Experimental Study on Fresh and Mechanical Properties of Manufactured Sand and Recycled Aggregate Mixed Self-Compacting Concrete

Self-compacting concrete (SCC) offers significant construction advantages but relies on natural coarse aggregate and river sand, resources under growing environmental pressure. This study investigates the incorporation of recycled concrete aggregate (RCA) and manufactured sand (M-Sand) as partial and full replacements for these natural constituents, evaluating both fresh and hardened SCC properties. Mixes were developed with RCA and M-Sand substitution levels of 0%, 50%, and 100%, varied independently and in combination, while maintaining a constant water-to-cementitious-materials ratio. Slump flow, 28-day compressive strength, split tensile strength, and flexural strength were assessed for each mix. Results showed a consistent, monotonic decline in all properties with increasing substitution, with RCA exerting the dominant influence due to residual adhered mortar, higher porosity, and elevated water absorption, while M-Sand's effect was comparatively secondary. Despite reductions of up to 15.92% in workability, 30.21% in compressive strength, 19.45% in tensile strength, and 23.98% in flexural strength at full replacement (R100M100), all mixes satisfied EFNARC workability criteria and exceeded IS 456:2000 strength requirements for M25-grade concrete. Flexural strength proved most sensitive to combined substitution, while tensile strength remained comparatively least affected. These findings confirm that RCA and M-Sand, even at full replacement, are technically viable, sustainable alternatives to natural aggregates for standard structural-grade SCC applications, supporting waste diversion and resource conservation in concrete construction.