How is concrete made?

Concrete is a construction material made from cement, aggregate, and water, possibly with complementary chemical admixtures and mineral additions. This combination of materials is placed while it is still plastic after mixing, on-site or in a precasting plant. It can be poured into molds (or forms) to take on many shapes. It gradually hardens as a monolithic unit. Its appearance, strength, resistance, etc. can vary enormously, depending on the mix design, placement conditions, and surface treatment.