Strain hardening ultra-high performance fiber reinforced cementitious composites: Effect of fiber type and concentration

An experimental work was carried out to investigate the effects of micro-steel, hooked-steel, and micro-glass fibers on the mechanical properties and ductility of Ultra-high Performance Cementitious Composites (UHPC). The aspect ratios of the of micro-steel, hooked-steel, and micro-glass fibers were 7.17, 55 and 722, respectively. At a water-binder ratio of 0.195, three groups of UHPCs containing 0.25, 0.5, 0.75, 1, 1.5, and 2% fiber volume fractions were produced and tested for compressive strength, splitting tensile strength, modulus of elasticity, flexural strength, load-displacement behavior, fracture energy, and characteristic length. Test results revealed that the mixes with 2% of micro steel fiber exhibited the best compressive strength of 180 MPa as well as the highest splitting tensile strength and modulus of elasticity. However, the mixes with 2% of hooked steel fiber displayed a strain hardening load-displacement behavior with a substantially enhanced ductility. The results also showed that the beneficial influence of using micro glass fiber began to decrease after 1.5% of the fiber volume.