Building Materials PDF

## Building Materials ### 1. Building Materials | Number | Fact | |---|---| | 1 | Bulking of sand is caused due to surface moisture | | 2 | The normal curing period for lime mortar is 7 days. | | 3 | Geologically marble is known as metamorphic rock | | 4 | Wrought iron is used for small sized wate...

## Building Materials ### 1. Building Materials | Number | Fact | |---|---| | 1 | Bulking of sand is caused due to surface moisture | | 2 | The normal curing period for lime mortar is 7 days. | | 3 | Geologically marble is known as metamorphic rock | | 4 | Wrought iron is used for small sized water pipes | | 5 | Solder material is an alloy which melts at a temperature above 400°C. | | 6 | Brazing is done at temperature above 600°C to 1100°C. Brazing joint is stronger than the solder joint. | | 7 | Corrugated sheet iron is made by passing plain sheets between grooved rollers. | | 8 | Strength and stiffness of corrugated sheets are considerably increased. | | 9 | Corrugated sheets are generally used on slanting roofs. | | 10 | The initial setting time of lime-pozzolona cement is 120 minutes. | | 11 | Bullet proof glass is made of thick glass sheet sandwiched by a layer of high test plastic | | 12 | Pig iron obtained from the furnace which is properly provided with fuel at a very high temperature is called grey or foundry pig | | 13 | Depending on the chemical composition and mechanical properties, iron may be classified as wrought iron | | 14 | Gneiss is obtained from sedimentary metamorphic rocks. | | 15 | Low heat cement | | | 1. It possesses less compressive strength | | | 2. Its initial setting time is about one hour | | | 3. Its final setting time is about 10 hours | | | 4. Its mainly used for mass concrete work | | 16 | If the furnace is provided with insufficient fuel at low temperatures the type of pig iron produced is called white or forge pig. | | 17 | Chemically marble is known as calcareous rock | | 18 | The clay to be used for manufacturing bricks for a large project is dugout and allowed to weather throughout the monsoon | | 19 | Polymerization helps to improve the property of strength, rigidity, elasticity | | 20 | The rocks formed by gradual deposition are called sedimentary rocks. | | 21 | The plastics made from cellulose resin are | | | 1. As clear as glass | | | 2. Tough and strong | | | 3. Possess excellent electrical properties | | 22 | The commonly used raw material in the manufacture of cement is, lime stone | | 23 | The property by virtue of which lime sets under water is known as hydraulicity | | 24 | Percentage content of silica in window glass is 70 to 75. | | 25 | The coefficient of hardness of stones used in road work should be greater than 17. | | 26 | For filling cracks in masonry structures the type of bitumen used is plastic-bitumen | | 27 | Plastics are | | | 1. An organic substance | | | 2. Consists of natural or synthetic binders | | | 3. Finished products are rigid and stable at normal temperature | | | 4. Capable of flow when necessary heat and pressure are applied | | 28 | Bitumen in | | | 1. Solid state is called asphalt | | | 2. Semi fluid state is called mineral tar | | | 3. Fluid state is called petroleum | | 29 | Galvanising means covering iron with a thin coat of zinc. | | 30 | Kaolin is chemically classified as argillaceous rock | | 31 | In basic bessemer process the steel heats the converter. | | 32 | In open-hearth process the furnace heats the steel. | | 33 | In siemens process the impurities of pig iron are oxidised by the oxygen of the ore. | | 34 | The process of manufacturing steel by heating short lengths of wrought iron bars mixed with charcoal in fire clay crucibles and collecting the molten iron into moulds is known as crucible process | | 35 | Ultimate strength to cement is provided by di-calcium silicate | | 36 | Elastomers can extend upto ten times their original dimensions | | 37 | Stainless steel contains 18% of chromium and 8% nickel | ### Building Materials (cont.) | Number | Fact | |---|---| | 38 | Initial setting time of cement for asbestos cement products should be not less than - 90 minutes | | 39 | Wrought iron contains carbon about 0.1% to 0.25% | | 40 | The main constituent of fly-ash is aluminium oxide, silica and ferrous oxide. | | 41 | Vanadium steel is generally used for axles and springs | | 42 | The variety of pig iron used for the manufacture of steel by bessemer process is bessemer pig | | 43 | For melting one tonne of cast iron | | | 1. 