Cementitious Composites with Hybrid UHMWPE and CF/PP Fiber: A Study on Compressive, Tensile, Flexural and Impact Performance

Ultra-high molecular weight polyethylene (UHMWPE) fibers have recently emerged as a promising reinforcement material in fiber-reinforced concrete (FRC). To investigate the synergistic effects and reinforcing mechanisms of fibers with different elastic moduli within the concrete matrix, a series of hybrid fiber-reinforced concrete (HFRC) specimens were prepared by incorporating 0.25 vol%, 0.5 vol%, and 0.75 vol% carbon fibers (CFs) or polypropylene (PP) fibers into concrete containing 1 vol% UHMWPE fibers. The mechanical performance of the prepared composites was systematically evaluated through compressive, splitting tensile, flexural, and drop-weight impact tests. The experimental results indicate that concrete reinforced solely with UHMWPE fibers exhibits higher compressive strength but lower tensile strength, flexural strength, ductility, and impact toughness than the hybrid fiber systems. For both UHMWPE-CF and UHMWPE-PP hybrid concretes, the initial cracking impact resistance and failure impact resistance increased progressively with increasing CF or PP content. At equivalent fiber volume fractions, UHMWPE-PP hybrid concrete demonstrated superior resistance to initial cracking, whereas UHMWPE-CF hybrid concrete exhibited better post-failure impact resistance. Furthermore, fractal theory was employed to quantitatively characterize the impact damage behavior of HFRC specimens. The impact damage evolution equation is established by using the two-parameter Weibull distribution model. The findings provide theoretical and experimental support for the design and optimization of hybrid fiber-reinforced concrete subjected to impact loading.