As per IS-456,nominal mix is Prescriptive type,means its
ingrediant ratio is fixed,more over the other parameters
like maximum size of Aggregate,w/c ratio,type of cement
etc.are also fixed,aiming that adherence to such
prescriptive specification will result in satisfactory
performance.
On the other hand,Designe mix is Performance based
concrete,where the properties of concrete like
strength,workability,durability etc. are specified and
ingredients ratio,maximum size of aggregate,type of cement
etc is user's choice.

The main difference between Nominal Mix and Design Mix is
that :-
In Nominal mix design we are considering the ratio of
ingradients like 1:1.5:3, Here no water cement ratio,Size
of agreegate, strength,durability, workability are
considered.
Where as in Design Mix apart from ingradients ratio other
factors like, w/c ratio, Size of aggregate ,workability etc
are kept in consideration while designing.

hence taking same ingradients two or more NOMINAL MIX
design may have differenth strength,
whereas in Mix design it is unlike the above.

Also the nominal mix design is less economical.
(SANTOSH AGNIHOTRI,Material Engineer in Multintional
Company)
Mob:00249905840111

Nominal mixes are those proportioned by the volume of the
main ingredients and usually written in order of the
ingredients thus Cement:Sand: Coarse aggregate (stone,
chippings). So a 1:3:6 is a nominal mix containing 1 volume
of cement, 3 volumes of sand and 6 volumes of coarse
aggregate.

Gauge boxes are generally used to batch the ingredients.
The problem with these types of mixes is that the quality
of the concrete is entirely dependant on the quality of the
materials. In other words, if you use the same gauge boxes
to weigh ingredients from different sources, you will most
likely have different concrete qualities.

Designed mixes on the other hand are specified as a grade
the producer of the concrete has to achieve usually in
terms of compressive strength but may include other
criteria (size of the stone, minimum amount of cement,
flexural strength, air content etc). So a grade 30 concrete
will be the same whether batched in Kansas City, Karachi,
Kingston-Upon-Hull or Kinshasa

Nominal Mix can be said as the mix prepared as per the
given standards in IS

Whereas Design mix is something which is prepared based on
the availabilty of the quality or type of the aggregates
(both coarse and fine) found on that locality or nearby
vicinity to meet the requirements of the strength of the
concrete.

There is no hard and fast rule for the quantity of the
materials should be either based on volume or weight.

nominal mix is an optimistic way of design,it provides us with strength greater than required.It is not economical.

whereas a mix design is carried out according to the stipulated codes of IS.It is cost effective and a mix design considers various parameters and gives us the required design strength.

Nominal mixes are those proportioned by the volume of the main ingredients and usually written in order of the ingredients thus Cement:Sand: Coarse aggregate (stone, chippings). So a 1:3:6 is a nominal mix containing 1 volume of cement, 3 volumes of sand and 6 volumes of coarse aggregate.

Gauge boxes are generally used to batch the ingredients. The problem with these types of mixes is that the quality of the concrete is entirely dependant on the quality of the materials. In other words, if you use the same gauge boxes to weigh ingredients from different sources, you will most likely have different concrete qualities.

Designed mixes on the other hand are specified as a grade the producer of the concrete has to achieve usually in terms of compressive strength but may include other criteria (size of the stone, minimum amount of cement, flexural strength, air content etc). So a grade 30 concrete will be the same whether batched in Kansas City, Karachi, Kingston-Upon-Hull or Kinshasa

nominal mix is a mixing ratio constant and also vary widely
strenght of concrete maximum size of aggregate ,design mix
is performance based the property like strenght durability
workability &cost of material is reduced

nominal mix:vary widely in strength due to less or more mix
in coarse and fine aggregate and another main factor it is
not ecnomical
design mix:designed by the engineers ,not much vary in
strength and it is economical

a)If column dimensions are 250*400mm , what will be
cutting length for 8mm stirrups and how to calculate it? b)
If beam dimensions are 200*400mm , beam coveris 25mm , slab
cover is 20mm , what will be the cutting length for
stirrups? c)Column dimensions are 250*400mm , reinf. is
12nos. bar of 16mm dia , stirrups provided are two legged,
what will be the length of each ring?
Regards