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Construction and demolition (C&D) waste is one of the largest waste streams generated globally, yet its recycling and reuse in concrete production remains minimal — especially in India where only about 1% is currently recycled. This study investigates the feasibility and strength performance of M25 grade concrete in which natural fine aggregate (river sand) is partially replaced with recycled fine aggregate (RFA) from C&D waste at 5%, 10%, 15%, and 20%, and natural coarse aggregate is simultaneously replaced with recycled coarse aggregate (RCA) at 10%, 20%, 30%, and 40%, respectively. Concrete mix was designed as per IS 10262:2009 with a water-cement ratio of 0.45. Cube specimens of 150×150×150 mm were cast and tested for compressive strength, and cylinder specimens for split tensile strength, at 7, 14, and 28 days of curing. Results show that Sample-3 (15% RFA + 30% RCA) achieved the highest compressive strength of 36.44 N/mm² and tensile strength of 4.9 N/mm² at 28 days, outperforming conventional concrete (24.2 N/mm² and 3.7 N/mm², respectively). Beyond 15% RFA and 30% RCA, strength declined. The study confirms that up to 15% RFA and 30% RCA can effectively replace natural aggregates in M25 concrete without compromise to structural performance, offering significant economic and environmental benefits.