1. What is Mix design. 2. Understand the different types of mix. 3. Design the mix proportion as per IS Method. 4. Design the mix proportion as per ACI Method.

1. Advanced Concrete Technology
Mix Design of Concrete
By
Dr. S.K

2. Concrete Mix Design
Concrete mix design may be defined as the art of selecting
suitable ingredients of concrete and determining their
relative proportions with the object of producing
concrete of certain minimum strength & durability as
economically as possible.
OR
“ Mix Design is the science of determining the relative
proportions of the ingredients of concrete to achieve the
desired properties in the most economical way.”

3. Objectives of Mix Design
• The purpose of concrete mix design is to ensure the most optimum
proportions of the constituent materials to fulfill the requirement
of the structure being built.
Mix design should ensure following objectives,
• To achieve the designed/ desired workability in the plastic stage
• To achieve the desired minimum strength in the hardened stage
• To achieve the desired durability in the given environmental
conditions
• To produce concrete as economically as possible.

4. Basis for selection and proportioning of materials
• The structural requirements of the concrete environmental
conditions
• The job site conditions, especially the methods of concrete
production, transport, placement, compaction and finishing
• The characteristics of the available raw materials
Basic Considerations
The following point must be considered while designing concrete
mixes
• Cost
• Specification
• Workability
• Strength and Durability

5. BasicConsiderations
1. Cost
The cost of concrete is made up of
•Material Cost
•Equipment Cost
•Labour Cost
•The variation in the cost of materials arises from the fact
that cement is several times costlier than aggregates.
•So it is natural in mix design to aim at as lean a mix as
possible. Therefore, all possible steps should be taken to
reduce the cement content of a concrete mixtures without
sacrificing the desirable properties of concrete such as
strength and durability.
Dr.S.Kavitha

6. BasicConsiderations
• 2.Specifications
• The following point may be kept in mind while designing concrete mixes
• Minimum Compressive Strength required
• Minimum water/ cement ratio
• Maximum cement content to avoid shrinkage cracks
• Maximum aggregate / cement ratio
• Maximum density of concrete in case of gravity dams
Dr.S.Kavitha Fig.1 Materials for Concrete

7. BasicConsiderations
3.Workability
•The following points related to workability shall be kept in mind
while designing concrete mixes.
•The consistency of concrete should no more than that necessary
for placing, compacting and finishing.
• For concrete mixes required high consistency at the time of
placing, the use of water-reducing and set-retarding
admixtures should be used rather than the addition of more
water
•Wherever possible, the cohesiveness and finishibility of concrete
should be improved by increasing sand/ aggregate ratio than by
increasing the proportion of the fine particles in the sand.

8. 4. Strength and durability
•Strength and durability require lower w/c ratio. It is usually
achieved not by increasing the cement content, but by
lowering the water at given cement content. Water demand
can by lowered by throughout control of the aggregate
grading and by using water reducing admixtures.
Dr.S.Kavitha Fig.2 Casting of Concrete

9. FactorsInfluencingChoiceofMix Design
According to IS456:2000 and IS1343:1980 the important influencing the design of
concrete mix are
• Gradeof Concrete
• Typeof Cement
• Maximum nominal Sizeof Aggregate
• GradingofCombined aggregate
• Maximum Water/ CementRatio
• Workability
• Durability
• Quality Control.
Gradeof Concrete
•The grade of concrete gives characteristic compressive
strength of concrete. It is one of the important factor
influencing the mix design
•Depending upon the degree of control available at site, the
concrete mix is to be designed for a target mean
compressive strength (fck) applying suitable standard
deviation.
Dr.S.Kavitha

10. FactorsInfluencingChoiceofMix Design
Typeof Cement
• The rate of development of strength of concrete is influenced by
the type of cement.
• The higher the strength of cement used in concrete, lesser will be
the cement content.
• The use of 43 grade and 53 grade of cement, gives saving in
cement consumption as much as 15 % and 25 % respectively, as
compared to 33 grade of cement. For concrete of grade M25 it is
advisable to use 43 and 53 gradeof cement.
Dr.S.Kavitha

11. FactorsInfluencingChoiceofMix Design
Maximum Nominal Sizeof Aggregates
• The maximum size of C.A is determined by sieve analysis. It is designated by the
sieve size higher than larger size on which 15 % or more of the aggregate is
retained. The maximum nominal size of C.A. should not be more than one-forth
of minimum thickness of the member.
• For heavily reinforced concrete members as in the case of ribs of main beams,
the nominal maximum size of the aggregate should usually be restricted to sum
less than the minimum clear distance between the main bars or 5 mm less the
minimum cover to the reinforcement, whoever issmaller.
• The workability of concrete increases with an increase in the maximum size of
aggregate. But the smaller size of aggregates provide larger surface area for
bonding with the mortar matrix which gives higherstrength.
GradingofCombined Aggregates
• The relative proportions of the fine and coarse aggregate in a concrete mix is
one of the important factors affecting the strength of concrete.
• For dense concrete, it is essential that the fine and coarse aggregate be well
graded. In the case when the aggregate available from natural sources do not
confirm to the specified grading, the proportioning of two or more aggregate
become essential Dr.S.Kavitha

