Which statement identifies a common durability problem in reinforced concrete bridges and a typical mitigation?

• A. Durability problems are negligible; no mitigation.
• B. Chloride-induced corrosion and carbonation are common; mitigations include adequate concrete cover, low-permeability concrete, protective coatings, proper drainage, and corrosion inhibitors.
• C. Thermal cracking is the sole durability issue; mitigation is painting steel.
• D. Water leakage is the sole durability issue; mitigation is increasing reinforcement size.

Answer: (B)

Chloride ingress and carbonation are common durability concerns for reinforced concrete bridges because they attack the steel reinforcement by removing or weakening the passive protective film and accelerating corrosion. Chlorides from de-icing salts or seawater can penetrate concrete and reach the rebar, turning the steel susceptible to rust; carbonation lowers the concrete’s pH, depassivating the steel and enabling corrosion even when chlorides are not high. If corrosion progresses, cracks and spalling can develop, reducing strength and service life.

Mitigation centers on limiting the pathways for those aggressive agents and protecting the steel: provide sufficient concrete cover to lengthen the diffusion path, use low-permeability concrete to slow water and ion ingress, apply protective coatings or barriers, ensure proper drainage to prevent moisture buildup, and consider corrosion inhibitors as part of the mix. Other options suggesting durability problems are negligible, or focusing on a single issue or ineffective mitigations, don’t align with how durability is managed in practice.