CONCRETE TECHNOLOGY

MODULE – IV

SYALLABUS:
Concrete Mix Proportioning Concept of Mix Design with and without admixtures, variables in
proportioning and Exposure conditions, Selection criteria of ingredients used for mix design,
Procedure of mix proportioning. Numerical Examples of Mix Proportioning using IS-10262

1. Introduction

The process of selecting suitable ingredients of concrete and determining their relative amounts
with the objective of producing a concrete of the required, strength, durability, and workability
as economically as possible, is termed the concrete mix design. The proportioning of ingredient
of concrete is governed by the required performance of concrete in 2 states, namely the plastic
and the hardened states. If the plastic concrete is not workable, it cannot be properly placed and
compacted. The property of workability, therefore, becomes of vital importance.

The compressive strength of hardened concrete which is generally considered to be an index of

its other properties, depends upon many factors, e.g. quality and quantity of cement, water and
aggregates; batching and mixing; placing, compaction and curing. The cost of concrete is made
up of the cost of materials, plant and labour. The variations in the cost of materials arise from the
fact that the cement is several times costly than the aggregate, thus the aim is to produce as lean a
mix as possible. From technical point of view the rich mixes may lead to high shrinkage and
cracking in the structural concrete, and to evolution of high heat of hydration in mass concrete
which may cause cracking.

The actual cost of concrete is related to the cost of materials required for producing a minimum
mean strength called characteristic strength that is specified by the designer of the structure. This
depends on the quality control measures, but there is no doubt that the quality control adds to the
cost of concrete. The extent of quality control is often an economic compromise, and depends on
the size and type of job. The cost of labour depends on the workability of mix, e.g., a concrete
mix of inadequate workability may result in a high cost of labour to obtain a degree of
compaction with available equipment.

2. Requirements of concrete mix design

The requirements which form the basis of selection and proportioning of mix ingredients are :
a ) The minimum compressive strength required from structural consideration
b) The adequate workability necessary for full compaction with the compacting equipment
available.
c) Maximum water-cement ratio and/or maximum cement content to give adequate durability
for the particular site conditions
d) Maximum cement content to avoid shrinkage cracking due to temperature cycle in mass
concrete.

in
 2.1 Types of Mixes

i. Nominal Mixes
In the past the specifications for concrete prescribed the proportions of cement, fine and coarse
aggregates. These mixes of fixed cement-aggregate ratio which ensures adequate strength are
termed nominal mixes. These offer simplicity and under normal circumstances, have a margin of
strength above that specified. However, due to thevariability of mix ingredients the nominal
concrete for a given workability varies widely in strength.

ii. Standard mixes

The nominal mixes of fixed cement-aggregate ratio (by volume) vary widely in strength and may
result in under- or over-rich mixes. For this reason, the minimum compressive strength has been
included in many specifications. These mixes are termed standard mixes.
IS 456-2000 has designated the concrete mixes into a number of grades as M10, M15, M20,
M25, M30, M35 and M40. In this designation the letter M refers to the mix and the number to
the specified 28 day cube strength of mix in N/mm2. The mixes of grades M10, M15, M20 and
M25 correspond approximately to the mix proportions (1:3:6), (1:2:4), (1:1.5:3) and (1:1:2)
respectively.

iii3. Designed Mixes

In these mixes the performance of the concrete is specified by the designer but the mix
proportions are determined by the producer of concrete, except that the minimum cement content
can be laid down. This is most rational approach to the selection of mix proportions with specific
materials in mind possessing more or less unique characteristics. The approach results in the
production of concrete with the appropriate properties most economically. However, the
designed mix does not serve as a guide since this does not guarantee the correct mix proportions
for the prescribed performance.
For the concrete with undemanding performance nominal or standard mixes (prescribed in the
codes by quantities of dry ingredients per cubic meter and by slump) may be used only for very
small jobs, when the 28-day strength of concrete does not exceed 30 N/mm2. No control testing
is necessary reliance being placed on the masses of the ingredients.

