Dynamic behavior of HPFRCC at high strain rate: the fiber role

High Performance Fiber Reinforced Cementitious Composites are characterized by high ductility and tension hardening behavior in statics. The high energy absorbed during the fracture process is associated to multiple cracking and pull-out phenomena. The good response highlighted in the static field by many researchers suggests to use these materials also for dynamic loading applications. However, very few investigations have been carried out in order to guarantee the improvement of the dynamic response. Current understanding of the impact resistance of cementitious composites, and especially of high-strength concrete, is very limited. An experimental research aimed at contributing to the understanding of the behavior of advanced fiber-reinforced cementitious composites subjected to low and high strain rates was carried out. The material investigated is a steel fiber reinforced mortar. Straight high carbon steel micro-fibers were used. The material behavior was investigated at three strain rates (0.1, 1 and 150 s−1) and the tests results were compared with their static behavior. Tests at intermediate strain rates (0.1–1 s−1) were carried out by means of a hydro-pneumatic machine (HPM), whilehigh strain rates (150 s−1) were investigated by exploiting a modified Hopkinson bar (MHB). A comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibers on the peak strength and post-peak behavior at high strain rates.