Effect of crumb rubber and polyethylene fiber on the strength and toughness of fly ash/slag-based geopolymer concrete

Although geopolymer concrete has been regarded as an eco-friendly alternative to traditional concrete, it exhibits the same features of high brittleness or low ductility as traditional concrete. To address these challenges and promote sustainability, this study investigated the effects of crumb rubber (CR) and polyethylene (PE) fiber on the physical properties, strength, and toughness of fly ash/slag-based geopolymer concrete, in which CR produced from recycled rubber was replaced by natural sand at volume fractions of 5 %, 10 %, and 15 %, while PEF was added at volume fractions of 0.25 %, 0.5 %, and 0.75 %. The test results show that while the mechanical strength of CR specimens was low, their toughness and failure characteristics improved. PEF greatly enhanced the mechanical strength and toughness, which enhanced the failure mode. Notably, the synergistic impact of mixing CR and PEF produced better results than using these toughening materials separately, hybrid mix of 5 % CR and 0.75 % PEF were found to provide optimum toughness and moderate strength. These results were validated by microstructural analysis, highlighting the enhanced bonding with PEF and the negative impact of excessive CR on the concrete matrix.