While more and more thermal power plant is built, the amount of bottom ash produced is rising dramatically due to fast globalization. It is often disposed of in an open area, taking up hundreds of acres of priceless land and seriously polluting the ecosystem. Expansive soil, which is widely distributed across India and around the globe, is one of the most studied materials in geotechnical engineering due to its rapid volume changes when exposed to moisture. Heavy buildings and embankments erected upon it suffer severe damage as a result of this volume change. As such, the application of different stabilizing techniques prevents the volume from altering the behavior of the soil. The objective of the current study was to understand the strength characteristics and swelling behavior of expansive soil mixed containing 0, 5, 10, 15, 20, 25, and 30% bottom ash by dry weight of the entire mix. Improvements in the index properties and strength of stabilized and unstabilized soil were compared to assess the effectiveness of the bottom ash. The application of bottom ash modified the hygroscopic character of the expansive soil, which enhance the soil’s strength and index properties, according to the present research work.