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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