Reliability analysis of chloride penetration in saturated concrete

Corrosion of reinforcement in concrete is a major durability problem of reinforced concrete structures. The corrosion is initiated by chloride penetration into the concrete, which is a diffusion-controlled process involving many complex physical and chemical mechanisms. Large random variation has shown in the corrosion damage of reinforced concrete structures, and there is a pressing need to develop a reliability analysis method for chloride penetration and for the onset of steel corrosion in concrete. In order to conduct a reliability analysis, a comprehensive material model for chloride concentration is developed and described, and some of the model parameters (water-cement ratio and curing time) are selected as random variables. By including uncertainties in the selected variables, the chloride penetration front at a point in time can be represented by a time-dependent probabilistic distribution. Similar to the concepts of supply and demand used in structural reliability analysis, the chloride penetration front at a target level (depth) with respect to time can be represented by the probability distribution of crossing the target level. A detailed description of the basic concepts and numerical examples are given. To include the effect of uncertainties of the material parameters, a recently developed Monte Carlo simulation program was used in numerical examples.