Concrete is the most extensively material composed of cement, sand, coarse and fine aggregates with is mixed with water that’s in turn hardens. During the formation of concrete mix, we can add plasticizers whether they are accelerating/retarding plasticizers which depends on the design mix considerations. Moreover, the temperature is the important factor that can affect the concrete and the mix design should have a good quality with high performance. The desired properties of structure is achieved by an economical extensively concrete mix.
DESIGN MIX-
is defined as the process of selecting the appropriate components of concrete and determining their relative proportions with the aim of producing concrete of as little strength and durability as possible economically.
There are many grades of design mix concrete like M-25, M-30, M-35, and M-40 etc.
M-25 1:1:2
M-30 1:1.5:2.8
M-35 1:1.53:2.88
M-40 1:1.74:2.75.
The above mix designs M-30,33,40 are designed as per the requirement of the project which includes cost rates with the contractor. In the above grades of concrete mix, the letter ‘M’ refers to Mix whereas the value like 25,30,35 and 40 etc indicate the compressive characteristic strength of concrete after 28 days considering suitable conditions. Unit of this compressive characteristic strength of concrete is Newton /mm2
- A design mix is a mix in which all the proportions of the mix are considered in terms of weight where the stable cost of concrete can be reduced.
- It is performance-oriented concrete.
- It has quality control.
- Material is considered to be the maximum size according to the aggregate
NOMINAL MIX-
specifies the fix or standard arbitrary proportion of the cement, sand, and aggregates.
There are many grades of nominal mix concrete like M-5, M-7.5, M-10, M-15, and M-20.
The ratio of various grades of concrete is being given below –
M-5 1:5:10
M-7.5 1:4:8
M-10 1:3:6
M-15 1:2:4
M-20 1:1.5:3
For example – For M-5 We can say 1(cement):5(fine aggregate or sand) :10(coarse aggregate). In the above grades of concrete mix, the letter ‘M’ refers to Mix whereas the value like 5,7.5,10,15, etc indicate the compressive characteristic strength of concrete after 28 days in specified conditions. Unit of this compressive characteristic strength of concrete is Newton /mm2
- The nominal mixture is a volume in which all the volume ratios are considered where the strength and cost of concrete vary.
- It is used in ordinary concrete which includes concrete grade which does not exceed M-20.
- Quality control is not required.
- Such type of concrete mix is generally used in small quantities or where the load is not high.
