Influence of polypropylene and steel fibers on the mechanical properties of ultra-high-performance fiber-reinforced geopolymer concrete

Ultra-high-performance geopolymer concrete (UHPGPC) was investigated in this paper using microsilica and granulated blast furnace slag (GBFS) comprising polypropylene fiber (PF) and steel fiber (SF). The first group of mixing ratios was used to develop a control mixture with maximum compressive strength for this purpose. In the second group, nine mixtures were used to evaluate the effect of the fibers on the compressive strength, split strength, flexural strength, and modulus of elasticity of UHPGPC. Furthermore, the SEM analyses were performed to understand the mechanism of strength improvement based on the reaction products and micromorphology. The results indicate that the presence of PF in samples containing SF enhances its mechanical properties. Moreover, the results indicate that replacing PF with SF reduces mechanical strength while increasing durability.