IRC 44-1976

TENTATIVE GUIDELINESFOR

CEMENT CONCRETEMIX DESIGN

FOR PAVEMENTS(FOR NON-AIR ENTRAINED AND CONTINUOUSLY

GRADED CONCRETE)

(First Revision)

THE INDIAN ROADS CONGRESS1996

IRC: 44-1976

TENTATIVE GUIDELINESFOR

CEMENT CONCRETEMIX DESIGN

FOR PAVEMENTS

(FOR NON-AIR ENTRAINED AND CONTINUOUSLYGRADED CONCRETE)

(First Revision)

Published byThe Indian Roads Congress,

Jamnagar House, Shabjahan Road,New Dellui-11001l

1996

Price Rs. 80/-(Plus Packing & Postage)

IRC: 44-1976

First PublishedFirst RevisionReprintedReprinted

August, 1972December, 1976August, 1996October, 2000

(Rights of Publication and of Translation are reserved)

Printed at Dee Kay Printers, New Delhi(500 copies)

IRC: 44-1976

TENTATIVE GUIDELINES FOR CEMENT CONCRETEMIX DESIGN FOR PAVEMENTS

(For Non-Air-Entrained and Continuously Graded Concrete)

1. INTRODUCrION

1.1. The problem of designing a mix for a given purpose canbe equated to obtaining a concrete of the required strength, durabilityand workability at lowest cost, by a suitable choice of materials andthe proportions in which these may be combined. In doing so, therelative importance of the different factors that influence the qualityof concrete should be understood. The strength of concrete dependsupon many factors, e.g. quality and quantity of cement, water andaggregates; batching; mixing; placing; compaction; curing; etc. Thewater-cement ratio is the principal controlling factor for strength ofconcrete. Since the quantity of water controls the workability for givenmaterials, different workabilities can be obtained by changing thewater content but keeping the water-cement ratio and hencestrength the same. The choice of proportions is governed by thesatisfactory condition of concrete in two states, namely, the plasticat~dthe hardened state. If the condition of the plastic concrete isnot satisfactory, a fully compacted, dense and/or uniform concretecan not be obtained and its structural value will be greatly reduced.1~heproperty of workability, therefore, becomes of vital importance.

1.2. Against this background, it is not possible to lay downany mathematical formulae that would enable us to obtain the bestpossible mix. The same holds true for the charts, tables or curvespresented by various organisations. These provide only a means ofarriving at a reasonably satisfactory choice of proportions. Since theaggregates may have widely differing characteristics, and the cementstrength may also vary considerably from factory to factory, it isalwaysdesirable to get the mix designed in laboratory with the mate-rials proposed to be utilised in the work. Moreover, depending onprocess and control variances in the field, one should also be prepa-red to make final adjustments in the mix at the site.

1.3. These Guidelines do not debar adoption of any otheraccepted method of mix design.

1.4. The Guidelines were prepared by the Cement ConcreteRoad Surfacing~Committee(personnel given below). These were then

I

IRC: 44-1976

processed and approved by the Specifications and Standards Com-mittee in their meeting held on the 18th and 19th November, 1971.Later, these were finally approved by the Executive Committee intheir meeting held on the 26th and 27th Aprih 1972 and by the Coun-cil in their 78th meeting held at Nainital on the 10th July, 1972.

PERSONNEL OF THE CEMENT CONCRETE ROADSURFACING COMMiTTEE

1. K.K, Nambiar Convenor2. Dr. R.K. Ghosh Member-Secretary

Members3. M. M. Bose 11. A.R. Satyanarayana Rao4. B.R. Chopra 12. N.y. Shastry5. Dr. M.P. Dhir 13. S.B.P. Sinha6. C.LN. Iyengar 14. S.N. Sinha7. M.D. Kale 15. N.S. Surya8. Dr. S.K. Khanna 16. H.G. Verma9. Col OP. Narula 17. Dr. H,C. Visvesvaraya

10. N. L. Patel1.5. The Guidlines were later amended by the Cement Con-

crete Road Surfacing Committee in their meeting held at NewDelhi on the 26th November 1974 and then processed by theSpecifications and Standards Committee. This publication containsthe revised Guidelines as finally approved for the use of the mem-bers of the profession.

