Mechanical and Environmental Performance of Eggshell Lime for Expansive Soils Improvement

Efficient and environmentally friendly alternative binders for expansive soils improvement are needed to practice sustainable geotechnics. This study evaluates the viability of a lime produced from eggshell waste as a green stabilization binder for expansive soils. Three contributions to the literature were achieved: (i) a comparison of the swelling, strength, stiffness, plasticity, and morphology of expansive soils stabilized with hydrated eggshell lime and hydrated industrial lime (i.e. commercially available lime), (ii) a statistical analysis of lime stabilization for swelling control and (iii) a life cycle assessment of eggshell lime versus industrial lime. Free-swell, unconfined compression, stiffness and Atterberg limits tests, and environmental assessment were performed to analyze the bentonite-kaolin-lime blends. Different proportions of bentonite-kaolin, dry density, lime content, and curing time were evaluated. Swelling data was correlated with the porosity/lime index. Results indicate that the alternative binder is a suitable option to improve the mechanical and swelling behavior of expansive soils, presenting higher strength and a reduction in expansion for all analyzed conditions, when compared to the industrial lime. Statistical analyses showed that bentonite content, lime content and dry unit weight factors should be focused for swelling reduction. For both studied limes, the adjusted porosity/lime index was an appropriate parameter to evaluate the swelling of stabilized soils. Life cycle assessment revealed that the alternative binder is a sustainable option as it avoids limestone mineral extraction and improvement.