Geometry of crack network and its impact on transport properties of concrete

This paper investigates the crack network geometry in concretes subjected to cyclic axial loading. A total of 24 cylinder specimens of two concretes (OPC and HVFC) were cast and eight levels of cracking extents were created for each concrete. Disks were extracted from the cylinders and the crack geometry was evaluated for sections both perpendicular and parallel to loading. The crack geometry is quantified by crack density, length, orientation and connectivity. The crack length is found to obey log-normal distribution, and the crack orientation and connectivity are correlated strongly with crack density. The volumetric density is identified as a consistent parameter to describe the impact of crack network on altered transport properties. The effective porosity, capillary sorptivity, gas permeability and electrical conductivity all have strong dependence on crack density. In particular, the gas permeability is proved to be sensitive to both small range and large range of crack density.