Concrete Mix Design.pdf

Unit no.4
Concrete Mix Design
Mr. Kiran R. Patil
Assistant Professor,
Department of Civil Engineering,
D. Y. Patil College of Engineering & Technology, Kolhapur

 Mix Design:
• Mix design is defined as the process of selecting suitable ingredients of concrete and
determining their proportions in order to produce concrete of certain minimum compressive
strength and durability, as economically as possible.
 Objectives of Mix Design:
• Following are the main objectives of mix design,
1) To achieve a specified characteristics compressive strength of 28 days period.
2) To achieved specified workability.
3) To have economy as much as possible.
4) To have satisfactory appearance.
5) To obey with certain other specified properties & not to have certain drawbacks such as
honey-combing & segregation etc.
 Factors Governing Mix design
• The design of concrete mix should be based on the following factors,
1) Grade designation
2) Type and grade of cement
3) Maximum nominal size of aggregate
4) Grading of combined aggregates
5) Water-cement ratio
6) Workability
7) Durability
8) Quality control

 Statistical Quality Control and Acceptance Criteria
• Statistical quality control provides a scientific approach to the concrete designer to
understand the realistic variations so as to specify the strength with proper tolerance for
the unavoidable variations.
• The acceptance criteria are based on statistical evaluation of the test results of samples
taken at random during execution. There will be variations in the strength of test cubes
tested randomly.
• If a number of test results are plotted on histogram, the curve follows a bell shape and
this curve is known as 'Normal Distribution Curve'.
• The normal distribution curve can be used to ascertain the variation of strength from the
mean. The area under the curve represents the total number of test results.
 Mean Strength :
• This is the average strength obtained by dividing the sum of strength of all the cubes by
the number of cubes.
 Variance :
• This is the measure of difference between any single observed data from the mean
strength.
 Standard Deviation (σ) :
• This is the root mean square deviation of all the results.

 Coefficient of Variation :
Problem: For following data, find average strength, standard deviation and coefficient of
variation

• Sampling and Acceptance Criteria as per IS 456 : 2000
• Sampling is an important step in quality control of concrete. A random sampling method
should be adopted so that each concrete batch will be tested. The sampling and casting of
cubes should be spread over the entire period of concreting.
• Frequency of Sampling:
• The frequency of sampling of concrete of each grade will be as shown in the below table
• Test Specimen:
• Three test specimens should be prepared for each sample for testing at 28 days. Additional
three specimens may be prepared for 7 days strength.
• Test Results:
• The test result of a sample is the average of the strength of three specimens. The individual
variation should not be more than 15 % of the average. If more, the test result of that
sample is rejected.

• Methods of Concrete Mix Design:
• Mix design according to Indian Standard Recommended Guidelines
• ACI (American Concrete Institute) Method
• DoE (British) mix design method.
1. Concrete Mix Design by Indian Standard Recommended Method (I.S. 10262:2009):
• This method is framed by taking into account the codal provisions for mix design in IS
456 : 2000. This method is widely used in India.
• This method is recommended for design mixes for general types of construction using the
ingredients of concrete normally available.
• The design is carried out for a specified compressive strength, workability and durability
of concrete using continuously graded aggregates.
• The basic assumption made in I.S. method is that the compressive strength of concrete is
based on the W/C ratio. Further, for a given type, shape, size and grading of aggregates,
the amount of water determines the workability for normal concretes.
• This method is applicable for ordinary and standard grades only i.e. from M 10 to M 55.
• Data required for Mix Design
1) Grade designation
2) Type of cement
3) Maximum nominal size of aggregate
4) Minimum cement content
5) Maximum W/C ratio
6) Workability slump in mm

7) Exposure conditions as per Tables 4 and 5 of IS 456 : 2000
8) Maximum temperature of concrete at the time of placing
9) Method of transporting and placing
10) Type of aggregate
11) Maximum cement content
12) Type of admixture

