ITZ volume fraction in concrete with spheroidal aggregate particles and application: Part I. Numerical algorithm

When the interfacial transition zone (ITZ) is treated as a separate phase, the ITZ volume fraction plays an essential role in determining the physico-mechanical properties of concrete. The intention of the present paper is to develop a numerical algorithm for the ITZ volume fraction in concrete with spheroidal aggregate particles. By applying a contact function for two spheroidal aggregate particles and introducing periodic boundary conditions, the distribution of spheroidal aggregate particles with various sizes within a cubic element is implemented. The Monte Carlo method is then adopted to evaluate the ITZ volume fraction. After the validity of the developed numerical algorithm is verified with the analytical solution for the ITZ volume fraction in concrete with spherical aggregate particles, the effects of various factors that affect the ITZ volume fraction are evaluated through sensitivity analysis. It is found that the ITZ volume fraction increases with the increase of the ITZ thickness, but decreases with the increase of the maximum aggregate diameter and the aspect ratio of spheroidal aggregate particles. It is also found that the aggregate gradation has a significant influence on the ITZ volume fraction. The paper concludes that the numerical algorithm developed in the paper can predict the ITZ volume fraction with reasonable accuracy.