Construction aggregate, or simply aggregate, is a broad category of coarse to medium-grained particulate material used in construction. Traditionally, it includes natural materials such as sand, gravel, and crushed stone. As with other types of aggregates, it is a component of composite materials, particularly concrete and asphalt.Aggregates are the most mined materials in the world, being a significant part of the 6 billion tons of concrete produced per year.
Aggregate serves as reinforcement to add strength to the resulting material. Due to the relatively high hydraulic conductivity as compared to most soil types, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under building foundations, roads and railroads (aggregate base). It has predictable, uniform properties, preventing differential settling under the road or building.