Concrete once set will take a superimposed load that compresses it, but, if used, say, as a beam, will fail if heavily loaded, because it is weak in tension. Steel, on the other hand, is strong in tension, so the two materials are combined to enable the concrete to perform well in tension as well as in compression by casting steel rods in the positions where reinforcing is necessary to improve tensile strength, especially in beams, lintels, etc. Reinforced concrete can be used to construct entire skeletal frames, floor-slabs, walls, etc., either pre-cast in a factory or in situ (on site, i.e. where it will be permanently). Also called ferro-concrete it lends itself to the creation of complex curved forms that may get their stability partly from shape, permitting its use in bridges and shell-roofs. See also prestressed concrete.
A. Allen (1988, 1992);Faber & Alsop (1976);Marsh (1907)