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This study aims to determine the effect of variations in the composition and size of red sand grains on concrete quality that made in the form of a 15x15x15 cm cube with SNI K-225 standard using a mixture 1:1,9:2,8 with FAS 0,6 with composition of red sand of (0, 2, 4, 5, 6.5)% of the weight of fine aggregate were used and variations in the size of red sand grains of (80, 100, 120)mesh. After treated in a water bath for 28 days, then its tested by the method of water absorption, pressure strength test, SEM and XRD. From the research results of SEM test variations of both affect the porosity of the concrete. XRD test results, obtained by the elements of SiO2, Ca(OH)2, CaCO3, with the highest intensity is SiO2 and the crystal structure formed is hexagonal. The results of the maximum concrete pressure strength test on the composition of 4% due to lower grain size variation of red sand with a grain size of 80 mesh red sand that is 32.3 MPa and has linearity from the results of testing the water absorption of concrete along with decreasing variations in the size of red sand grains.