Sustainable Concrete Development Using Fly Ash and Scrap Tire Rubber

The construction industry is one of the largest contributors to global carbon dioxide emissions due to extensive cement consumption. To address this environmental challenge, the present study investigates the feasibility of producing green concrete by incorporating fly ash as a partial cement replacement and scrap tire rubber as a coarse aggregate substitute in M25 grade concrete. Experimental investigations were conducted on mixes with fly ash replacements of 20%, 25%, and 30% and scrap tire replacements of 10%, 20%, and 30%. The performance of the modified concretes was evaluated in terms of workability, compressive strength, flexural strength, and split tensile strength at 7, 14, and 28 days of curing. The results indicate that the inclusion of fly ash improved the workability and contributed to long-term strength development due to its pozzolanic activity, while higher proportions of scrap tire reduced strength because of poor bonding at the interfacial transition zone. The optimum mix was observed at 25% fly ash and 20% scrap tire replacement, which achieved compressive strength of 26.0 MPa at 28 days, slightly higher than the control mix (24.9 MPa), along with an improvement of 13–14% in flexural strength and 11–14% in split tensile strength. However, beyond 30% replacement of either material, strength reductions became significant. This study demonstrates that the combined use of fly ash and waste tires can produce a sustainable and structurally viable concrete, contributing