Mechanical and sustainability assessment of sugarcane bagasse ash and polypropylene fiber in Class C fly ash geopolymer concrete

Abstract

• Partial replacement of fly ash with 5–10 % SCBA improved compressive, tensile, and flexural strengths of geopolymer concrete. • 5 % SCBA achieves highest compressive and tensile strengths with improved matrix density. • 10 % SCBA shows maximum flexural strength in ambient-cured GPC. • UPV and SEM results show that SCBA-based geopolymer concrete exhibits a denser microstructure with diminished internal defects. • Sustainability ratios indicate 5 % SCBA for strength-to-cost and strength-to-carbon efficiency. This study investigates the combined effect of sugarcane bagasse ash (SCBA) and polypropylene (PP) fibers in Class C fly ash-based geopolymer concrete (GPC) under ambient curing, focusing on mechanical performance, microstructural behavior, and eco-efficiency. Mixes with 0 %, 5 %, and 10 % SCBA were evaluated, and the results show that SCBA-5 substitution produced the optimum balance of properties, with compressive strength improving by 41 % at 28 days, splitting tensile strength by 29 %, and fracture energy by 56 % compared with the control. Meanwhile, SCBA-10 enhanced flexural strength by 9.3 %, although this was accompanied by higher brittleness. SEM and UPV analyses revealed that SCBA-5 refined the pore structure, strengthened fiber-matrix bonding, and improved crack resistance, whereas SCBA-10 exhibited clustered gel phases and larger pores that restricted further benefits. Sustainability analysis demonstrated that SCBA-5 improved the strength-to-embodied carbon ratio by 52 % and the strength-to-cost ratio by 53 %, while achieving a 25–30 % reduction in embodied CO₂ emissions compared with Portland cement concretes of similar grade. This is the first study to integrate SCBA with PP fibers in Class C FA-based GPC under ambient curing, directly linking mechanical behavior, microstructure, and eco-efficiency. The findings indicate that SCBA substitution up to 5 % with PP fibers is most suitable for structural applications requiring enhanced tensile performance, toughness, and reduced environmental impact, offering a scalable pathway for sustainable construction in sugar-producing regions.

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