Effect of RHA–GGBS Blending on the Engineering Performance and Microstructural Characteristics of Alluvial Soil

The majority of the land in Bihar is made up of alluvial soil, which falls into the category of problematic soils in the context of engineering applications. Therefore, to improve the properties and the long-term performance of such soil as a subgrade, one technique known as stabilization needs to be employed. On the other hand, using waste materials to construct roads is an environmentally friendly option. The objective of this paper is to evaluate the effect of rice husk ash–ground granulated blast furnace slag (RHA–GGBS) blending on the engineering performance and microstructural characteristics of alluvial soil. A novel approach was used to determine elastic modulus utilizing light weight deflectometer (LWD) testing on a California bearing ratio (CBR) mold. Otherwise, laboratory testing was conducted in accordance with Indian/American standard codes. It was observed that adding a combination of GGBS and RHA as a hybrid binder in a ratio of 70∶30 significantly improves certain soil characteristics. It was found that when the hybrid binder was added, the soil’s strength based on unconfined compressive strength (UCS), CBR, and elastic modulus (EM) increased, but its liquid limit (LL) and plasticity index (PI) significantly dropped. The optimum binder content recommendation is 10% hybrid binder, based on the findings of the UCS, CBR, and EM tests. Furthermore, it was revealed by the mineralogical and morphological analyses of soil specimens stabilized with optimum binder content that the interaction between the clayey alluvial soil and the binder led to the development of cementitious compounds and hydrated particles. Test results suggest that utilizing GGBS mixed with RHA as a hybrid binder to stabilize alluvial soil is a promising option for environmentally conscious and cost-effective construction.