Sand and Gravel
Sand and gravel are unconsolidated, granular mineral materials produced by the natural disintegration of rock caused by weathering. The terms sand, gravel, clay and silt relate to grain size rather than composition. Sand is material passing through a number 4 (4.76 mm) sieve and remaining on a number 200 (74 µm [micron]) sieve. Gravel is granular material remaining on a number 4 sieve and ranging up to about 9 cm. Material finer than 200 mesh is called silt or clay.
Sand and gravel are used as fill, base and finish material for highway construction, as coarse and fine aggregates in concrete and asphalt production, and as fine aggregates in mortar and concrete blocks. They are also used as backfill in mines, along with cement and mill tailings. Industrial-quality sand is also used in the manufacture of glass, pottery and bricks and in water filtration. "Sandy" soils are favourable to certain types of agriculture.
Deposits are widespread throughout Canada although there are shortages of this resource in some regions. Operators have established plants as close to major consuming centres as possible. In addition to large aggregate operations, usually associated with some phase of the CONSTRUCTION INDUSTRY, many small producers serve local markets. Exploitation is generally by power shovel or loader and trucks or conveyor systems; processing consists of washing, crushing and screening.
Worldwide, sand and gravel, as well as crushed stone aggregates, are becoming recognized as strategic resources in the context of land-use planning and sustainable development.
See alsoCEMENT INDUSTRY.