TI. NELSON, Vulcan Materials and W.P. BOLEN U.S. Geological Survey

摘要

Construction aggregates - primarily stone, sand and gravel - are recovered from widespread, natu-rally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical pro-cesses, glass production and other products. The growth of cities, their buildings and the highways that connect them have created demand for enormous quantities of aggregates.The aggregates industry is the largest mining in-dustry in the United States in terms of production by weight, by volume and by number of active operations. About 80 percent of concrete pavement and more than 90 percent of asphalt pavement is composed of aggre-gates. Because the products have a very high weight relative to their value and, thus, high transportation cost relative to value at the mine, a large percentage is consumed near the mines. About 80 percent of ag-gregates production is transported by truck to local markets versus 7 percent by rail and 4 percent by water to more distant markets. The remainder is made into concrete products at or near the production site.