Sustainable soil stabilization with sodium carbonate-activated slag, pumice, rice husk, and sugarcane bagasse ashes: A life cycle assessment approach

• Aluminosilicate gels enhance mechanical properties without new mineral formation. • Sodium carbonate activation leads to delayed but sustained soil strength gain. • OPC addition accelerates early strength development via hydration reactions. • Life cycle assessment highlights environmental benefits of pumice-based mixtures. • Alkali activation with Na 2 CO 3 is a sustainable alternative for soil stabilization. This study investigates the use of sodium carbonate (Na 2 CO 3 )-activated aluminosilicate waste materials as a sustainable alternative to conventional soil stabilization methods, such as ordinary Portland cement (OPC) and traditional high-alkalinity alkali-activated slag systems. The proposed approach employs regionally available waste materials—pumice, sugarcane bagasse ash (SBA), and rice husk ash (RHA)—in partial replacement of slag, with Na 2 CO 3 serving as a low-carbon, cost-effective, and safer alkaline activator. Microstructural analyses confirmed the formation of key binding phases that contributed to improved mechanical performance. Incorporating 50 wt.% of these supplementary materials with slag, under identical curing and activation conditions, resulted in unconfined compressive strength (UCS) values that were 1.24, 0.76, and 0.20 times that of the slag-only binder for pumice, SBA, and RHA blends, respectively. Among the tested blends, a 50:50 mixture of slag and pumice, activated solely with Na 2 CO 3 , achieved a UCS of 3772.39 kPa after 28 days of curing. In comparison, the same slag-pumice blend activated using a combination of Na 2 CO 3 and OPC attained a higher UCS of 4492.03 kPa under identical curing conditions. Importantly, life cycle assessment (LCA) results highlighted the environmental trade-off between these systems. While the OPC-containing mixture emitted 31.00 kg CO₂-eq per m 3 of stabilized soil (climate change impact category), the Na 2 CO 3 -only activated system emitted just 23.09 kg CO 2 -eq—representing a 25.5% reduction in carbon emissions for comparable strength performance. These findings support the use of waste-derived materials and low-alkalinity activation strategies in sustainable geotechnical applications, promoting material circularity and significant carbon footprint mitigation in construction.