Thickness of interfacial transition zone and cement content profiles around aggregates

Abstract

Interfacial transition zones (ITZ) in concrete constitute the weakest link in the concrete matrix and significantly affect the properties of concrete. To evaluate quantitatively the effect of ITZ on the physical and mechanical behaviour of concrete, it is imperative to characterise the microstructure of ITZ. The intention of this paper is to investigate the characteristics of ITZ microstructure in a statistical manner. In this paper, an algorithm is developed to simulate the distribution of cement particles between aggregates in concrete. After verifying the developed algorithm with experimental data, models for the thickness of ITZ and the cement area density between aggregates are developed as a function of the water-to-cement ratio, maximum cement diameter and the distance from the aggregate surface. It is found that the thickness of ITZ is in a range of 9 to 51 μm for normal concrete. A merit of the developed models is that they are closely related to design parameters of concrete used by practitioners. It is concluded that the thickness of ITZ and cement content profiles around aggregates can effectively explicate the characteristics of ITZ microstructure.