CONCRETE TECHNOLOGY

Coarse Aggregates
Coarse aggregates are excavated from natural deposits of gravel or stones and then washed to remove dirt, salts, and clay. This term describes materials such as natural gravel, crushed gravel, or crushed stone that will not pass through a 5mm sieve. Larger stones are often crushed to make smaller pieces. The processes of washing, crushing, and sieving usually take place at the excavation site. A coarse aggregate used for concrete typically passes through a 19mm sieve but remains on a 10mm sieve.

Fine Aggregates
The terms "concreting sand," "sharp sand," or "fine aggregate" are used to describe natural sand, crushed stone, sand, or similar materials that pass through a 5mm sieve but are coarser and less well-graded than the soft sands used in mortars. This material is often referred to as "fine aggregate" to distinguish it from soft sand. Being coarser than soft sand, fine aggregate is not used for mortars as it produces an unworkable mix and causes difficulties in achieving a good finish when jointing.