Impact of various fibers on mode I, III and I/III fracture toughness in slag, fly Ash, and silica fume-based geopolymer concrete using edge-notched disc bend specimen

There is ongoing research aimed at developing cement-free concrete that not only exhibits enhanced mechanical properties but also incorporates environmentally sustainable materials. Geopolymer represents a novel inorganic cementitious material recently developed, which facilitates utilising resources derived from solid waste from industrial operations. Geopolymer is considered an ecologically sustainable substitute for Ordinary Portland cement. It significantly reduces energy usage and minimizes carbon dioxide emissions, contributing to environmental sustainability. This study investigates the combined influence of granulated blast furnace slag, fly ash and silica fume on geopolymer concrete (GC) fracture resistance. This research aims to assess the fracture toughness of GC under modes I, III, and I/III loading conditions. Four distinct fiber types, comprising both short and long steel fibers and polypropylene fibers at 1.5 % dosage, were utilized to mitigate brittleness and enhance the ductility of the material. In addition, the microstructure of GC was analysed using X-ray diffraction and scanning electron microscopy. Findings reveal that the inclusion of short and long polypropylene fibers in GC increased mode I fracture toughness by 20.98 % and 29.62 %, respectively, compared to the fiber-free specimen, with long fiber showing superior performance due to its enhanced crack-bridging ability. Steel fibers provided a more pronounced improvement, with short and long fibers increasing mode I fracture toughness by 77.77 % and 109.87 %, respectively, attributed to their capacity to hinder crack propagation and enhance fracture toughness. The long fibers exhibited an excellent fracture resistance than the short fibers and mode III is more critical than the mode I loading.