Role of porosity in controlling the mechanical and impact behaviours of cement-based materials

This work deals with the influence of porosity on the tensile, the compressive and the impact behaviours of two fine cementitious mortars—one with silica fume and one without. The addition of silica fume is shown to change the pore size distribution. The mix without silica fume is characterized by porosity at the scale of the grains of fine sand (approximately 100 μm), while silica fume addition results in a more porous matrix with pore sizes of millimetre-length size. The mortar with silica fume shows a higher quasi-static compressive and flexural strength whereas the mix without silica fume is observed to be less compressible (by irreversible reduction of volume) under heavy confinement pressure (quasi-oedometric tests) and shows better ballistic performance. A numerical simulation of the impact tests employing the Krieg, Swenson and Taylor model, which accounts for both deviatoric and volumetric inelastic behaviour of the material, was undertaken using the data from quasi-oedometric tests. These calculations follow the experimental results and confirm the influence of the macroscopic porosity on the impact performance of cement-based materials.