3. Factors affecting the choice of mix proportions

The various factors affecting the mix design are:

Compressive strength
It is one of the most important properties of concrete and influences many other describable
properties of the hardened concrete. The mean compressive strength required at a specific age,
usually 28 days, determines the nominal water-cement ratio of the mix. The other factor affecting
the strength of concrete at a given age and cured at a prescribed temperature is the degree of
compaction. According to Abraham’s law the strength of fully compacted concrete is inversely
proportional to the water-cement ratio.

Workability
The degree of workability required depends on three factors. These are the size of the section to
be concreted, the amount of reinforcement, and the method of compaction to be used. For the
narrow and complicated section with numerous corners or inaccessible parts, the concrete must
have a high workability so that full compaction can be achieved with a reasonable amount of
effort. This also applies to the embedded steel sections. The desired workability depends on the
in
 compacting equipment available at the site.

Durability
The durability of concrete is its resistance to the aggressive environmental conditions. 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 water-cement ratio to be used.

Maximum nominal size of aggregate

In general, larger the maximum size of aggregate, smaller is the cement requirement for a
particular water-cement ratio, because the workability of concrete increases with increase in
maximum size of the aggregate. However, the compressive strength tends to increase with the
decrease in size of aggregate.
IS 456:2000 and IS 1343:1980 recommend that the nominal size of the aggregate should be as
large as possible.

Grading and type of aggregate

The grading of aggregate influences the mix proportions for a specified workability and water-
cement ratio. Coarser the grading leaner will be mix which can be used. Very lean mix is not
desirable since it does not contain enough finer material to make the concrete cohesive.
The type of aggregate influences strongly the aggregate-cement ratio for the desired workability
and stipulated water cement ratio. An important feature of a satisfactory aggregate is the
uniformity of the grading which can be achieved by mixing different size fractions.

Quality Control
The degree of control can be estimated statistically by the variations in test results. The variation
in strength results from the variations in the properties of the mix ingredients and lack of control
of accuracy in batching, mixing, placing, curing and testing. 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.

4 Mix Proportion designations

The common method of expressing the proportions of ingredients of a concrete mix is in the
terms of parts or ratios of cement, fine and coarse aggregates. For e.g., a concrete mix of
proportions 1:2:4 means that cement, fine and coarse aggregate are in the ratio 1:2:4 or the mix
contains one part of cement, two parts of fine aggregate and four parts of coarse aggregate. The
proportions are either by volume or by mass. The water-cement ratio is usually expressed in
mass

Factors to be considered for mix design

 The grade designation giving the characteristic strength requirement of concrete.
 The type of cement influences the rate of development of compressive strength of
concrete.
 Maximum nominal size of aggregates to be used in concrete may be as large as possible
within the limits prescribed by IS 456:2000.
 The cement content is to be limited from shrinkage, cracking and creep The workability
of concrete for satisfactory placing and compaction is related to the size and shape of
section, quantity and spacing of reinforcement and technique used for transportation,
in
 placing and compaction.

Factors to be considered for mix design

 The grade designation giving the characteristic strength requirement of concrete.
 The type of cement influences the rate of development of compressive strength of
concrete.
 Maximum nominal size of aggregates to be used in concrete may be as large as possible
within the limits prescribed by IS 456:2000.
 The cement content is to be limited from shrinkage, cracking and creep.
 The workability of concrete for satisfactory placing and compaction is related to the size
and shape of section, quantity and spacing of reinforcement and technique used for
transportation, placing and compaction.

