RSM-based and environmental assessment of eco-friendly geopolymer mortars containing recycled waste tire constituents

In recent years, there has been a growing emphasis on incorporating recycled materials into the production of eco-friendly construction materials. Additionally, the substantial disposal of end-of-life tires poses significant environmental challenges. Using waste tire constituents in the geopolymer materials as binders a feasible and sustainable alternative to conventional concrete with Portland Cement, effectively resolving environmental problems and promoting the advancement of eco-friendly building material production. This research focuses on producing eco-friendly alternatives to Portland Cement-based products. Moreover, it is aimed to explore the utilization of all components of the end-of-life tires (crumb rubber, textile, and steel fibers) in the mixture and replace Portland Cement with a geopolymer matrix in mortar mixtures. To achieve this, recycled waste tire materials were added to the geopolymer mixtures based on the design of experiments using a central composite design approach. An RSM-based assessment was applied to determine the effect of incorporating recycled materials on the durability and mechanical properties of the geopolymer mixtures. Moreover, the environmental impacts of mixtures were evaluated based on global warming potential and gross energy requirements. The analysis of experimental results revealed that incorporating recycled materials not only substantially mitigated the environmental impact but also improved mixture properties, i.e. reduced water absorption, enhanced resistance to salt scaling, and increased impact resistance. However, there was a slight decrease in compressive strength. Considering all aspects, the final optimized mixture saved 1172.77 MJ/ton energy and reduced 52.33 kg CO2eq/ton per 1 m3 compared to the mixture without recycled materials.