Recent developments of reinforcement corrosion in concrete structures in the ocean

Reinforced concrete is an option for pontoons for offshore wind and other energy-related facilities. It has the potential for lower maintenance in situ and ease of construction but despite its long successful applications history, concern persists about the risk of reinforcement corrosion. Recent investigations have concluded that chloride-induced corrosion is unlikely, short-term or long-term, for well-made, well-compacted and low permeability concretes. This experience is briefly reviewed. Initiation of corrosion occurs as pitting corrosion, irrespective of chloride concentration, and for reinforced concrete only within wet air-voids in the concrete at the steel–concrete interface. Experimental evidence shows that in parallel to this, a gradual loss of concrete alkalis to the external environment occurs, thereby eventually lowering the pH of the porewater solution sufficient for general corrosion of the steel to become thermodynamically feasible, irrespective of chloride concentration. A model for the development of corrosion loss as a function of period of exposure and of concrete permeability is described. It is concluded that reinforcement corrosion in marine environments is not a significant risk for high-quality, well-compacted, low permeability concretes made with non-reactive aggregates. This has direct implications for the construction and inspection of new reinforced concrete structures in seawater and ocean waters.