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A differential effective medium scheme for the chloride diffusivity of concrete with spheroidal aggregate particles is presented. By taking the interfacial transition zone (ITZ)-coated aggregate particle as an "equivalent aggregate particle," the three-phase concrete is reduced to a two-phase composite material. The differential effective medium theory is then adopted to derive an analytical approximation for the chloride diffusivity of concrete. After the validity of the analytical approximation is verified with two sets of experimental results, the effects of various key factors on the chloride diffusivity of concrete are evaluated quantitatively. Numerical results indicate that the chloride diffusivity of concrete increases with an increase in chloride diffusivity and thickness of ITZ, but decreases by increasing the aggregate aspect ratio and maximum aggregate diameter. It is also found that the aggregate gradation has a significant influence on the chloride diffusivity of concrete.

The purpose of this paper is to present a lattice method for predicting the Youngs modulus of concrete with two types of elliptical aggregate. After distributing fine and coarse aggregates within a rectangular unit, the finite element method is adopted to estimate the Youngs modulus of concrete. Compared with previous studies, the method considers the aggregate shape effect and the difference in Youngs modulus between fine aggregate and coarse aggregate. After the validity of the method is verified with two sets of experimental results, the effects of various factors on the Young s modulus of concrete are quantified. It is found that the Young's modulus of concrete increases with an increase in aggregate aspect ratio, minimum aggregate diameter, or both, but decreases by increasing the interfacial transition zone thickness. It is also found that the maximum aggregate diameter and aggregate gradation have little effect on the Young's modulus of concrete.