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IRC 101-1988

GUIDELINESFOR

DESIGN OF CONTINUOUSLY

REINFORCED CONCRET E

PAVEMENTWITH

ELASTIC JOINTS

THE INDIAN ROADS CONGRESS

1991

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1RC: 1OI-1~$S

GUI DELINESFOR

DESIGN OF CONTINUOUSLY

REINFORCED CONCRETE

PAVEMENTWITH

ELASTIC JOINTS

Published by

THE INDIAN ROADS CONGRESS

Jamnagar House, Shabjahan Road,

New Delhi-I10 011

1991

Price Rs~~S. ~(Pus packing & po~tagc~

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IRC: tOi-1988

First publishe9 : June, 1988Reprinted: March, 1991

(Rights ofPublication andofTranslation are Reserved)

Printed at Sagar Printers & Publishers. New Delhi(1000 copies)

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IR C : 1014988

GUIDELINES FOR DESIGN OF CONTINUOUSLY REINFORCEDCONCRETE PAVEMENT WITH ELASTIC JOINTS

I. INTRODUCTION

1.1. Guidelines for Design of Continuously ReinforcedConcrete Pavement with Elastic Joints prepared by the Central

Road Research Institute were discussed and approved by tieCement Concrete Road Surfacing Committee (personnel givenbelow) in their meeting held at Lucknow on the 3rd February,1985.

K.K, Nambiar ... ConvenorYR. Phull Member-Secretor,

1 - 1 . 8 . Bhalia D.G.B.R. (Maj. Gen. J.M. RaitT.A.E. Dsa A Rep. of Cement Research

P.V Kamat Institute of IndiaOP. Lal Director, U.P. iW,D. ResearchP.J. Mehta Institute (PD.. Agrawal)V. Raghavan City Engineer (Roads), MunicipalC. Raman Corporation ofBombayA. Sankaran D.C. ~R.D.) -Ex-officloN, Sivaguru President, IRC -Ex-offIclo

Adviser, 1 RC -fix-officioSecretary, IRC -Ex-officlo

1.2. These Guidelines were considered by the Specifica-tions & Standards Committee in their meetings held at NewDelhi on the 28th August, 1986 and 23rd April, 1987 and werereturned back to the Cenient Concrete Road Surfacing Commi-ttee for further consideration. These Guidelines were then finaL-sed by Dr. M.P. Dhir, the present Convenor and Shri S.S. Seehra,the present Member-Secretary of the Committee, The documentreceived from the Cement Concrete Road Surfacing Committee

was reconsideredby the Highways

Specifications&

StandardsCommittee in their meeting held on the 25th April, 198% at NewDelhi and approved. These Guidelines received the approval olthe Executive Committee and the Council in their meetings heldon the 26th April and 7th May. 1988 respectively

1.3. The technique of continuously reinlorccd concretepavement (CRCP) obviates the need for expansion and contrac-tion joints, thus permitting very long slab lengths with impro-

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IRC : 101-1988

ved riding comfort and reduced maintenance as compared tplain concrete pavements. Conventional CRCP requires relatively high percentage of steel of the order of0.7-1.0 per cent o

concrete cross-section. The technique of CRCPconstruction

witelastic joints (CRCP-EJ) enables significant reduction in quantitof steel required (0.40.5 per cent) and also eliminates the random cracks which occur in conventional continuously reinforced concrete pavements.

1.4. The provision of continuous reinforcement in CRCof the conventional type results in the formation oftransversecracks in the pavement which are held tightly closed by the steel

without impairment of structural strength. The closely helcl~acksensure load transfer across the cracks through aggregatinterlocking and also prevent the ingress of water and grit intthe cracks. The width and spacing ofsuch cracks are dependanton the amount ofsteel reinforcement provided. The greater theamount of steel, the closer is the spacing of the cracks and thsmaller is their opening. An optimum amount of longitudinareinforcement is called for so that the cracks are neithe

too widely spaced with resulting over-stressing of steelloss in load transfer provided by aggregate inter-lock and accelerated corrosion of steel; nor too closely spaced so as to causdisintegration ofthe slab.

1,5. The elastic joints consist ofdummy contractionjointwith the reinforcement continuous through them. The reinforcment is painted with a bond-breaking medium over a specifiedesign length on either side of the joint groove to provide ad

quate gauge length for limiting the steel strains due to joinmovement. A typical elastic joint for the solved example givein Appendix, is shown in Fig. 1 .

