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L David Nealey

Crushed stone and sand and gravel are the main types of natural aggregate used in the United States. Aggregate is used in nearly all residential, commercial, and industrial building construction, and in most public works projects including roads and highways, bridges, railroad and light rail beds, airports, water and sewer systems, and tunnels. Much of the infrastructure built during the 1950s and 1960s has deteriorated to a point that requires extensive repair or replacement. All this construction requires enormous amounts of aggregate. In Colorado, for example, nearly 45 million tons of aggregate, or about 12 tons per person, were produced during 1994.
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