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8/6/2019 Mix Design 10262
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Meet specified strength
Should be durable in the environment
in which it is expected to serve
Workable to be placed in the structure
Economical
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Durability - the service life of a materialunder given environmental conditions
Durability of concrete can be ensured bymaintaining
certain minimum binder content,
maximum limit on w/ b ratio andminimum cover to the reinforcement
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Exposure
Plain Concrete Reinforced Concrete
MinCement kg/
m3
Maxw/c
MinGrade
MinCement kg/m3
Maxw/c
MinGrade
Mild 220 0.60 - 300 0.55 M20
Moderate
240 0.60 M15 300 0.50 M25
Severe 250 0.50 M20 320 0.45 M30
V.Severe
260 0.45 M20 340 0.45 M35
Extreme 280 0.40 M25 360 0.40 M40
NOTES1 Cement content prescribed in this table is irrespective of the grades of cement and it is inclusive of add-ons mentioned in 5.2. The additions such as fly ash or ground granulated blast furnace slag may be takeninto account in the concrete composition with respect to the cement content and water-cement ratio if thesuitability is established and as long as the maximum amounts taken into account do not exceed the
limit of pozzolana and slag specified in IS 1489 (Part I) and IS 455 respectively.2 Minimum grade for plain concrete under mild exposure condition is not specified.
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Type of cement
Grade designation (compressive / flexural strength)
Maximum nominal size of aggregate
Minimum and maximum cement contents
Maximum water-cement ratio
Workability and Workability retention
Exposure Conditions as per IS 456
Method of transporting and placement of concrete
Temperature of concrete at the time of placement, if
required. Characteristics of aggregates.. Sp. Gr., WA, grading
etc.
Chemical and mineral admixture
Early age strength requirements, if any
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ft = fck + K * s
where,ft = Target mean compressive strength
at 28 days,fck = Target mean compressive strength
of concrete at 28 daysk = usually 1.65 for acceptable failure
rate of 1 in 20s = standard deviation
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Grade of Concrete Assumed
StandardDeviation
M10 3.5 Mpa
M15M20 4 Mpa
M25
M30 5 Mpa
M35
M40
M45
M50
If sufficientdata isavailable forthe grade, usethe s value
If sufficientdata is notavailable,value can beassumed fromthe table
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If past data on relationship between Strength andfree water-cement ratio are available, it may beused Else, water-cement ratio given in Table 5 of IS 456for the respective exposure condition may be usedas starting point. The free water-cement ratio selected should be
checked against the limiting water-cement ratio forthe durability .choose the lower of the twovalues.
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Source: IS 10262: 1982 re-affirmed 1989
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Water Content of Concrete depends on:
AggregatesShape/ Size/ Texture
Workability
W/c ratio
Cement/ Cementitious Content
Chemical Admixtures
Environmental conditions
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S.No.
NominalMaximum Size of
Aggregatemm
Maximum WaterContent (1)
Kg
i) 10 208
ii) 20 186iii) 40 165
Note These quantities of mixing water are for use in computing cementitious materialcontent for trial batches.(1) Water content corresponding to Saturated Surface Dry Aggregate.
Table 2 Maximum Water Content per cubic meterof Concrete for Nominal Maximum Size ofAggregate
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Description AdjustmentAngular C.Agg. 20 50 mmslump
0
Sub-angular Aggregate - 10 kg/ m3
Gravel with some crushedparticles
- 20 kg/ m3
Rounded Gravels - 25 kg/ m3
Plasticizers - (5% 10%)
Super Plasticizers - (20% - 30%)
Increase in slump by 25 mm + 3% and/ or establish bytrial
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Calculate the Cementitious Contentfrom w/c ratio and the final watercontent worked out after adjustments.
Adopt the Higher of the Cementitiouscontent as calculated above and that
recommended from the durability requirement.
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Adjustments to Minimum Cement Contents forAggregates Other Than 20 mm Nominal Maximum SizeAggregates as per IS 456:2000
MSA Adjustment
10 mm + 40 Kg/ m3
20 mm 0
40 mm - 30 kg/ m3
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Description Adjustment
W/c ratio of 0.5 0
Every + 0.05 change in w/cratio
- 0.01
Every - 0.05 change in w/cratio
+ 0.01
For Pumpable Mix - 10%
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A) Volume of Cement = (Mass of Cement/ S.G. of
cement)*1/1000
B) Volume of Water= (Mass of Water/ S.G. of water)*1/1000
C) Volume of Admixture = (Mass of Admixture/ S.G. ofadmixture)*1/1000
D) Volume of Aggregates= 1 (A+B+C)
E) Volume of Coarse Aggregate = (D) * Vol. % of C.A. (as perS4) * S.G. of C.A. *1000
F) Volume of Fine Aggregate= (D) * Vol. % of F.A. (as per S4)
* S.G. of F.A. * 1000