Civil and Construction Technology
What this domain tests
Civil and Construction Technology tests the materials, structural elements, construction methods and site controls used in buildings and simple infrastructure.
Core rules
- Concrete is cement, fine aggregate, coarse aggregate and water, with the water/cement ratio controlling strength and durability: lower w/c gives higher strength but lower workability. Curing keeps moisture for hydration and must not be skipped.
- Nominal mixes (for example 1:2:4 cement:sand:coarse aggregate by volume) are used for ordinary work; design mixes are proportioned by weight and tested.
- Workability is measured by slump; strength by cube or cylinder tests at 7 and 28 days. 28-day strength is the design value.
- Loads: dead (self-weight), imposed/live, wind and settlement effects. Beams carry bending and shear, columns carry axial compression, slabs span one or two ways.
- Foundations spread load: strip footings for walls, isolated pad footings for columns, rafts for weak ground. Soil bearing capacity governs size.
- Surveying: a level establishes reduced levels from a benchmark; backsight and foresight differences give fall or rise; a total station measures angles and distances.
Worked example
A slab 5 m × 4 m × 0.15 m needs 3.0 m³ of concrete (5 × 4 × 0.15). For a 1:2:4 nominal mix with 300 kg cement per m³ and w/c 0.5, cement = 900 kg, water = 0.5 × 900 = 450 kg ≈ 450 litres. Cement is ordered in 50 kg bags: 18 bags. Volume batching must allow for bulking of damp sand.
Traps
Specifying w/c by volume rather than mass; ignoring bulking of sand; using 7-day strength as the design value; confusing dead and live load; sizing a footing from the column load alone without soil capacity; adding water to improve workability on site.