Sand is mined for many applications, but the largest use by far is for fine aggregate in concrete. Smaller quantities of sand are used for fracking, water treatment (filtration), metal casting, and making glass, silicon chips, and ceramics. Concrete consists of cement, water, fine aggregate (sand), and coarse aggregate (gravel). Aggregate makes up about 60–70 percent of the concrete volume, with 40–50 percent of the aggregate consisting of sand. The nearly 20-year-long construction boom in Asia, beginning in China, India, and Singapore, shows more signs of spreading than abating, with major projects for high-speed train lines, airports, roadways, and commercial and residential buildings planned in Indonesia, Malaysia, the Philippines, Thailand, and Vietnam. As a result, the demand for sand is huge. See also: Asia; Cement; Ceramics; Concrete; Glass; Hydraulic fracturing (fracking); Metal casting; Sand; Water treatment
The United Nations Environmental Programme (UNEP) estimated that more than 20 billion tonnes of sand are consumed annually worldwide, with about 75 percent of it used in concrete. Not all sand is suitable for construction, however. Desert sand grains are too round and smooth to bind well in a concrete mixture. The best construction-grade sand comes from glacial deposits, river channels, river flood plains, and lakebeds. Marine sand contains chlorine, which corrodes steel and therefore is less suitable for reinforced concrete unless it is washed. At present, the amount of sand being mined, particularly in Asia, is unsustainable, considering that weathering of rock to sand particles—ranging in size from 63 micrometers to 2 millimeters in diameter—takes hundreds of thousands of years, or longer. Vietnam, for example, expects it may run out of sand by 2020. Supply aside, the environmental cost (impact) of sand mining may be even greater. See also: Corrosion; Desert; Eolian landforms; Floodplain; Fluvial sediments; Glacial geology and landforms; Marine mining; Marine sediments; Reinforced concrete; River; Weathering processes
Dredging rivers and lakes or mining (quarrying) inland deposits for sand destroys and pollutes natural habitats, including forests, farmland, and commercial fisheries. Streambed mining may also lead to streambed and bank erosion as well as lowering of groundwater tables, leaving nearby drinking-water wells and wetlands dry. Mining of marine sands has resulted in the disappearance of entire islands near Jakarta, Indonesia, and beaches in Morocco and the Caribbean. Beach-sand, dune, and barrier-island mining may also result in increased storm surges from tropical cyclones (hurricanes) and tsunamis. See also: Barrier islands; Dune; Erosion; Fisheries ecology; Forest ecosystem; Freshwater ecosystem; Groundwater hydrology; Hurricane; Mining; Nearshore processes; Placer mining; Quarrying; Surface mining; Tsunami; Wetlands
As construction-sand sources become scarce, the price of sand is expected to increase, opening the door for alternative materials. At present, rock crushed to sand particle size, called manufactured sand, is a promising alternative. Manufactured sand could also be produced close to a construction site, which would reduce transportation costs and associated greenhouse-gas emissions. Crushed construction and demolition waste concrete is already being used as coarse aggregate in concrete mixes and research is underway for using crushed concrete as a sand replacement. Recycled concrete is also seen as an alternative to landfilling construction waste. See also: Crushing and pulverizing; Rock
