In recent years, significant attention has been given by researchers to use recycled concrete aggregate (RCA) instead of natural aggregate (NA) in concrete mixes to decrease the demand on the natural aggregate resources and to reduce its environmental effects. This research work was carried out to investigate the efficiency of using RCA in concrete mixes in place of natural coarse aggregate. 90 cubes of (100 x 100 x 100 mm) with different percentages of RCA (0%, 30%, 45%, and 60%) at water to cement ratio of 0.4 and using 0% and 2.5% super plasticizer were casted. For that mix which was prepared with 45% of RCA 54 cubes of (100 x 100 x 100 mm) were casted with different percentages of iron powder in place of fine aggregate (10%, 15%, and 20 %). Hardened test was examined to measure the compressive strength after 7, 14 and 28 days of curing. Fresh property test was conducted (Slump test) to study the efficiency of using RCA on workability. The results of the study showed that the fresh property was decreased by increasing the RCA replacement. The compressive strength of the RCA was deceased by increasing the RCA replacement. For specimens casted using 45% of the RCA the compressive strength was increased by increasing iron powder replacement.
