In this research the strength and durability parameters of recycled aggregates are studied to determine the optimum quantity of recycled aggregates that can be used as substitute for natural aggregates without affecting the strength of concrete. Compression test, Water penetration Test and Rapid Chloride penetration test were conducted on specimens of Grade M40, M50 and M60 with 0, 40, 60 and 80 % of replaced aggregates. For compression test the cube was cured for 28, 56 and 90 days, and for durability test (Water penetration Test and Rapid Chloride penetration test) cube was cured for 28 days. The result is obtained and compared with that of natural coarse aggregate. It is found that use of recycled aggregates does not decrease the strength of concrete substantially.