Stabilization of expansive black cotton soils with alkali activated binders

Abstract

The black cotton soil is mainly composed of clay minerals of Smectite group and is highly expansive when exposed to moisture. The present paper proposes a method of geo-polymerizing the black cotton soil with alkali activated binders (AAB). AAB is produced by the reaction between an aluminosilicate precursor (primarily Class F fly ash and/or slag) and an alkali activator solution of sodium hydroxide and sodium silicate. The water to solids ratio is maintained at 0.3. Mineralogical and microstructural characterizations through X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) are carried out for both untreated and treated soil to identify the changes in chemical composition and surface morphology. The index properties, compaction characteristics, unconfined compressive strength (UCS) and swelling characteristics of both untreated and treated soil are carried out. It is observed that the AAB reduces the plasticity index and free swell of black cotton soil by 15–25%, while the UCS values are increased by 10–12%. Recommendations on practical implementation of this technique for stabilization of expansive soils are proposed based on the findings of this study.