IRC 101-1988

GUIDELINESFOR

DESIGN OF CONTINUOUSLYREINFORCED CONCRET E

PAVEMENTWITH

ELASTIC JOINTS

THE INDIAN ROADS CONGRESS1991

1RC: 1OI-1~$S

GUI DELI NESFOR

DESIGN OF CONTINUOUSLYREINFORCED CONCRETE

PAVEMENTWITH

ELASTIC JOINTS

Publishedby

THE INDIAN ROADS CONGRESSJamnagarHouse, ShabjahanRoad,

New Delhi-I10 0111991

Price Rs~~S. ~(P’us packing & po~tagc~

IRC: tOi-1988

First publishe9: June,1988Reprinted:March, 1991

(RightsofPublicationandof TranslationareReserved)

Printedat SagarPrinters& Publishers.New Delhi(1000copies)

IRC : 1014988

GUIDELINES FOR DESIGN OF CONTINUOUSLY REINFORCEDCONCRETE PAVEMENT WITH ELASTIC JOINTS

I. INTRODUCTION

1.1. Guidelines for Design of Continuously ReinforcedConcrete Pavementwith Elastic Joints preparedby the CentralRoad Research Institute were discussed and approvedby tieCement Concrete Road Surfacing Committee(personnelgivenbelow) in their meetingheld 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. D’sa A Rep.of CementResearchP.V Kamat Instituteof IndiaOP. Lal Director, U.P. iW,D. ResearchP.J.Mehta Institute (PD.. Agrawal)V. Raghavan City Engineer(Roads),MunicipalC. Raman Corporationof BombayA. 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 & StandardsCommittee in their meetings held at NewDelhi on the 28th August, 1986 and 23rd April, 1987and werereturned back to the CenientConcreteRoad SurfacingCommi-tteefor further consideration.TheseGuidelineswere then finaL-sedby Dr. M.P. Dhir, the presentConvenorandShri S.S.Seehra,the presentMember-Secretaryof the Committee, The documentreceivedfrom the CementConcrete Road Surfacing Committeewasreconsideredby the Highways Specifications & StandardsCommitteein their meetingheld on the 25th April, 198% at NewDelhi andapproved. TheseGuidelines receivedthe approval ol’the ExecutiveCommittee and the Council in their meetingsheldon the 26th April and 7th May. 1988 respectively

1.3.’ The technique of continuouslyreinlorccd concretepavement (CRCP) obviatesthe need for expansionand contrac-tion joints, thus permittingvery long slab lengths with impro-

IRC : 101-1988

ved riding comfort and reduced maintenanceas comparedtoplain concretepavements. ConventionalCRCP requires relati-vely high percentageof steel of the order of 0.7-1.0 percent ofconcretecross-section.The techniqueof CRCPconstructionwithelasticjoints (CRCP-EJ) enablessignificant reductionin quantityof steel required(0.4—0.5per cent)and also eliminatesthe ran-dom cracks which occur in conventional continuouslyrein-forcedconcretepavements.

1.4. The provisionof continuous reinforcementin CRCPof the conventional type results in the formation of transversecracksin the pavementwhich areheld tightly closedby the steelwithout impairment of structural strength. The closely heldcl~acksensure load transfer acrossthe cracksthrough aggregateinterlocking and also preventthe ingressof water andgrit intothe cracks. The width and spacingof such cracksaredependanton the amountof steel reinforcementprovided. The greatertheamount of steel,the closer is the spacingof the cracksand thesmaller is their opening. An optimum amount of longitudinalreinforcement is called for so that the cracks are neithertoo widely spaced with resulting over-stressing ofsteel,loss in load transferprovided by aggregateinter-lock and accel-erated corrosionof steel; nor too closelyspacedso asto causedisintegration ofthe slab.

1,5. The elasticjoints consistof dummycontractionjointswith the reinforcementcontinuousthroughthem. The reinforce-ment is painted with a bond-breakingmedium overa specifieddesign length on eitherside of the joint groove to provide ade-quate gauge length for limiting the steel strainsdueto jointmovement. A typical elastic joint for the solvedexamplegivenin Appendix, is shown in Fig. 1.

