Interaction and optimisation study of the influence of calcium-carbide-waste, crumb rubber, and fly-ash on the mechanical properties of a developed self-compacting-rubberized concrete for sustainable manufacturing processes

This study presents an innovative approach to developing ecologically sustainable self-compacting concrete. It utilises high-volume fly ash (HVFA) and scrap rubber as partial replacements for fine aggregate and cement. Additionally, it incorporates calcium carbide waste as an additive to cementitious constituents. The researchers employed Response Surface Methodology (RSM) to study the interactions, create numerical models, and optimise the mixes using rubber content, calcium carbide waste, and HVFA variables. Twenty different combinations were prepared and tested, varying the percentages of rubber (0%, 10%, 20%, 30%, and 40%) as a volume replacement for fine aggregate, calcium carbide waste (0%, 5%, 10%, 15%, and 20%) as a weight addition to cementitious materials, and HVFA (0%, 20%, 40%, 60%, and 80%) as a volume replacement for cement. The responses considered in the RSM were compressive strength (CS), flexural strength (FS), splitting tensile strength (STS), and water absorption (WA). The proposed models showed a strong correlation between the variables and responses. An optimised mixture of HVFA and scrap rubber with adjusted calcium carbide waste can be achieved by replacing 40% CR, 1.08842% CCW, and 20.001% HVFA too was achieved with 1.7852% H2O, 3.5 STS, 5.7283 FS, and 44.3676 CS having desirability of 0.980. Experimental results demonstrated improved properties for most of the optimised mixtures. The maximum passing ability was obtained in a 6% higher performance mixture than the control mixture. The model developed could predict the CS with 99%, FS with 93%, STS with 98%, and WA with 84%. Furthermore, calcium carbide waste enhanced the pozzolanic reactivity of fly ash at early ages, resulting in better performance of the optimised mixtures. However, the durability properties of the optimised mixtures were slightly reduced compared to the control self-compacting concrete. Based on the findings, it is recommended to use fly ash as a partial replacement for cement in self-compacting concrete and explore the beneficial properties of scrap rubber in self-compacting concrete, such as damping ratio and fatigue performance.