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Use of Class C fly ashes for the stabilization of an expansive soil

Excessive heave associated with swelling of expansive soils can cause considerable distress to lightweight civil engineering structures. Several methods have been suggested to control this problem. The most commonly used method is addition of stabilizing agents, such as lime or cement to the expansive soil. In this study, high-calcium and low-calcium class C fly ashes from the Soma and Tuncbilek thermal power plants, respectively, in Turkey, were used for stabilization of an expansive soil. An evaluation of the expansive soil-lime, expansive soil-cement, and expansive soil-fly ash systems is presented. Lime and cement were added to the expansive soil at 0–8% to establish baseline values. Soma fly ash and Tuncbilek fly ash were added to the expansive soil at 0–25%. Test specimens were subjected to chemical composition, grain size distribution, consistency limits, and free swell tests. Specimens with fly ash were cured for 7 days and 28 days, after which they were subjected to oedometer free swell tests. Based on the favorable results obtained, it can be concluded that the expansive soil can be successfully stabilized by fly ashes.