A Lattice-type Model For Predicting The Chloride Diffusivity Of Concrete

Chloride diffusivity of concrete is one of the important parameters for the durability design and assessment of concrete. Therefore, it is necessary to determine the chloride diffusivity of concrete by experiments and theoretical methods.This paper attempts to predict the chloride diffusivity of concrete by the lattice-type model and to quantitatively evaluate the factors that affect the chloride diffusivity of concrete. Based on the principle of energy equivalence, an analytical relationship of chloride diffusivity between the beam element and continuum body is derived. By modeling concrete as a three-phase composite material, composed of aggregates, interfacial transition zone (ITZ) and cement paste, composite circle and ellipse element cells are presented for predicting the chloride diffusivity of concrete. A numerical solution for the chloride diffusivity of concrete is obtained by applying the finite element method. By comparing with the experimental results, the validity of the two composite element cell models is verified. Based on the numerical results, the effects of the maximum aggregate diameter, chloride diffusivity of ITZ, aggregate gradation, ITZ thickness and aggregate shape on the chloride diffusivity of concrete are evaluated. By selecting an appropriate square simulation domain to simulate the distribution of circular and elliptical aggregates and by combining lattice discretization with the finite element method, a direct method is developed for predicting the chloride diffusivity of concrete. Thus, the effect of the connectivity between ITZs on the chloride diffusivity of concrete is taken into account. Based on the numerical results, the effects of various parameters on the chloride diffusivity of concrete are evaluated, with special emphasis on the effect of aggregate shape on the chloride diffusivity of concrete.