Rebar provides concrete with significantly more strength than it otherwise has, especially in the area of tensile strength, which makes it necessary for concrete used in infrastructure subject to heavy loads and stress. Rebar, or reinforcing steel, significantly increases the ability of concrete to handle loading pressure and stress. Reinforcing steel is much more flexible and withstands more tension than concrete, making it an ideal additive for concrete that must hold high weights or endure significant amounts of stress.
With rebar, like other concrete materials, engineers and construction officials must calculate the correct steel for the project. Failing to do so reduces the strength of concrete, and may have diminished structural integrity. Successful placement of rebar requires proper spacing, too, which helps distribute weight across the concrete's surface.