2. GUIDELINES2.1. Basic Data for Mix Design2.1.1. The following are required to be specified for design of

a cement concrete mix:(a) Minimum compressive strength/flexural strength of con-

crete in the field at 28 days.(b) Maximum size of aggregate to be used and its type.(c) Degree of workability, related to the compaction equip-

ment available.(d) Degree of quality controlexpected to be exercisedvery

good, good or fair-and permissible coefficient of variationor standard deviation.

(e) Accepted tolerance level.2.1 .2. The specific stipulations in respe~tof the above items

should conform to requirements laid down in IRC: l5~1970*,if the*Standard Specifications and Code of Practice for Construction of ConcreteRoads

2

IRC:44-1976

work pertains to concrete pavement. For other works, stipulations

of relevant specifications may be consulted.

2.2. Tests for Materials

For design of mix, it will be necessary to carry out the followingtests on materials:

(a) Cement: (i) Compressive strength of cement at 7 days(IS: 269~1967*).

(ii) Specific gravity of cement (IS: 269~l967*)(Assume a value of 3.15, if test is not pos-sible).

(b) Aggregate: (i) Specific gravity (IS:2386 Part 111-1963+).(ii) Per cent water absorption (IS: 2386 Part

111-1963+).(iii) Sieve analysis (IS: 2386 Part I-19634-~).

2.3. Selection of Aggregate Grading2.3.1. The aggregate grading should conform to IS:3831970@.

Insofar as the grading of coarse aggregates is concerned, there are nospecific requirements laid down in the above Indian Standard. How-ever, to achieve good results with normal aggregates at comparativeease, it is advisable to have suitable grading zonesfor coarse aggregatesfor the purpose of guidance, as exist in many international standardssuch as British, German, American, Russian, etc. Of course, thesegrading should in no sense be regarded as ideal gradings, and itmay sometimes be necessary to make final adjustments in thegradings at site, though such adjustments generally involve onlyminor alterations in the ratio of fine to coarse aggregate. The coarseaggregate gradings suggested by the Transport and Road ResearchLaboratary, U.K., are given in Table I. Out of the three zones inTable 1, zone B is considered more suitable than zones A and C.

*Ordinary, Rapid Hardening and Low Heat Portland Cement.Specific Gravity, Density, Voids, Absorption and Bulking.

+ +Particle Size and Shape.@Coarse and Fine Aggregates from Natural Sources for Concrete.

3

IRC: 441976

TABLE 1: SUGGESTED COARSE AGGREGATE GRADINGS

Nominal maximumsize ofaggregate(mm)

Zone

A

Per cent passing I.S. sieve sizes (mm)

40

100

20

34-40

10

16-18

4.75

040 B

C

A

100100

100

40-4545-53

100

18-2020-25

21-32

00

020 B

C100100

100100

31-4040-52

00

Note: Allowance for oversize in the nominal maximum size of aggregatesshall be limited to 5 per cent.

2.3.2. Sometimes it may be necessary to combine two or morecoarse aggregate fractions to obtain a grading approximating to theone required. Among the several methods available for this purposethe trial method is simple and convenient to apply. The same isdescribed in Annexure I.

2.4. Design Strength for Concrete2.4.1. Jn order to get the specified minimum compressive stren-

gth in the field, the concrete mix has to be designed for somewhathigher average compressive strength depending on the degree of qua-lity control (denoted through permissible coefficient of variation orstandard deviation) and the tolerance level. The average strength(S) at28 days for which the mix might be designed is given by the equation:

S1 t.v/lOO (1)

where ,~= minimum compressive strength (kg/sq. cm.) in thefield at 28 days,

t = factor (dimensionless) depending on specified tolerancelevel, and

v = coefficient of variation (per cent) specified.2.4.2. The values of tin equation (1) for different tolerance

levels are given in Table 2.

