Difference between nominal mix and design mix of concrete -
Concrete is most extensively used mix to
achieve desired properties of structure.
There are two methods to prepare the concrete mix.
2- Design mix
Nominal mix- Nominal mix specifies the fix proportion of the cement , sand and aggregates.
- Ingredients of concrete are mixed on the basis of volume.
- It is a site level mixing of ingredients to prepare concrete mix.
- Such type of concrete mix is generally used in small quantity or where load is not high.
There are many grade of nominal mix concrete like M-5, M-7.5, M-10, M-15 and M-20.
In above grades of concrete mix the letter 'M' refers to Mix where as the value like 5,7.5,10,15 etc indicates the compressive characteristic strength of concrete after 28 days in specified conditios. Unit of this compressive characteristic strength of concrete is Newton /mm2.
The ratio of various grade of concrete is being given below -
1(cement):5(fine aggregate or sand) : 10(coarse aggregate)
Design mix - Design mix is a process to prepare concrete by testing all necessary properties (like properties of cement, fine aggregate and coarse aggregate) of concrete ingredients.
- Ingredients of concrete are mixed on the basis of weight.
- It is generally designed from ready Mix Concrete (RMC) plant .
- This method to prepare concrete mix is used in heavy structures or where load is very high.
In above grades of concrete mix the letter 'M' refers to Mix where as the value like 25,30,35 and 40 etc indicates the compressive characteristic strength of concrete after 28 days considering suitable conditios. Unit of this compressive characteristic strength of concrete is Newton /mm2.
Ratio can vary on the basis of site condition and requirements.
# After preparing concrete on the basis of design mix, trail is done to check various important properties of concrete like strength, durability and workability etc.
Gyan of engineering (Mukesh Kumar)