Percolation of ITZs in Concrete and Effects of Attributing Factors

Abstract

In view of the importance of percolation of the interfacial transition zones (ITZs) in concrete to its transport properties, it is necessary to determine the ITZ percolation threshold for any aggregate gradation and ITZ thickness. This paper presents a numerical method for predicting the ITZ percolation threshold of concrete. To represent the mesostructure of concrete as realistically as possible, a simulation algorithm for the distribution of aggregate particles and ITZs in concrete with periodic boundary conditions is proposed. By analyzing and studying the numerical results, it is shown in this paper that, for a given aggregate volume fraction and element size, the ITZ percolation probability tends to be a constant for a sufficient number of simulations and that the slope of the ITZ percolation probability curve becomes vertical as the element size increases. Finally the results produced by the proposed numerical method are verified by experimental results obtained from the research literature. Based on the results presented in this paper, the effects of the ITZ thickness, the maximum aggregate diameter, and the aggregate gradation on the ITZ percolation threshold are evaluated in a quantitative manner. It can be concluded that the numerical method developed can be used to predict the ITZ percolation threshold with reasonable accuracy.