1700 m³ air is required | | | 2. 20 kg limestone is required | | | 3. One quintal coke is required | | 44 | Bitumen felts are | | | 1. Used as water proofing material | | | 2. Used as damp proofing material | | | 3. Made from bitumen and hessian fibres | | 45 | In the method of condensation polymerization | | | 1. Low molecular substances are removed from the high molecular substance | | | 2. The reaction proceeds with an evolution of ammonia | | | 3. The reaction proceeds with an evolution of hydrogen chloride | | 46 | In the cement the compound quickest to react with water is tri-calcium aluminate | | 47 | The rocks which are formed due to cooling of magma at a considerable depth from earth's surface are called plutonic rocks. | | 48 | Quartzite is a silicious rock. | | 49 | The rocks in which argil (or clay) predominates are called argillaceous rocks. | | 50 | A badly mixed cement concrete results in honey combing | | 51 | The variety of pig iron used for manufacture of wrought iron is white forge pig | | 52 | Sand stone is sedimentary rock. | | 53 | Resins are used in varnishes. | | 54 | Refractory bricks are used for combustion chambers. | | 55 | Inner part of a timber log surrounding the pitch is called heart wood | | 56 | The filler used in plastic bitumen is asbestos powder | | 57 | Soft stones are required for carving. | | 58 | Light stones are required for arches. | | 59 | Hard stones are required to stand high pressure. | | 60 | Name the type of cement for canal linings sulphate resisting cement | | 61 | A good brick earth should contain | | | 1. About 20% to 30% of alumina | | | 2. About 50% to 60% of silica | | | 3. Not more than 5% of lime | | | 4. About 5 to 6% of oxide of lime | | 62 | Expanded metals are | | | 1. Manufactured from steel sheets | | | 2. Used for reinforced concrete in road pavements | | | 3. Measured in term of swm (short way mesh) and lwm (long way mesh) | | 63 | Due to attack of dry rot the timber reduces to powder | | 64 | Brittleness of cold is due to an excess of phosphorus | | 65 | Asbestos cement | | | 1. Is brittle | | | 2. Warps due to changes in humidity | | | 3. Strength is lowered when saturated by water | | 66 | Mastic asphalt is generally used for damp proof course and water proof layer. | | 67 | The theory of formation of concrete is based on the phenomena of formation of voids. | | 68 | The bulking of sand is taken into account while volumetric proportioning of the aggregates. | | 69 | The dry sand and the sand completely flooded with water have practically the same volume. | | 70 | The expansion and contraction joints are provided if concrete structures exceed 12 m in length. | | 71 | In stone arches the stones are placed with their natural beds radial. | | 72 | In cornices the stones are placed with their natural beds as vertical. | | 73 | In stone walls the stones are placed with their natural beds as horizontal. | | 74 | Good quality stones must be durable, free from clay and resist action of acids. | | 75 | Sewer pipes are made of stone ware | | 76 | Black marble is generally found in the district of jaipur | | 77 | The most fire resistant paints are asbestos paints. | | 78 | In a mortar the binding material is cement | | 79 | Lacquer paints are | | | 1. Generally applied on structural steel | | | 2. Less durable as compared to enamel paints | | | 3. Consist of resin and nitro-cellulose | | | 4. Contain alcohol as thinner | | 80 | The commonly used lime in white washing is fat lime | ### Building Materials (cont.) | Number | Fact | |---|---| | 81 | Shingle is decomposed laterite | | 82 | For thin structures subjected to wetting and drying, the water cement ratio should be 0.45. | | 83 | For mass concrete structures subjected to wetting and drying, the water