Synergistic effects of limestone powder and waste rubber on the mechanical and environmental performance of geopolymer concrete

Abstract Geopolymer concrete (GPC) has gained popularity in recent times as a more environment friendly solution to the ordinary Portland cement concrete (OPCC) and is accepted as one of the sustainable materials in the field of construction. Although GPC has a comparable mechanical performance to OPCC, its brittle failure mode remains a concern in structural applications. This study aimed to assess the synergistic impact of waste tire rubber aggregates and limestone powder (LSP) on the mechanical and environmental properties of fly ash and ground granulated blast furnace slag (GGBFS) based geopolymer concrete. Rubber aggregates replaced 10%, 20%, and 30% of the coarse aggregates, while LSP replaced 15%, 30%, and 45% of the precursors. Mechanical performance was evaluated through compressive, split tensile, and flexural strength tests, along with modulus of elasticity and toughness derived from stress–strain analysis. Chemical phase composition was examined through X‐ray diffraction (XRD), and sustainability performance was assessed using life cycle impact assessment (LCIA). The mix containing 30% rubber and 30% LSP compared to the mix with 30% rubber and no LSP showed 34%, 3.6%, and 1.3% improvements in compressive, split tensile, and flexural strengths, respectively. The LCIA results showed reductions of 67% in global warming potential (GWP) and better results among other ecological impact indicators compared to OPC concrete. It was noted that the combined use of LSP and rubber aggregates significantly enhanced strength and toughness while improving the environmental performance of GPC. This study provides a feasible design approach for sustainable and ductile geopolymer concrete incorporating industrial and recycled waste.