Concrete Mix Design shmmd-13-1

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By : Dr.(Mrs.) V. Tare
Professor. Civil Engg. & applied
Mechanics Deptt. ,S.G.S.I.T.S. ,Indore
1
 Process
of selecting suitable ingredients
of concrete and determining their
relative proportions with object of
producing concrete of certain minimum
strength and durability as economically
as possible.
2

Concrete mix proportion should be such as to ensure the
workability of the fresh concrete and when concrete is
hardened it shall have the required strength, durability
and surface finish.

DMC (Design Mix Concrete)

NMC (Nominal Mix Concrete)

≤ M20 – nominal may be used with permission of engineer
in-charge and likely to consume more cement.
3
 W/C
ratio
 Cement content or Aggregate Cement
ratio
 Gradation of Aggregate
 Workability
 Admixtures
4
5
 Minimum
--- will lubricate the mass while fresh
and after hardening will bind the aggregate
Particles together and fill the space between
them.
 More --- Excess paste greater cost, greater
drying shrinkage, greater susceptibility to
percolation of water.
 Aggregate Cement ratio
1:2:4 --- A/C =6
1:1.5:3 --- A/C = 4.5
6
Minimum voids.
 Well graded agg.
 Minimum voids --- will require minimum paste--- less
cement ----economy
 Paste is weaker link in concrete
 If paste is more --- permeable, attack of aggressive
chemicals, greater drying shrinkage, more cost,
hence importance of good grading.
 Sieve analysis is done
 Grading limits for CA. IS-383
 Grading limits of fine agg. IS-383

7
8
9
A
workable conc. is one that in cohesive,
flows well, and without segregation be
fully compacted. It depends on
types of aggregate – rounded, angular,
flaky
grading of CA & FA
Quantity of cement paste
Consistency of the paste
10
CF 0.75 TO 0.80
UsingFlowTable
11
 Plasticizers
 Superplastisizers
 Grouting
Admixtures
 Pozzolonic Admixtures
 Fungicidal, germicidal and insecticidal
12

The action of plasticizer is mainly to fluidify the mix and
improve the workability of concrete, mortar or grout.
When Plasticizers are used ,they get adsorbed on the
cement particles. The adsorption of charged polymer on
the particles of cement creates particle-to-particle
repulsive forces which overcome the attractive forces. This
repulsive forces called Zeta Potential. the overall result is
that the cement particle are deflocculated and dispersed.
when cement particles are deflocculated, the water
trapped inside the flocs gets released and now available to
fluidity the mix
13

The mechanism of action of super plasticizer are more or
less same as ordinary plasticizer. Only thing is that the
super plasticizer are more powerful as dispersing agents
and they are high range water reducers.
14
In concrete variables are material and construction
process. Strength varies from batch to batch &
within batch.
 The aim of quality control is to limit the variability
as much as practicable.
 The basis of acceptance of sample is that a
reasonable amount of concrete work can be
provided by ensuring probability of test result falling
below the design strength is not more than a specific
tolerance level.
 Assumed standard deviation as per IS 456-200.

