Valorization of dredged sludge into sustainable subgrade materials through a novel industrial solid waste-derived...

The development of sustainable and cost-effective stabilizers is urgently needed for the valorization of dredged sludge from riparian and lakeside engineering construction. Conventional cement-based methods have high environmental footprints, while traditional alkali-activated systems relying on sodium silicate remain costly. This study replaces conventional alkali activator with a silica fume (SF)-based activator to develop a novel, eco-friendly stabilizer derived from industrial solid wastes (ISW) for stabilizing dredged sludge as sustainable subgrade material. The mechanical, microstructural and environmental characteristics of the stabilized sludge were investigated and compared with the traditional stabilized sludge. Results demonstrate that the ISW-derived stabilized sludge, recommended at 100% compaction degree, 15% moisture content, and 12% stabilizer dosage, meets all mechanical criteria for highway base and subbase courses. Microstructural analyses confirm the formation of calcium aluminosilicate hydrate (C-A-S-H) gel, which densifies the structure and converts harmful pores into less harmful ones. Durability tests further reveal deterioration mechanisms that residual unreacted components undergo secondary reactions that partially mitigate structural damage under dry-wet cycles. In contrast, freeze-thaw cycles lack such secondary reactions, leading to more severe pore coarsening, cracking, and mass loss. Notably, a 16% ISW-derived stabilizer dosage achieves equivalent strength to 20% cement, while reducing cost by 2.36% and CO₂ emissions by 79.62%. This study offers a cost-effective, low-carbon, and high-performance solution for dredged sludge valorization.