Materials
Materials examines the selection, storage and simple field testing of bricks, blocks, cement, sand, aggregates, lime, water and reinforcement. The exam expects you to connect material properties to use: a good brick for external load-bearing work is not the same as a rejected brick with high absorption or efflorescence.
Core rules
- Common burnt clay bricks are covered by IS 1077; concrete blocks by IS 2185. Modular brick size is 190 × 90 × 90 mm, giving a 200 × 100 × 100 mm module with 10 mm mortar joints.
- Good bricks are sound, sharp-edged and give a clear ringing sound; excessive water absorption, efflorescence or deep cracks indicate rejection.
- Cement is supplied in 50 kg bags, stored off the floor, away from damp, and used in rotation; lumps or caking mean rejection.
- Sand must be clean, well graded and free from clay and organic matter; damp sand bulks, so volume batching needs allowance.
- Aggregate grading, size and shape affect concrete workability and strength.
Worked example
Find the number of modular bricks per cubic metre of brickwork. One brick with joints occupies 0.20 × 0.10 × 0.10 = 0.002 m3. Therefore 1 ÷ 0.002 = 500 bricks per m3. For 3.45 m3 of walling, the nominal requirement is 3.45 × 500 = 1,725 bricks; adding 5% for breakage gives about 1,811 bricks.
Traps that cost marks
Using the actual brick size instead of the nominal size with joints, ignoring wastage, or accepting dusty, damp cement are frequent errors. High water absorption does not make a brick stronger; it increases damp risk and reduces mortar bond.
Key points
- Modular brick: 190 × 90 × 90 mm; nominal with joint: 200 × 100 × 100 mm.
- 1 m3 of nominal modular brickwork needs about 500 bricks before wastage.
- Store cement dry, off the floor and use older stock first.
- Bulking changes sand volume batching.
- Reject cracked, efflorescent or excessively absorptive bricks.