1.6. The use of elastic joints,apartfrom resulting inredu-ction of steel stressesby about50 per centand enablingthe useof less quantity of steel,also precludethe randomcrackingasso-ciated with conventionalconstruction,since the weakenedplaneprovided atsuchjoints localisesthe cracking. The usual spacingof suchjoints works outto about4 to 5 m.

2. DESIGN

2.I. Calculation for Steel Percentage and Stressesin Steeland Concrete due to Continuity at Elastic Joints

2.1.1. The continuity of steel at elasticjoints leadsto res-traint in the slab movementdueto shrinkageand temperature

2

‘~ 1 9cm

0

oc

RE INFORCDIENT16 mm 0 ~ 26 cr~Vc/c

LO~ITUbINhL REI~CRCEMEMF COItED )~ITH ?ITt1IEN TO9REAJ( 9OND ~1TH CO~CRETEDyES This LENOTH CF 150 cm.

ISO ~

Fig. 1. Detailsof elasticjoint section

tR( lt)1-l985

change, and thus induces stresses in both steeland concrete.However, if steel is provided at mid-depth ofthe slab, as is theusual practice,no stresswill developin it dueto wheel load andwa rp i ng.

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 Eisenmannequationswhich aregiven below

lOt) ~. a ~‘,h.E.,Es k . 2

ri IT”Ffll—%.’j”+’(IOOh.Er.)) g/c

2.LT.f &.E.and - jTE~~iTTjTh”1’~,Ec. kg/cm2

w herc

a Coefficient of thermalexpansionof concreteper ‘C,

1’ ‘• Difference het~~eenthe meantemperaturesof thestabat the timeof constructionandthe coldestperiodin ~C,

At ‘: Maximum temperaturedifferential betsseenlop and bottom ofthe slab,

Note While finding out the temperaturestressat the edge,IRC:58-1988 recommendsdefinitevaluesof temperaturedifferen-tial in different states of India, This differentialhasbeendesignatedas Ai in IRC: 58-1988andis different from ATwhich is usedin this text to designatetemperaturedifferencebetween theminimum of minimumsandthe meantempera-ture at the time of construction. Ar is not a function otstab thickness whereasAs the temperaturedifferentialdependson the thicknessof slab,

Fi Slab thicknessin em.

I ‘ Modabsof ela ;ticity of concretein kgfem2

-; Modulus of cba~tieityof s tcel in kg/cm’

ft == Cross-sectionof steel in t in width of the slab in cm~

= Ratio of free, unbondedlength of the steel to the slablength

betweentwo consecutiveelastic joints,

2.1.3. The chartsin Figs. 2 and 3 show steeland concretestressesper °Cof ~ T for steel percentagerangeof 0.1—0.6andfor ratio, A rangeof 0.1—0.4. The steel stressesso determinedshould not exceed the permissiblevalue of 1400kgtcm2. Theconcretestressesare additive to the load and temperaturewarp-ing stressesand are required to be taken intoaccountwhiledesigning the pavement. The transversesteel may be taken as25 per cent of longitudinal steel.

4

I.,‘1aUV

aU141

C

IRC: 101-3988

~=Ratio of unbonded length of steel to spacingof elasticjoints

Fig. 2. Designchartsl’oi’ calculationof stressesin steel

5

IRC : 101-1988

aU

V

aU

C

H~

0.-

°-~

,0.,

o.:

c~_1

-

\ ~O.5%

\\\

\\N

~~

~

\\.~\

N~4%~

~,

~

~

—MM

.

~

~__

-

020 .30 Q.—5

,—Ratio of unbondedlength of steel to spacingof elastic joints

Fig. 3. Designcharts for calculationof stressesin concrete

aRC: 101-1988

2.1.4. The provision of steel enablessomeincreasein theeffective slab thicknessand its continuity at elasticjoints provi-des additional load transfer over and abovethat providedbyconventional dummy contraction joint. At the same time,thepercentageof steel is small enough not to induce any restraintto bending of the slab at elastic joints due to effect of wheelload and temperaturewarping.

