Methods of Mix Design:

For the given concrete materials, the several factors to be considered in specifying a concrete mix are:

(a) Water-cement ratio,

(b) Cement content or cement-aggregate ratio,

(c) Gradation of the aggregates, and

(d) Consistency of the fresh concrete.

In general, all these factors cannot be chosen arbitrarily. Usually two or three of the factors are specified and others are adjusted to give minimum workability and economy. The requirements are usually dictated by general experience with regard to structural design conditions, conditions and durability of placing.

Water-cement ratio expresses the dilution of the paste. Cement content depends upon the amount of paste. Through varying the amount of given fine and coarse aggregate, gradation of aggregate is controlled. Consistency depends upon the practical requirement of placing of concrete.

Following are the methods, which are used for proportioning.

(a) Nominal proportion method

(b) Maximum density method

(c) Fineness modulus method

(d) Voids method

(e) Talbot-Richart Method

(f)  Trial and error method

(g) ACI mix design method

(h) Road Note No. 4 method