Construction aggregate

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, 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,^[1][2] being a significant part of 6 billion tons of concrete produced per year.^[3]

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.

Aggregates are also used as a low-cost extender that binds with more expensive bitumen to form asphalt concrete or with Portland cement to form concrete.

Self-binding aggregate refers to angular crushed material (quarrystone rubble) comprising a mixture of finer and coarser particles that interlock after being compacted.^[4] More recently, recycled concrete, steel and carbon fibres as well as geosynthetic materials have also been used as aggregates.