The durability of an organic soil treated with fly ash and alkaline activators

Organic soils have low shear strength and high compressibility, which make these soils unsuitable for some engineering applications. The resistance of soil stabilizers to wetting-drying cycles is important to maintain the long-term stability and strength of the stabilized soils. Using waste products such as fly ash (FA), is a convenient and sustainable procedure for many soil improvement methods. In this study, FA-based geopolymer was used to increase the shear strength and durability of an organic soil. Different ratios of alkali solutions (sodium hydroxide and sodium silicate) were used to produce the geopolymer. The specimens were initially cured at (45, and 65°C)and then cured for 28 days at room temperature. The FA-stabilized specimens had poor performance during the wetting-drying cycle, as they collapsed during the first cycle. The geopolymer-stabilized specimens passed 12 cycles of wetting-drying with less than 4% loss in weight and without any observed volume change. Furthermore, the increase in the Unconfined compressive strength values was as high as 56%. FA-based geopolymer is considered an effective additive to improve organic soils due to the high strength and long-term stability of the geopolymer bonds.