ratio should be 0.55. | | 84 | For thin structures which remain continuously under water, the water -cement ratio by weight should be 0.55. | | 85 | For massive concrete structures which remain continuously under water, the water cement ratio by weight should be 0.65. | | 86 | If P is the percentage of water required for normal consistency, water to be added for determination of initial setting time is 0.85 P. | | 87 | A pug mill is used for tempering brick earth. | | 88 | For slaking of 10 kg of CaO the theoretical amount of water is 3.2 kg | | 89 | Method of sawing timber, tangentially to annual rings is known as tangential method. | | 90 | In four quarters such that each board cuts annual rings at angles not less than 45° is known as quarter sawing method. | | 91 | Cut out of quarter logs parallel to the medullary rays and perpendicular to annual rings is known as radial sawing. | | 92 | Clay and silt content in a good brick earth must be at least 50% | | 93 | Wrought iron contains carbon upto 0.25% | | 94 | The polymineralic rock is granite. | | 95 | A good quality stone absorbs water less than 5% | | 96 | Dr. L. Bakeland a belgian scientist prepared a product known as bakelite. | | 97 | Pollark an austrian scientist prepared a substance from urea and formaldehyde and called it plastic. | | 98 | Plywood is made from teak wood only | | 99 | Soundness test of cement determines quality of free lime | | 100 | The slag which floats on the surface of the molten iron generally contains lime (CaO) 45%, silica (SiO2) 35%, alumina (Al2 03) 12%, MGO, CaSO4, KMnO2 and FeO 8% | | 101 | Minimum of 40% of iron is available in black band | | 102 | The standard size of masonry bricks is 19 cm x 9 cm x 9 cm. | | 103 | Air binding materials are gypsum, acid-resistant cement and quick lime. | | 104 | Bessemer process is used for the manufacture of steel | | 105 | The portion of the brick without a triangular corner equal to half the width and half the length is called king closer. | | 106 | Rocks formed due to alteration of original structure due to heat and excessive pressures are called metamorphic rocks. | | 107 | The compound of portland cement which contributes to the strength after two to three years is di -calcium silicate. | | 108 | The commonly used colour pigment in paints is ambers, carbon black, tron oxide and lamp black. | | 109 | Varnish is a transparent or semi-transparent solution of resinous substances in alcohol, linseed, turpentine | | 110 | The commonly used drying oil for oil paints is acetate of lead. | | 111 | Initial setting of cement is caused due to tri-calcium aluminate. | | 112 | The phenol is carbolic acid. The phenol is either extracted from coal-tar or prepared from benzene. Phenol reacts with formaldehyde to form phenol formaldehyde resin. | | 113 | The plastics prepared from phenol-formaldehyde are used for paints, varnishes and wc seats. | | 114 | Fibre boards can be used for furniture | | 115 | Catalysts are added to assist and accelerate the hardening of resin. | | 116 | The fillers are inert materials and they impart strength and hardness. | | 117 | Fibrous fillers increase thermal resistance. | | 118 | For the manufacture of plywood veneers are placed so that grains of adjacent veneers run at right angles | | 119 | A 1st class brick immersed in water for 24 hours should not absorb water (by weight) more than 20%. | | 120 | Cast steel is manufactured by crucible process | | 121 | The proportions of charcoal saltpetre and sulphur in gun powder by weight are respectively 15, 75, 10 | | 122 | The foliated structure is very common in metamorphic rocks | | 123 | Turpentine oil is used in paints as drier | | 124 | The substance which consists of one primary chemical is known as monomer. | ### Building Materials (cont.) | Number | Fact | |---|---| | 125 | The polymer consists of thousands of monomers joined together. The polymer molecule is called macro -molecule. | | 126 | A polymetric material consists of a large number of long-chain molecules. | | 127 | Quick setting cement is produced by adding less amount of gypsum in very fine powdered form | | 128 | The type of steel used for precision levelling staff is invar | | 129 | During pudding | | | 1. Molten metal is kept clear of the fuel | | | 2. Carbon is converted into carbonic acid gas | | | 3. Silicon forms a slag | | | 4. Metal is heated by the burning of gases | | 130 | The weight of 1 m³ of brick earth is about 1800 kg | | 131 | Pozzolana (or surkhi) is used in lime to impart hydraulicity | | 132 | The hardest rock is diamond | | 133 | The silica is used for preparing silica bricks, coke oven and lining for glass furnaces. | | 134 | Wrought iron is manufactured from pig iron by refining, pudding, shingling and rolling. | | 135 | For the manufacture of stainless steel is mixed with chromium | | 136 | Portland pozzolana cement possesses | | | 1. Higher resistance to chemical attack | | | 2. Lower heat of hydration | | | 3. Lower shrinkage on drying | | | 4. Water tightness | | 137 | Iron ore may contains carbon, silicon, sulphur, phosphorus and manganese | | 138 | Quick lime is obtained by burning of pure lime stone. | | 139 | Hydraulic lime is obtained by burning lime stone containing clay 5% to 30%. | | 140 | Poor lime is obtained by burning lime stone containing impurities more than 5%. | | 141 | German silver is an alloy of copper, nickel and zinc | | 142 | Lime stone is a sedimentary rock, stratified rock, aqueous rock but not a metamorphic rock. | | 143 | The size of modular bricks is 19 x 9 x 9 cm. | | 144 | Plastics are chemical resistant. Plastics are durable. Plastics are excellent electric insulators. | | 145 | Fibre boards are used for thermal and acoustic control, fibre boards are used for light weight standing members. Fibre boards are obtained by impregnating a resin product on fibres. | | 146 | Dextrine is rubber based adhesive | | 147 | Stones used for ornamental work must be soft | | 148 | A prime coat is given to steel work with a mixture of white lead and lead paint | | 149 | The presence of original rounded surface on the manufactured piece of timber is called wane. | | 150 | Quartzite a metamorphic stone is hard, brittle, crystalline, compact | | 151 | Plastics have generally low melting point. | | 152 | Ground glasses are | | | 1. Made by grinding its one side | | | 2. Made by melting powdered glass paints surface | | | 3. Used for getting light without transparency | | 153 | Formula for quick lime is CaCO3 | | 154 | The process of decarbonising the pig iron completely and then adding proper percentage of carbon for manufacturing steel is called cementation process | | 155 | In paints the pigment is responsible for colour | | 156 | The operation of removal of impurities or clay adhering to iron ores is known as dressing | | 157 | If water required for 1 bag of cement is 30 litres then water cement ratio is 0.60. | | 158 | Portland cement manufactured from pure white chalk and clay but free from iron-oxide is known as white cement. | | 159 | Pig iron is manufactured from the ores by dressing, calcination and roasting, smelting | | 160 | The coefficient of thermal expansion of plastics is about three times than that of steel. | | 161 | The acoustical boards prepared by impregnating fibre-glass with phenolic resins has absorption coefficient of about 0.67. | | 162 | Polymers is obtained from condensation polymerization of phenol formaldehyde, carbamide, melamine-formaldehyde | | 163 | The minimum compressive strength of 1st class bricks should be 100 kg/cm². | | 164 | A volatile substance added to a paint to make its application easy and smooth is known as solvent. | | 165 | The cement becomes unsound by the presence of excess sulphur, magnesia and lime | | 166 | The main ingredient of a good quality brick earth is alumina | | 167 | Bitumen is generally obtained from petroleum product | ### Building Materials (cont.) | Number | Fact | |---|---| | 168 | The kiln which may work throughout the year is hoffman's kiln | | 169 | The percentage of water for normal consistency is 15% to 25% | | 170 | The plywood do not split or crack due to changes in atmosphere. | | 171 | The commercial plywood's are available upto 150 cm wide and upto 300 cm long. | | 172 | The plywood's possess uniform tensile strength in all directions. | | 173 | The plywood's are light in weight. | | 174 | For one cubic metre of brick masonry number of bricks required is 500 | | 175 | The rocks which are formed due to pouring of magma at the earth's surface ave called volcanic rocks | | 176 | The steel which contains fissures and cavities is manufactured by cementation process | | 177 | The volcanic rock relates with basalt. | | 178 | Putty is | | | 1. Made with finely powdered chalk and linseed oil | | | 2. Used for fixing glass panes | | | 3. Softened by a solution of pearl ash and quick-lime soaked in water | | 179 | The initial setting time of hydraulic lime is 120 minutes. | | 180 | PVC stands for polythene vinyl chloride | | 181 | Generally wooden moulds are made from shisham wood | | 182 | In stone masonry stones (stratified rocks) are so placed that the direction of pressure to the plane of bedding is right angles | | 183 | The most durable varnish is oil varnish | | 184 | The plutonic rock is granite. | | 185 | In a rock calcium carbonate predominates whether it is calcareous rock | | 186 | In order of increasing percentage of silica the correct sequence is calcareous clay, pure clay and sandy clay. | | 187 | For sanitary pipes and chemical stonewares salt glazing is used | | 188 | The baked earth is called terra-cotta. | | 189 | The articles prepared from clay which is burnt at low temperature and cooled down slowly are called earthen-ware. | | 190 | The articles prepared from refractory clays which as mixed with stone and crushed pottery are called stone ware. | | 191 | The articles prepared from fine earthen ware which is white thin and semi-transparent are called porcelain. | | 192 | Jhumb bricks are over burnt | | 193 | Knots in timber are signs of branches cut off. | | 194 | The heating of a material to redness in contact with air is known as calcinations. | | 195 | The property of lime by which it sets or hardens in damp places having no free circulation of air is called setting. | | 196 | The product that remains after calcinations of limestone is called lime. | | 197 | The distinct plane of division along which a stone can easily be split is called natural bed of stone. | | 198 | The naturai bed of sedimentary rocks is along the planes of stratification. | | 199 | The natural bed of igneous rocks is not defined. | | 200 | Invar contains 36% of nickel | | 201 | The lime which contains mainly calcium oxide and slacks with water is quick lime | | 202 | Softer variety of steel may be obtained by bessemer process | | 203 | Based on flow quality the sequence of pipes is c.i. pipes, g.i. pipes, a.c. pipes and pvc pipes. | | 204 | The commonly used thinner in oil paints is naptha and turpentine. | | 205 | Steel produced by open hearth process is milder than that obtained by the bessemer process. | | 206 | Engineers prefer open hearth steel for structural purpose as it is more homogenous. | | 207 | Basic bessemer process is suitable for converting poor ore containing a large proportion of sulphur and phosphorus into steel. | | 208 | Cast irons are | | | 1. Obtained by purifying pig iron | | | 2. Manufactured in required shapes | | | 3. Contain 2 to 5 per cent of carbon with other impurities | | | 4. Remelted in a cupola furnace | | 209 | Asbestos are | | | 1. Corrugated sheet used for roofing | | | 2. An incombustible fire proof material | | | 3. An organic substance | | | 4. Bad insulator for sound and heat | | 210 | The pigment used in paints for corrosive resistance is red lead | | 211 | The average crusning strength of nand mouidea orickS is 5000 t/m*. | | 212 | The average tensile strength of hand moulded brick is 200 t/m². | ### Building Materials (cont.) | Number | Fact | |---|---| | 213 | The average shearing strength of hand moulded brick is 600 t/m². | | 214 | The cracks which extend from bark towards the sap wood in the cross section of a tree are called star shakes. | | 215 | Plastic bitumen is generally used for crack fillings | | 216 | The timber having maximum resistance against white ants is obtained from shisham | | 217 | Sea