[Physics] Why is steel-reinforced concrete stronger than ordinary concrete

Question

Is it only because steel has higher elasticity? What other factors are involved?

Answer 1

Concrete is very strong in compression but weak in extension, so it isn't good at supporting stretching or bending forces. By contrast steel is able to cope well with stretching and bending forces. So by combining the two you have a composite structure that resists compression as well as concrete and resists stretching and bending as well as steel.

In many cases the steel is held under tension while the concrete is setting. This produces pre-stressed concrete. Because this type of concrete is under compression even when bearing no load it is even better at resisting stretching and bending. As a result it is often used for elements like beams that are subjected to bending forces.