Procedure for Concrete Mix Design – IS456:2000

1. Determine the mean target strength ft from the specified characteristic compressive
strength at 28-day fck and the level of quality control.
ft = fck + 1.65 S
Where, S is the standard deviation obtained from the Table of approximate contents given
after the design mix.
2. Obtain the water cement ratio for the desired mean target using the empirical
relationship between compressive strength and water cement ratio so chosen is
checked against the limiting water cement ratio. The water cement ratio so chosen is
checked against the limiting water cement ratio for the requirements of durability given
in table and adopts the lower of the two values.
3. Estimate the amount of entrapped air for maximum nominal size of the aggregate from
the table.
4. Select the water content, for the required workability and maximum size of aggregates
(for aggregates in saturated surface dry condition) from table.
5. Determine the percentage of fine aggregate in total aggregate by absolute volume from
table for the concrete using crushed coarse aggregate.
6. Adjust the values of water content and percentage of sand as provided in the table for
any difference in workability, water cement ratio, grading of fine aggregate and for
rounded aggregate the values are given in table.
7. Calculate the cement content form the water-cement ratio and the final water content
as arrived after adjustment. Check the cement against the minimum cement content
from the requirements of the durability, and greater of the two values is adopted.
8. From the quantities of water and cement per unit volume of concrete and the
percentage of sand already determined in steps 6 and 7 above, calculate the content of
coarse and fine aggregates per unit volume of concrete from the following relations:

in
 Where, V = absolute volume of concrete = gross volume (1m3) minus the volume of
entrapped air
Sc = specific gravity of cement
W = Mass of water per cubic metre of concrete, kg C = mass of cement per cubic metre of
concrete, kg
p = ratio of fine aggregate to total aggregate by absolute volume
fa, Ca = total masses of fine and coarse aggregates, per cubic metre of concrete,
respectively, kg, and
Sfa, Sca = specific gravities of saturated surface dry fine and coarse aggregates, respectively
9. Determine the concrete mix proportions for the first trial mix.
10. Prepare the concrete using the calculated proportions and cast three cubes of 150
mm size and test them wet after 28-days moist curing and check for the strength.
11. Prepare trial mixes with suitable adjustments till the final mix proportions are
arrived at.

5. Examples of concrete mix proportioning

5.1 Problems

1 - M40 pumpable concrete

Design stipulations for proportioning

a Grade designation : M40
)
b Type of cement : OPC 43 grade confirming to IS
) 8112
cMaximum nominal size of aggregates : 20 mm
)
d Minimum cement content : 320 kg/m3
)
e Maximum water cement ratio : 0.45
)
f Workability : 100 mm (slump)
)
g Exposure condition : Severe (for reinforced concrete)
)
h Method of concrete placing : Pumping
)
i Degree of supervision : Good
)
j Type of aggregate : Crushed angular aggregate
in
 )
k Maximum cement content : 450 kg/m3
)
l Chemical admixture type : Superplsticiser
)

TEST DATA FOR MATERIALS

a) Cement used : OPC 43 grade confirming to IS 8112
b) Specific gravity of cement : 3.15
c) Chemical admixture : Superplasticiser conforming to IS 9103
d) Specific gravity of
Coarse aggregate : 2.74
Fine aggregate : 2.74
e) Water absorption
Coarse aggregate : 0.5 percent
Fine aggregate : 1.0 percent
f) Free (surface) moisture
Coarse aggregate : Nil (absorbed moisture also nil)
Fine aggregate : Nil
g) Sieve analysis
Coarse aggregate : Conforming to Table 2 of IS: 383
Fine aggregate : Conforming to Zone I of IS: 383

TARGET STRENGTH FOR MIX PROPORTIONING

Where ’
ck = ffck + 1.65 s

in
 f’ck= Target average compressive strength at 28 days,
fck = Characteristic compressive strength at 28 days,
s= Standard deviation
From Table 1 standard deviation, s = 5 N/mm2
Therefore target strength = 40 + 1.65 x 5 = 48.25 N/mm2

SELECTION OF WATER CEMENT RATIO

From Table 5 of IS:456-2000, maximum water cement ratio = 0.45
Based on experience adopt water cement ratio as 0.40
0.4 < 0.45, hence ok

SELECTION OF WATER CONTENT

From Table-2, maximum water content = 186 liters (for 25mm – 50mm slump range and for
20 mm aggregates)
Estimated water content for 100 mm slump = 186 + 6/100 x186 = 197 liters
As superplsticiser is used, the water content can be reduced up to 20 percent and above
Based on trials with SP water content reduction of 29 percent has been achieved.
Hence the water content arrived = 19 x 0.71 =140 liters