sand used in structures causes dampness, efflorescence and disintegration. | | 218 | The compound of portland cement which reacts immediately with water and also sets first is tri-calcium aluminate | | 219 | Distemper is a paint consisting of powdered chalk, pigments and water. | | 220 | Seasoning of timber is essential to remove sap from timber | | 221 | The melting point of silica is 1730°C. | | 222 | The steel used in r.c.c. work is mild steel | | 223 | Non acid-resistant asbestos is chrysolite asbestos | | 224 | Stones used for the construction of retaining walls must be heavy | | 225 | In arches stratified stones are placed so that their planes are radial | | 226 | Acid test is done to find out the weathering quality of stones. | | 227 | Attrition test is done to find out the rate of wear of stones which are used in road construction. | | 228 | Crushing test is done to find out the compressive strength of the stone. | | 229 | Impact test is done to determine toughness of a stone. | | 230 | The fire clay contains pure hydrated aluminium silicate | | 231 | Refractory bricks resist high temperature | | 232 | When a brick is immersed in water for 24 hours and then dried if | | | 1. No grey or white deposits appear on the surface, then brick is free from soluble salts | | | 2. 10 percent surface is covered with grey or white deposits the brick has slight efflorescence | | | 3. 50 per cent surface is covered with grey or white deposits the brick has serious efflorescence | | 233 | The stones obtained by blasting are used as road metal. | | 234 | Characteristic of pyroxene are | | | 1. It forms octagonal crystals | | | 2. It converts to chlorine by hydration | | | 3. Its density is 2.3 to 3.6 g/cm² | | | 4. Its hardness is 5 to 6 | | 235 | The weight of a good quality brick when immersed in water for a period of 16 hours should not exceed the weight of dry brick 20% | | 236 | The rocks which are formed due to cooling of magma at a relatively shallow depth from the earth's surface are called hypabyssal rocks | | 237 | The thermosetting plastic | | | 1. Becomes rigid when moulded at suitable pressure and temperature | | | 2. At 127°C to 177°C permanently set and further application of heat does not soften it is at 343°C | | 238 | The synthetic resin are melamine resin, phenolic resin, resorcinol resin, urea resin | | 239 | Slacking of lime is affected by immersing the lime in water. | | 240 | The most commonly used synthetic abrasive is aluminium carbide, boric acid, silicon | | 241 | For light and ornamental casting the most unsuitable pig iron is mottled pig | | 242 | Acrylic is the name of methyl metha crylate | | 243 | Glazing of clay products is done | | | 1. To improve their appearance | | | 2. To protect them from atmospheric effect | | | 3. To pro tect them from corrosive action | | 244 | Stainless steel resists' corrosion due to chromium | | 245 | Lacquer paints are alcohol. | | 246 | Cellulose paints is ethyle acetate. | | 247 | Oil paints are naptha. | | 248 | Distemper is water. | | 249 | Good quality sand is never obtained from sea | | 250 | Snowcrete is one of the patent forms of water proof cement paints | | 251 | The usual percentages of clay and metal in cement are 80%, 20%. | | 252 | The base material for distemper is chalk | | 253 | | | 254 | Muscovile is also known as white mica and potash mica. | ### Building Materials (cont.) | Number | Fact | |---|---| | 255 | Biotite is also known as black mica. | | 256 | Blister steel | | | 1. Obtained by cementation process | | | 2. Full of fissures and cavities | | | 3. Cannot be forged | | | 4. Can be easily welded | | 257 | Lime is available in free state. Lime is available by dissolving calcium carbonate in water. | | 258 | Lime is available by calcining calcium carbonate at 900°C. Lime is nothing but calcium chloride. | | 259 | The rocks having alumina or clay as their major constituents are known as argillaceous rocks | | 260 | Calcination of iron ores is done | | | 1. To remove moisture | | | 2. To remove carbonic acid | | | 3. By roasting in heaps | | | 4. After dressing | | 261 | Strength of cement concrete