The long-term durability of reinforced concrete structures exposed to aggressive marine environments

Marine environments usually are aggressive and can be deleterious for the long-term corrosion resistance of reinforced concrete structures. Modern structures often show evidence of reinforcement corrosion within a decade or two of construction. Usually this is attributed to the ingress of aggressive chlorides that initiate and foster the corrosion of steel reinforcement. In contrast, some structures have lasted a long time even in aggressive marine environments. Two examples are examined using an archaeological approach. The Maria Island cement silos on the Tasmanian coast are more then 90 years old and the recently demolished Hornibrook bridge near Brisbane was 75 years old. In both cases reinforcement corrosion was very modest. Other cases, including a number of structures constructed during the Second World War, also show good long-term corrosion resistance. Possible reasons are explored by comparing with recent research findings and with observations from thermodynamics and corrosion science research. The implications for durability design of reinforced concrete structures are discussed.