2.1.5. While in CRCP without elasticjoints the permissiblestress in steel is2800kg/cm2 (i.e. the steel isallowed to be stre-ssed upto the yield point), the permissiblevalue in CRCP withelasticjoints is restricted to1400 kg/cm2 only (i.e. normal work-in~ stress in steel used in conventional structures). Thelower permissiblestressin steel in CRCP withelasticjoints ena-bles taking advantageof the effectiveincreasein concreteslabthickness due to provision of steel,while thepermissibleyieldstress limit in steel in the caseof CRCP without elastic jointprecludessuch 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 concretetensile stressshould be accountedfor as indicatedin para2.1.3.

2.2.2. ihe effective increase in slab thickness duetoprovision of steel reinforcement may be worked out by usingMallinger’s chart given in Fig. 4. The equivalent CRCP slabthickness may then be calculated by reducingthe thicknesscalculated in para 2.2.!. by the amount of the effectiveincrease in slab thickness usingFig. 4 the averageof steel inlongitudinal andtransversedirection may be taken.

2.2.3. Outline of design procedure

Step I Assume a thicknessand examine wheel load andtempera-ture stresses as per IRC:58-l988.

Step II For a proposedvalue,chooseasteel percentagefroni Fig. 2such that the steel stressis within the permissible value.Calculate the concretestress from Fig. 3. In calculatingthese stressesthe ordinates are to be multiplied by thecorrespondingvalue of t, as applicable to the particularlocation.

7

IRC It)l-1988

o .

0.40

C0U — 0.30I- a00c.

a

ci 0209.C 0.

.0 >~

°~ U

00,0 —

~ 0.10

j o.oe,~ 0.06

0,04

Fig. 4. Mallingcfs chart sho~cingtheeffect of reinforcementon rigid pavements

Step Ill Add the concrete stress calculated inStep Ii tothe valueobtained in Stc~t and the final total stresses shouldbewithin the flexural strengthof concrete. The trials mayberepeated till the assumedthicknessin Step I meetsthcrequirement.

Stcp IV Calculate the effective increase in slab thickness duetoprovision of reinforcementas per Fig.4 (vide para2.2.2.)andreducethcthickness obtainedin Step III to accountfortheincrease.

An illustratIve exampleis given in Appendix.

2.3. Cement ConcreteMix Design

The mix should be designedon the basisof absolutevolumemethodas per IRC 44-1976 ‘~TentativeGuidehnesfor Cement

8

IRC : 101-1988ConcreteMix D~sigri”. The fkxural strengthof concreteat 28

daysin 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. Coarseand Fine Aggregate

Should conformto IS : 383-1980.

3.3. Steel

The diameterof steel bars shouldbe so choosenas 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 cleanand free from injurious amountof deleterious matterandshouldconform to IS : 456-1978. Potablewater is generally consideredsatisfactory.

4. CONSTRUCTION DETAILS

4.1. General

The construction details are the sameas in the caseofplain cementconcretepavements(vide 1RC : 15-1981)except thefollowing.

4.2. Construction of Joints

4.2.1. Elastic joints: These aredummy type joints whichshould be inducedat regularintervals similar to that for dummycontractionjoints. The joint grooves may be formed as in thecaseof conventionaldummyjoint, and filled with sealing com-pound. Alternatively, bitumen-coatedplywood strips of 5 cmwidth and 3 mm thicknessmay be inserted therein. On eitherside of the elasticjoint, steelshould be coatedwith bitumen fora length of 1/3-1/4joint spacing in order to break the bond ofsteel with concreteand to provide greater length for elongationof the steel dueto joint opening for reducingthe stressin thereinforcing steel.

4.2.2. Expansion joints: The expansion joints are provi-

9

IRC: 101-1988

ded only at the ends of the CRCP-EJ sections and thereis noneedof providing these joints in-between. The width of suchexpansionjoints is kept upto double that of conventional con-cretepavement to accommodatethe greater end movements.Detailsof thesejoints should be as shownin IRC : 15-1981.