primarily depends upon water-cement ratio | | 262 | Plastics are compounds of carbon with element hydrogen, nitrogen, oxygen | | 263 | The rock which is not a sedimentary rock dolerite | | 264 | For a good building stone its specific gravity should the greater than 2.7. | | 265 | The plastic bottles are made by the process of blowing. The plastic sheets are made by the calendaring process in which the plastic material is allowed to pass between cylindrical rollers. | | 266 | The application of thermo-setting resins on sheets of paper is called laminating process. | | 267 | The plastic article made by placing raw material in the desired moulds is known as moulding process. | | 268 | The constituent of good brick earth whose excess causes the raw bricks shrink and warp during drying and burning alumina | | 269 | Rapid hardening cement contains tri-calcium silicate | | 270 | Inhaling of fly-ash over a long period causes silicosi, fibrosis of lungs, bronchitis, pneumonitis | | 271 | Minimum required water cement ratio for a workable concrete is 0.40. | | 272 | Water paints are white wash, colour wash, whiting and distemper | | 273 | For construction of structures under water the type of lime used is hydraulic lime | | 274 | Rust is due to formation of oxides. | | 275 | Seasoning is a process of removing sap. | | 276 | Seasoning of timber is done to remove water | | 277 | Lime mortar is generally made with hydraulic lime | | 278 | Duco paints are plastic paints, cellulose paints, emulsion paints, bituminous paints, oil paints | | 279 | The specific gravity of marble is 2.72. | | 280 | The percentage of absorption for firebricks varies from 5 to 10. | | 281 | The percentage of silica in silica bricks is to the extent of about 95 to 97 percent. | | 282 | Roughly 1 to 2 percent of lime in silica bricks is added to act as binding material. | | 283 | The compressive strength of silica bricks is about 150 kg/cm². | | 284 | For lime concrete | | | 1. Slump is 50 to 75 mm | | | 2. Flexural strength at 90 days is 0.2 N/mm² | | | 3. Compressive strength at 90 days is 1.5 N/mm² | | | 4. Compressive strength at 26 days is 1.2 N/mm² | | 285 | Pig iron made from haematite ores free from sulphur phosphorus and copper is known as bessemer pig. | | 286 | Whitworth compressed steel is obtained when molten steel is subjected to a pressure of 9 kg/mm² | | 287 | Spirit varnish generally consists of spirit and shellac | | 288 | Roasting is not necessary if iron ore is an oxide. | | 289 | Impurities float on the molten iron as slag. | | 290 | The slag contains lime about 45%. | | 291 | The molten iron is made to run in a long channel formed in sand called sow | | 292 | Melamine is obtained from calcium carbide. | | 293 | Formaldehyde is prepared synthetically from methane. | | 294 | The melamine when reacted with formaldehyde forms the melamine-formaldehyde resin. | | 295 | The plastics made from melamine formaldehyde resin are used for electrical insulators. | | 296 | Steel contains carbon approximately 0.05% to 1.75% | | 297 | Blisters in the finished wrought iron are caused due to the reaction between oxide of iron and carbon. | | 298 | The edges of a finished wrought iron are rough the red shortag | | 299 | Pig iron (charcoal) is manufactured from magnetic ore (Fe 204) | ### Building Materials (cont.) | Number | Fact | |---|---| | 300 | For the manufacture of wrought iron non-sulphurous fuel is not necessary. | | 301 | Lacquer is spirit varnish | | 302 | Bull's trench kiln a trench excavated in ground. | | 303 | Hoffman's kiln is constructed over ground. Tunnel kiln is constructed as a tunnel. | | 304 | Good quality cement contains higher percentage of tri-calcium silicate | | 305 | Soundness of cement is tested by le-chatelier apparatus | | 306 | To give a brilliant finish the type of varnish used is spirit varnish | | 307 | The softest rock is talc. | | 308 | A well seasoned timber may contain moisture up to 10 to 12%. | | 309 | Oil varnish generally consists of resin, oil and turpentine | | 310 | Bitumen may be dissolved in carbon disulphide | | 311 | Rusting is caused due to combined action of