CALCULATION OF CEMENT CONTENT

Water cement ratio = 0.40
Cement content = 140/0.40 = 350 kg/m3
From Table 5 of IS: 456, minimum cement content for severe exposure condition = 320 kg/m3
350 kg/m3 > 320 kg/m3, hence OK

PROPORTION OF VOLUME OF COARSE AGGREGATE AND

FINE AGGREGATE CONTENT
From Table 3, volume of coarse aggregate corresponding to 20 mm size aggregate and fine
aggregate (Zone I) for water-cement ratio of 0.50 =0.60
In the present case w/c= 0.40. The volume of coarse aggregate is required to be increased to
decrease the fine aggregate content. As w/c ratio is lower by 0.10, increase the coarse aggregate
volume by 0.02 ( at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio).
Therefore corrected volume of coarse aggregate for w/c of 0.40 =0.62

Note: In case the coarse aggregate is not angular, then also the volume of CA may be required
to be increased suitably based on experience

For pumpable concrete these values should be reduced by 10 percent

Therefore volume of coarse aggregate = 0.62 x 0.9 = 0.56
Volume of fine aggregate content = 1- 0.56 = 0.44

in
 MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows

a) Volume of concrete = 1 m3

b) Volume of cement =
= [350/3.15] x [1/1000] = 0.111 m3

c) Volume of water = [140/1] x [1/1000] = 0.140 m3

d) Volume of chemical admixture = [7/1.145] x [1/1000] = 0.006 m3

( SP 2%by mass of cement)

e) Volume of all in aggregates (e) =a – (b + c + d)

= 1 – (0.111 + 0.140 + 0.006) = 0.743 m3

f) Volume of coarse aggregates = e x Volume of CA x specific gravity of CA

= 0.743 x 0.56 x 2.74 x 1000 = 11140 kg

g) Volume of fine aggregates = e x Volume of FA x specific gravity of FA

= 0.743 x 0.44 x 2.74 x 1000 = 896 kg

MIX PROPORTIONS FOR TRIAL NUMBER 1

Cement = 350 kg/m3
Water = 140 kg/m3
Fine aggregate = 896 kg/m3
Coarse aggregates = 1140 kg/m3
Chemical admixture = 7 kg/m3
Water cement ratio = 0.40

Aggregates are assumed to be in SSD. Otherwise corrections are to be applied while calculating
the water content. Necessary corrections are also required to be made in mass of aggregates.

The slump shall be measured and the water content and dosages of admixture shall be
adjusted for achieving the required slump based on trials, if required. The mix proportions shall
be reworked for the actual water content and checked for durability requirements.

Two more trials having variation of ± 10 percent of water cement ratio in A-10 shall be
carried out keeping water content constant, and a graph between three water cement ratios
and their corresponding strengths shall be plotted to work out the mix proportions for the
given target strength for field trials. However, durability requirements shall be met.

in
 2. Problem 2
Illustrative examples on concrete mix proportioning [M40 pumpable concrete with fly ash]
Design stipulations for proportioning
m) Grade designation : M40
n) Type of cement : OPC 43 grade confirming to IS 8112
o) Type of mineral admixture : Fly ash confirming to IS 3812 (Part-1)
p) Maximum nominal size of aggregates : 20 mm
q) Minimum cement content : 320 kg/m3
r) Maximum water cement ratio : 0.45
s) Workability : 100 mm (slump)
t) Exposure condition : Severe (for reinforced concrete)
u) Method of concrete placing : Pumping
v) Degree of supervision : Good
w) Type of aggregate : Crushed angular aggregate
x) Maximum cement content : 450 kg/m3
y) Chemical admixture type : Superplsticiser

TEST DATA FOR MATERIALS

h) Cement used : OPC 43 grade confirming to IS 8112
i) Specific gravity of cement : 3.15
z) Fly ash used : Fly ash confirming to IS 3812 (Part-1)
j) Specific gravity of fly ash : 2.2
k) Chemical admixture : Superplasticiser conforming to IS 9103
l) Specific gravity of
Coarse aggregate : 2.74
Fine aggregate : 2.74
m) Water absorption
Coarse aggregate : 0.5 percent
Fine aggregate : 1.0 percent
n) Free (surface) moisture
Coarse aggregate : Nil (absorbed moisture also nil)
Fine aggregate : Nil
o) Sieve analysis
Coarse aggregate : Conforming to Table 2 of IS: 383
Fine aggregate : Conforming to Zone I of IS: 383

