Predicting the chloride diffusion in concrete incorporating fly ash by a multi-scale model

A prediction model was developed in this paper to quantify the effect of fly ash on the chloride diffusion process in concrete samples. To capture the hierarchical characteristics of constituents at multiple scales, the model adopted the general self-consistent (GSC) method to calculate the effective chloride diffusivity of fly ash concrete. Moreover, the proposed model adopted the Papadakis model to estimate the amount of hydration products of fly ash pozzolanic reaction as well as cement hydration. In addition, the chloride diffusivity of fly ash concrete was corrected by introducing the filling effect of unreacted fly ash particles and the aggregate tortuosity factor. Beside the theoretical modelling, this study also carried out RCM and RCPT tests on concrete samples with different replace ratio of fly ash, whose measurements were used to validate the proposed model. A good agreement was obtained between model calculations and experimental measurements demonstrates the proposed model can successfully characterize the effect of fly ash on chloride diffusion in concrete samples, which can be an effective means to assessing the durability of fly ash concrete materials and structures in practical engineering.