Study of interfacial microstructure, fracture energy, compressive energy and debonding load of steel fiber-reinforced mortar

Abstract

The properties of the interfacial transition zone (ITZ) of steel fiber and the bulk matrix were quantified using the backscattered electron imaging analysis (BSE-IA) and the scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and their relationship with the mechanical properties of steel fiber-reinforced mortars was studied. The water and binder ratio (w/b) of mortar, the amount of silica fume and steel fiber were varied. From the quantitative analysis, a higher build-up of calcium hydroxide was found from the steel fiber’s interface up to 2 or 4 μm distance away and its build-up was reduced with the 10% cement replacement by silica fume. Porosity in the ITZ and bulk matrix decreased the fracture energy, compressive energy and debonding load of steel fiber-reinforced mortar. However, its effect became marginal if a substantial amount of C–S–H or steel fibers appeared in the ITZ and bulk matrix, which increased the studied mechanical properties.