In the construction industry, treating weak foundation soil poses significant challenges due to its poor bearing strength and high compressibility. This experimental study focused on assessing the engineering and morphological behavior of weak soil stabilized using geopolymer to enhance its engineering performance and suitability for construction. Geopolymer is an eco-friendly alternative to conventional soil stabilizers as it creates a novel stabilization solution amalgamated with industrial waste. There are multiple phases of methodology involved in this study. Primarily, the characteristics of weak soil, such as its properties and deficiencies, are investigated. Subsequently, the formulation of amalgamated geopolymer with industrial waste such as Cashew nut shell ash (CNSA) at different proportions was prepared and applied to the selected soil sample. During the pre- and post-stabilization stages, a comprehensive test series examines the soil’s engineering behaviors. Next to this, the microstructure modification caused during stabilization was analyzed and also, the thermal expansive nature of the stabilized sample during thermal curing was investigated at different temperatures to understand the impact of geopolymer concentration. The results of this study are significant for the advancement of sustainable geotechnical engineering practices, as they provide valuable insights into the effectiveness of geopolymer-based soil stabilization techniques. These findings can be a valuable resource for future researchers, engineers, and stakeholders in the field of geotechnical engineering while also addressing environmental concerns associated with the sustainable utilization of industrial waste.