The issue of the size and shape of the aggregates in concrete is one of the most challenging subjects in the building industry, in order to reach maximum strength and ductility. To investigate this issue, two types of aggregate were selected. One was the river aggregate – gravel with rounded grains and the second was a crushed stone with sharp-edged grains, both with the maximum sizes of 9.5, 12.5, 19, and 25 mm respectively. The cement content was 250, 350, 450, and 550 kg/m3, and the water to cement ratio was equal to 0.4. At first, the compressive strength and stress-strain relationship were examined. According to the test results, the compressive strength increases with increasing cement content, as expected. The aggregate with the largest grain size of 12.5 mm gives the highest compressive strength and ductility compared to other grain sizes and it was selected as the optimal choice and finally, the sharp-edged aggregates have higher compressive.