How does corrosion of reinforcement affect concrete structures?

• A. It strengthens the bond between steel and concrete.
• B. It causes no change to the cross-section.
• C. It causes loss of cross-section, cracks, spalling, and reduced bond between steel and concrete.
• D. It increases ductility of concrete.

Answer: (C)

Corrosion of reinforcement weakens concrete structures because rust forms when steel reacts with moisture and chlorides or carbon dioxide. The rust occupies more volume than the original steel, creating internal pressure that cracks and spalls the surrounding concrete cover. As the steel slowly eats away, its cross-section is reduced, lowering the reinforcing capacity. The rust and cracking also degrade the bond between steel and concrete, so the composite action is compromised and the structure becomes less able to carry loads. All of these effects—loss of cross-section, cracking, spalling, and reduced bond—together reduce strength and durability.