Effect of silica fume, steel fiber and ITZ on the strength and fracture behavior of mortar

Two sets of parameters known to affect the quality and thickness of the interfacial transition zone (ITZ), i.e. water/binder ratio and content of silica fume were varied in a series of mortars without and with steel fiber. Compressive and three-point bending tests were performed and the dissipated energies were calculated. Nanoindentation characteristics of the steel fiber–matrix and fiber–matrix-aggregate interfacial zones in the steel fiber reinforced mortars were studied. Influence of water/binder ratio, steel fiber, silica fume and ITZ on the strength and toughness of the mortar was analyzed, respectively. It is found that mortar compressive strength can be increased with low volume addition of steel fiber if the air content is well controlled; the interfacial characteristic and microstructural morphology near the fiber surface play a critical role on the three-point bending strength and the toughness of the steel fiber reinforced mortar.