Concrete is a mixture of cement (usually Ordinary Portland cement), acting as a binder, fine aggregates such as sharp sand, and coarse aggregates such as gravel or crushed stone. Alternatively, fine and coarse aggregates may come pre-mixed as all-in ballast. Water is added to form a paste with the cement, which covers the surface area of every stone and aggregate particle in the mix, binding them together to form a solid mass when the concrete hardens. The aggregates are not physically altered in any way, but are firmly set into the hardened, rock-like cement paste.
Concrete has numerous applications, among them the foundations of buildings, oversite concrete under suspended timber ground floors, solid floor slabs, driveways, paths, benching in man-holes, and many others.
In some cases a chemical plasticizer is mixed with the water in order to make the concrete easier to work and to protect it from frost while it sets.