51314-4364-Rebar Corrosion in Submerged Concrete Structures - Field Results and Modeling

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Product Number: 51314-4364-SG

ISBN: 4364 2014 CP

Author: Michael T. Walsh

Publication Date: 2014

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Reinforcing steel in submerged concrete structures has generally been regarded as immune from corrosion given the limited availability of oxygen at the rebar surface for the cathodic reaction. As durability expectations and requirements for submerged RC structures have increased however the need for data associated with the actual condition and fate of the embedded reinforcing steel has increased. A series of autopsies was conducted on actual bridge piles decommissioned after a 60 year service life and a predictive computer model was developed for a partially submerged RC bridge pile. The corrosion rate of the steel in the decommissioned piles was evaluated based on direct measurement of corrosion-induced section loss. The actual corrosion rate was found to be substantial based an estimate of the initiation period derived from empirical and historical data. The corrosion rate of the reinforcing steel in the pile model was evaluated under varying degrees of depassivation. The rate was found to be small given uniform depassivation of the steel but substantial in cases that involved highly localized anodes even if the overall cathodic reaction rates were small. Additional predictive modeling indicated that the implementation of corrosion control measures in the splash/evaporation zone (e.g. pile jacketing) could in some instances increase vulnerability to corrosion of steel in the submerged zone. The findings of both studies were correlated for generalization in the prognosis of reinforcing steel in existing structures and the design and application of corrosion protection systems