Probabilistic corrosion initiation assessment of marine concrete bridge components via exposure tests and numerical simulations

Durability performance is crucial for the premaintenance of marine concrete bridges. To assess the probability of corrosion initiation, long-term exposure tests are conducted first to obtain the chloride diffusion properties. The chloride binding coefficients, surface chloride concentrations and age reduction factors are analyzed on the basis of the test results. A stochastic chloride diffusion model and a numerical simulation method for chloride diffusion are established. The influences of the actual aggregate morphology on chloride diffusion are investigated via numerical simulations. Finally, a method for assessing the probability of corrosion initiation is developed, and a case study is completed. The results show that in the atmosphere zone, the chloride binding coefficient increases with depth, whereas the growth rate decreases. In the splash zone, the binding coefficient first decreases but then increases when the depth is less than 10 mm. After that, the binding coefficient increases rapidly to approximately 0.90 and remains stable. With increasing exposure period, the surface chloride concentration increases logarithmically. The age reduction factor is 0.6129 for the reported exposure tests. The incorporation of actual aggregate leads to randomness in the chloride concentration at the same depth. There is a critical depth in concrete component, before which the blocking effect of aggregate increases the chloride concentration and after which the blocking effect decreases the chloride concentration. The critical depth increases with increasing exposure period. Through the proposed method for assessing the probability of corrosion initiation, the residual durability life, which incorporates the randomness of chloride diffusion behavior and the critical chloride concentration, can be obtained, which is crucial for maintenance decision-making. According to the case study, the tensile stress level of the concrete has a significant influence on the residual durability life, and the residual durability life of the corner rebar is obviously lower than that of the noncorner rebar.