Fly Ash-Based Geopolymerization for Enhancing Clayey Soils in Canal Linings: An Experimental and Numerical Analysis Using SEEP/W

Growing environmental concerns and the increasing need for sustainable water infrastructure have stressed the importance of eco-friendly alternatives to conventional canal lining materials. In this study, the potential of Fly Ash (FA)-based geopolymers to improve the impermeability of clayey soils for canal lining applications was examined. Laboratory tests were performed on untreated and geopolymer-treated soils after 7 and 14 days of curing, during which permeability and water flux were measured. The untreated clay soil exhibited a permeability coefficient of 8.00 × 10⁻⁷ cm/s. Noticeable improvements were observed after geopolymer treatment. The optimum mixture contained 30% FA activated by the AA/FA1 system, with a ratio of sodium silicate to lime of 0.4. This treatment reduced permeability to 1.80 × 10⁻⁷ cm/s, representing a 77.5% decrease, and lowered water flux by approximately 87.93%. In comparison, the AA/FA2 activator, with a ratio of sodium bicarbonate to lime of 0.6 and 30% FA, reduced permeability to 4.30 × 10⁻⁷ cm/s, corresponding to a 46.25% reduction. Also, it resulted in an 86.93% decrease in water flux but yielded lower impermeability than the AA/FA1 mixture. The superior performance of AA/FA1 is attributed to its higher alkalinity and the formation of denser geopolymer gels, which refine and stabilize the soil pore structure. The numerical simulations conducted using SEEP/W were closely aligned with the laboratory findings, further validating the proposed treatment approach. Overall, FA-based geopolymer-treated soils demonstrate a promising, durable, and environmentally sustainable method for minimizing seepage in earthen canals and enhancing water conservation.