United States Department of Transportation
i
Durability performance of submerged concrete structures - phase 2.
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2015-09-01
[PDF-3.12 MB]
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Abstract:This project determined that severe corrosion of steel can occur in the submerged
portions of reinforced concrete structures in marine environments. Field studies of decommissioned
pilings from Florida bridges revealed multiple instances of strong corrosion localization, showing
appreciable local loss of steel cross-section. Quantitative understanding of the phenomenon and its
causes has been developed, and a predictive model was created based on that understanding.
Corrosion rate estimates and the extent of corrosion localization from the field observations were
consistent with the results of the predictive model. The most likely explanation for the phenomenon is
that cathodic reaction rates under oxygen diffusional limitation that are negligible in cases of uniform
corrosion can support substantial corrosion rates in cases of localized corrosion. Modeling projected
that, with use of sacrificial anode cathodic protection, corrosion in the submerged zone could be
virtually eliminated, together with significant reduction of the rate of corrosion damage progression in
the low elevation zone above water. Continuation work should be conducted to define an alternative
limit state other than visible external cracks and spalls for submerged reinforced concrete, and for
determination of the possible structural consequences of this form of corrosion, as well as to assess
the technical feasibility and cost/benefit aspects of incorporating protective anodes in new pilings.
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