Present limitations of models for predicting chloride ingress into reinforced concrete structures

Abstract
Models to predict chloride ingress are numerous but all of them have serious limitations that restrict the present use for long term predictions. An overview is given of the fundamental differences between various models, from those based on Fick's 2nd with constant or time-dependent diffusion coefficients and surface chloride contents, to those based on chloride transport equations with or without a multi-species approach. The key advantages and limitations of each type of model are identified and the research needs are summarized and discussed. The three main limitations are shown to be (i) the lack of understanding the time-dependency of the apparent chloride diffusion coefficients, (ii) the lack of good long-term data, the chloride content increase with time close to the exposed surface and (iii) the difficulties in quantifying the boundary conditions for sophisticated ingress models.