Aggregates are a granular material used in construction. The most common natural aggregates of mineral origin are sand, gravel and crushed rock. An end-product in themselves as railway ballast or armourstones, aggregates are also a raw material used in the manufacture of other vital construction products such as ready-mixed concrete (made of 80% aggregates), pre-cast products, asphalt (made of 95% aggregates), lime and cement.
Aggregates are produced from natural sources extracted from quarries and gravel pits and in some countries from sea-dredged materials (marine aggregates). Secondary aggregates are usually by-products from other industrial processes, like blast or electric furnace slags or china clay residues. Recycled aggregates derive from reprocessing materials previously used in construction, including construction, demolition residues.