Aggregate: Aggregates are granular materials formed from a natural rock substance. It can be further defined in one of several ways:
Source—primary, secondary, recycled
Geology—limestone, granite, etc.
Primary aggregate: These are extracted directly from the ground. They can be sand, gravel, or hard rock. Sand and gravel can come from any kind of rock, but it must have already been broken into pieces. This is accomplished through the natural processes of weathering and water or ice movement. The aggregate is then deposited in a loose form.
Secondary aggregate: These are produced as by-products of other mining or quarrying activities.
Recycled aggregates: These materials are produced by recycling construction and demolition waste. They can be crushed concrete, bricks, glass, bits of asphalt removed during road construction.
Crushed rock aggregate: Many rocks are suitable for use as aggregate once they’re crushed. Lower quality aggregates may work as constructional fill, while higher quality aggregates can be utilized for more demanding applications like road pavements and concrete.
Limestone: Limestones are sedimentary rocks primarily composed of calcium carbonate. They are very common rocks and are often uses as aggregates. Fine-grained limestone, or chalk, is soft and porous and generally unsuited for use as an aggregate.
Igneous rocks: Igneous rocks, rocks formed through the cooling and solidification of lava, tend to make strong aggregates. Their high skid resistance makes them good for road surfacing, as well as use deeper in the road.
Sandstone: Sandstones are sedimentary rocks made up of of sand-sized particles of quartz, feldspar, and other tiny fragments in a mineral cement. The strength, durability, and porosity of sandstone determines its suitability as aggregate. Older sandstones tend to be tougher and more suitable for aggregate use.
Crushed stone: is a form of construction aggregate, typically produced by mining a suitable rock deposit and breaking the removed rock down to the desired size using crushers. It is distinct from gravel which is produced by natural processes of weathering and erosion, and typically has a more rounded shape.
Construction aggregate: or simply “aggregate” is a broad category of coarse 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.