 Tables from IS 10262:2009, IS 456:2000 and IS 383:1970
• Tables from IS 10262:2009
• Table 1: Assumed Standard Deviation
• Table 2 : Maximum Water Content per Cubic Metre of Concrete for Nominal Maximum
Size of Aggregate
Grade of Concrete Assumed Standard Deviation N/mm²
M10
M15
3.5
M20
M25
4.0
M30
M35
M40
M45
M50
M55
M60
5.0
Nominal Maximum Size of
Aggregate
Maximum Water Content
kg
10 208
20 186
40 165

• The water content in Table 2 is for 25 to 50 mm slump range. For the desired workability
(other than 25 to 50 mm slump range), the required water content may be established by an
increase by about 3 percent for every additional 25 mm slump or alternatively by use of
chemical admixtures.
• Table 3: Volume of Coarse Aggregate per Unit Volume of Concrete for Different Zones of
Fine Aggregate
• The values for aggregate volume given in Table 3 are for a water-cement ratio of 0.50,
which may be suitably adjusted for other water-cement ratios.
Nominal
Maximum Size of
Aggregate (mm)
Volume of Coarse Aggregate per Unit Volume of
Concrete for Different Zones of Fine Aggregate
Zone IV Zone III Zone II Zone I
10 0.50 0.48 0.46 0.44
20 0.66 0.64 0.62 0.60
40 0.75 0.73 0.71 0.69

• Tables from IS 456:2000:
• Table 4: Environmental Exposure Conditions
Sr.No. Environment Exposure Conditions
i) Mild Concrete surfaces protected against weather or aggressive conditions,
except those situated in coastal area
ii) Moderate Concrete surfaces sheltered from severe rain or freezing whilst wet
Concrete exposed to condensation and rain
Concrete continuously under water
Concrete in contact or buried under non-aggressive soil or ground
water
Concrete surfaces sheltered from saturated salt air in coastal area
iii) Severe Concrete surfaces exposed to severe rain, alternate wetting and drying
or occasional freezing whilst wet or severe condensation
Concrete completely immersed in sea water
Concrete exposed to coastal environment
iv) Very severe Concrete surfaces exposed to sea water spray, corrosive fumes or
severe freezing conditions whilst wet
Concrete in contact or buried under aggressive sub-soil or ground
water
v) Extreme Surface of members in tidal zone
Members in direct contact with liquid/ solid aggressive chemicals

• Table 5: Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade
of Concrete for Different Exposures with Normal Weight Aggregates of 20 mm Nominal
Maximum Size
• Table 6: Adjustments to Minimum cement Contents for Aggregates other than 20 mm
Nominal Maximum Size
Sr.
No.
Exposure Plain Concrete Reinforced Concrete
Minimum
Cement
Content
kg/m³
Maximum
Free W/C
Ratio
Minimum
Grade of
Concrete
Minimum
Cement
Content
kg/m³
Maximum
Free W/C
Ratio
Minimum
Grade of
Concrete
i) Mild 220 0.60 300 0.55 M20
ii) Moderate 240 0.60 M15 300 0.50 M25
iii) Severe 250 0.50 M20 320 0.45 M30
iv) Very
severe
260 0.45 M20 340 0.45 M35
v) Extreme 280 0.40 M25 360 0.40 M40
Sr.
No.
Nominal Maximum Aggregate Size
mm
Adjustments to Minimum Cement
Content in Table 5
kg/m³
i 10 40
ii 20 0
iii 40 -30

