Comparative study on the effect of steel and plastic synthetic fibers on the dynamic compression properties and microstructure of ultra-high-performance concrete (UHPC)

Abstract

Ultra-high-performance concrete (UHPC) shows great potential in constructing concrete structures subjected to impact and explosive forces. In order to make UHPC structures more ductile and cost-effective, this study used four-volume fractions of plastic synthetic fiber (PSF) instead of conventional steel fibers (SF) to prepare ultra-high-performance hybrid fiber-reinforced concrete (UHP–HFRC) with a total fiber weight of 2%. The dynamic compression properties at four strain rates were also investigated using a split Hopkinson pressure bar (SHPB) test. The results show that the addition of PSF reduces the flowability and compressive strength of UHPC but contributes significantly to the flexural strength of UHPC. UHP-HFRC demonstrates higher integrity under impact loading and significant sensitivity to strain rates. As the strain rate increases, both the dynamic compressive strength and dynamic growth factor of UHP-HFRC increase, with the optimal mixing ratio of PSF and SF being 1:3.Combined with the SEM and nanoindentation test results, it can be found that the bonding ability of PSF to the substrate is stronger, and the interface zone between PSF and the substrate is 10um smaller than that between sf and the substrate. It can be concluded that it is difficult for PSF to fully replace steel fiber in referencing UHPC, while hybrid fibers should be a good choice to produce excellent UHPC composite.