Optimum mix design for quarry waste-based masonry blocks with alkali-activated rice husk ash and eggshell ash as a binder

Using suitable waste materials as a replacement for cement and natural sand presents a viable and pragmatic approach to tackle the challenges associated with the construction sector's scarcity of building materials and environmental issues. Additionally, this approach aids in conserving a substantial quantity of waste. This study explored the possibility of geopolymer technology in manufacturing masonry blocks by utilizing eggshell ash, rice husk ash, quarry waste, and caustic soda. Various permutations of the mixture were evaluated to ascertain the components' optimal blending ratios. The ideal composition for block manufacturing was determined by studying many factors, including compressive strength, water absorption rate, energy demand, and carbon dioxide emissions during production. It was found that a geopolymer mortar comprising 2.5% eggshell ash, 7.5% rice husk ash, and 4% caustic soda mixed with quarry waste yielded the most favorable results. The findings indicate that the geopolymer blocks could meet the strength requirements of 1.2 MPa outlined in the SriLankan standard SLS 855 for non-load-bearing masonry when combined in specific ways. Yet, it should be noted that the geopolymer mortar's compressive strengths were relatively lower than those of the cement-quarry waste mortar. The geopolymer mortar with the optimum mix showed 14.1% less energy embodied per unit strength and 15.4% less CO2 emission per unit strength, respectively, compared to the control mortar.