Building Materials and Construction
Concrete and masonry
Know Ordinary Portland Cement types: Type I general, II moderate sulfate resistance, III high early strength, IV low heat of hydration, V high sulfate resistance. Concrete is specified by f′c at 28 days, with the water–cement ratio controlling strength and durability and the slump test controlling workability at placement. Standard cylinders are 150 × 300 mm; curing is typically 7 days. Masonry: a 400 × 200 mm concrete hollow block laid with 10 mm joints yields about 12.5 units per square metre; mortar and plaster are commonly 1:3 cement–sand; vertical reinforcement is grouted into cells and horizontal bars laid in the block courses.
Steel, timber and finishes
Reinforcing steel grades are commonly 230, 275 and 414 MPa; cover is roughly 20 mm for slabs, 40 mm for beams and 50–75 mm for footings. Timber is graded by species and defects; steel connections, welding versus bolting, and fireproofing come up as recognition items. For finishes, match the material to the exposure: waterproofing on wet areas with upturned edges, vapour barriers on the warm side in air-conditioned envelopes, and expansion joints where movement is expected.
Traps and a rule of thumb
Trap: confusing high-early-strength cement (Type III) with sulfate resistance (Type V), or assuming a higher slump means stronger concrete - the opposite is generally true. Another trap offers plaster as waterproofing. Rule of thumb: one 40 kg bag of cement yields about 0.028 m³ of concrete. A 100 mm slab therefore needs roughly 3.5 bags per square metre before wastage, so order about 5–10% extra.