Sustainable strength improvement of clay soil via steel slag and hydrothermal solidification: A geochemical approach using the role of chemical compositions, Ruxton Ratio, and cementation index

Abstract

Clay soils often exhibit low load-bearing capacity and significant volumetric instability under variable moisture conditions. This study assesses the effectiveness of steel slag as a stabilizing agent for clay soils through hydrothermal solidification, aiming to enhance compressive strength, control shrinkage, and improve resistance to moisture-induced deformation. This study quantified the effect of steel slag on the compressive strength of clay soils with various liquid limits. A total of 71 natural and 164 stabilized soil datasets were analyzed, assessing both chemical composition (SiO₂: 20.1 %–65.7 %, Al₂O₃: 2 %–38.8 %, CaO: 0.21 %–29.8 %) and physical properties (liquid limit: 30 %–65.2 %, plasticity index: 9.2 %–35.4 %, density: 0.78–1.87 g/cm³). Key influencing parameters included steel slag content (0 % % −50 %), Ca (OH)₂ (0 % % % −60 %), curing time (0–120 days), and temperature (20 °C −195 °C). Experimental results demonstrated significant improvements in compressive strength (21–5865 kPa), primarily attributed to pozzolanic reactions and the formation of calcium silicate hydrate (C–S–H). A pure quadratic model demonstrated high predictive accuracy (R² = 0.76 for training and R² = 0.74 for testing), confirming a strong correlation between steel slag content, hydrothermal conditions, and soil strength enhancement. This research highlights the potential of steel slag as a sustainable alternative for soil stabilization, addressing both geotechnical performance and environmental sustainability through the recycling of industrial by-products.