4

IRC: 44-1976

TABLE 2: VALUES OP TOLERANCE FACTOR (t)

No. of samplesTolerance level

1 in 10 1 in 15 1 in 20 1 in 40 tin 100

102030c~(Infinite)

1.37 1.65 1.81 2.23 2.761.32 1.58 1.72 2.09 2.531.31 1.54 1.70 2.04 2.4~1.28 1.50 1.64 1.96 2.33

Note: In case of a major concreting job, where large number of sampleswill be tested, it would be appropriate to adopt a tolerance Lctorcorresponding to infinite number of samples.

2,4.3. In Table 3 are worked out the average design strengthsfor concrete for different combinations of specified minimum stren-gth, tolerance level and coefficient of variation corresponding to aninfinite number of samples. On smaller jobs where only a finitenumber of samples will be tested, the corresponding average designstrengths can be obtained by application of appropriate tolerancefactors from Table 2 in equation (1).

TABLE 3: AVERAGE DESIGN STRENGTHS FOR CONCRETE FORDIFFERENT DEGREES OF QUALITY CONTROL ANDTOLERANCE LEVELS

Minimum specified concrete strength at 28 days (kg/cm)

Notes: I. The average design strengths given in the table are for tole-rance factors corresponding to infinite number of samples asgiven in Table 2.

2. According to IRC: 15-1970, the tolerance level and permis-sible coefficient of variation for paving concrete are 1 in 15and 10 per cent respectively.

Degree of qua-lity control

Very goodGoodFair

U

V0I-

tin 15I in 101 in 10

101520

235250270

linl5 7linlS 10linlO 15

310325340

1 in 201 in 15

710

400415

5

IRC : 44-1976

U

L~~J

zaI.

I,

N

2.5. Selection of Water-Cement Ratio2.5.1. As the cement strength may vary widely from factory

to factory, it is not possible to have a single curve of correlationbetween water-cement ratio and compressive strength of concrete.A set ofsuch curves with 7-days compressive strength of cement asthe third parameter is given in Fig I for purpose of guidance. Thesecurves are the same as those under Appendix A of IS: 456~1964*but drawn in different form. From Fig.!, for a particular cement

400

3 00

200

I 00

00.4 04 0.6 1.0

WATER-CEMENT RATIO BY WT.

Fig. I. Design curve for cement concrete mixes in relation to7-days compressive strength of cement

the compressive strength at 7 days, of which is known, the water-cement ratio for the average compressive strength (S of equation 1)of concrete for which the mix is to be designed can be selected.Where design is based on fiexural strength of concrete, the approxi-mate relationship between compressive and fiexural strength ofconcrete may be obtained from Annexure II.

* Code of Practice for Plain and Reinforced Concrete

6

IRC : 44-1976

2.6. Selection of Water and Sand Content2.6.1. To design the mix, water and sand contents per unit

volume of concrete are to be estimated in the first instance and this. depends upon the maximum size of aggregate, moisture content in the

aggregate, workability, type of aggregate, etc. The values of waterand sand contents for different maximum sizes of crushed (angular)aggregate are given in Table 4 for a particular water-cementratio of 0.50, slump of 25 mm and fineness modulus of 2.60 for sand.

TABLE 4: APPROXIMATE SAND AND WATER CONTENTS PERCunic METRE OF CONCRETE (FOR W/C = 0.50,

SLUMP = 25 MM AND SAND F.M. = 2.60)Maximum sizeofaggregate (mm)

8t) mm (3)

Water content on saturatedsurface dry basis per cu.m.of concrete (kg)*

Sand in per centof total aggr. byabs. vol. (%)

172.0 28.04Omm(ll)25 mm (1)

175.0177.5

33.538.0

20 mm (i) 178.0 40.0*Note: By saturated surface dry condition, it is understood that the

aggregates are fully saturated but there is no free moisturepresent at the surface. If the aggregates are not in this condition,water to be added in the mixer shall be required to be increasedor decreased to make up the difference depending on whether theaggregates are dry or wet.

