IRC : 60-1976

TENTATIVE GUIDELINESFOR

THE USE OF LIME-FLY ASHCONCRETE AS PAVEMENT

BASE OR SUB-BASE

THE INDIAN ROADS CONGRESS

JRC:6G1976

TENTATIVE GUIDELINESFOR

THE USE OF LIME-FLY ASHCONCRETE AS PAVEMENT

BASE OR SUB-BASE

Publishedb~’THE INDIAN ROADS CONGRESS

Jamnagar House,Shabjahan Road,New Deihi-ilOOll

1976

PdceR s4~24(plus Packing& Postage)

IRC 60-1976

First published:March 1976

(RightsofPublicationand ~fTranslation are reserved~

Printed alPRINTMD, New Delhi

IRC 60-1976

TENTATIVE GUIDELINES FOR THE USE OFLIME-FLY ASH CONCRETE AS PAVEMENT

BASE OR SUB-BASE

1. INTRODUCTION

1.1. Theseguidelineswereapprovedby the CementConcreteRoadSurfacingCommittee (personnelgiven below)in their meet-ing held at Chandigarhon the 1st March, 1975.

K.K. Nambiar —Canvenor

Dr. aK. Ghosh —Member-Secretary

MEMBERS

D.C. Chaturvedi K C. MitalDr. M.P. Dhir N,L. PatelBrig. GobindarSingh P.S.SandhawiliaC.L.N. Iyengar A.R. SatyanaráyanaRaoP.J.Jagus S.B.P.SinhaM.D. Kale N. SivaguruBrig. R.K. WaIra Dr. H.C. VisvesvarayaDr. 5K. Khanna DirectorGeneral(RoadDcv.) ex-officia

C.V. Padmanabban(co-opted)

These were processedby the SpecificationsandStandardsCommitteein their meetingheld on the 13th December 1975 andlater approved by :the Executive Committee andthe Councilintheir meetingsheld on the 22nd December 1975 and 3rdJanuary1976 respectively.

1.2. General

Lime-fly ash concreteis a semi-rigid materialhavingdistinctlysuperiorload dispersioncharacteristicsas comparedto conventionalgranularbasesand sub-baseslike water-boundmacadam. As sucha smallerthicknessof this material canbe usedto replacethe con-ventionalbaseandsubbasecoursesin flexible and rigid pavementconstruction. IRC: 15-1970 “StandardSpecificationsandCodeofPractice for Construction of Concrete Roads (First Revision)”permits the useof 10 cm thick lime-pozzolana concrete in placeof15 cm thick water-bound macadamas subbaseunder concretepavement.

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IftC :60-1976

Besides superior load spreadingproperties,lime-fly ashcon-creteis resistantto softeningunder water actionandcan serveas agood working platform on softer foundations. These propertiesmake this material particularlysuitable for use in heavy rainfallareas, black cottonsoil areas(when laid overlime-stabilisedblackcotton soil) and in areas wheregood quality stonefor basecourseshas to beobtainedfrom longdistances. Lime-fly ash concretewillenable20-30per cent reductionin thicknessvis-a-visgranular basecourses.

As disposal of fly ash from thermal power stationsis a re-cognisednational problem,useof lime-fly ashconcrete as astruc-turally superior pavinglayerwill also contributetowardsrelievingthis problem.

2. THICKNESS DESIGNOF LIME-FLY ASH CONCRETE

BASE/SUBBASE LAYER

2.1. As BaseCoursein Flexible Pavement

The thickness of lime-fly ash concrete layerfor useas basecoursein flexible pavementshouldbe designedin accordancewiththe CBR methodof design,vide JRC: 37-1970“Guidelines for theDesign of Flexible Pavements,”using an equivalency factor of1.25-1.5 dependingon the discretionof the designer. Thicknessof lime-fly ash concretelayershould,however, in no case be lessthan 10cm.

2.2, As Subbase Courseunder RigidPavement

The thickness oflime-fly ash concretelayerfor useas a sub-basecourseunder cement concrete pavementshould be as perIRC: 15-1970 “Standard Specificationsand Code of Practice forConstruction of Concrete Roads(First Revision)’~. IRC : 15-1970 recommends the provision of 10 cm thickness of lime-pozzolana concrete subbase in lieu of 15 cm thickness of waterbound macadam.

3. MATERIALS FOR LIME-FLY ASH CONCRETE

3.1. Lime

Lime usedfor lime-fly ash concreteshould, as far aspossible,conformto Class C variety asper IS: 712-1972: “StandardSpecifi-cations for Building Limes.” The purity shall, however,not belessthan 60 per cent. Lime shall beused in hydratedform.

