Concrete Mix Design and Advantages

What is Concrete Mix Design?  

Concrete is an extremely versatile building material because,  it can be designed for strength ranging from M10 (10Mpa) to M100 (100 Mpa) and workability ranging from 0 mm slump to 150 mm slump. In all these cases the basic ingredients of concrete are the same, but it is their relative proportioning that makes the difference.

Basic Ingredients of Concrete: –

1. Cement – It is the basic binding material in concrete.
2. Water – It hydrates cement and also makes concrete workable.
3. Coarse Aggregate – It is the basic building component of concrete.
4. Fine Aggregate – Along with cement paste it forms mortar grout and fills the voids in the coarse aggregates.
5. Admixtures – They enhance certain properties of concrete e.g. gain of strength, workability, setting properties, imperviousness etc

Concrete needs to be designed for certain properties in the plastic stage as  well  as in the hardened stage.

Properties desired from concrete in plastic stage: –

• Workability
• Cohesiveness
• Initial set retardation

Properties desired from concrete in hardened stage: – 

• Strength
• Imperviousness
• Durability

Concrete mix design is the method of correct proportioning of ingredients of concrete, in order to optimise the above properties of concrete as per site requirements.

In other words, we determine the relative proportions of ingredients of concrete to achieve desired strength & workability in a most economical way.

Advantages of mix design

Mix design aims to achieve good quality concrete at site economically.

1. Quality concrete means

• Better strength
• Better imperviousness and durability
• Dense and homogeneous concrete

1. Economy

a) Economy in cement consumption

It is possible to save up to 15%  of cement for M20 grade of concrete with the help of concrete mix design.  In fact higher the grade of concrete more are the savings. Lower cement content also results in lower heat of hydration and hence reduces shrinkage cracks.

b) Best use of available materials:

Site conditions often  restrict the quality and  quantity of ingredient materials. Concrete mix design offers a lot of flexibility on type of aggregates to be used in mix design. Mix design can give an economical solution based on the available materials if they meet the basic IS  requirements.  This  can  lead  to  saving  in transportation costs from longer distances.

c) Other properties:

Mix design can help us to achieve form finishes,  high early strengths for early deshuttering, concrete with better flexural strengths, concrete with pumpability and concrete with lower densities.