Each year, India generates almost 30 million metric tonnes of coal bottom ash/boiler slag (CBA). Communities in the area are put at risk due to the dumping of ash from adjacent thermal power facilities. CBA disposal issues may be effectively mitigated by its productive use. This research is being done to determine how practical it would be to use CBA as natural fine aggregate (NFA) in construction projects. The compressive strength (CS) of both Concrete 'A' and Concrete 'B' was planned to be 38N/mm2 and 34N/mm2, respectively. CBA is used to substitute NFA in the two kinds of concrete at varying percentages (20, 30, 40, 50, 75, and 100).