15
Grade of conc.
M10
M15
M20
M25
M30
M35
M40
M45
M50
Assumed standard
deviation N/mm2
3.5
4.0
5.0
16

Target strength = fck + ks
fck= characteristics compressive strength
k = Himsworth constant
s = standard deviation
17
Percentage of results below
the characteristic strength
k
50
0
16
1
10
1.28
6.6
1.5
5
1.65
2.5
1.96
1.0
2.33
0.5
2.58
0
Infinity
Target strength = Fck+1.65s
18
 IS
method
 ACI method
 DoE method
 Murdock method
19
 Data
required:Characteristics compressive strength fck
Maximum Size of agg.
shape of agg.
workability
Type of exposure
Sp. Gravity Of cement
Sp. Gravity Of FA.
Sp. Gravity Of CA.
20
1.)Target mean strength = fck + ks
2.)Selection of W/C ratio (graph is available)
21
3. Estimation of entrapped air :Max. size of agg.(mm)
Entrapped air as % of
volume
10
3.0
20
2.0
40
1.0
22
4.) Selection of water content and fine to total
aggregate:-
23
5.) Correction applied for water content and fine
to total aggregate :Change in condition Stipulated
For tables
Adjustment required in
Water
content
% Sand in Total
Aggregate
For sand conforming to grading
zone I, zone III or zone IV of
table 4, IS:383-1979
0
+1.5% for Zone I
-1.5% for Zone III
-3% for Zone IV
Increase or decrease in the
value of compacting factor by
0.1
` 3%
0
Each 0.05 increase or decrease
in water-cement ratio
0
` 1%
-15kg
-7%
In water-cement ratio for
rounded aggregate
24
6.)Calculation of cement content
Cement Content = Water Content / W/C ratio
7.)Calculation of aggregate content :V = [W+(C/Se)+(1/P) x(FA/Sfa)]x(1/1000)
CA = (1-p)/p)x(FA)x(Sca/Sfa)
8.)Calculation of mix proportion
25
Example:Design data :
Characteristic comp. strength Fck = 30mpa
MSA = 20mm
Degree of workability = 0.85 (CF)
Sp. gravity of cement = 3.15
Sp. gravity of fine agg.= 2.7
Sp. gravity of coarse agg. = 2.7
26
Steps of design
1) Target mean strength = 30+1.64x4=36.6 MPa
2) W/C ratio from graph = 0.45
3) Selection of water content = 175 kg/cum
4) Percent sand = 35%
5) Change in condition
Change in condition
Percent adjustment required
Water content
Sand in total
aggregate
For decrease in w/c ratio by (0.60-0.45) that
is for (-0.15)
0
-3.0 (` 1% for
w/c=0.6)
For increase or decrease in compacting factor
(0.8-0.85),that is for (+ 0.05)
+1.5 (` 3%for cf=0.8)
0
For sand conforming zone ii
of table 4, IS:383-1970
0
0
Total
+1.5
-3.0
27
Therefore required sand content as
percentage of total aggregate by
absolute volume = 35 - 3.0
= 32.0
Required water content = 175 + (175 x 1.5/100)
= 177.62 kg/cum
6.Determination of cement content :W/C ratio = 0.45
Water = 177.62 ltr
Cement = 177.62 /0.45
= 394.7
= 395 kg/cum (say)
28
7.Determination of fine and coarse
aggregate contents:0.98=[177.62 +(395/3.15)+(1/0.32)
x(FA/2.7)]x(1/1000)
980=[177.62 +125.4+FA/0.864]
FA= [980- 177.62 -125]x0.864
FA= [980- 303]x0.864
= 585 kg(say)
Ca = [(1-0.32)/.32] x 585 x 2.7/2.7 ]
= 2.125 x 585
= 1243
29
8.Proportion :Cement: Sand: agg
395 : 585 : 1243
1 : 1.48 : 3.15 By Weight
[(1x1400)/ 1400] : [(1.48 x 1400)/1600] : [(3.15 x 1400)/1800]
By volume
30

The code includes the use of 10 types of cement
OPC,RHPC,PSC(Portland Slag Cement),PPC (fly ash
based),PPC (calcined clay based),HC (Hydrophobic
Cement), LHPC (Low Heat Portland Cement), SRPC
(Sulphate Resistance Portland Cement).

Aggregate should comply with IS 383.

For RCC 20 mm aggregate is mostly used, sometime 40
mm may be permitted.

Potable water should be used for making concrete.

Admixtures if used should comply with IS 9103.
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
Min. grade of concrete should not be less than M20
for RCC works.
M10,M15,M20- Ordinary Concrete.
M25-M55- Standard Concrete.
M60-M80- High Strength Concrete.

Flexural Strength= 0.7 X (fck)1/2
fck – Cube Compressive Strength N/mm2

EC=5000 (fck)1/2
32

Thermal Expansion 0C (10-5)
Quartzite=1.2-1.3
Granite=0.7-0.95
Sand Stone=0.9-1.2
Basalt=08-0.95
Lime Stone=0.6-0.9

Workability has been specified in terms of slumps
mm.

Durability clause has been enlarged.
Exposure-mild, moderate, severe, very severe,
Extreme.
33
Data required :Characteristics compressive strength fck
Maximum Size of agg.
shape of agg
Type of exposure
workability (Slump)
Sp. Gr. Of cement
Sp. Gr. Of FA
Sp. Gr. Of CA
Finess modulus of fine aggregate
Bulk density of dry roded coarse aggregate
34
1.)Target mean strength
= fck + ks
2.)Selection of W/C ratio
35
36
3.) for given slump at MSA find out water content
in kg/cum
37
4.) find out cement content in kg/cum=
water content /water cement ratio
5.) for msa and Finess modulus of sand find out
bulk volume of dry rodded coarse aggregate per
unit volume of concrete
38
6.) find out weight of coarse aggregate
CA= result of step 5 x bulk density of dry rodded
coarse aggregate in kg/cum
7.) From density of concrete calculate
(FA = Density – cement – Coarse Aggregate – water )
kg/cum
8.) Proportion = Cement : Fine agg. : Coarse agg.
9.) Allowance for bulking, water absorption, moisture
content, evaporation are made in field.
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