Strength development in high plasticity clayey soil using alkali-activated rice husk ash geopolymer

This study investigates the utilisation of rice husk ash (RHA) to produce an alumina-silicate-rich geopolymer to improve the mechanical strength of high-plasticity clayey soils. Based on the strength performance, the optimum RHA content was found to be 20% by dry weight of soil. The key factors examined were variations in alkali concentration, alkali-activator ratio, alkali-binder ratio, and curing period. The optimal geopolymer content was found at an alkali-binder ratio of 0.6, alkali-activator ratio of 2, 12 M molarity, and 7-day curing, with a strength improvement factor of 9.32. MINITAB was used for response surface analysis and optimisation. The full quadratic model best fits the experimental data, indicating significant interaction effects, with a composite desirability of 0.9795. The regression shows molarity as the most significant factor. The geopolymer-treated clay withstood 12 wetting-drying cycles under ambient conditions. Microstructural and mineralogical variations from RHA and geopolymer treatments were analysed by XRD, SEM, and FTIR.