Prediction of time dependent chloride transport in concrete structures exposed to a marine environment

Abstract A survey of 11 concrete bridges located in a marine environment at 0.65–48.65 years was examined in terms of chloride transport. As a result, the apparent diffusion coefficient ( D ) and the surface chloride concentration ( C S ) are time dependent; the D exponentially decreased with time and the C S increased in the form of a logarithm function to time. Using these data, governing equations for the D and C S were derived to predict the chloride transport in a long term. The time dependent model indicated the higher chloride ingresses in ordinary Portland cement (OPC) concrete than the time independent model, due to a build-up of the C S with time, but ground granulated blast furnace slag (GGBS) concrete indicated a similar range of the chloride ingresses, due to the rapid decrease in the D . To ensure the accuracy of the model that the present study suggested, the fitted model was compared to the well known model of the LIFE 365 together with a chloride profile obtained from an in-situ examination. Then it was found that the model in the present study well predicted the rate of chloride transport, while the LIFE 365 indicated a poor description of the chloride ingress in a long term, due to a constant C S and an overwhelming rapid decrease in the D .

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