Stabilization of Expansive Clay Soil Using Pulverized Ceramic Waste, Cement Kiln Dust, and Alkali Activation: Material Characterization and Swell Analysis

Abstract

Expansive clay soils present major geotechnical challenges because of their excessive swell-shrink behavior, which leads to pavement heaving, differential settlement, cracking of foundations, and deterioration of transportation infrastructure. Cement kiln dust (CKD) was incorporated as the calcium-rich alkali activator that supplies Ca(OH) 2 on hydration, thereby triggering pozzolanic reactions with the reactive silica and alumina of the pulverized ceramic waste (PCW) to form cementitious and geopolymeric gels within the soil matrix. Conventional stabilization methods based on cement and lime have proven effective; however, their environmental impacts and high carbon emissions have intensified the search for sustainable stabilization alternatives. This study investigated the stabilization of expansive clay soil using pulverized ceramic waste (PCW) and alkali activator through material characterization, consistency evaluation, and swell analysis. Laboratory investigations included particle size distribution, specific gravity, Atterberg limits, free swell index (FSI), X-ray diffraction (XRD), and X-ray fluorescence (XRF) analyses. Stabilization was performed using varying replacement levels of ceramic waste and cement kiln dust (CKD), alongside alkali activation. The untreated expansive clay soil exhibited high plasticity and severe swelling characteristics, with a liquid limit of 89.68%, plasticity index of 67.47%, and free swell index of 193.75%, confirming its highly expansive nature. XRD and XRF analyses revealed significant silica-, alumina-, and calcium-bearing phases within the stabilization materials, indicating strong geopolymerization and pozzolanic potential. The incorporation of ceramic waste and CKD significantly improved the consistency and swell behavior of the soil. The liquid limit decreased to 48.50%, while the plasticity index and free swell index reduced to 15% and 12%, respectively, at the optimum combined stabilization of 25% CW and 15% CKD. These improvements were attributed to flocculation, cation exchange, cementitious bonding, and geopolymeric gel formation within the soil matrix. The study demonstrates that pulverized ceramic waste and alkali activation can effectively reduce the expansiveness and moisture susceptibility of problematic clay soils. The combined stabilization approach offers a sustainable and environmentally friendly alternative for expansive soil treatment while simultaneously promoting beneficial reuse of ceramic waste materials in geotechnical engineering applications.