Experimental study on the flexural fatigue performance of slag/fly ash geopolymer concrete reinforced with modified basalt and PVA hybrid fibers

Geopolymer, owing to its inherent low-carbon emission advantages, emerges as a potential substitute to diminish reliance on high-carbon-emitting Portland cement. Nonetheless, similar to ordinary Portland cement concrete, geopolymer concrete tends to exhibit brittle fracture under cyclic bending loads. To improve its flexural fatigue performance, this paper incorporated the modified basalt (MB) fiber and PVA fiber in hybrid form into the geopolymer concrete. The flexural fatigue behavior of hybrid fibers reinforced geopolymer concrete was investigated, with a focus on the influence of varying hybrid fibers volume fractions. Digital Image Correlation technology was utilized to accurately track the evolution of crack length and the local strain field during the fatigue failure process. The results revealed that the incorporation of both MB and PVA fibers effectively delayed the initiation and propagation of cracks, leading to a more complex path of fatigue cracks. The PVA fiber demonstrated significant efficacy in inhibiting microcracks, while the MB fiber played a crucial role in controlling the expansion of macroscopic cracks. When the proportion of MB fiber was predominant in the hybrid mix, the crack development pattern mirrored that of samples containing MB fiber alone, exhibiting a greater extent of crack length. At a volume fraction of 0.9% for MB fiber and 0.2% for PVA fiber, a significant improvement in the fatigue life of the concrete was observed, resulting in a remarkable 136.23% increase compared to the control. This study has developed geopolymer concrete featuring enhanced crack resistance and superior flexural fatigue endurance under cyclic loading, promoting the application of environmentally friendly building materials in practical engineering.