Influence of sodium chloride on cement kiln dust-treated clayey soil: strength properties, cost analysis, and environmental impact

This research investigates the microstructural and geotechnical properties, environmental impact, and economic benefit of cement kiln dust (CKD)-treated kaolinite clay with the addition of sodium chloride (NaCl). As a chemical admixture, NaCl is expected to enhance the strength properties of the clay soil stabilized by CKD. To verify this issue, the geotechnical characteristics of CKD-treated soils with different contents of NaCl (2.5, 5, and 10%) were examined. To this end, the Atterberg limits, standard Proctor, unconfined compressive strength and California bearing ratio (CBR) tests were conducted. Besides, scanning electron microscopy (SEM) analysis was used to observe the microstructural changes resulting from using additives. It was found that the addition of NaCl to the CKD-stabilized clay caused the maximum dry density to increase and the optimum moisture content to decrease. 10% NaCl enhanced the unconfined compressive strength of the CKD-treated soil to 18.7% and 8% higher than that of the NaCl-free specimen during 7 and 28 days of curing, respectively. These results were in accordance with the consequences extracted from the CBR behavior diagram. Moreover, cementitious compounds products in the mixtures were presumed to be the significant factor contributing to strength improvements based on the SEM results. The stabilized clayey soil with 15% CKD and 10% NaCl as environment-friendly method could significantly reduce energy consumption, e-CO 2 emission, and cost of soil stabilization.