2.6.2. For other conditions of water-cement ratio, slump andfineness modulus of sand, and for rounded aggregate, certain adjust-ments in the water and sand contents are necessary, which are givenin Table 5.

TABLE 5 ADJUSTMENT OF VALUES IN WATER AND SANDCONTENTS FOR OTHER CONDITIONS

Changes in conditions stipulatedin Table 4

Adjustment required inWater content Sand content

Each 0.05 increase or decreasein w/c ratioEach 0.1 increase or decreasein F.M. of sandEach 25 mm increase or decreasein slumpRounded aggregate

0

0

4%15 litre(ad hoc)

1%

0.5%

0 6 to 8%

7

IRC: 44-1976

2.7. Determination of Aggregate-Cement Ratio2.7.1. Knowing the water-cement ratio, water requirement,

cement content (from water-cement ratio and water requirement)and proportion of sand in total aggregate by absolute volume, thesand and coarse aggregate contents per unit volume of concrete maybe calculated separately from

v= (w-_~- +-4- . ~) i~oo ,... (2)and

v Iw C 1 A\ 1 3 + S~+ 1P Sa 1 1000

where,V = absolute volume of the wet mix = gross volume (1 cu.

m.) minus the volume of entrapped air (see clause 2.7.2)W wt. of water in kg (=litre) per cu.m. of concreteC = wt. of cement in kg per cu.m. of concreteS = wt. of sand in kg per cu.m. of concreteA = wt. of coarse aggregate in kg per cum. of concreteP = proportion (in decimal fraction) of sand in total aggre-

gate determined on the basis of absolute volume, andSC,SE,S~,= specific gravities of cement, sand and coarse aggregate

respectively.The quantities of sand, coarse aggregate, cement and water

required to determine the mix proportions of a concrete mix are thusknown.

2.7.2. Approximate amounts of entrapped air in the wet con-crete mix for different maximum sizes of aggregate are indicated inTable 6.

TABLE 6 : APPROXIMATE AMOUNTS OF ENTRAPPEDAIR IN NON-AIR-ENTRAINED CONCRETE

Maximum size 10of aggregate

12.5 20 25 40 50 80 160

(mm)Entrapped air 3 2.5 2 1.5 1.0 0.5 0.3 0.2(approximate) (% byvolume)Volume of entra- 0.030 0.025 0.020 0.015 0.010 0.005 0.003 0.002pped air per cu.m.gross volume ofconcrete (cu.m.)

S

IRC 44-19762.8. Trial MixWith the above mix proportions, the mix is prepared and the

workability measured. If the workability is different from the stipu-lated value (workability is usually very low for paving concrete),the water content may be adjusted in accordance with Table 5 forincreasing or decreasing the slump. The mix proportions are there-after recalculated with adjusted water content as per equations (2)and (3) for three water-cement ratios comprising the pre-selectedwater-cement ratio and two other values, one higher and the otherlower than the pre-selected ratio by 0.05. Since the design adoptedis on absolute volume basis, the yield for the three cases will remainthe same. The strength of concrete (compressive and flexural streng-ths in case of paving concrete and compressive strength for otherstructural concretes) with the three water-cement ratios is thendetermined in accordance with IS : 516-l969~. The values ofstrength obtained are then plotted against water-cement ratios andthe appropriate water-cement ratio chosen from the plot for therequired strength. The final mix proportions are then recalculatedfor this water-cement ratio, other parameters remaining thesame.

