concrete mix design

1. Topic:
“IS MATHOD OF CONCRETE MIX
DESIGN ”
Subject Name: Concrete Technology
Subject Code:3360602
Semester: 5th
Prepared by: Bhavesh Hathila
En no: 156300306047
Civil Engineering Department
Government Polytechnic,
Zhalod Road, Dahod

2. Index
1. Introduction
2. Target mean strength
3. Selection of water content
4. Selection of water
5. Calculation of cenmentitious material content
6. Estimation of coarse aggregate proportion
7. Estimation of mix proportion

3. Initially, guidelines regarding concrete mix proportioning
were published by the beuro of Indian standards wide IS:10262-1982, but
in the revision of IS:456-2000, a mortar of changes were introduce in
IS:456, which necessitated the revision in IS:10262-1982. the guidelines
given in the revised IS:10262-2009 are presented below
Data required for mix proportioning:
the following data are required for mix proportioning of a particular
grade of concrete:
 Grade of concrete, M-20, M-25 etc.
 Maximum nominal size of aggregates.
 maximum cement content.
 maximum W/C ratio.
Introduction

4. Workability of terms of slump.
 Exposure condition.
 maximum temperature of concrete at the time of placing.
 Early age strength requirements, if required.
 Type of aggregate.
 Minimum cement content.
 Whether an admixture shall of shall not be used and the type of
admixture.
 Specific gravity of all material used, etc.

5. Step-1 Target mean strength:
In order that not more than 5% of test results are likely to fall below
the characteristics strength, the concrete mix has to be proportioned for
higher target mean compressive strength f´ck given bye the relation:
f´ck = fck + 1.65 S
Where,
f´ck= target mean compressive strength at 28 days in N/mm2
fck = characteristic compressive strength at 28 days in
N/mm2
S= Standard deviation
The value of standard deviation (S) may be taken from table-1

6. Sr. No. Grade Of Concrete Assume Standard Deviation
N/mm²
1 M-10 3.5
2 M-15
3 M-20 4.0
4 M-25
5 M-30 5.0
6 M-35
7 M-40
8 M-45
9 M-50
10 M-55
Table No 1 : Assumed Standard Deviation

7. Since different cement and aggregates of different maximum size,
grading, surface texture, shape and other characteristics may produce
concretes of different compressive strength for the same free water
cement ratio, the relationship between strength and free water cement
ratio should preferably for the materials actually may be used. In the
absence of such data, the preliminary free water cement ratio (by mass)
corresponding to the target strength at 28 days may be selected from the
relationship shown in figure.
Otherwise, the w/c ratio given in table- of is:456-2000 for
respective environment exposure conditions may be used as starting
point, as given below:
Step-2: selection of water cement ratio:

9. Sr. No. Exposure Maximum free w/c ratio
1 Mild 0.55
2 Moderate 0.50
3 Severe 0.45
4 Very severe 0.45
5 Extreme 0.40
Table No. 2 : Maximum Free W/C Ratio
[IS : 456-2000, Table-5]

10. The water content of concrete is influenced by a number of
factors, such as aggregate size, aggregate shape, aggregate texture,
workability, w/c ratio, cement and other supplementary cementitious
material type and content, chemical admixture and environmental
conditions.
an increase in aggregate size, a reduction in w/c ratio and
slump, and use of rounded aggregate and water reducing admixture
will reduce water demand. On of the other hand increase
temperature, cement content, slump, w/c ratio aggregate angularity
and decrease in the proportion of the coarse aggregate to fine
aggregate will increase water demand.
the quantity of maximum decrease water per unit volume of
concrete may be determined from table-3 given below.
Step-3 Selection of water content

11. Sr. No. Nominal Maximum Size of
Aggregate (mm)
Maximum water content
(kg)
1 10 208
2 20 186
3 40 165
Table No. 3 : Maximum Water Content Per Cubic Metre Of
Concrete For Nominal Size Of Aggregate
[for slump 25 to 50 mm]

12.  the water content given in table- is for angular coarse aggregate and
for 25 to 50 mm slump range.
 the water estimate in table- can be increase by approximately 10kg
for sub-angular aggregates, 20kg for gravel with some crushed
particles and 25 kg for rounded gravel to produce same workability.
 for the desire workability (other than 25 to 50mm slump) the
required water content may be established by trial or an increase by
about 3% for every additional 25mm slump for alternatively by use of
chemical admixtures.
 water reducing admixtures or super plasticizers usually decrease
water content by 5% to 10% and 20% and above respectively at
appropriate dosages.

13. The content and supplementary cementitious material content per
unit volume of concrete may be calculated from the free w/c ratio and the
quantity of water per unit volume of concrete.
The cementitious material contents so calculated shall be checked
against the minimum content for the requirement of durability and garter of
the two values adopted. The minimum cement content shall be in
accordance with IS: 456-2000. table-
The minimum cement content and maximum w/c apply to 20mm
nominal maximum size aggregate. For other size of aggregate they should
be changed as given in table- of IS: 456-2000, reproduce as below.
Step-4 calculation of cementitious material content

14. Table No 4 : Adjustment To Minimum Cement Contents For
Aggregates Other Than 20 mm Nominal Maximum Size
[IS : 456-2000, Table-6]
Sr.
No.
Nominal Maximum
aggregate size(mm)
Adjustments to minimum
cement content in table-5 kg/m³
1 10 +40
2 20 0
3 40 -30

15. Aggregate of essentially the same nominal maximum size,
type and grading will produce concrete with satisfactory workability
when a given volume of coarse aggregate per unit volume of total
aggregate in used. Approximate values of this aggregate volume are
given in table- 5, for a w/c ratio of 0.5. this aggregate volume may be
adjusted for other w/c ratios as below:
 for every decrease of w/c ratio by 0.05, the coarse aggregate volume
may be increase by 1.0% to reduce the sand content.
 for every increase of w/c ratio by 0.05,the coarse aggregate volume
may be decrease by 1.0% to increase the sand content.
for more workable concrete mixes which is some times
required placement is by pump or when the concrete is required to be
worked around congested reinforcement, it my be desirable to reduce the
estimated coarse aggregate content determined using table- 5 up to 10%.
Step – 5 Estimation of coarse aggregate proportion.

16. Table no:5-Volume of course aggregate per unit volume of
total aggregate for different zones of fine aggregate
[for w/c = 0.50]
Sr.
No.
Nominal
maximum size
of
aggregates(mm)
Volume of course aggregate per unit volume of
total aggregate for different zone of fine aggregate
Zone-IV Zone-III Zone-II Zone-I
1 10 0.50 0.48 0.46 0.44
2 20 0.66 0.64 0.64 0.60
3 40 0.75 0.73 0.71 0.69

17. Combination of different coarse aggregate fraction:
coarse aggregate of different sizes may be combined in suitable
proportion so as to result in a overall grading conforming to table-6 of
IS:383.

18. Up to step-5, all the ingredients have been estimated except
the coarse and fine aggregate content. these quantities are determined
by finding out the absolute volume of cementitious material, water and
the chemical admixture; by dividing there mass by their respective
specific gravity, multiplying by 1/1000 and subtracting the result of
their summation from unit volume (i.e. 1m3). The result will be the
absolute volume of coarse and fine aggregates put together. We know
the volume of coarse aggregate and hence volume of fine aggregate can
be calculated.
The weight of coarse aggregate and fine aggregate are in
saturated and surface dry conditions. Depending upon the absorption or
presence of surface moisture, field corrections are made.
Step-6 Estimate of fine aggregate proportion:

20. Thank you