Investigation on effects of sludge and limestone in sustainable infrastructure: From performance optimization to carbon reduction

This study presents a novel sludge ash and limestone cementitious (SSLC) composite tailored for construction, addressing the critical needs for durability, sustainability, and resilience in harsh environments. The experimental work systematically evaluates the flowability, mechanical properties, and chloride ion resistance of the SSLC paste under varying mix proportions. Through advanced techniques such as SEM, XRD, and thermodynamic simulations, the hydration mechanisms and microstructural evolution are comprehensively explained. The findings reveal that the synergistic incorporation of sludge ash and limestone optimizes pore structures, enhances the formation of carbonate-based hydration products, and significantly improves long-term properties, including a 34 % reduction in chloride ion concentration and a 5.98 % increase in flexural strength after 365 days. Additionally, the SSLC paste demonstrates a 23.43 % reduction in carbon emissions and a 22.22 % decrease in production costs, offering a low-carbon, cost-effective solution for infrastructure. These results underscore the SSLC paste’s potential as a sustainable construction material for applications, providing enhanced durability, reduced environmental impact, and economic viability to meet the challenges of modern engineering.