Compressive low-cycle fatigue behavior of nano-silica enhanced geopolymer composites with hybrid fiber reinforcement

This study investigates the fatigue behavior of nano-silica-enhanced geopolymer composites under uniaxial compression, with a focus on the influence of fiber reinforcement. Constant-amplitude fatigue tests were conducted at three stress levels to evaluate the effects of varying proportions of hooked steel and polypropylene fibers on failure modes, deformation characteristics, fatigue life, and damage evolution. The results indicate that an optimal balance of these fibers significantly enhances fatigue performance, whereas excessive fiber content leads to a decline. The most effective combination - 2 % hooked steel fibers and 0.2 % polypropylene fibers at a stress level of 0.7 - achieved the highest fatigue life improvement compared to ordinary concrete. Scanning electron microscopy (SEM) analysis confirmed the synergistic effects of fiber hybridization in improving composite performance. Furthermore, a novel fatigue damage assessment model was developed based on strain evolution, effectively capturing nonlinear damage progression and demonstrating strong alignment with experimental data. This research provides valuable insights for optimizing fiber-reinforced geopolymer composites and expanding their engineering applications