Synergy effect of hybrid steel-polyvinyl alcohol fibers in engineered cementitious composites: Fiber distribution and mechanical performance

Abstract

The fiber distribution is a crucial factor governing the superb strain-hardening and multiple cracking behavior of engineered cementitious composites (ECC). However, the desired uniform distribution of fibers is challenging in ECC with large amounts of binders and fibers, especially for hybrid fiber system. In the present study, we employed image analysis to investigate the fiber distribution characteristics in hybrid steel-polyvinyl alcohol (PVA) fiber ECC and its influence on the mechanical performance. Special attention was paid to the impact of additional steel fiber content and its size. The results show that the dispersion coefficient of PVA fibers in hybrid fiber system was at most 50% higher than that of mono fiber system. Fiber hybridization rendered more fibers distributed in smaller angles of 0°–40°, which helped to enhance the fiber bridging capacity. The addition of steel fibers significantly improved the flexural properties of ECC, with maximized strength at steel fiber content of 1.0% and maximized deformability at 0.6% dosage. The incorporation of steel fibers greatly enhanced the crack control ability of hybrid fiber ECC. The average crack width was reduced to 36.1 μm when the volume fraction of steel fiber gone to 1.0%. Furthermore, larger sized steel fibers played a more pronounced role in improving the fiber dispersion, fiber orientation and mechanical properties than that with smaller size. Synergy effect of hybrid steel-PVA fiber on fiber distribution and mechanical properties was revealed. The findings are expected to contribute to the blending ratio design of hybrid fibers and the selection of fiber size in preparing ECC. And the obtained robust ECC can provide strong support for performance enhancement and maintenance of building engineering.