Maximum Cement Content: Cement content not including fly ash and ground blast furnace
slag in excess of 450 kg/ m³ should not be used.
• Tables from IS 383 - 1970
• Table 7: Grading limits for Fine Aggregate
• Table 8: Grading limits for Combined Coarsed Aggregate
Sieve Size Percentage passing for
Zone I Zone II Zone III Zone IV
10 mm 100 100 100 100
4.75 mm 90 – 100 90 – 100 90 – 100 95 – 100
2.36 mm 60 – 95 75 – 100 85 – 100 95 – 100
1.18 mm 30 – 70 55 – 90 75 – 100 90 – 100
600 micron 15 – 34 35 – 59 60 – 79 80 – 100
300 micron 5 – 20 8 – 30 12 – 40 15 – 50
150 micron 0 – 10 0 – 10 0 – 10 0 – 15
Sieve Size Percentage passing for graded aggregate of nominal size
40 mm 20 mm 16 mm 12.5 mm
40 mm 95 – 100 100 - -
20 mm 30 – 70 95 – 100 100 100
16 mm - - 90 – 100 -
12.5 mm - - - 90 – 100
10 mm 10 – 35 25 – 55 30 – 70 0 – 45
4.75 mm 0 – 5 0 – 10 0 – 10 0 – 10
2.36 mm - - - -

• Target Strength (f’ck)
f’ck = fck + K.s
Where,
fck= characteristic compressive strength below which certain percentage of test results are
expected to fall
K = constant depending on the probability of certain number of results likely to fall below
fck
s= standard deviation
• The characteristic strength is defined by IS 456 – 2000 as the strength of material below
which not more than 5 percent (1 in 20) results are expected to fall. For this case, the
value of K will be 1.65 and the equation for target strength will be,
f’ck = fck + 1.65.s

• Mix Design for M 30 by IS method
• Reference: IS 10262-2009, IS 456- 2000, IS 383-1970

• Mix Design of M30 concrete by using fly ash (IS 10262: 2009)

• Concrete Mix Design by ACI (American Concrete Institute) Method
• Procedural Steps:
1. Data to be collected:
• Fineness Modulus of F.A.
• Unit weight of C.A,
• Specific gravity of C.A. and F.A.
• Water absorption of C.A. and F.A.
• Specific gravity of cement
2. Estimate the mean design strength fm from the minimum strength specified by using
standard deviation.
fm = fmin + ks
• where, fmin = minimum strength or specified design strength
• k = probability factor = 1.64 (assuming 5 % of results are allowed to fall below
specified design strength)
• s = standard deviation
3. Find the W/C ratio from the strength point of view from Table 2. Also, find the W/C
ratio from the durability point of view from Table 3. Adopt the lower value.
4. Decide the maximum size of aggregate to be used. Generally for RCC work 20 mm
and prestressed concrete 10 mm size are used.

5. Decide the workability in terms of slump for the type of job in hand. General guidance can
be taken from Table 4.
6. The total water content is read from Table 5 with the selected slump and selected
maximum size of aggregate.
7. Cement content is computed by dividing the total water content by W/C ratio.
8. From Table 1 the bulk volume of dry rodded coarse aggregate per unit volume of concrete
is selected, for the particular maximum size of coarse aggregate and fineness modulus of fine
aggregate.
9. The weight of C.A. per cubic meter of concrete is calculated by multiplying the bulk
volume with bulk density.
10. The solid volume of C.A. in one cubic meter of concrete is calculated by knowing the
specific gravity of C.A.
11. Similarly the solid volume of cement, water and volume of air is calculated in one cubic
meter of concrete.
12. The solid volume of F.A. is determined by subtracting the sum of solid volumes of the
C.A., cement, water and entrained air from the total volume of concrete.
13. Weight of F.A. is calculated by multiplying the solid volume of F.A. by specific gravity of
F.A.

