Long-term durability of reinforced concrete piles from the Hornibrook Highway Bridge

After more than 75 years continuous exposure to the Pacific Ocean waters on the Queensland coast, the 879 reinforced concrete driven piles that supported the superstructure of the Hornibrook Highway Bridge appeared to be in remarkably good condition when the bridge was demolished during 2011-2012. Detailed investigations revealed excellent, very hard concrete with pH values still around 12 and very little evidence of serious corrosion of the steel reinforcement. The concrete chloride content at the reinforcement was considerably more than the usually accepted limits. However, a few isolated occurrences of very severe localised reinforcement corrosion were found during demolition even though there was little visual external evidence. Possible reasons for the various observations are discussed, together with the practical implications.