Construction Materials and Basic Building Science
What this domain tests
This domain checks whether you can identify, test and select the materials that go into a building - brick, stone, cement, sand, aggregate, steel, timber and mortar - and apply the basic science of heat, light, ventilation and damp prevention to a real site.
Core rules and concepts
- Bricks (IS 1077): modular size 190 × 90 × 90 mm; with a 10 mm mortar joint each brick occupies 200 × 100 × 100 mm, so 1 m³ of brickwork takes about 500 bricks.
- First-class brick: water absorption not more than 20% after 24-hour soaking, compressive strength around 10 N/mm² or more, sharp metallic ringing when struck, no efflorescence, frog filled and facing up.
- Cement: OPC grades 33, 43 and 53 denote 28-day strength in N/mm²; field checks are grey colour, smooth feel, no lumps, and a handful that sinks in water instead of floating. Store on timber pallets, not more than 10 bags high, and use within about 90 days.
- Aggregates: fine aggregate passes the 4.75 mm sieve; a jar test should show silt under 3% for concrete work.
- Building science: in hot climates keep the long axis east–west; damp-proof course at plinth level in 1:2 cement mortar, continuous and turned up at junctions; plinth 450–600 mm above ground; window area roughly one-tenth to one-fifth of floor area for daylight and air.
Worked example
A 3 m long, 3 m high wall in 230 mm brickwork: volume = 3 × 3 × 0.23 = 2.07 m³. Bricks = 2.07 × 500 = 1035. Add 5% breakage and wastage (52) = 1087, so order 1100 bricks. Reasoning shown line by line is what earns marks - state the constant 500 and the wastage separately.
Traps that cost marks
Using 500 bricks/m³ for non-modular local bricks; forgetting wastage; reversing the cement float test; assuming cement strength is checked at 7 days; soaking AAC blocks like clay bricks.