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Correct OPTION is (b) MANGANESE dioxide

Easiest explanation: COLOURING pigments are added to the raw MATERIALS while manufacturing of the glass in order to make coloured glass. Manganese dioxide is added to the glass in order to make its colour violet.

The correct answer is (d) Lead monoxide

The EXPLANATION: LITHARGE is lead monoxide which is one of the raw MATERIALS needed to manufacture potash-lead GLASS. Other raw materials required are potassium carbonate and pure sand.

Right option is (a) COWNOSE

The EXPLANATION is: A cownose brick is moulded with a double BULLNOSE on the end. A bullnose brick is moulded with a ROUNDED angle and is used for a rounded quoin.

The CORRECT choice is (c) Down-draught kiln

Explanation: CONTINOUS kilns are continuous in OPERATION which means that in these kilns, LOADING, firing, cooling and unloading, all are carried out simultaneously. The various types of continuous kilns are bull’s trench kiln, Hoffman’s kiln and tunnel kiln.

The correct option is (d) Pugging

Best explanation: The process of grinding CLAY with water and making the clay plastic is called pugging. Unsoiling is the removal of the top layer of soil which is full of impurities. In digging, clay is dug out from the ground and then spread on the LEVELLED ground. In the process of weathering, clay is exposed to the atmosphere for SOFTENING.

Correct answer is (b) False

The explanation: There are two WAYS of moulding – hand moulding and machine moulding. Moulds are rectangular boxes that are OPEN at the bottom and the TOP. They can be of either wood or STEEL. Steel moulds used in the process of moulding for the manufacturing of bricks are more durable than the brick moulds.

The correct choice is (c) 72 hours

The best explanation: In the manufacturing of tiles, four different operations are INVOLVED. These are the preparation of the CLAY, moulding, DRYING and burning. Tiles are burnt in kilns. The time required to complete the process of burning the tiles is about 72 hours.

The CORRECT choice is (a) True

To elaborate: Lime generally does not occur in the free STATE in nature. The major source of obtaining lime is limestones OBTAINED from nature. Kankar is an impure limestone while white CHALK is pure limestone.

Right ANSWER is (a) 12-50 mm

Easiest EXPLANATION: The DIFFERENT types of tiles depending on the USE to which they are put are drain tiles, floor tiles and roof tiles. Floor tiles may be of square or hexagonal shape. The thickness of the floor tiles varies from 12-50 mm.

Correct option is (a) Orthoclase FELSPAR

The explanation: Orthoclase felspar is used for the production of CLAY in nature. It is predominantly FOUND in igneous rocks. It is GREYISH, whitish or pinkish in colour.

Right choice is (B) Pure lime

Easy explanation: FAT lime is ALSO called pure lime. It is also known as HIGH calcium lime, rich lime or white lime. Fat lime is widely used in whitewashing and plastering walls.

Right option is (d) Alumina and silica

Explanation: In ORDER to develop hydraulicity, it is necessary to have alumina and silica PRESENT in chemical combination with the LIMESTONE. Silicates of magnesium, aluminium and CALCIUM are responsible for hydraulicity.

The correct option is (b) False

For explanation I WOULD say: On heating, GLASS becomes soft and soft as the temperature is increased. It finally gets transformed into a mobile LIQUID. The manufacturing process of glass has become EASY using this property.

Right CHOICE is (c) It should not produce a clear ringing sound when STRUCK

Easy explanation: A GOOD tile should be well burnt and free from any bends or CRACKS. It should be REGULAR in size and shape and should produce a clear ringing sound when struck.

The correct choice is (b) False

Best EXPLANATION: Pantiles are SHORT and heavy. POT TILES are ordinary half ROUND country tiles. Pantiles are less curved than pot tiles.

Right OPTION is (c) CALCIUM silicate and POTASSIUM silicate

For explanation: Potash-lime glass is a mixture of calcium silicate and potassium silicate. This TYPE of glass fuses at high TEMPERATURES and does not melt very easily.

The correct CHOICE is (a) RED

To explain I would say: The PERCENTAGE of iron oxide desirable in GOOD brick EARTH is 5-6%. Iron oxide imparts a red colour to the bricks.

Right choice is (b) Best quality of lime is produced by this PROCESS

Explanation: BURNING of limestones to manufacture lime is generally carried out in one of the following – CLAMPS, continuous kilns and INTERMITTENT kilns. Clamp burning is used for manufacturing lime on a small SCALE. It is uneconomical to manufacture lime by this process on a large scale because the quantity of fuel required in this process is more and quality of lime produced by this process is not good.

The correct choice is (a) True

To elaborate: The RAW materials required to manufacture glass usually contain traces of compounds of iron. Ferric oxide gives a very light YELLOW TINT to the glass while ferrous oxide imparts a green COLOUR. Decolorizers are added in ORDER to avoid such effects.

