Modelling the Effect of Microcracks on the Transport Properties of Concrete in Three Dimensions

This paper investigates the effect of microcracks on transport properties of concrete using a three-dimensional model. Concrete is idealised as consisting of aggregate particles (1-10 mm, 60% vol.), cement paste matrix and microcracks with widths of 1-50 mu m. Using aligned meshing, aggregate particles are discretised with tetrahedral elements and the microcracks are incorporated as interface elements. The microcracks are either bond cracks at the aggregate-paste interface or matrix cracks that span nearest neighbouring aggregate particles. A finite-element model is applied to simulate diffusion and permeation. The model is used to perform a sensitivity analysis to examine the effect of microcrack width, density and percolation. It is found that the effect of microcracks is more pronounced for concretes with denser matrix. Furthermore, the effect of microcracks in non-percolated networks increases up to a finite limit, the value of which is independent of crack width but depends on other crack characteristics and transport property of the matrix. In all cases, microcracking has a greater effect on permeation than diffusion and this is more pronounced for percolated crack networks.