Novel geotechnical properties of lime-stabilized clay strength via hydrothermal solidification: Impact of leaching coefficient, chemical interactions, and silica-sesquioxide ratio for sustainable Geotechnics

Hydrothermal solidification offers an effective, sustainable method for stabilizing clay soil, addressing environmental concerns while improving geotechnical properties. Facilitating pozzolanic reactions between lime and clay under controlled temperature and pressure significantly enhances compressive strength and soil durability. This process promotes calcium silicate hydrate (C–S–H) formation, reduces industrial waste, and supports lime reuse, making it an energy-efficient soil improvement approach. This study investigates the impact of lime addition (0–20%) and various chemical and physical parameters on clay soil compressive strength. Key chemical components include SiO₂ (20.1–76.9%), Al₂O₃ (7.6–34.8%), Fe₂O₃ (0.6–32.9%), CaO (0.1–43.5%), MgO (0–9.56%), Na₂O (0.01–2.8%), and K₂O (0.1–3.9%). Physical properties such as density, plasticity index (6–34.5%), and liquid limit (24–65.2%) were analyzed alongside process parameters like heating temperature (60–1000 °C), curing time (0–120 days), and curing temperature (20–41 °C). Using a dataset of 152 samples divided into training and testing groups, the statistical analysis focused on the leaching coefficient (Lc) and silica-sesquioxide ratio (Kr). Lc emerged as the most significant factor, achieving an R² of 0.89 and an RMSE of 1.13 MPa. This study found that the compressive strength of lime-treated clay soils varied from 0.02 MPa to 11.9 MPa, influenced by lime concentration, chemical composition, and processing factors. Increased lime additions, particularly when combined with hydrothermal treatment, led to significant strength enhancements owing to improved pozzolanic activity. The plasticity index (PI) markedly diminished with lime stabilization, enhancing workability and mitigating volumetric variations. The density of treated soils rose from 0.8 g/cm³ to 2.1 g/cm³, signifying improved particle compaction and less porosity. The mechanical enhancements indicate that hydrothermal solidification efficiently converts expanding clay into a robust and stable material appropriate for geotechnical applications. Increased Lc improved compressive strength through enhanced pozzolanic activity and density, while higher Kr values, indicating lower CaO availability, yielded limited strength gains. Lc consistently outperformed Kr and other chemical compositions in enhancing clay soil compressive strength.