Experimental Evaluation of Eggshell Waste as an Eco-Friendly Stabilizer for Marly Soil

Resumo

This study investigates the potential use of eggshell waste as an eco-friendly stabilizing agent for marly soil (GCM) from the Manaa region, located in eastern Algeria. The increasing accumulation of eggshell waste represents an environmental concern, while its high calcium carbonate content offers promising potential for soil improvement. To evaluate this potential, eggshell powder (ESC) was incorporated into the natural soil at proportions of 3%, 6%, 9%, and 12% by dry weight. A series of laboratory tests were conducted, including Atterberg limits, methylene blue value (MBV), Standard Proctor compaction, direct shear, and total swelling tests. The results show that the addition of eggshell waste reduces the soil plasticity index and methylene blue value, indicating a decrease in clay activity. The optimum water content decreases slightly, while the maximum dry density increases with higher additive content. Furthermore, the shear strength parameters, cohesion and internal friction angle, show notable improvement, particularly at 9% eggshell content. The total swelling potential of the treated soil decreases significantly compared with the untreated sample, confirming the stabilizing effect of the additive. In addition, microstructural observations using scanning electron microscopy (SEM) reveal the formation of denser soil matrices and improved particle bonding after eggshell addition. X-ray diffraction (XRD) analyses further indicate the formation of new calcium-bearing phases and a partial reduction in clay mineral activity, providing insight into the chemical and structural mechanisms underlying soil stabilization. Overall, eggshell waste appears to be an effective and sustainable alternative material for improving the mechanical and volumetric behavior of marly soils.