Study on Mechanical Properties and Mechanism of Special-Shaped Cross-Section Polypropylene Fiber Reinforced Shotcrete

In order to study the mechanical properties and reinforcement mechanism of special-shaped cross-section polypropylene fiber reinforced shotcrete, compressive, splitting tensile, and flexural tests were conducted on benchmark shotcrete and special-shaped cross-section polypropylene fiber reinforced shotcrete, and SEM micro scanning tests were carried out. The results showed that the addition of special-shaped cross-section polypropylene fibers can improve the compressive strength, splitting tensile strength, and flexural strength of sprayed concrete. The most significant improvement was observed when the fiber content was 6 kg/m³, the compressive strength at 1 day, 3 days, and 28 days, splitting tensile strength at 28 days, and flexural strength at 28 days were increased by 13.9%, 5.8%, 5.1%, 26.8%, and 8.1%, respectively, compared to the benchmark concrete group. The toughness of sprayed concrete is enhanced by adding special-shaped cross-section polypropylene fibers, and the failure mode changes from brittle to ductile. Special-shaped cross-section polypropylene fibers can reduce the proportion of large pores in the concrete matrix, improve the compactness of the matrix, and reduce the width and number of microcracks at the interface between coarse aggregates and matrix, provide a bridging effect to absorb destructive energy, and enhance the strength and toughness of sprayed concrete. The research results can provide a theoretical basis for the application of special-shaped cross-section polypropylene fiber reinforced shotcrete.