Binding capacity and diffusivity of concrete subjected to freeze-thaw and chloride attack: A numerical study

Existing concrete structures in cool coastal areas are prone to be attacked by both chloride penetration and freeze-thaw cycles (FTCs). This study establishes a multi-phase and multi-component ionic transport model for concrete serving in cold-climate coast or ocean engineering, aiming at further exploring chloride transport mechanism under freeze-thaw cycles in a quantitative manner. Unlike the most of existing work, herein the time-varying porosity is described and involved in both the binding isotherm and diffusion coefficient to consider the pore evolution induced by FTCs. By solving the modified mass conservation equations, the time-dependent relationship between the bound and free chlorides as well as the spatial-temporal distributions of multi-species is obtained by using this model, and its reliability is validated against third-party experimental data. Parametric analysis is carefully performed on a series of significant influencing factors (i.e., water-to-cement ratios, hydroxyl concentrations, external chloride concentrations and internal temperature variations), which affect chloride binding remarkably during freeze-thaw actions. Bayesian sense is applied to combine the common regularity of numerical models and individual information of experimental by updating the penetration depth, which can calculate a more reasonable penetration depth.