Mechanical and structural behaviors of ultra-high-performance fiber-reinforced concrete subjected to impact and blast

This study comprehensively investigates impact and blast resistances of ultra-high-performance fiber-reinforced concrete (UHPFRC) by considering various influential factors. At a material level, rate-dependent fiber pullout behavior, dynamic compressive behavior, and impact tensile and flexural behaviors were examined in detail, and the benefits of using UHPFRC to improve the impact resistance of ordinary concrete were discussed. It was obvious that (1) UHPFRC is able to dissipate much higher energy by impact than ordinary concrete with and without fibers, (2) the use of long straight steel fiber is effective in improving the impact resistance of UHPFRC compared to that of deformed steel fibers at high volume fractions, (3) fiber orientation significantly influences the impact resistance of UHPFRC: when more fibers are aligned in the tensile load direction, better impact resistance is achieved, and (4) size effect on the dynamic increase factor versus strain-rate relationship is insignificant. Impact and blast resistances of UHPFRC beams, slabs, columns, and composite structures were also examined at structural level, and several useful conclusions were drawn. (1) UHPFRC is favored for impact- or blast-resistant structures as compared with ordinary concrete due to its much better impact and blast resistance at identical dimensions, reinforcement configuration, and load magnitude, (2) the use of high-strength steel rebar provides the better blast resistance of UHPFRC beams or slabs as compared with that of normal-strength steel rebar, and (3) seismic detailing applied in UHPFRC columns leads to better blast resistance than is seen for columns without seismic detailing. Further research is suggested to address the remaining complicated problems or conflicts and to inspire proper design of structural UHPFRC members in an attempt to increase the use of UHPFRC.