Probabilistic model for predicting time-dependent chloride ingress in water repellent reinforced concrete structures exposed to marine environments

Corrosion of steel reinforcement due to chloride penetration is a major concern for the long-term durability of reinforced concrete (RC) structures exposed to marine environments. In practice, the time of the initiation of steel corrosion in RC structures exposed to marine environments is usually shorter than its designed service life. Therefore, supplementary countermeasures are often needed to protect the concrete as well as the internal steel reinforcement. Water repellent impregnation is one of the surface treatment methods that has been widely used in engineering practice for the durability enhancement of RC structures. However, up to date, little information is available on the durability design method due to lack of appropriate mathematical approach for analyzing the chloride diffusion process in a two-layer material. On this account, an explicit solution for predicting diffusion in a two-layer material based on Fick’s second law is provided in this study to predict the chloride ingress in water repellent concretes and validated by the finite element analysis (FEA) result. The time-dependency of both the diffusion coefficient and the surface chloride content are also taken into account. The calculation time of the developed solution is just a millionth of that needed for the FEA consumption. Therefore, based on this solution, the probabilistic analysis on the service life of RC structures exposed to marine environments can be conducted. In the end, a case study is also presented to illustrate how to implement the developed theoretical models for assessing the durability failure possibility of an actual port RC structure treated with water repellent agents.