1.6. The use ofelastic joints, apart from resulting in redction of steel stresses by about 50 per cent and enabling the usof less quantity of steel, also preclude the random cracking assciated with conventional construction, since the weakened plan

provided at such joints localises the cracking. The usual spacinof such joints works out to about 4 to 5 m.

2. DESIGN

2. I. Calculation for Steel Percentage and Stresses in Steand Concrete due to Continuity at Elastic Joints

2.1.1. The continuity of steel at elastic joints leads to retraint in the slab movement due to shrinkage and temperatur

2

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~ 1 9cm

0

oc

RE INFORCDIENT16 m m 0 ~ 26 cr~Vc/c

LO~ITUbINhLREI~CRCEMEMF COItED )~ITH?ITt1IEN TO9REAJ( 9OND ~1TH CO~CRETE DyES This LENOTH CF 150 cm.

I SO ~

Fig. 1. Details ofelastic joint section

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tR( lt)1-l985

change, and thus induces stresses in both steel and concrete.However, if steel is provided at mid-depth ofthe slab, as is theusual practice, no stress will develop in it due to wheel load andw a r p i n g.

2. 1.2. The stresses (due to continuity of steel at elasticjoints) in steel, (eTc), and concrete, (~),in the vicinity of elasticjoints may he calculated from Eisenmann equations which aregiven below

lOt) ~. a ~,h.E.,Es k . 2ri ITFfll%.j+(IOOh.Er.)) g/c

2.LT.f &.E.and - jTE~~iTTjTh1~,Ec. kg/cm

2

w herc

a Coefficient ofthermal expansion ofconcrete per C,

1 Difference het~~eenthe mean temperatures ofthe stab at the timeofconstruction and the coldest period in ~C,

At : Maximum temperature differential betsseen lop and bottom o

the slab,

Note While finding out the temperature stress at the edge, IRC:58-1988 recommends definite values oftemperature differetial in different states of India, This differential has beendesignated as Ai in IRC: 58-1988 and is different from Awhich is used in this text to designate temperature differencebetween the minimum of minimums and the mean temperature at the time of construction. Ar is not a function ostab thickness whereas As the temperature differentialdepends on the thickness ofslab,

Fi Slab thickness in em.

I Mod abs ofela ;ticity ofconcrete in kgfem2

-; Modulus ofcba~tieityof s tcel in kg/cm

ft == Cross-section ofsteel in t in width of the slab in cm~

= Ratio of free, unbonded length of the steel to the slab length

between two consecutive elastic joints,2.1.3. The charts in Figs. 2 and 3 show steel and concrete

stresses per Cof ~ Tfor steel percentage range of0.10.6 andfor ratio, A range of 0.10.4. The steel stresses so determinedshould not exceed the permissible value of 1400 kgtcm2. Theconcrete stresses are additive to the load and temperature warp-ing stresses and are required to be taken into account whiledesigning the pavement. The transverse steel may be taken as

25 per cent of longitudinal steel.4

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I.,1

a

U

V

aU

1 4 1

C

IRC: 101-3988

~=Ratio ofunbonded length of steel to spacing of elastic joints

Fig. 2. Design charts l o i calculation of stresses in steel

5

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IRC : 101-1988

aU

V

aU

C

H~0.-

-~

,

0.,

o.:

c~_1

-

\ ~O.5%

\\

\

\\N~

~

~

\

\.~\

N~4%

~~,

~

~

MM

.

~

~__

-

020 .30 Q.5

,Ratio ofunbonded length ofsteel to spacing ofelastic joints

Fig. 3. Design charts for calculation of stresses in concrete

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aRC: 101-1988

2.1.4. The provision ofsteel enables some increase in theeffective slab thickness and its continuity at elastic joints provi-

des additional load transfer over and above that provided byconventional dummy contraction joint. At the same time, thepercentage of steel is small enough not to induce any restraintto bending of the slab at elastic joints due to effect of wheelload and temperature warping.

