The Effect of Using Coal Fly Ash as a Fine Aggregate Substitute on the Compressive Strength of Concrete

Abstract

Concrete is a composite material consisting of Portland cement, fine and coarse aggregates, and water that hardens into solid mass. Coal fly ash, a pozzolanic by-product of coal combustion, exhibits comentitous properties due to its high silica content, which reacts chemically with calcium hydroxide. This study investigates the effect of coal fly ash as a partial fine aggreagate replacement on the compressive strength of concreate at 28 days. The results demonstrate that te incorporation of coal fly ash enhances compressive strength compared to conventional concrete. The mixture with 15% fly ash substitution achieved a compressive strength of 25.08 MPa, while the 30% substitution reached 29.33 MPa, both exceeding the target strength of 20 MPa. The finding highlights the potential of coal fly ash as a sustainable alternative to natural fine aggegate in concrete production.