparency', 'inherit', 'closed', 'closed', '', '1809-revision-v1', '', '', '2023-02-27 13:21:33', '2023-02-27 07:51:33', '', 1809, 'https://civilengineeringlectures.com/?p=1829', 0, 'revision', '', 0);
