Concrete is a very complex material. Its properties as fresh as well hardened concrete is a function of the right mix of constituents of concrete, which if not done properly will adversely affect the properties of concrete. Hence the right judicious proportion of all the constituents is most important.
Therefore, the scientific and systematic process of choosing economical relative proportion of various ingredients from available material which gives cohesive concrete of the desired workability in fresh stage and desired strength and durability in the hardened stage. It is the step by step procedure for selection of water-cement ratio, water content and estimation of coarse aggregate content and fine aggregate content done in a laboratory with actual material which is going to be used.
The object of concrete mix design is to achieve the predetermined minimum strength and durability in the most economical manner. The cost of concrete mainly depends on two main factors:
- Cost of materials
- Cost of labour (i.e formwork, batching, mixing, transporting, placing, curing etc.)
Therefore it is very important to keep in mind the cost of materials for concrete mix design. Since the cost of cement is many times more than the other constituents, attention is mainly focussed to the use of as optimum cement as possible consistent with desired strength and durability.
The selection of proper concrete ingredients is also very important for transporting the concrete, especially where pumping of the concrete is done. Setting time, bleeding in concrete, ease of finishing is also interlinked with concrete mix design.
A good concrete mix should have the following important properties.
1- It should meet the strength requirement of the structure, which is measured in compressive strength.
2- Fulfill the durability requirement
3- It should be mixed, transported and easily compacted
4- It should be economical.
Therefore, good concrete, which makes your house safe for life and ultimately saves your money.