This is sand produced as a result of crushing rock passing on sieve 5.0mm but retained on 75-micron sieve. There are two types of crushed rock sand; washed and unwashed quarry dust. Ratio of silt content/fines in washed quarry dust intended for heavy floor concrete can go up to a maximum of 9; for other light weight concrete works, the silt content/fines ratio for unwashed quarry dust, the limit is a maximum of 16 (BS 882:1992).
Quarry dust is used in concreting (ready mix concrete, precast works), mechanical stabilization of natural gravel, mortar and brick/block laying works.
Advantage of using crushed rock sand:
- When washed thoroughly well, it performs comparatively to washed clean lake sand.