Note: In case of paving concrete the correlation between flexural and com-pressive strength may be established, if quality control in the fieldis proposed to be exercised on the basis of compressive strengthonly.

2.9. Worked-out Example on Mix DesignAn example illustrating the mix design procedure is worked

out in Annexure III.

+ Methods of Test for Strength of Concrete

9

IRC: 44-1976

Annexure!

TRIAL METHOD FOR COMBINING AGGREGATES OF DIFFERENTGRADINGS

The individual sieve analyses for the different aggregate fractions arefirst arranged in a tabular form and the optimum percentage of each forcombination worked out on trial and error basis, This is done by visual inspec-tion of the individual analyses and comparison between stipulated grading andcombined grading on trial. A few trials may be necessary. A typical examplein tabular form is given below to illustrate the procedure using two differentsizes of coarse aggregate.

EXAMPLE: COMBINATION OF Two COARSE AGGREGATEFRAcTioNs

Per cent of different fractionsPer cent passing eachsieve

Grading of aggre.. Stipu-gate fractions latedas available com-

binedgrading

1st trial

I I!70% 30%

Sievesizes(mm)

40

20

10

4.75

I

100

14

8

2

II

100

100

34

6

Com-bined100%

100

39.8

15.8

3,2

2nd trial

1132%

32

32

10.9

1.9

I68%

68

9.5

5,4

1.4

100

40

18

0

Com-bined100%

100

41.516.3

3.3

70

9.8

5.6

1.4

3D

30

10.2

1.8

10

IRC: 44-1976

Annexure iiCORRELATION BETWEEN FLEXURAL AND COMPRESSIVE

STRENGTH OF CONCRETE (For Guidance OnI~)

40 40 t~.CRUSHED STOWE

~3O .~\ ~ GRAVEL

I40O~

300 ~

S

200k

WATE.R-CEV4ENT RATIO (~(wT)(For Nvery Iowa to low workabilIty correaportdingto a BI~ap0-25 ma)

0.40

11

IRC 44-1976

Annexure IIIWORKED-OUT EXAMPLE FOR CEMENT CONCRETE MIX DESIGN

A) Design StipulationsI) Minimum compressive strength required in the

held at 28 days : 280 kg/cm2) Maximum size of aggregate: 40 mm (angular aggregate)3) Degree of workability : 25 mm slump4) Degree of quality control : good (co-efficient of variation 10%)5) Accepted tolerance level 1 in 156) Type of job: Major work involving testing of a large number of

samples, i.e., z=l.50B) Test Data for Materials:

1) Compressive strength of cement with single-sized standard sand at7 days : 210 kgcrn2

2) Specific gravity of cement : 3.153) Specific gravity of both coarse aggregate and fine aggregate : 2.654) Water absorption:

i) Coarse aggregate : 0.4%ii) Fine aggregate 0.6%

5) Free (surface) moisturei) Coarse aggregate : nil (absorbed moisture also nil)

ii) Fine aggregate : 2%6) Sieve analysis

Coarse aggregate Fine aggregatefractions

IS. Per cent passing I,S. Per cent Cumulative Fine-sieve sieve passing per cent nesssize size retained modulus(mm) Fraction Fraction

I II

40 100 100 475 mm 100 0

20 14 100 2.36 mm 98 2

10 8 34 1.18mm 90 102.48

475 2 6 600~i 50 50

30O~& 11 891501& 3 97

12

IRC : 44-1976(C) Combination of Coarse Aggregate Fractions:

I:S, Per. cent passing (individual) Percent passing (combined grading)sievesize(mm) Grading of aggre Combined 1st trial 2nd trial

gate available grading ___________ _______ ______________________________________ required

(Table 1) I II Comb- I II Comb-I II 70% 30% med 68% 32% med

grad- grad-ing ing

40 100 100 100 70.0 30.G 100.0 68.0 32.0 100.0

20 14 100 40 9.8 30.0 39.8 9.5 32.0 41.5

10 8 34 18 5.6 10.2 15.8 5.4 10.9 16.3

4.75 2 6 0 1.4 1.8 3.2 1.4 1.9 3.3

Aggregates may, therefore, be combined in the proportion 68:32(by weight).