TARGET STRENGTH FOR MIX PROPORTIONING

’
ck = fck
+ 1.65 s
f
Where
’
= Target
ck f average compressive strength at 28 days,
fck = Characteristic compressive strength at 28 days,
s= Standard deviation
From Table 1 standard deviation, s = 5 N/mm2
Therefore target strength = 40 + 1.65 x 5 = 48.25 N/mm2

in
 SELECTION OF WATER CEMENT RATIO
From Table 5 of IS:456-2000, maximum water cement ratio = 0.45
Based on experience adopt water cement ratio as 0.40
< 0.45, hence ok

SELECTION OF WATER CONTENT

From Table-2, maximum water content = 186 liters (for 25mm – 50mm slump range and for
20 mm aggregates)
Estimated water content for 100 mm slump = 186 + 6/100 x186 = 197 liters
As superplsticiser is used, the water content can be reduced up to 20 percent and above
Based on trials with SP water content reduction of 29 percent has been achieved.
Hence the water content arrived = 19 x 0.71 =140 liters

CALCULATION OF CEMENT CONTENT

Water cement ratio = 0.40
Cement content = 140/0.40 = 350 kg/m3
From Table 5 of IS: 456, minimum cement content for severe exposure condition = 320 kg/m3
350 kg/m3 > 320 kg/m3, hence OK

For proportioning fly ash concrete, the suggested steps are;

Decide the percentage of fly ash to be used based on [project requirement and quality of
materials

In certain situations increase in cementitious material content may be warranted. The decision
on increase in cementitious material content and its percentage may be based on experience
and trial.

The example is with increase of 10% of cementitious material content

Cementitious material content 1.1 x 350 = 385 kg/m3

Water content = 140 kg/m3
Water cement ratio = 140/385 = 0.364 ≈0.40

Let us use fly as at 30 percent of cementitious material content in addition to

cement Fly ash = 385 x 0.3 = 115 kg/m3

Cement =385-115=270 kg/m3

(Saving of cement compared to previous design = 350-279 = 80 kg/m3 and

fly ash utilization = 115 kg/m3)

PROPORTION OF VOLUME OF COARSE AGGREGATE AND

in
 FINE AGGREGATE CONTENT
From Table 3, volume of coarse aggregate corresponding to 20 mm size aggregate and fine
aggregate (Zone I) for water-cement ratio of 0.50 =0.60

In the present case w/c= 0.40. The volume of coarse aggregate is required to be increased to
decrease the fine aggregate content. As w/c ratio is lower by 0.10, increase the coarse aggregate
volume by 0.02 (at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio).
Therefore, corrected volume of coarse aggregate for w/c of 0.40 =0.62.

Note: In case the coarse aggregate is not angular, then also the volume of CA may be required
to be increased suitably based on experience

For pumpable concrete these values should be reduced by 10 percent

Therefore volume of coarse aggregate = 0.62 x 0.9 = 0.56
Volume of fine aggregate content = 1- 0.56 = 0.44

MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows

h) Volume of concrete = 1 m3

i) Volume of cement =
= [270/3.15] x [1/1000] = 0.086 m3

j) Volume of fly ash = [115/2.2] x [1/1000] = 0.052 m3

k) Volume of water = [140/1] x [1/1000] = 0.140 m3

l) Volume of chemical admixture = [7.7/1.145] x [1/1000] = 0.007 m3

( SP 2%by mass of cementitious
material)
m) Volume of all in aggregates (e) =a – (b + c + d)
= 1 – (0.086 + 0.052 + 0.140 + 0.007) = 0.715 m3

n) Volume of coarse aggregates = e x Volume of CA x specific gravity of CA

= 0.715 x 0.56 x 2.74 x 1000 = 1097 kg

o) Volume of fine aggregates = e x Volume of FA x specific gravity of FA

= 0.715 x 0.44 x 2.74 x 1000 = 862 kg

MIX PROPORTIONS FOR TRIAL NUMBER 1

in
 Cement = 270 kg/m3
Fly ash = 115 kg/m3

Water = 140 kg/m3

Fine aggregate = 862 kg/m3
Coarse aggregates = 1097 kg/m3
Chemical admixture = 7.7 kg/m3
Water cement ratio = 0.364

