Modification of Expansive Soil Characteristics by Employing Agro-waste Eggshell Powder: An Experimental Study

Expansive soils show significant volume changes associated with water content, so as to pose a substantial challenge for civil engineering projects. In order to enhance the mechanical load-bearing characteristics of shallow foundations and subgrade pavement, expansive soil is often treated by the incorporation of an additional material. This experimental study used an agro-waste eggshell powder, which was pulverized and mixed with the natural Nanyang expansive soil in varying proportions of 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, and 18% by the dry weight of the soil. The experimental results indicated that the optimal concentration of eggshell powder for improving this type of soil is approximately 14%. Adding eggshell powder improves soil index properties by decreasing the consistency, free swelling index, and swelling pressure by 44%, 42.6%, and 40% while increasing mechanical properties, the unsoaked and soaked CBR by 158 and 194%, respectively. Moreover, it increased the permeability of soil up to 100 times. The XRD and SEM results demonstrated that the addition of eggshell powder helps to transform the soil’s dispersed structure into a flocculated structure, which is highly favorable for enhancing engineering characteristics. Overall, eggshell powder enhances expansive soil’s index and mechanical properties while presenting a viable and eco-friendly solution for reducing agro-waste.