2.1.5. While in CRCP without elastic joints the permissiblestress in steel is 2800 kg/cm

2 (i.e. the steel is allowed to be stre-ssed upto the yield point), the permissible value in CRCP with

elastic joints is restricted to 1400 kg/cm2 only (i.e. normal work-in~ stress in steel used in conventional structures). Thelower permissible stress in steel in CRCP with elastic joints ena-bles taking advantage of the effective increase in concrete slabthickness due to provision of steel, while the permissible yieldstress limit in steel in the case of CRCP without elastic jointprecludes such increase.

2.2. DesIgn of Slab Thickness

2.2.1. Initially, the thickness of plain cement concretepavement should be worked out as per IRC:58-1988. Whileworking out the thickness, the additional concrete tensile stressshould be accounted for as indicated in para 2.1.3.

2.2.2. ihe effective increase in slab thickness due toprovision of steel reinforcement may be worked out by usingMallingers chart given in Fig. 4. The equivalent CRCP slabthickness may then be calculated by reducing the thicknesscalculated in para 2.2.!. by the amount of the effectiveincrease in slab thickness using Fig. 4 the average of steel inlongitudinal and transverse direction may be taken.

2.2.3. Outline of design procedure

Step I Assume a thickness and examine wheel load and tempera-ture stresses as per IRC:58-l988.

Step II For a proposed value, choose a steel percentage froni Fig. 2such that the steel stress is within the permissible value.Calculate the concrete stress from Fig. 3. In calculatingthese stresses the ordinates are to be multiplied by thecorresponding value of t, as applicable to the particular

location.

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IR C It)l-1988

o .

0.40

C0U 0.30I- a00

c.a

ci 020

9.C 0.

.0 >~

~ U

00,0

~ 0.10

j o.oe,~ 0.06

0,04

Fig. 4. Mallingcfs chart sho~cingthe effect of reinforcementon rigid pavements

Step Ill Add the concrete stress calculated in Step Ii to the valueobtained in Stc~t and the final total stresses should bewithin the flexural strength of concrete. The trials maybe repeated till the assumed thickness in Step I meets thcrequirement.

Stcp IV Calculate the effective increase in slab thickness due to

provision of reinforcement as per Fig. 4 (vide para 2.2.2.)and reduce thc thickness obtained in Step III to account forthe increase.

An illustratIve example is given in Appendix.

2.3. Cement Concrete Mix Design

The mix should be designed on the basis of absolute volume

method as per IRC 44-1976 ~TentativeGuidehnes for Cement

8

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IRC : 101-1988

Concrete Mix D~sigri. The fkxural strength of concrete at 28

days in the field should not be less than 40 kg/cm2.

3. MATERIALS

3.1. Cement

Should conform to IS :269 1976 or IS : 8112-1976.

3.2. Coarse and Fine Aggregate

Should conform to IS : 383-1980.

3.3. Steel

The diameter of steel bars should be so choosen as to keepthe spacing, between bars around 25 to 35 ems. Steel shouldconform to IS : 432 (Part I)-1982.

3.4. Water

Water used for both mixing and curing should be clean

and free from injurious amount of deleterious matter and shouldconform to IS : 456-1978. Potable water is generally consideredsatisfactory.

4. CONSTRUCTION DETAILS

4.1. General

The construction details are the same as in the case of

plain cement concrete pavements (vide 1RC : 15-1981) except thefollowing.

4.2. Construction of Joints

4.2.1. Elastic joints: These are dummy type joints whichshould be induced at regular intervals similar to that for dummycontraction joints. The joint grooves may be formed as in thecase of conventional dummyjoint, and filled with sealing com-pound. Alternatively, bitumen-coated plywood strips of 5 cmwidth and 3 mm thickness may be inserted therein. On eitherside of the elastic joint, steel should be coated with bitumen fora length of 1/3-1/4 joint spacing in order to break the bond ofsteel with concrete and to provide greater length for elongationof the steel due to joint opening for reducing the stress in thereinforcing steel.

4.2.2. Expansion joints: The expansion joints are provi-

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IRC: 101 -1988

ded only at the ends of the CRCP-EJ sections and there is noneed ofproviding these joints in-between. The width ofsuchexpansion joints is kept upto double that of conventional con-

crete pavement to accommodate the greater end movements.Details ofthese joints should be as shown in IRC : 15-1981.

