Abstract: This research paper presents a comprehensive investigation into the impact of fly ash replacement on the strength and workability of concrete. The study included the development of concrete mixes with varying amounts of cementitious content (300 to 500 kg/cum) and fly ash replacement levels (ranging from 0 percent to 50 percent ). To maintain a consistent slump value of 200 mm 25 mm, the concrete mixes were proportioned using the absolute volume approach and contained a high-range superplasticizer. The study's findings contribute to a better understanding of the behaviour of fly ash mixed concrete, allowing engineers and researchers to make more informed decisions regarding its practical applications.The findings show that fly ash substitution has the potential to improve the performance and sustainability of concrete, while also revealing any limitations or issues related with its use. This research is a great resource for the concrete industry