Right CHOICE is (d) Lead silicate and POTASSIUM silicate

For explanation I would SAY: Potash-lead glass is a mixture of lead silicate and potassium silicate. It fuses very READILY and can be easily attacked by AQUEOUS solutions. The specific gravity of this glass is about 3-3.3.

The correct option is (a) Brickwork is more watertight in COMPARISON to stonework

For EXPLANATION I would say: Stonework is much stronger than brickwork. BRICKS can resist fire BETTER than stones. Brickwork is less watertight in comparison to stonework. Stonework results in the development of better architectural effects.

Right option is (d) Keramos

Best explanation: The TERM CERAMICS is derived from the Greek word keramos which means potter’s earth. The ceramic products are mainly classified into three categories – CLAY products, refractories and GLASS.

The CORRECT answer is (a) Air binding

The EXPLANATION is: The binding materials are CLASSIFIED into three CATEGORIES – air binding materials, autoclave binding materials and hydraulic binding materials. Acid-resistant cement and gypsum are examples of air binding materials.

The CORRECT OPTION is (d) 30%

To ELABORATE: Poor lime CONSISTS of more than 30% of clay. Poor lime slakes very slowly and is ALSO known as lean lime.

Correct option is (c) ANNEALING

To explain: The PROCESS of SLOW and gradual cooling of glass articles is known as annealing. There are two methods of annealing of glass. These are FLUE TREATMENT and oven treatment.

Correct OPTION is (c) Structural glass

Explanation: There are many varieties of glass such as bullet-proof glass, foam glass, wired glass, safety glass, structural glass, SOLUBLE glass, shielding glass, ETC. Structural glass is popularly called glass bricks. This TYPE of glass is used for lantern lights.

The correct choice is (c) 30%

The best explanation: With an increase in the PERCENTAGE of clay in HYDRAULIC lime its hydraulic PROPERTY increases and the SLAKING becomes difficult. With about 30% of clay, hydraulic lime resembles natural CEMENT.

Right answer is (d) Calcination

To explain: The process of heating to REDNESS in the presence of AIR is called calcination. Hydraulicity is the property of lime by which it SETS in damp PLACES or thick MASONRY walls where the free circulation of air is absent.

Correct choice is (B) Cullet

The explanation is: For all the types of glass, in addition to the raw MATERIALS, cullets and decolorizers are also added. Cullet is used to indicate pieces of BROKEN glass or WASTE glass.

The correct ANSWER is (b) Their external surface is smooth

To explain I would say: Pressed and wire CUT bricks are much heavier than the ordinary hand-moulded bricks. These bricks have SHARP edges and CORNERS. They exhibit UNIFORM texture and their external surface is smooth.

The correct choice is (d) It is a pure limestone

Best explanation: Kankar is an impure limestone which is used to MANUFACTURE natural hydraulic lime. It is available in two forms – nodular and BLOCK form. Kankar in nodular form can withstand heat WITHOUT disintegration and CONTAINS a higher percentage of CLAY.

The correct option is (a) Tin

Easiest explanation: In the silvering of glass, a THIN coat of tin is first APPLIED on which SILVER is then deposited. Then, a suitable paint is applied in order to PROTECT it against atmospheric effects.

Right OPTION is (c) It is a mark of depth about 10-20 cm

To explain: A FROG is used to indicate the TRADE name of the manufacturer. It is a mark of depth about 10-20 mm. It is placed on RAW BRICKS during moulding and serves as a key for holding mortar.

Correct option is (a) Pugmill

To explain: Tempering is usually done in a pugmill in order to MANUFACTURE good bricks on a LARGE scale. A pug mill is fixed on a TIMBER base and consists of a conical iron tub with cover at the top of it.

The correct OPTION is (b) False

The explanation: The SIZE of moulds should be kept larger than the FULLY burnt bricks. This is because bricks shrink during the process of drying and burning. Thus, moulds are made LONGER in all the directions by 8-12%.

Right choice is (a) 5%

Explanation: Fat lime is prepared by calcination of a COMPARATIVELY pure CARBONATE of lime. It should be COMPOSED of about 95% CALCIUM oxide. The percentage of impurities in limestones should not exceed 5% for preparing fat lime.

Right choice is (c) Limestone

Explanation: Lime is obtained from the CALCINATION of limestone. Carbon DIOXIDE and moisture are REMOVED from it due to calcination and the PRODUCT which remains is CALLED lime.

Right choice is (d) Emery

The best EXPLANATION: Glass can be MADE opaque by grinding the surface of the glass with emery. It can also be done chemically by APPLYING hydrochloric acid.

The CORRECT option is (b) Vinyl-resin

Easiest EXPLANATION: Bullet-proof glass is made of many LAYERS of PLATE glass. ALTERNATE layers of vinyl-resin plastic are present in this type of glass. This glass does not allow the bullet to pierce through it.