Prescribed mix method is the most popular method of concrete mix prescription, where the consultant structural engineer will give the proportions of the cement, sand, gravel and water to be used for the concrete production with the targeted strength. On field, it is noticed that the actual strength of concrete is always less than the targeted strength. This research aims at determining the amount of cement needed to be added to the actual mix of 1:2:4 in order to get the targeted strength. Six various set of concrete cubes were produced by increasing the cement proportion by 10%,20%,30%,40% and 50% after producing the control mix from 1:2:4 mix ratio. Compressive strength test was carried out using the automatic digital compression machine. Cubes were crushed at 7,14,21 and 28 days respectively.at 28 days, the characteristics strength of concrete for the control mix ,10% ,20%,30%,40% and 50% cement increase yielded 8.86, 9.65,10.23,10.45,11.01 and 11.43 N/mm2 respectively.

Keywords : Prescribed Mix, Concrete, Targeted Strength, Characteristic Strength.