This project investigated the effect of high reactivity Iraqi High-Reactivity Attapulgite (HRA) on some properties of concrete (e.g., compressive strength, splitting tensile strength and flexural strength) when mixing proportions were changed. Three mixes of concrete were made (1: 1.69: 2.13), (1: 1.13:1.68) and (1: 0.89: 1.96), with (water/cement) ratios (0.48, 0.41 and 0.32), for 35, 45 and 60 N/mm2 target compressive strength respectively. The percentage increase in the compressive strength at 28 days were 48.29%, 49.64% and 42%, respectively, compared with compressive strength for the same mix at 7 days. In addition, the increase in splitting tensile strength at 28 days was 45.27%, 31% and 30%, and in flexural strength at 28 days was 30%, 52.47% and 26.18%, for the above mixes respectively, compared with strength for the same mix at 7 days.