Effect of Rice Husk Ash Incorporation on the Strength Development and Microstructural Properties of Stabilized Clayey Soil

Recently, there has been increasing interest in integrating eco-friendly materials, such as agricultural wastes, into soil stabilization. Among these wastes, rice husk ash (RHA) has emerged as a sustainable and cost-effective alternative. Thus, this study examined soil-cement-RHA mixtures with cement contents of 15% and 20% by wet soil weight. Additionally, the RHA dosage (0-30%) was utilized to investigate its effect on the strength of mixtures, while the RHA replacement ratio ranging from 10 to 50% was evaluated to assess its potential to partially replace cement in soil mechanical behavior improvement. The testing methodology comprised the unconfined compressive strength (UCS), SEM (Scanning Electron Microscope), and XRD (X-ray Diffractometry) analyses were used to study the role of RHA in the formation of cementitious products. For analyzed cement contents of 15% and 20%, the optimum RHA dosage for attaining the maximum UCS of stabilized soil was 20%. Moreover, RHA could effectively replace cement in soil stabilization, with replacement levels from 10 to 20%, depending on cement content. The SEM images and XRD analysis clearly demonstrate the formation of calcium silicate hydrate (CSH) gel and the development of a denser, more compact structure in the soil-cement mixture due to the presence of RHA. The study revealed that the UCS of stabilized soil is greatly influenced by the duration of curing. Specifically, with longer curing times, the strength of RHA-stabilized soil is considerably higher than that of cement-only stabilized soil, which is likely due to the time-dependent pozzolanic reactions.