increased by about 40% by increasing the strain-rate from 10 4 to 10 1/s. The fiber volume content has no significant effect on the strain-rate sensitivity. In contrast to the quasi-static loading condition, the use of twisted steel fibers reduced the tensile strength by about 10% compared to straight steel fibers at a high strain-rate of 10 1/s. UHPFRC exhibited approximately twice the strength flexural strength and three or four times higher dissi- pated energy than conventional fiber-reinforced concrete (FRC).