Materials
What the domain tests
Materials tests properties, selection, storage and testing of cement, aggregates, concrete, timber, steel, bricks, plastics and insulation.
Core rules
- Store cement dry, off the floor, and use oldest stock first. Lumpy cement has deteriorated.
- Aggregates must be clean, hard and graded. Sharp sand is used for concrete; soft sand is more common in mortar.
- Normal concrete uses aggregate up to about 20 mm, controlled water-cement ratio and testing by slump and cubes.
- Steel reinforcement must have the specified grade, cover and corrosion protection.
- Timber is selected by species, grade, moisture content and defects; treat it where termites or damp are a risk.
- Bricks and blocks are selected for strength, absorption and appearance.
Worked example
Choose a material for a damp-proof course in a masonry wall. A flexible polythene DPC is suitable because it is impermeable and accommodates minor movement. Mortar is not suitable because it is porous and brittle. Reasoning: select by function, durability and compatibility with adjacent materials.
Traps
- Using cement that has set into lumps.
- Measuring sand by loose wet volume without allowing for bulking.
- Using untreated timber in ground contact.
- Selecting the wrong aggregate size for the section.
- Storing cement on a damp floor.