12. GradingofCombinedAggregates
Durability
• Durability require low water/Cement ratio. It is usually achieved not
by increasing the cement content, but by lowering the water demand
at a given cement content.
• Water demand can be lowered by through control of the aggregate
grading and by using water reducingadmixtures
Dr.S.Kavitha

13. Compressive strength of concrete
• Concrete compressive strength considered as the most important
concrete property. It influences many other describable properties of
the hardened concrete.
• The mean compressive strength (fcm) required at a specific age,
usually 28 days, determines the nominal water-cement ratio of the
mix.
• ISO 456-2000, British Standard, and Eurocode utilize the term mean
compressive strength which is slightly greater than characteristic
compressive strength. However, ACI Code do not use such term.
• Other factors which influences the concrete compressive strength at
given time and cured at a specified temperature is compaction
degree.
• Finally, it is demonstrated that, concrete compressive strength of
fully compacted concrete is inversely proportional to the water-
cement ratio.

14. Fig.3 Compressive strength
Fig.4 Split Compressive strength

15. Workability of concrete
• Concrete workability for satisfactory placement and compaction
depends on the size and shape of the section to be concreted, the
amount and spacing of reinforcement, and concrete transportation;
placement; and compaction technique.
• Additionally, use high workability concrete for the narrow and
complicated section with numerous corners or inaccessible parts.
This will ensure the achievement of full compaction with a
reasonable amount of effort.
• Frequently, slump test values used to evaluate concrete workability.
• Lastly, ACI 211.1 provides slump test values for various reinforced
concrete sections which ranges from 25 mm to 175 mm.

16. Fig.5 Workability of Concrete
Fig.6 Pouring of SCC

17. Durability of concrete
• The ability of concrete to withstand harmful environment conditions
termed as concrete durability.
• High strength concrete is generally more durable than low strength
concrete.
• In the situations when the high strength is not necessary but the
conditions of exposure are such that high durability is vital, the
durability requirement will determine the utilized water-cement ratio.
• Concrete durability decreases with the increase of w/c ratio.
•

18. Fig.6 Durabilty of Concrete
Fig.7 Aggregate types

19. Quality Control at site
• The degree of control could be evaluated by the variations in test
results.
• The variation in strength results from the variations in the
properties of the mix ingredients, in addition to lack of control of
accuracy in batching, mixing, placing, curing and testing.
• Finally, the lower the difference between the mean and minimum
strengths of the mix lower will be the cement-content required. The
factor controlling this difference is termed as quality control.

20. Grade of Concrete
The concrete shall be in grades designated

22. TYPES OF CONCRETE MIXES
1. NOMINAL MIX
Mixes of fixed proportions, IS:456-2000 permits nominal
mixes for concretes of strength M20 or lower
2. DESIGN MIX
Designed on the basis of requirements of the concrete in fresh
and hardened states.

23. 1. Nominal Mix Concrete
• The wide use of concrete as construction materials has led to
the use of mixes of fixed proportion, which ensures adequate
strength. These mixes are called nominal mixes.
• They offer simplicity and Under normal circumstances, has
margin of strength above that specified.
• Nominal mix concrete may be used for concrete of grades M5,
M 7.5, M10, M15 and M20.

24. Proportions of Ingredients in Nominal Mixes
The proportions of materials for nominal mix shall be in
accordance.

25. 2. Design Mix Concrete
• The concrete mix produced under quality control keeping in view
the strength, durability, and workability is called the design Mix.
• Others factors like compaction equipment's available, curing method
adopted, type of cement, quality of fine and coarse aggregate etc.
have to be kept in mind before arriving at the mix proportion.
• The design mix or controlled mix is being used more and more in
variety of important structures, because of better strength, reduced
variability, leaner mixed with consequent economy, as well as greater
assurance of the resultant quality.

26. Method of Concrete Mix Design
Some of the commonly used mix design methods are,
• I.S. Method
• A.C.I method
• Road Note 4 method ( U.K. Method)
• IRC 44 method
• Arbitrary method
• Maximum Density method
• Fineness modulus method
• Surface area Method
• Mix design for high strength Concrete
• Mix design for
• DOE (British) Mix despumpable Concreteign method

27. PRINCIPLES OF MIX DESIGN
1 The environment exposure condition for the structure
2 The grade of concrete, their characteristic strength’s and standard deviations
3 The type of cement
4 The types and sizes of aggregates and their sources of supply
5 The nominal maximum sizes of aggregates
6 Maximum and minimum cement content in kg/m3
7 Water cement ratio
8 The degree of workability of concrete based on placing conditions
9 Air content inclusive of entrained air
10 The maximum/minimum density of concrete
11 The maximum/minimum temperature of fresh concrete
12 Type of water available for mixing and curing
13 The source of water and the impurities present in it.

28. I.S. Method-Refer
IS 10262-2009

29. 2. A.C.I method:
• In 1991,the American Concrete Institute(ACI)
published guidelines for normal, heavyweight and mass
concrete mix design.
• The absolute volume method of mix design as described
by ACI committee 211 is presented
• ACI method of concrete mix design is based on the
estimated weight of the concrete per unit volume.
• This method takes into consideration the requirements for
consistency, workability, strength and durability

30. ACI Method of Concrete Mix Design
Required Data:
Before starting concrete mix design, basic information on raw materials
shall be prepared which include:
• Sieve analysis of fine and coarse aggregates.
• Unit weight (dry rodded density) of coarse aggregate.
• Bulk specific gravities and absorptions or moisture content of
aggregates.
• Mixing-water requirements of concrete developed from experience
with available aggregates.
• Specific gravities of Portland cement and other cementitious
materials, if used.
• Relationships between strength and water-cement ratio or ratio of
water-to-cement plus other cementitious materials, for available
combinations of cements, other cementitious materials if considered,
and aggregates.

31. Procedure for ACI Method of Concrete Mix Design
1. Choice of slump
• If slump is not specified, a value appropriate for the work can be
selected from Table 11.7 The values provided in table can be used
only when vibration is used to consolidate concrete.

32. 2. Choice of maximum size of aggregate
• Generally, maximum aggregate size should be the largest that is
economically available and consistent with dimensions of structural
element. ACI 211.1-91 specify that, maximum aggregate size shall
not surpass:
• One-fifth of the narrowest dimension between sides of forms.
• one-third the depth of slabs
• 3/4-ths of the minimum clear spacing between individual reinforcing
bars, bundles of bars, or pre-tensioning strands.
• These limitations may be ignored provided that workability and
methods of consolidation are such that the concrete can be placed
without honeycomb or void.

33. 3. Estimation of mixing water and air content
• The quantity of water per unit volume of concrete required to
produce a given slump is dependent on:
- Nominal maximum size
- Particle shape
- Grading of the aggregates
- Concrete temperature
- Amount of entrained air
- Use of chemical admixtures.
• Table 2 and Table 3 provide estimates of required mixing water for
concrete made with various maximum sizes of aggregate, for non-
air and air-entrainment concrete, respectively.

35. 4. Selection of water-cement or water-cementitious material ratio:
• Strength, durability, and determine water to cement ratio:
Without strength vs. w/c ratio data for a certain material, a conservative estimate
can be made for the accepted 28-day compressive strength from Table 11.5.
• Additionally, if there are severe exposure conditions, such as freezing and thawing,
exposure to seawater, or sulfates, the w/c ratio can be obtained from table 11.6.

38. 5. Calculation of cement content
• The amount of cement is fixed by the determinations made in Steps 3
and 4 above.
Fig.8 Cement

39. 6. Estimation of coarse aggregate content
• The most economical concrete will have as much as possible space
occupied by coarse aggregate since it will require no cement in the
space filled by coarse aggregate.
• The percent of coarse aggregate to concrete for a given maximum
size and fineness modulus is given by Table 6. Coarse aggregate
volumes are based on oven-dry rodded weights obtained in
accordance with ASTM C 29.

41. 7. Estimation of fine aggregate content
• There are two standard methods to establish the fine aggregate
content, the mass method and the volume method. the “volume”
method will be used because it is a somewhat more exact procedure.
• The volume of fine aggregates is found by subtracting the volume of
cement, water, air, and coarse aggregate from the total concrete
volume.
• Then once the volumes known the weights of each ingredient can be
calculated from the specific gravities.
• The volume occupied in concrete by any ingredient is equal to its
weight divided by the density of that material (the latter being the
product of the unit weight of water and the specific gravity of the
material).

42. 8. Adjustments for aggregate moisture
Aggregate weights
• Aggregate volumes are computed based on oven dry unit weights,
but aggregate is typically batched based on actual weight.
• Therefore, any moisture in the aggregate will increase its weight and
stockpiled aggregates almost always contain some moisture. Without
correcting for this, the batched aggregate volumes will be incorrect.
Amount of mixing water
• If the batched aggregate is anything but saturated surface dry it will
absorb water (if oven dry or air dry) or give up water (if wet) to the
cement paste.
• This causes a net change in the amount of water available in the mix
and must be compensated for by adjusting the amount of mixing
water added.

43. Fig.8 Aggregate water content

44. 9. Trial Batch Adjustments
• The ACI method is written on the basis that a trial batch of concrete
will be prepared in the laboratory, and adjusted to give the desired
slump, freedom from segregation, finishability, unit weight, air
content and strength.
Refer the problems in IS 10262-2019 and ACI Code
(Available in Course material)

45. THANK YOU