5. REINFORCEMENT

The steel mats,assembledat site, areplaced oversuitablechairsat mid depth of the slab before concreting is done. Thebars shouldbe continuousacrosselasticjoints andany construc-tion joints. Whereveroverlapof barsis required,a minimumoverlapof 30 diameters should be provided. Such overlapsshouldbe staggered. It should also be ensuredthat no overlapof steelbars are provided at the location of elastic joints.

IRC : 101-19$8

Appendix

AN ILLUSTRATIVE EXAMPLE OF DESIGN OF SLAB THICKNESS

I. Design Parameters

Locationof Pavement

Design WheelLoad, FPresentTraffic IntensityDesignTyre Pressure,p

FoundationStrength,IcConcreteFlexuralStrength,fR

Ec = 3.0 x 10’ kg/cm’

:~ =0.15

Delhi

5100kg300 veh/day7.2 kg/cm’

6 kg/cm’40 kg/cm’

= 10 x

= 14VC againstthicknessof 25cm

2. DesIgn Procedure:Step I : Assume!. = 25 cm, spacingof elasticjoints = 4.5 m

As per IRC : 58—1988ale = 18,50kg/cm’~ve= 15.50kg/cm’

a Total = 34.00 kg/cm’

Step11: For ?. = 0.33 and j~ = 20CC

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

<1400kg/cm’

OKFrom Fig. 3, a, = 0.235 x 20 .-~ 4.7 kg/cm’

Step[II : From StepI total e — 34.00kg/cm’From Step II a~= 4.70 kg cm’Total a = ~8.70 kg/cm’. say39.00kg/cm’

The total stress39.00kg/cm’ is less than the flexural strength of concrete40 kg cm’ and therefore thethicknessof 25 cm is O.K.

StepIV : Averagesteel reinforcement~+ 25%of 0.004 ~ — 025 percent

11

IRC: 101-1988

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

Reducingthe thicknessproportionately

= 19.08 ~m

l)esign thicknessof pavementslab 19 cm

12

IRC: 101-1988

1.1ST OF OTHERSTANDARDS, GUIDELINES AND SPECIALPUBLICATIONS RELATING TO CONCRETE ROADS

Price pet’copy

StandardSpecifications& Codeof Practice for Construction ofConcreteRoads(SecondRevision)

Recommended Practicefor Tools,Equipment and AppliancesforConcretePavementConstruction

TentativeGuidelinesfor CementConcreteMix Design (for RoadPavements for non-air entrainedand continuouslygraded concrete)(First Revision)

Recommended PracticeforSealing of Joints in ConcretePavements

Guidelinesfor the Designof RigidPavementsfor Highways

Tentative Guidelines for theDesign of Gap GradedCementConcreteMixes for RoadPavements

l’entative Guidelinesfor the Useof Lime Flyash ConcreteasPavementBaseor SubBase

TentativeGuidelines for theConstructionof CementConcretePavementsin Hot Weather

TentativeGuidelineson CementFlyash Concretefor RigidPavementConstruction

TentativeGuidelinesfor Lean-CementConcrete andLean-Cement-FlyashConcreteas aPavementBaseor Sub Base

TentativeGuidelinesforStructural StrengthEvaluation 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

- ..______

IRC 101-1988

12. IRC : 77-1979 TentativeGuidelinesfor Repair ofConcretePavementsUsingSyntheticResin 15-00

13. IRC : 84-1983 Codeof Practicefor Curing ofCementConcretePavements 8-00

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

15. IRC : 91-1985 TentativeGuidelinesfor Construc-tion of CementConcretePave-mentsin Cold Weather 8-00

16. IRC: SP-ll Handbookof Quality Control forConstructionof RoadsandRunways(SecondRevision) 32-00

17. 1RC : SP-16 SurfaceEvennessof HighwayPavement 7-00

18. IRC SP-17 RecommendationsaboutOverlayson CementConcretePavements 15-00

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

20. MOST Manual for Maintenance ofRoads 24-00

21. MOST Specificationsfor Road&Bridge Works (SecondRevision) 80-00