Dynamic mechanical properties of steel-polypropylene hybrid fiber reinforced concrete

Fibers with high and low elastic modulus present different crack resistance mechanisms, and reasonable use of hybrid fibers can produce synergistic effects. However, limited research exists on the dynamic mechanical behavior of hybrid fiber-reinforced concrete. Therefore, in this study, steel fiber (SF) content, polypropylene fiber (PP) content and impact voltage were selected as variable parameters, and the dynamic loading test of steel-polypropylene hybrid fiber reinforced concrete (SPFRC) with 16 diverse mix proportions was carried out by electromagnetically-driven split Hopkinson pressure bar (SHPB) device. The stress-strain curves of SPFRC under diverse design parameters were measured, and the effect of diverse design parameters on the dynamic mechanical properties was analyzed. The research shows that with the addition of fibers, the failure mode of concrete gradually transforms from brittleness to plasticity. As the single fiber content increases, the peak stress, peak strain and energy consumption of specimen increase. Under the same impulse voltage and different contents of PP, the dynamic peak stress of specimens S 1.5 P 0.1 shows the largest increase, all exceeding 9 %, the hybrid fiber-reinforced concrete specimens always show the largest increase in the dynamic peak strain, all exceeding 17 %. Under the same fiber content, SPFRC displays apparent strain rate effect as the strain rate increases. Based on the traditional HJC constitutive model, an improved HJC dynamic constitutive relation of SPFRC is proposed, which provides a suitable basic model for the deformation of SPFRC under high-speed impact load. • The impact test results of SPFRC were measured. • The failure modes of SPFRC specimens under 16 kinds of combinations were observed. • The relationships between design parameters and dynamic response were analyzed. • The strengthening mechanism of steel-polypropylene hybrid fiber was revealed. • The improved HJC dynamic constitutive model of SPFRC was proposed.