Sensitivity analysis of chloride ingress models: Case of concretes immersed in seawater

Reinforced concrete structures exposed to a marine environment deteriorate as a result of chloride-induced corrosion of the steel rebars. A wide variety of models to predict chloride ingress in water-saturated concretes have already been developed to understand and predict the underlying transport processes. The majority of these models focus on the initiation period of chloride-induced corrosion in order to predict the service life of reinforced concrete structures. They require information on the concrete properties, the concrete cover thickness, the definition of corrosion initiation, etc. These models combine well-known mechanisms, i.e. diffusion of relevant ions, electrical interactions between ions, and interactions between these ions and the solid matrix. As the mechanisms to consider are well identified, the objective here is to perform a probabilistic analysis of some common models. A general framework is proposed to calculate a reliability service life for reinforced concrete structures under chloride attack in case of continuous immersion in seawater. Then a sensitivity analysis is performed in terms of the most relevant mechanisms and influencing input data. The results point out the crucial role of the concrete cover thickness, the critical chloride content and, to a lesser extent, the effective chloride diffusion coefficient. The difficulty to use the Freundlich isotherm for chloride binding is highlighted; it seems to be due to the non-linearity of the description which is still difficult to control.