Mix Design for M45, Indian Standard method of mix design, Mix design for Pumpable Concrete, Mix design by IS456-2000

2. Design a concrete mix for M45 grade of concrete with the following data. (by IS Method)
Type of Cement OPC 43 Grade
Maximum Size Of Aggregate 20 mm
Type of Exposure Sever (RCC)
Workability 125 mm slump
Minimum Cement Content 320kg/cum
Specific gravity of cement 3.15
Specific gravity of coarse aggregates 2.80
Specific gravity of fine aggregates 2.70
w/c ratio 0.42
Method of placing of concrete Pumping
Degree of Supervision Good
Type of aggregate Crushed angular Agg.
Super plasticizer will be used 20%
Water Absorption
Coarse Aggregate
Fine Aggregate
0.5%
1%
Free Surface Moisture
Coarse Aggregate
Fine Aggregate
Nil
Nil
Grading of Coarse agg. Conforming to Table 2 of IS 383
(p) Grading of Fine agg. Conforming to grading zone II

3. 9.2.4.2 (IS 456-2000) Assumed standard
deviation
Where sufficient test results for a
particular grade of concrete are not
available. the value of standard
deviation given in Table8 maybe
assumed for design of mix in the
first instance. As soon as the results
of samples are available, actual
calculated standard deviation shall
be used and the mix designed
properly.

4. Step-1 Target Mean Strength
• F’ck= fck + 1.65 s
= 45 + 1.65 X 5 = 53.33 N/SQM
Where F’ck- Target mean compressive strength at 28 days.
fck - Characteristic Compressive strength at 28 days.
s- Standard Deviation. ( Table 8, page no 23, IS 456)

5. Step-2 Selection Of Water Cement Ratio
Clause 8.2.4.1 (IS 456-2000) The free water-cement ratio is an
important factor in governing the durability of concrete and
should always be the lowest value. Appropriate values for
minimum cement content and the maximum free water-cement
ratio are given in Table 5 for different exposure conditions. The
minimum cement content and maximum water-cement ratio
apply to 20mmnominal maximum size aggregate. For other sizes
of aggregate they should be changed given in Table6.(IS 456 )

7. • For Severe Exposure (RCC) and maximum nominal size of aggregate 20 mm.
As per IS Water Cement ratio is 0.45
Adopted W/c Ratio is 0.42 < 0.45
Hence, Its Ok.

8. Step-3 Selection of Water Content
• Clause 4.2 (IS 10262-2009) The water content of concrete is
influenced by a number of factors, such as aggregate size,
aggregate shape, aggregate texture, workability, water-cement
ratio, cement and other supplementary cementitious material
type and content, chemical admixture and environmental
conditions. An increase in aggregates size, a reduction in water-
cement ratio and slump, and use of rounded aggregate and
water reducing admixtures will reduce the water demand. On
the other hand increased temperature, cement content, slump,
water-cement ratio, aggregate angularity and a decrease in the
proportion of the coarse aggregate to fine aggregate will
increase water demand

9. Clause 4.2 (IS 10262-2009)- The quantity of maximum mixing water per unit
volume of concrete may be determined from Table 2.(IS 10262-2009) The
water content in Table 2 is for angular coarse aggregate and for 25 to 50 mm
slump range. The water estimate in Table 2 can be reduced by approximately
10 kg for sub-angular aggregates, 20 kg for gravel with some crushed particles
and 25 kg for rounded gravel to produce same workability. For the desired
workability (other than 25 to 50 mm slump range), the required water content
may be established by trial or an increase by about 3 percent for every
additional 25 mm slump or alternatively by use of chemical admixtures
conforming to IS 9103. This illustrates the need for trial batch testing of local
materials as each aggregate source is different and can influence concrete
properties differently. Water reducing admixtures or super plasticizing
admixtures usually decrease water content by 5 to 10 percent and 20 percent
and above respectively at appropriate dosages.

11. From Table-2.(IS 10262-2009)
Maximum water content is 186 liters. This is for 50 mm slump.
Estimated water content for 125 mm slump (3% increase for every 25
mm slump and above 50 mm slump, There fore total increase in water
content is by 9%)= 186 + ( 186x 9/100) = 203 liter.
It is given that super plasticizer used as 20%. Therefore actual water to
be used = 203 x 0.80 = 162 Liter.

12. Step-4 Calculation Of Cement Content
Water Cement Ratio= Water Content/Cement Content.
Water Cement Ratio – 0.42
Water Content - 162 liters
Cement Content = Water Content/ Water Cement Ratio
= 162/0.42
= 385.70 kg/cum
This cement content checked against minimum cement content mentioned in
Table No. 5 of IS 456 for Durability requirement.
The minimum cement content mentioned in Table 5 is 320 kg/cum for mild
exposure there fore calculated cement content is more, so Its ok.

14. Step-5 Calculation of Coarse and Fine Aggregates.
• • Clause 4.4.(IS 10262-2009)
Estimation of Coarse Aggregate- Proportion Aggregates of essentially the
same nominal maximum size, type and grading will produce concrete of
satisfactory workability when a given volume of coarse aggregate per unit volume
of total aggregate is used . Approximate values for this aggregate volume are given
in Table 3 for a water-cement ratio of 0.5, which may be suitably adjusted for other
water cement ratios . It can be seen that for equal workability, the volume of
coarse aggregate in a unit volume of concrete is dependent only on its nominal
maximum size and grading zone of fine aggregate. Differences in the amount of
mortar required for workability with different aggregates, due to differences in
particle shape and grading, are compensated for automatically by differences in
roadded void content.

16. As per Clause 4.4.(IS 10262-2009) Volume of coarse aggregate corresponding to
20 mm size aggregate and fine aggregate zone II, for w/c ratio found out to be 0.62.
In the present case w/c ratio is 0.42 i.e. it is less by 0.08. As the
w/c reduced it is desirable to increase the coarse aggregate proportion to reduce
the fine aggregate content.
The coarse aggregate is increased at the rate of 0.01 for every decrease
in w/c ratio of 0.05.
:. (0.01/0.05) x 0.08= 0.016
There For correct volume of CA = 0.62+0.016 = 0.636
For Pumpable Concrete coarse aggregate can be reduced by 10%.
:. Volume of CA = 0.636 x 0.90 = 0.57
:. Volume of FA = 1-0.57 = 0.43

17. Step-6 Calculation Of Mix Proportions.
Assume Volume of Concrete = 1 CUM -------(A)
Volume Of Cement = = = 0.122 CUM ------(B)
Volume of water = = = 0.162 CUM ------(C)
Volume of all Aggregates = A- ( B + C) = 1- ( 0.122 + 0.162)= 0.716 CUM ----(D)

18. Mass of Coarse Aggregates = D x Sp. Gravity CA x Volume of CA x 1000
= 0.716 x 2.7 x 0.57 x 1000
= 1024.5 kg
Mass of Fine Aggregates = D x Sp. Gravity FA x Volume of FA x 1000
= 0.716 x 2.65 x 0.43 x 1000
= 891.77 kg

19. Step-7 Mix Proportion
Cement = 385.75 kg
Fine Agg.= 891.77 kg
Coarse Agg= 1024.5 kg
Cement = 1 Therefore Mix Proportion for M45 Concrete
FA = = 2.31
1 : 2.31 : 2.65
CA = = 2.65

20. Step-8 Site Corrections