Reinforcing steel —rods, bars, or mesh—Reinforcement for concrete is provided by embedding deformed steel bars (rebar) or welded wire fabric (wire mesh, sheets or rolls) within freshly made concrete at the time of casting.

The purpose of reinforcement is to provide additional strength for concrete where it is needed. The steel provides all the tensile strength where concrete is in tension, as in beams and slabs; it supplements the compressive strength of concrete in columns and walls; and it provides extra shear strength over and above that of concrete in beams.