Geotechnical characteristics of an expansive clay stabilized with lime and steel slag

Abstract

This study rigorously investigates the geotechnical characteristics of expansive soil when stabilized using lime and steel slag. Expansive soils are notoriously challenging in the field of civil engineering due to their propensity for significant volume changes in response to moisture variations. Such soils often lead to foundational instability in constructions, making their stabilization a topic of paramount importance. Lime and steel slag, recognized for their soil-stabilizing properties, are the focus of this study. Extensive laboratory experiments were conducted to evaluate the impact of these stabilizers on the geotechnical properties of expansive soil. The experimental design included varying percentages (wt %) of lime and steel slag, specifically 3%, 6%, 9%, 12%, and 15%. Additionally, combinations of lime and steel slag were tested, with ratios such as 1.5% lime with 1.5% steel slag, 3% lime with 3% steel slag, 6% lime with 6% steel slag, and 7.5% lime with 7.5% steel slag. All samples were meticulously prepared under optimal conditions: a moisture content of 25% and a maximum dry density of 15.17 kN/m3. These samples underwent rigorous unconfined compressive testing at intervals of 3, 7, 14, and 28 days. The results were illuminating: samples with a 15% lime content exhibited the highest strength, reaching 419 kN/m2, while those with steel slag and a combination of admixtures showed strengths of 342 kN/m2 and 339 kN/m2, respectively. An intriguing observation was made regarding the samples' preservation method. Stored in a desiccator and sealed in zip-locker plastic bags, the samples did not gain strength significantly after fourteen days, attributable to the hindrance of the cementation reaction in the absence of water. This insight underscores the critical role of environmental conditions in soil stabilization processes. Moreover, the study found that samples with a lime mixture containing 99% CaO outperformed those with steel slag and the combination of lime and steel slag in terms of strength enhancement. The swelling potential and pressure of the soil were observed to decrease with increasing additive amounts, with a 9% admixture ratio identified as optimal for reducing the swelling index. Additionally, the pH levels exhibited stable conditions when the lime and steel slag combination was utilized. A comprehensive microstructural analysis, conducted using Scanning Electron Microscopy (SEM), revealed significant insights. The formation of a distinct microstructure was noted, along with a marked improvement in the soil's mechanical strength. This study contributes valuable knowledge to the field, offering practical solutions for addressing the challenges posed by expansive soils through the use of lime and steel slag.