Road Note No. 4 Method:

The experimental investigation is the main base of this method. The designed concrete must be satisfactory both in plastic as well as in the hardened state. The choice of mix proportions is governed by both the above conditions. Strengths produced by different cements are not same at same water-cement ratio. The required water-cement ratio to produce the designed strength depends upon the properties of concrete. Since strength is proportional to water-cement ratio for a provided type of cement, the Road Note No. 4 technique presents a set of curves relating water-cement ratio and compressive strength at different ages and for different types of cement.