Aggregates are assumed to be in SSD. Otherwise corrections are to be applied while calculating
the water content. Necessary corrections are also required to be made in mass of aggregates.

The slump shall be measured and the water content and dosages of admixture
shall be adjusted for achieving the required slump based on trials, if required. The mix
proportions shall be reworked for the actual water content and checked for durability
requirements.

Two more trials having variation of ± 10 percent of water cement ratio in A-10
shall be carried out keeping water content constant, and a graph between three water
cement ratios and their corresponding strengths shall be plotted to work out the mix
proportions for the given target strength for field trials. However, durability
requirements shall be met.

3. Problem 3

Design of M20 concrete mix as per IS:10262-2009, Concrete mix proportioning-guidelines(First

revision)

Design stipulations for proportioning

i. Grade designation : M20
ii. Type of cement : OPC 43 grade confirming to IS 8112
iii. Maximum nominal size of aggregates : 20 mm
iv. Minimum cement content : 320 kg/m3
v. Maximum water cement ratio : 0.55
vi. Workability : 75 mm (slump)
vii. Exposure condition : Mild
viii. Degree of supervision : Good
ix. Type of aggregate : Crushed angular aggregate
x. Maximum cement content : 450 kg/m3
xi. Chemical admixture : Not recommended

TEST DATA FOR MATERIALS

p) Cement used : OPC 43 grade confirming to IS 8112
q) Specific gravity of cement : 3.15
r) Specific gravity of
Coarse aggregate : 2.68
Fine aggregate : 2.65
in
 s) Water absorption
Coarse aggregate : 0.6 percent
Fine aggregate : 1.0 percent
t) Free (surface) moisture
Coarse aggregate : Nil (absorbed moisture full)
1

Fine aggregate : Nil

u) Sieve analysis
Coarse aggregate : Conforming to Table 2 of IS: 383
Fine aggregate : Conforming to Zone I of IS: 383

TARGET STRENGTH FOR MIX PROPORTIONING

’
ck = fck
f + 1.65 s
Where

in
 ’
=
Target
f
ck average compressive strength at 28 days,
fck = Characteristic compressive strength at 28 days,
s= Standard deviation
From Table 1 standard deviation, s = 4 N/mm2
Therefore target strength = 20 + 1.65 x 4 = 26.60 N/mm2

SELECTION OF WATER CEMENT RATIO

From Table 5 of IS:456-2000, maximum water cement ratio = 0.55 (Mild exposure)
Based on experience adopt water cement ratio as 0.50
< 0.55, hence ok

SELECTION OF WATER CONTENT

From Table-2, maximum water content = 186 liters (for 25mm – 50mm slump range and for
20 mm aggregates)
Estimated water content for 75 mm slump = 186 + 3/100 x186 = 191.6 liters

CALCULATION OF CEMENT CONTENT

Water cement ratio = 0.50
Cement content = 191.6/0.5 = 383 kg/m3 >320 kg/m3(given)
From Table 5 of IS: 456, minimum cement content for mild exposure condition = 300 kg/m3
Hence OK

PROPORTION OF VOLUME OF COARSE AGGREGATE AND

FINE AGGREGATE CONTENT
From Table 3, volume of coarse aggregate corresponding to 20 mm size aggregate and fine
aggregate (Zone I) for water-cement ratio of 0.50 =0.60

MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows

a) Volume of concrete = 1 m3

b) Volume of cement =
= [383.16/3.15] x [1/1000] = 0.122 m3

c) Volume of water = [192/1] x [1/1000] = 0.192 m3

d) Volume of all in aggregates (e) =a – (b + c)

