Natural aggregate consists of manufactured crushed stone and sand created by crushing bedrock, or naturally occurring unconsolidated sand and gravel. It is a major component of asphalt and concrete and is required in streets, highways, railroads, bridges, buildings, sidewalks, sewers, power plants, and dams—just about every part of the built environment apter 2 Asphalt and Asphalt Paving Materials - APAI2016-9-9 · inert materials such as sand, gravel, crushed stone, slag, or rock dust. Properly selected and graded aggregates are mixed with the cement-ing medium asphalt to form pavements. Aggregates are the principal load-supporting components of an Asphalt Concrete pavement. They total 90 to 95 percent of the mixture by weight and 75 to 85 percent by volume.