Influence of cement matrix porosity on the triaxial behaviour of concrete

This article focuses on the influence of the cement matrix porosity on the triaxial behaviour of concrete in the presence of high confining pressures. It offers new experimental results on two concretes, respectively a high performance concrete (HPC) and a low performance concrete (LPC). These results complement recent studies on ordinary concrete (OC), in using the same large-capacity triaxial press. This paper serves to better characterise the behaviour of these 3 concretes, whose porosities are very different in terms of volume and size; moreover, it emphasises that the contribution of cement matrix strength (mainly linked to its porosity) decreases at high confining pressures and that concrete behaviour is governed by the granular skeleton, even when the capillary porosity is low or the entrapped air porosity is high. To reach this level of residual behaviour, higher confining pressures are needed for HPC, even if the amount of porosity compacted is smaller.