Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, 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 foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties, or as a low-cost extender that binds with more expensive cement or asphalt to form concrete. Although most kinds of aggregate require a form of binding agent, there are types of self-binding aggregate which require no form of binding agent.
A limestone quarry.
10 mm graded crushed basalt rock or aggregate, for use in concrete, called "blue metal" in Australia.
20 mm graded aggregate.
A gravel and sand extraction facility in Međimurje County, Croatia.
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass.
Sand dunes in the Idehan Ubari, Libya
Depiction of sands: glass, dune, quartz, volcanic, biogenic coral, pink coral, volcanic, garnet, olivine. Samples are from the Gobi Desert, Estonia, Hawaii and the mainland United States. (1×1 cm each)
Heavy minerals (dark) in a quartz beach sand (Chennai, India)
Sand from Coral Pink Sand Dunes State Park, Utah. These are grains of quartz with a hematite coating providing the orange color.