D) Design Strength for Concrete (5):

S 280 280S LV = 1.5x 10 0.85 329 kg/cm (say, 330 kg/cm)I- 100

F) Selection of Water-Cement Ratio

From Fig. I, using curve E corresponding to 7 days cement strength of210 kg/cm, for design strength of concrete of 330 kg/cm,the water-cement ratio required0.43.

F) Selection of Water and Sand Contents:

From Table 4, for water-cement ratio of 0.50, slump of 25 mm, F.M.of sand of 2.60 and angular aggregate, of 40 mm maximumsize, water content per cu.m. ofconcrete=175 kg and sandcontent as per cent of total aggregate by absolutevolume.~33.5 per cent.

For changes in the values of water-cement ratio, fineness modulus

13

IRC : 44-1976

of sand and slump, the adjustments required in the mix are:

Changes in condition Adjustment required inWater content Sand content

(kg) (%)(i) decrease in w/c

(0.50O.43)=0,07 0(ii) decrease in F.M. of sand

(2.602.48)=0,12 0(iii) Slump (25mm25mm)~0 0

1.4

0.60

Total 0 2.0%

Therefore, required water content per cu.m. of concrete=l75 kg andsand content as per cent of total aggregate by absolute volume~~.(33,52,0)%3I.5%

(G) Determinationof Cement Content:Water-cement ratio= ~ =0.43, but W= 175 kg (from step F); or

0.43

C=407kg

(H) Determination of Aggregate-Cement Ratio:From Table 6, for thespecified maximum size of aggregate of 40 mm,the amount of entrapped air in the wet concrete is 1 per cent.Taking this factor into account and applying equation 2,

I 407 1 S \I0.99 cu,m.=i~l75+~j~f3~+~~i3~.2.65S= 572.5 kg.

Applying equation 3,/ 407 1 A \ 1

0.99 cu.m.= ~l7S-l--jB_+ 0.685 3)Ti5~A=1244.9 kg.The mix proportions are therefore:Water Cement Sand Coarse aggregate Total aggregate175 kg 407 kg 572.5 kg, 1244.9 kg 1817,4 kg

or, 0.43 : I : 1.41 : 3.06 4.47Aggregatecement ratio= 4.47: 1

14

IRC : 44-1976

(I) Actual Quantities Required for the Mix per Bag of Cement:The mitc is 0.43:1:1.41:3.06 (by wt.)1. Cement 50 kg

2. Aggregate=(without moisture adjustment)(i) Fine aggregate=~50 x 1.41 = 70.5 kg

(ii) Coarse aggregate = 153.0 kg(a) Fraction 1(68%) = 104.0 kg(b) Fraction 11(32%) = 49.0 kg

3. Water(i) For water-cement ratio of 0.43 water required = 21.5 litre

(ii) Extra water to be added for absorption in case of coarseaggregate, at 0.4% by weight = 0.4% of 153.0=0.61 litre

(iii) Water to be deducted for free moisture present in fine aggregate,at 2% by weight = 2% of 70.5=1.41 litre

(iv) Actual quantity of water to be added=21.5+0.61.1.41=20.70litre

4. Actual quantity of fine aggregate required after allowing for weightof free moisture = 70.5 + 1.41 71.91 kg.

5. Actual quantity of coarse aggregate required(i) Fraction I = (104.000.42) kg = 103,58 kg

(ii) Fraction II = (49.000.19) kg = 4881 kgTherefore the actual quantities of different constituents required for the

mix areWater = 20.70 litreCement = 50.00 kgFine aggregate 71.91 kg

Coarse aggregateFraction I = 103.58 kgFraction II = 48.81 kg

01: