Synergism of steel fibers and polyvinyl alcohol fibers on the fracture and mechanical properties of ultra-high performance concrete

The influence of the volume fraction of steel fibers, polyvinyl alcohol (PVA) fibers and their hybrid fibers on the mechanical and fracture mechanical properties of ultra-high performance concrete (UHPC) was studied in this paper. To analyze the synergistic effect of steel fibers and PVA fibers on the deformation properties of UHPC, the gain ratio of mechanical parameters of hybrid fibers reinforced UHPC to steel fibers reinforced UHPC, obtained by two ways, equal total fibers volume fraction and equal steel fibers volume fraction. The results show that steel fibers and PVA fibers reduce the compressive strength of UHPC to some extent, and with the increasing of fibers volume fraction, the flexural-compressive ratio and tension-compression ratio increase gradually. The fracture mechanical properties of fibers reinforced UHPC were significantly is improved by the participation of steel fibers and PVA fibers, and the latter are superior to former in improving the deformation properties of UHPC. Except compressive strength, the mechanical parameters gain ratio of hybrid fibers UHPC to steel fibers UHPC calculated with equal steel fibers volume fraction is higher than the corresponding results of the equal total fibers volume fraction, which indicates that 0.25 v% PVA fibers as the modified component is mixed with steel fibers reinforced UHPC, can further improve its bending tensile and fracture mechanical properties.