Strengthening of Montmorillonitic and Kaolinitic Clays with Calcium Carbide Residue: A Sustainable Additive for Soil Stabilization

Fine-grained soils are often problematic if they are used to construct certain types of earth structures or pavement foundation layers. If the use of poor site-specific fine-grained soils is desired for cost reasons, it can be useful to perform chemical stabilization to improve their engineering properties. Calcium carbide residue (CCR) is a by-product of the acetylene production process, which can be used as a cost effective and sustainable cementing agent for soils. This paper examines the effects of CCR content and curing times on the engineering characteristics of CCR stabilized fine-grained soils. In this study, a green bentonite (having a predominantly montmorillonite mineralogy) and white kaolin (having a predominantly kaolinite mineralogy) were used as representative clay minerals that needed stabilization. Compaction, unconfined compression strength (UCS), and direct shear tests were performed to assess the engineering properties of the stabilized clay soils. From the test results, it was observed that in both clays the optimum water content tended to increase and the maximum dry density tended to decrease as the CCR content increased. The UCS test results showed that 9% and 12% CCR contents yielded optimal strength gain for the montmorillonitic and kaolinitic clays, respectively. The direct shear test results also showed significant gains in cohesion and friction angle for both soils at their optimum stabilization levels.