WHAT IS THE DIFFERENCE BETWEEN NOMINAL MIX AND DESIGN MIX CONCRETE?

Mix design is a process of selecting suitable ingredients and determining their relative proportions with the objective of producing concrete of having certain minimum workability, strength and durability as economically as possible.

Concrete

Concrete

A mix design can be designed in two ways as explained below

  1. Nominal Mix
  2. Design

Nominal Mix

It is used for relatively unimportant and simpler concrete works. In this type of mix, all the ingredients are prescribed and their proportions are specified. Therefore there is no scope for any deviation by the designer. Nominal mix concrete may be used for concrete of M-20 or lower. The various ingredients are taken as given in the table below

Grade

Max. quantity of dry Aggregates per 50 kg of cement

Fine Aggregate to Coarse Aggregate Ratio, by mass

Max. Quantity of water in litres

M-5

800

Generally 1:2 but may varies from 1:1.5 to 1:2.5

60

M-7.5

625

45

M-10

480

34

M-15

330

32

M-20

250

30

Design Mix

It is a performance based mix where choice of ingredients and proportioning are left to the designer to be decided. The user has to specify only the requirements of concrete in fresh as well as hardened state. The requirements in fresh concrete are workability and finishing characteristics, whereas in hardened concrete these are mainly the compressive strength and durability.

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