Effects of fiber geometry and cryogenic condition on mechanical properties of ultra-high-performance fiber-reinforced concrete

This study examined the effect of steel fiber geometry on the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) under cryogenic conditions (approximately −162 °C). For this, compressive and tensile tests were performed using UHPFRCs containing three types of straight steel fibers and one type of twisted steel fiber. To investigate the mechanical properties of UHPFRCs under various temperatures, mechanical tests were performed in three different conditions: ambient temperature, cryogenic temperature, and recovered ambient temperature. The test results demonstrated considerable increases in both the compressive strength and tensile performance, including strength and fracture energy, for UHPFRCs with straight fibers at the cryogenic temperature, whereas that containing the twisted fibers demonstrated the poorest energy absorption capacity at the cryogenic temperature, due to the fiber fracturing. Finally UHPFRCs containing longer straight fibers most effectively achieved excellent mechanical properties at the cryogenic temperature, compared to those with short straight and twisted fibers.