5 . REINFORCEMENT

The steel mats, assembled at site, are placed over suitablechairs at mid depth ofthe slab before concreting is done. Thebars should be continuous across elastic joints and any construc-tion joints. Wherever overlap of bars is required, a minimum

overlap of 30 diameters should be provided. Such overlapsshould be staggered. It should also be ensured that no overlapof steel bars are provided at the location of elastic joints.

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IRC : 101-19$8

Appendix

AN ILLUSTRATIVE EXAMPLE OF DESIGN OF SLAB THICKNESS

I. Design Parameters

Location ofPavement

Design Wheel Load, F

Present Traffic IntensityDesign Tyre Pressure, p

Foundation Strength, Ic

Concrete Flexural Strength,fR

Ec = 3.0 x 10 kg/cm

:~ =0.15

Delhi

5100kg

300 veh/day

7.2 kg/cm

6 kg/cm

40 kg/cm

= 10 x

= 14VC against thickness of25cm

2. DesIgn Procedure:

Step I : Assume!. = 25 cm, spacing ofelastic joints = 4.5 m

As per IRC : 581988

ale = 18,50 kg/cm

~ve= 15.50 kg/cm

a Total = 34.00 kg/cm

Step 11: For ?. = 0.33 and j~= 20CC

r 0.4 per cent (Steel reinforcement)From Fig. 2, a~= 56 x 20 = 1120 kg/cm

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IRC: 101-1988

From Fig. 4, for ra~ D25~ 1~eeffecti~e inciea~ein slab ihkkncssis 31 % .

Reducing the thickness proportionately

= 19.08 ~m

l)esign thickness of pavement slab 19 cm

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IRC: 101-1988

1.1ST OF OTHER STANDARDS, GUIDELINES AND SPECIAL

PUBLICATIONS RELATING TO CONCRETE ROADS

Price petcopy

Standard Specifications & Codeof Practice for Construction ofConcrete Roads (Second Revision)

Recommended Practice for Tools,Equipment and Appliances for

Concrete Pavement ConstructionTentative Guidelines for CementConcrete Mix Design (for RoadPavements for non-air entrained

and continuously graded concrete)(First Revision)

Recommended Practice forSealing of Joints in ConcretePavements

Guidelines for the Design of RigidPavements for Highways

Tentative Guidelines for the

Design ofGap Graded CementConcrete Mixes for RoadPavements

lentative Guidelines for the Useof Lime Flyash Concrete asPavement Base or Sub Base

Tentative Guidelines for theConstruction of Cement ConcretePavements in Hot Weather

TentativeGuidelines

on CementFlyash Concrete for RigidPavement Construction

Tentative Guidelines for Lean-Cement Concrete and Lean-Cement-Flyash Concrete as aPavement Base or Sub Base

Tentative Guidelines forStructural Strength Evaluation ofRigid Airfield Pavements

1. IRC 15-1981

2. IRC 43-1972

3. IRC 44-1972

4. IRC : 57-1974

5. IRC : 58-l988

6. 1RC : 59-1976

7. IRC : 60-1976

8. IRC : 61-1976

9.IRC

: 68-1976

10 . IRC :74-1979

II. 1RC :76-1979

16-00

12-00

8-00

3-00

16-00

5-00

5-00

5-00

6-00

8-00

10-00

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IRC 101 -1988

12. IRC : 77-1979 Tentative Guidelines for Repair ofConcrete Pavements UsingSynthetic Resin 15-00

13. IRC : 84-1983 Code ofPractice for Curing ofCement Concrete Pavements 8-00

14 . IRC : 85-1983 Code of Practice for AcceleratedStrength Testing & Evaluation ofConcrete for Road and AirfieldConstructions 8-00

15 . IRC : 91-1985 Tentative Guidelines for Construc-

tion ofCement Concrete Pave-ments in Cold Weather 8-00

16. IRC: SP-ll Handbook ofQuality Control forConstruction ofRoads andRunways (Second Revision) 32-00

17. 1RC : SP-16 Surface Evenness of HighwayPavement 7-00

18. IRC SP-17 Recommendations about Overlayson Cement Concrete Pavements 15-00

19. MOST Handbook on Road ConstructionMachinery (1985) 32-00

20. MOST Manual for Maintenance ofRoads 24-00

21. MOST Specifications for Road &Bridge Works (Second Revision) 80-00