INVESTIGATING STABILISATION OF EXPANSIVE SOILS USING EGGSHELL POWDER AS AN ECO-FRIENDLY ADDITIVE

Abstract

Expansive soils, characterized by shrink-swell behavior due to clay minerals, present significant challenges in engineering applications like road pavements and waste containment. To mitigate these issues, eggshell powder (ESP) geopolymer was used as a stabilizing agent. This study, conducted in two phases, first assessed the natural soil properties, including specific gravity, Atterberg limits, particle size distribution, compaction characteristics, and volumetric shrinkage strain (VSS) at varying molding water contents. The second phase involved incorporating ESP at varying percentages (0%, 2.5%, 5%, 7.5%, and 10%) to evaluate its stabilization effectiveness. The soil was classified as A-7-5 (AASHTO) and CL (USCS) with a specific gravity of 2.59, a liquid limit of 45.05%, and a plastic limit of 32.9%. ESP addition reduced the specific gravity to
2.44 at 7.5%, while the plasticity index increased. The optimum moisture content (OMC) decreased from 20% (natural soil) to 17% at 7.5% ESP, and maximum dry density increased from 1.66 Mg/m³ to 1.705 Mg/m³ at 10% ESP. VSS significantly decreased with higher ESP percentages, achieving the allowable threshold of 4%. Statistical analysis confirmed that ESP significantly improved soil properties. The calcium carbonate in ESP decomposes into calcium oxide, which reacts with silica to form calcium silicate, enhancing soil stability. An ESP content of 7.5% was identified as optimal for mitigating volumetric shrinkage, making the soil suitable for waste containment. This study recommends ESP as a sustainable soil stabilizer for structurally unstable soils. Incorporating ESP by professionals improves soil properties while addressing environmental challenges of eggshell waste disposal sustainably.