Why is rebar used in concrete?

Rebar, or reinforcing steel bars, is primarily used in concrete to improve its tensile strength. Concrete is exceptionally strong under compression but lacks the same strength when subjected to tensile forces. This lack of tensile strength makes concrete susceptible to cracking and structural failure when under tension, such as in scenarios involving bending or lateral loads.

Incorporating rebar into concrete helps address this weakness. The high tensile strength of steel helps the composite material withstand tensile forces, significantly improving the overall durability and load-bearing capacity of the concrete structure. As the concrete expands and contracts due to temperature changes or stress, the rebar provides the necessary support to resist these tensile stresses, reducing the likelihood of cracking and extending the lifespan of the concrete.

While options related to enhancing compressive strength or reducing weight may seem relevant in a general construction context, they do not accurately describe the primary role of rebar. Concrete inherently has high compressive strength, and adding rebar does not significantly change its weight. Additionally, rebar doesn't contribute to molding but rather to the structural integrity of the concrete.