Flexural behavior and impact resistance of high-strength concrete containing micro-steel and macro-polyolefin fibers

This paper investigates the effects of micro-steel fibers (MSF) and macro-polyolefin fibers (MPF) on the flexural behavior and impact resistance of high-strength concrete (HSC). For this purpose, eleven mix compositions with four different volume fractions of MPF (0.25%, 0.5%, 75% and 1%), four volume fractions of MSF (0.25%, 0.5%, 75% and 1%), and also three mixes with the combination of micro-steel and macro-polyolefin fibers at a total fiber volume fraction of 1.0% were designed. The compressive strength, post-crack behavior, flexural behavior, and impact resistance were studied. The highest equivalent flexural strength ratios were achieved in hybrid mixes combining MSF and MPF, reaching up to 79.1% for the M25-75 mix, indicating the synergistic benefits of fiber hybridization. Moreover, the flexural performance test indicated that the energy absorption capacity was significantly larger for the hybrid mixes. The results showed that while MPF mixes exhibited higher impact resistance at the first crack for a given fiber volume fraction, the hybrid fiber mixes displayed the best overall impact resistance at failure.