Abstract
This paper presents a review of the chloride penetration process in concrete structures. It includes an examination of the mechanisms controlling chloride penetration and corrosion in concrete, and an assessment of service-life modeling of concrete structures exposed to chloride penetration. It is shown that important progress have been achieved in understanding the controlling mechanisms, but at the same time, much work needs to be done. It is well known now that beside diffusion, several other mechanisms can be involved in the chloride penetration process. These mechanisms include absorption, permeation, moisture flow and evaporation, and chloride binding. Some of these mechanisms have been included in chloride penetration models. However, there is still a substantial lack of reliable data to improve the accuracy of important parameters, describing the mechanisms of chloride penetration. Such parameters include chloride thresholds, parameters describing the dependency of the diffusion coefficient on time, chloride binding coefficients, and parameters describing non-saturated water flow. Service-life models range from overly simplistic to very sophisticated models. Simple models describe chloride penetration as a diffusion process with constant diffusion coefficient and constant chloride concentration at the exposed concrete surface, thus overlooking significant mechanisms affecting chloride penetration. Sophisticated models account for mechanisms other than diffusion, but end up requiring a lot of input parameters, which are unavailable or highly uncertain making the predictions uncertain.
