Sustainable Utilization of Waste Slurry in Road Construction: Development and Evaluation of Solidification Methods Using Industrial Byproducts

Waste slurry from construction, tunneling, and dredging generates hundreds of millions of tons annually, straining landfills and polluting ecosystems. This study focuses on sustainable stabilization methods using industrial byproducts—CCR, FA, and GGBS—to transform slurry into durable road subbase material. Artificial soils with silt-to-clay ratios of 0.2 to 0.8, kaolin fractions from 0.2 to 0.8, organic matter up to 30%, and sand up to 25% were prepared, representing Unified Soil Classification System categories, including low-plasticity silt, high-plasticity clay, and organic variants. Atterberg limit tests revealed that higher silt and kaolin contents lowered the liquid limit from 48.4% to 30.9%, while organic matter increased it to 58.9%. Two curing agents were tested: a high-calcium silicate sulfate agent (CSC) and an alkali-activated composite agent (AAS). Unconfined compressive strength tests showed the former excelled in clay-rich soils, achieving 2.61 MPa at 28 days via C-S-H formation, while the latter reached 4.16 MPa in silt-rich soils through C-A-S-H gels. SEM-EDS confirmed dense gel structures, though organic soils exhibited reduced strength. These byproduct-based solutions enable sustainable slurry reuse, reducing environmental impact, and advancing circular economy principles in road construction.