Suitability of Fly Ash-Cement Kiln Dust Columns for Stabilizing Expansive (Black Cotton) Soils

Abstract

The paper focuses on the potential use of industrial wastes, which are fly ash (FA) and cement kiln dust (CKD), to stabilise expansive soils like black cotton (BC) soil for construction purposes. Although many soil stabilisation methods exist, the placement of columns consisting of industrial wastes has yet to be tested. Knowing the pozzolanic action and mechanism between the waste product and the soil, this method of placing the industrial waste as a remedy should be trialled. Therefore, this paper proposes and investigates the placement of FA-CKD columns into the soil via a series of laboratory experiments using myriad mixtures and combinations of placement of such columns. The effect of moulding water content and curing time on the BC soil’s consolidation and strength behaviour was also assessed here. Through the experiments, it is found that the optimum mixture of FA-CKD for the columns is at 90%-10%, respectively. This column mixture has been evidenced to improve the unconfined compressive strength of the soil significantly, where its performance improves with curing time. The highest strength improvement can be found at optimum moisture content, followed by wet of optimum and dry of optimum, respectively. By placing the columns in the soil with 4.5D spacing, better consolidation behaviour with a reduced swelling potential of BC soil can be found. Based on the above findings, using FA-CKD columns can improve the BC soil’s engineering behaviour, contributing to waste-to-wealth and sustainable soil stabilisation approaches.