• Various tables from ACI 211.1 – 91
• Table 1
• Dry Bulk Volume of Coarse Aggregate per Unit Volume of Concrete according to ACI
211.1-91
• Note: The values given will produce a mix that is suitable for reinforced concrete
construction. For less workable concrete the values may be increased by about 10
percent. For more workable concrete such as pumpable concrete the values may be
reduced by up to 10 percent.
Maximum Size of
Aggregate (mm)
↓
Bulk volume of dry rodded coarse aggregate per unit volume of concrete for
fineness modulus of sand of
F.M. → 2.40 2.60 2.80 3.00
10 0.50 0.48 0.46 0.44
12.5 0.59 0.57 0.55 0.53
20 0.66 0.64 0.62 0.60
25 0.71 0.69 0.67 0.65
40 0.75 0.73 0.71 0.69
50 0.78 0.76 0.74 0.72
70 0.82 0.80 0.78 0.76
150 0.87 0.85 0.83 0.81

• Table 2
• Relation between water/ cement ratio and average compressive strength of concrete,
according to ACI 211.1-91
• Note: Measured on standard cylinders. The values given are for a maximum size of
aggregate of 20 to 25 mm and for ordinary Portland cement and for recommended
percent of air entrainment shown in Table 5
Average compressive strength
at 28 days
Effective water/ cement ratio
(by mass)
MPa Non-air ertrained concrete Air ertrained concrete
45 0.38 -
40 0.43 -
35 0.48 0.40
30 0.55 0.46
25 0.62 0.53
20 0.70 0.61
15 0.80 0.71

• Table 3
• Requirements of ACI 318-89 for W/C ratio and strength for special Exposure Conditions
• Note: The upper limit of slump may be increased by 20 mm for compaction by hand.
Sr.
No.
Exposure Condition Maximum W/C
ratio, normal
density aggregate
concrete
Minimum design
strength, low
density
aggregate
concrete MPa
I Concrete intended to be watertight
(a) Exposed to fresh water 0.50 25
(b) Exposed to brackish or sea water 0.45 30
II Concrete exposed to freezing and thawing in a
moist condition
(a) Kerbs, gutters, guard rails or thin sections 0.45 30
(b) Other elements 0.50 25
(c) In presence of de-icing chemicals 0.45 30
III For corrosion protection of reinforced
concrete exposed to de-icing salts, brackish
water, sea water or spray from these sources
0.40 33

Type of construction Range of Slump
mm
Reinforced foundation walls and footings 20 – 80
Plain footings, caissons and substructure walls 20 – 80
Beams and reinforced walls 20 – 100
Building columns 20 – 100
Pavements and slabs 20 – 80
Mass concrete 20 – 80
Table 4
Recommended values of slump for various types of construction according to ACI 211.1-91

• Table 5
• Approximate requirements for mixing water and air content for different
workabilities and nominal maximum size of aggregates according to ACI 211.1-91
Workability
or
Air content
Water content, kg/m3 of concrete for indicated maximum aggregate size
10 mm 12.5 mm 20 mm 25 mm 40 mm 50 mm 70 mm 150 mm
Non air-entrained concrete
Slump
30-50 mm 205 200 185 180 160 155 145 125
80-100 mm 225 215 200 195 175 170 160 140
150-180 mm 240 230 210 205 185 180 170 -
Approximate entrapped
air content percent 3 2.5 2 1.5 1 0.5 0.3 0.2
Air-entrained concrete
Slump
30-50 mm 180 175 165 160 145 140 135 120
80-100 mm 200 190 180 175 160 155 150 135
150-180 mm 215 205 190 185 170 165 160 -
Recommended average
total air content percent
Mild exposure 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0
Moderate exposure 6.0 5.5 5.0 4.5 4.5 4.0 3.5 3.0
Extreme exposure 7.5 7.0 6.0 6.0 5.5 5.0 4.5 4.0

• Table 6
• First estimate of density (unit weight) of fresh concrete according to ACI 211.1-91
Maximum size of
aggregate mm
First estimate of density of fresh concrete
Non air-entrained concrete
kg/m3
Air-entrained concrete
kg/m3
10 2285 2190
12.5 2315 2235
20 2355 2280
25 2375 2315
40 2420 2355
50 2445 2375
70 2465 2400
150 2505 2435

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