A chloride diffusion model for cementitious material with pore-solution viscosity enhancement

Abstract

A promising approach to retard chloride attack has been proposed by increasing the pore solution viscosity in contrast to the traditional methods, but the dependence of chloride diffusion coefficient on viscosity has not been included in the current transport models. This paper presents a model for the diffusion of chloride in cementitious materials based on the viscosity-enhancing behavior of pore solution using viscosity modifying admixtures (VMAs). The parameters affecting the diffusion of chloride in the viscosity-enhancing solution are proposed to be the VMA molecular shape factor and VMA volume fraction based on the Maxwell approximation of spherical inclusions in the effective medium approximation theory. VMA shape factor is modeled with VMA molecular mass as a key variable. VMA volume fraction is calculated as a function of water-cement ratio, hydration age, initial VMA volume fraction, and VMA leaching residual fraction. This chloride diffusion model is developed and validated, which is based on the modification of Fick's second law and takes into account the pore solution viscosity-enhancing behavior and VMA-induced pore coarsening. This model differs from traditional models based on ion transport paths and provides a new reference for concrete durability design in terms of the intrinsic properties of the pore solution.