ABSTRACT Expansive black cotton soil (BCS) exhibits low volumetric stability due to moisture imbalance. Traditional binders like lime and cement show a massive impact on environment by releasing greenhouse gases. In the present study, an attempt was made to improve the geomechanical properties of BCS using alkali activated binder (AAB) with polypropylene (PPF) and glass fiber (GF) at different proportions of fly ash and slag. AAB was produced by compounding an alkali activator solution of sodium silicate and sodium hydroxide with aluminosilicate precursors. The influences of varying dosages of fibers in AAB treated BCS showed a significant improvement in strength properties. The results of 0.4% PPF reinforced AAB treated BCS showed higher bonding interaction and tensile resistance. Furthermore, non-linear best-fit equations were proposed to relate experimental test results with model-predicted results in terms of unconfined compressive strength, indirect tensile strength and California Bearing Ratio for fiber-reinforced AAB treated BCS.