††††Concrete is a building material composed of cement, stone, sand and water.
Concrete has been used since Roman and Egyptian times. Modern concrete evolved from the Discovery of Portland cement in 1824. During the 20th century, concrete has been increasingly used as a cheaper alternative to materials such as brick and wood.
Reinforced concrete has metal bars, rods or mesh embedded in it for extra strength.
Prestressed concrete is kept compressed by steel wires, so that it is less likely to buckle in use.
