Probabilistic Model for Service Life Prediction of Water Repellent RC Structures in Marine Environments

Corrosion of steel reinforcement due to chloride penetration is a major concern for the long-term durability of reinforced concrete (RC) structures. In practice the time to the initiation of steel corrosion in RC structures exposed to marine environments is short. Therefore, supplementary countermeasures are usually needed to protect the concrete as well as the steel reinforcement. Water repellent impregnation is one of the surface treatment methods that are widely used in engineering practice for the durability enhancement of RC structures. This paper proposed theoretical solutions for predicting the service life of water repellent RC structures in marine environments considering various uncertainties and the time-dependency of the design variables. An explicit solution is provided to solve the Fick’s second law to predict the chloride ingress in a two-layer concrete material (i.e., consisting of water repellent concrete and normal concrete). Monte-Carlo simulation is adopted to describe the random characteristics of various design parameters such as the concrete cover depth, the diffusion coefficient of concrete, the surface chloride content and the impregnation depth of water repellent agent. As a result, the time-dependent probability of steel corrosion can be predicted and the service life of the structures can be defined given a specific confidence level. A case study is also presented to illustrate how to implement the theoretical models to assess the durability failure possibility of an actual port RC structure treated with water repellent agents.