Using nano-silica to improve mechanical and fracture properties of fiber-reinforced high-volume fly ash cement mortar

Abstract

Using nano-silica (NS) in cement-based materials has attracted extensive attention. However, whilst most studies focused on the hydration, fresh, mechanical and durability properties, there is limited information on the effect of NS on the fracture properties of fiber-reinforced high-volume fly ash mortars (HVFAM). In this paper, a series of experiments were carried out to evaluate the effect of NS on the fracture and mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced HVFAM, with the fly ash/binder ratio fixed at 50% by weight. Four NS/binder weight ratios of 0% 0.5%, 1.0% and 1.5%, and four PVA fiber volume dosages of 0%, 0.2%, 0.5% and 1.0% were adopted. Compared to 0.2–1.0 vol% PVA fiber-reinforced HVFAM without NS, the addition of 0.5 wt% NS could further increase the flexural strength, fracture energy, fracture toughness, critical crack tip opening displacement and brittleness index by 3–5%, 8–29%, 17–28%, 18–38% and 34–95%, respectively; the addition of 1.0 wt% NS could increase the flexural strength, fracture energy, fracture toughness, critical crack tip opening displacement and brittleness index by 4–9%, 15–41%, 26–46%, 18–48%, and 62–79%, respectively. The mineralogy and microstructure characterizations showed that the NS condensed the fiber/matrix interface. These findings provide insights into designs and applications of fiber-reinforced high-volume pozzolan cement-based materials with nano-particles.