Reinforced concrete. Workmen constructing a reinforced concrete wall by filling a steel mould (lower frame) with concrete from a hopper (at upper centre). Reinforced concrete consists of concrete which has steel rods running through it. The material properties of concrete mean that it can cope well under compression, but would be liable to fail under tensile stresses. The steel and concrete form a bond and stresses can be transferred from one to the other. Concrete is an ideal building material because it is cheap, durable, strong (when reinforced) and can be moulded to the required shape at the construction site.