Multi-scale modelling and statistical analysis of heterogeneous characteristics effect on chloride transport properties in concrete

The transport properties of concrete are closely related to its heterogeneous features. In this study, by considering the multi-scale microstructural characteristics, the chloride transport properties of concrete are comprehensively analysed. Based on the selected representative elementary volumes from bulk cement paste to concrete, a multi -scale predictive model was first proposed for diffusivity prediction of bulk cement paste, mortar and concrete. By taking the hydration process, the presence of sand/interfacial transition zones (ITZs) and the aggregate shape into account, the predicted diffusivities of each scale were validated against the experimental results. To further analyse the weights of different heterogeneous characteristics on chloride transport properties of cementitious materials, a statistical analysis method (principal component analysis) was then adopted based on the modelled results. The analysed results indicated that the capillary pore and C-S-H parts dominate the diffusivity estimation of bulk cement paste, and the consideration of ITZ and multi-species ions interaction can enhance the prediction accuracy for diffusivities of mortars and chloride penetration depths in concrete, respectively. The proposed multi-scale framework provides a novel perspective to study the chloride penetration in concrete by considering the effects of both the multi-scale microstructural characteristics and multi-species interactions, which can also enhance the understanding of deterioration mechanisms for reinforced concrete structures serving in a complex or marine environment.