= 1 – (0.122 + 0.192) = 0.686 m3

e) Volume of coarse aggregates = e x Volume of CA x specific gravity of CA

in
 = 0.686 x 0.6 x 2.68 x 1000 = 1103 kg

f) Volume of fine aggregates = e x Volume of FA x specific gravity of FA

= 0.686 x 0.4 x 2.65 x 1000 = 727 kg

MIX PROPORTIONS FOR TRIAL NUMBER 1

Cement = 383 kg/m3
Water = 191.6 kg/m3
Fine aggregate = 727 kg/m3
Coarse aggregates = 1103 kg/m3
Water cement ratio = 0.50
Yield =2404.6 kg

Aggregates are assumed to be in SSD. Otherwise corrections are to be applied while calculating
the water content. Necessary corrections are also required to be made in mass of aggregates.

Trial mixes: Laboratory study

4. Problem 4

Design of M30 concrete mix as per IS:10262-2009, Concrete mix proportioning-guidelines(First

revision)

Design stipulations for proportioning

xii. Grade designation : M30
xiii. Type of cement : OPC 43 grade confirming to IS 8112
xiv. Maximum nominal size of aggregates : 20 mm
xv. Minimum cement content : 350 kg/m3
xvi. Maximum water cement ratio : 0.50
xvii. Workability : 25 - 50 mm (slump)
xviii. Exposure condition : Moderate
xix. Degree of supervision : Good
xx. Type of aggregate : Crushed angular aggregate
xxi. Maximum cement content : 450 kg/m3
xxii. Chemical admixture : Not recommended

TEST DATA FOR MATERIALS

v) Cement used : OPC 43 grade confirming to IS 8112
w) Specific gravity of cement : 3.15
x) Specific gravity of
Coarse aggregate : 2.68
Fine aggregate : 2.65
y) Water absorption
Coarse aggregate : 0.6 percent
Fine aggregate : 1.0 percent
z) Free (surface) moisture
Coarse aggregate : Nil (absorbed moisture full)
in
 Fine aggregate : Nil
aa) Sieve analysis
Coarse aggregate : Conforming to Table 2 of IS: 383
Fine aggregate : Conforming to Zone I of IS: 383

TARGET STRENGTH FOR MIX PROPORTIONING

’
ck = fck
f + 1.65 s
Where

in
 Module I Concrete Technology

’
ck f = Target average compressive strength at 28 days,
fck = Characteristic compressive strength at 28
days, s= Standard deviation
From Table 1 standard deviation, s = 5 N/mm2
Therefore target strength = 30 + 1.65 x 5 = 38.25 N/mm2

SELECTION OF WATER CEMENT RATIO

From Table 5 of IS:456-2000, maximum water cement ratio = 0.50 (Moderate
exposure) Based on experience adopt water cement ratio as 0.45 as the cement is 53
grade
0.45 < or =0.5, hence ok

SELECTION OF WATER CONTENT

From Table-2, maximum water content = 186 liters (for 25mm – 50mm slump range and
for
20 mm
aggregates) Estimated water content for 25-50 mm slump = 186 liters

CALCULATION OF CEMENT CONTENT

Water cement ratio = 0.45
Cement content = 186/0.45 = 413 kg/m3 >350 kg/m3(given)
From Table 5 of IS: 456, minimum cement content for moderate exposure condition = 300
kg/m3 Hence OK
PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE
AGGREGATE CONTENT
From Table 3, volume of coarse aggregate corresponding to 20 mm size aggregate and fine
aggregate (Zone I) for water-cement ratio of 0.50 =0.60. Modify this as w/c is 0.45. The new
value is 0.61. Volume of fine aggregate is 0.39.

MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows

g) Volume of concrete = 1 m3
h) Volume of cemen
= [413/3.15] x [1/1000] = 0.131 m3
i) Volume of water = [186/1] x [1/1000] = 0.186 m3

j) Volume of all in aggregates (e) =a – (b + c)

= 1 – (0.131 + 0.186) = 0.683 m3

RYMEC, BELLARY Page 17

 Module I Concrete Technology

k) Volume of coarse aggregates = e x Volume of CA x specific gravity of CA

= 0.683 x 0.61 x 2.68 x 1000 = 1117 kg

l) Volume of fine aggregates = e x Volume of FA x specific gravity of FA

= 0.683 x 0.39 x 2.65 x 1000 = 706 kg

MIX PROPORTIONS FOR TRIAL NUMBER 1

Cement = 413 kg/m3
Water = 186 kg/m3
Fine aggregate = 706
kg/m3 Coarse aggregates =
3
1117 kg/m Water cement ratio
= 0.45
Yield =2422 kg

CONCRETE MIX DESIGN EXAMPLE – M50 GRADE CONCRETE

Grade Designation = M-50
Type of cement = O.P.C-43 grade
Brand of cement = Vikram (
Grasim ) Admixture = Sika
[Sikament 170 ( H ) ] Fine
Aggregate = Zone-II

Sp. Gravity
Cement = 3.15
Fine Aggregate = 2.61
Coarse Aggregate (20mm) =
2.65 Coarse Aggregate
(10mm) = 2.6
Minimum Cement (As per
contract) =400 kg / m3
Maximum water cement ratio
(As per contract) = 0.45

Mix Calculation: –

1. Target Mean Strength = 50 + (5 X 1.65 ) = 58.25 Mpa

2. Selection of water cement ratio:-

Assume water cement ratio = 0.35

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 Module I Concrete Technology

3. Calculation of water: –
Approximate water content for 20mm max. Size of aggregate = 180 kg /m3 (As per Table
No. 5, IS : 10262 ). As plasticizer is proposed we can reduce water content by 20%.
Now water content = 180 X 0.8 = 144 kg /m3

4. Calculation of cement content:-

Water cement ratio = 0.35
Water content per cum of concrete = 144 kg
Cement content = 144/0.35 = 411.4 kg / m3
Say cement content = 412 kg / m3 (As per contract Minimum cement content 400 kg / m3)
Hence O.K.
5. Calculation for C.A. & F.A.: –
Volume of concrete = 1 m3
Volume of cement = 412 / (3.15 X 1000) = 0.1308 m3
Volume of water = 144 / (1 X 1000) = 0.1440 m3
Volume of Admixture = 4.994 / (1.145 X 1000) = 0.0043 m3
Total weight of other materials except coarse aggregate = 0.1308 + 0.1440 +0.0043 =
0.2791 m3

Volume of coarse and fine aggregate = 1 – 0.2791 = 0.7209 m3

Volume of F.A. = 0.7209 X 0.33 = 0.2379 m3 (Assuming 33% by volume of total
aggregate) Volume of C.A. = 0.7209 – 0.2379 = 0.4830 m3
Therefore weight of F.A. = 0.2379 X 2.61 X 1000 = 620.919
kg/ m3 Say weight of F.A. = 621 kg/ m3
Therefore weight of C.A. = 0.4830 X 2.655 X 1000 = 1282.365
kg/ m3 Say weight of C.A. = 1284 kg/ m3
Considering, 20 mm: 10mm = 0.55:
0.45 20mm = 706 kg.
10mm = 578 kg.
Hence Mix details per m3
Increasing cement, water, admixture by 2.5% for this trial

Cement = 412 X 1.025 = 422 kg

Water = 144 X 1.025 = 147.6 kg
Fine aggregate = 621 kg
Coarse aggregate 20 mm =
706 kg Coarse aggregate 10
mm = 578 kg
Admixture = 1.2 % by weight of cement = 5.064 kg.

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 Module I Concrete Technology

Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043

Observations from Concrete Mix Design: –

A. Mix was cohesive and homogeneous.

B. Slump = 120 mm
C. No. of cube casted = 9 Nos.
7 days average compressive strength = 52.07 MPa.
28 days average compressive strength = 62.52 MPa which is greater than
58.25MPa Hence the mix accepted

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