Short Notes on Design of concrete mix

 Design of concrete mix

The aim of concrete mix design is to determine the proportions in which cement, fine aggregate, coarse and water should be mixed to produce concrete of required strength, workability and durability with minimum cost.The design of concrete mix can be done following methods. 

i.Normal mix:

When the proportions of cements, aggregate and water are adopted based on arbitrary standard, the concrete produced is termed as nominal mix concrete.

ii.Design mix: 

Design mix can be defined is the process of selecting the ingredient of concrete and determine their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible . The purpose of designing as can be seen from the about definitions is two-fold .The first object is to achieve the stipulated minimum strength and durability. The second object is make to the concrete the most economical manner.

Variables in Proportioning 

With the given materials, the four variable factors to be considered in correction with specifying a concrete mix are :

a) Water cement ratio

b) Cement content or cement aggregate raito

c) Gradation of the aggregates 

d) Consistency

In general all four these inter related variables can not be chosen or manipulated arbitrarily. Usually two, three factors are specified and the others are adjusted to give optimum values of strength, workability and economy.