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IRC: 60-1976

3.2. Fly Ash

Fly ash should conform to IS: 3812 (Part11)4966:Standard

Specificationsfor Fly Ash: PartII.3.3. Aggregates

Coarseaggregatefor use in lime-fly ash concrete should beeithernaturalstoneaggregateconformingto IS: 383-1970:StandardSpecificationsfor CoarseandFine Aggregatesfrom NaturalSourcesfor Concrete(Revised),or brokenbrick conformingtoIS: 3068-1965:Specificationfor Broken Brick Coarse Aggregate for Use in LimeConcrete,or Cinder aggregateconformingto IS: 2686-1964:Specifi-cationsfor cinderaggregatesfor use in lime concrete, dependingupon the situationof use. Similarly, fine aggregatefor use in lime-fly ashconcreteshould conform to IS: 383-1970:Specifications forCoarseandFine Aggregatesfrom Natural Sourcesfor ConcreteorIS: 3182-1967:Specificationfor Broken Brick FineAggregatefor usein Lime Mortar. Aggregatesconformingto IS: 2686-1964andhavingthe requiredgrading for fine aggregateas stipulatedin IS: 3834970mayalso be considered. In selectingthe aggregates,the strengthrequirementstipulatedin para4.1. should bekept in view.

3.4. WaterWaterusedin-mixing or curing of concrete should be clean

andfree from injurious amounts of deleterious matter. Potablewater is generallyconsideredsatisfactoryfor this purpose.

4. PROPORTIONING OF LIME FLY ASH CONCRETE

4.1. Mix DesignCriteria

To actas a semi-rigidpavementlayer, lime-fly ash concreteshould be designedto give a minimum compressivestrength of40-60kg/cm2at 28 daysin the field, as specified in IRC: 15-1970.As compactionin the field is doneby rolling, workability shouldbekept low, with zeroslump.

4.2. Mix Design

4.2.1. Like leancement concrete, the mix proportionsforlime-fly ash concreteare designedby trial anderror method. Tofacilitate selectionof suitableproportionsof thetrial mix,particularsfor a few lime-fly ashconcretemixes, designedwith fly ashhavinglime-reactivityof 40-50kg/em2,lime of 60 percentpurity, mediumcoarsesand,andgood quality crushed coarse aggregateof 20 mmmax.size aregiven in Table 1.

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IRC 60-1976

TABLE IPARTICULARS OP TYPICAL LIME~FLY ASH CONCRETE Mixrs

S. No, Mix Proportions(by weight)

Lirne:FIy Ash:Sand:CoarseAggregate

WaterContent(% by dryweight of mixmaterials)

28-daysstrength

Cornpres-sive

Flexural

I. I : 2.0 : 4.0 : 9.0 10.7 36 5.72. 1: 2.0:4.0:9.0 9.7 49 8.03. 1: 2.0 : 2.5 : 5.25 10.0 69 14.84. 1: 2.0 : 2.25: 675 10.8 72 11.65. 1: 2.0: 2.7: 6.3 11.0 75 14.86. 1 : 1,5 : 3.3 : 7.5 9.7 60 8.07. 1 : 1.5 2.7 : 8.3 7.0 69 11.68. 1 1.5 : 2.25: 5.25 9.7 75 14.8

The maximum size of the coarse aggregatein the mix islimited by the thicknessof the lime-fly ash concrete layer to belaid, andshouldgenerally not exceed40 mm for 10 cm thickness.For thicknessesexceeding10 cm, multilayerconstructionshould beadoptedwhen compactionis effectedthrough rolling. While select-ing trial mix proportionsfrom Table 1, allowance should be madefor changein the maximum size andshapebf aggregate,as increasein maximum sizeof aggregaterequires reductionin water content,changein shapefrom angular(crushedaggregate)to rounded (un-crushedgravel) requiresreductionin both water andsandcontents,andincreaseor decreasein finenessmodulusof sand,a like changein sandcontent. Significantly lower strengthmaybeexpectedwhenbrokenbrick or cinder is usedas coarse and/or fine aggregateinsteadof crushedstone. As a rough guide, for the stipulated28dayscompressivestrengthof 40-60 kg/cm2, the approximate totalaggregate/binder(lime+fly ash)ratio maybe between2.5 and 3.5(by wt.) with water contentabout 10-li per cent by wt. of totaldry materials,when crushedstoneis usedas coarseaggregate.

4.2.2. To ensuremm. 28 day field cOmpressivestrengthof40-60 kg/cm2, allowing for processvariancesin the field, thelaborarorymix shouldbe designedfor 1.25 timesthe requiredfieldstrength.

4.2.3. Whereverpracticable,both cubeandbeamtestsamplesshouldbe madefor the trial mixes to determinecompressiveaswell as flexural strengthof the mixes. Where castingandtesting

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IkC : 6t~-1976

beamsamplesis not feasible,only cube samplesfor determinationof compressivestrengthmay be made. In the latter case, flexuralstrengthof lime-fly ash concrete (in the rangeof 40.60 kg/cm2compressivestrength) shouldbe assumedto be 1/6th of the com-pressivestrength. The strength testsshould be conductedasperrelevantIndian Standardspecificationsfor cementconcrete.

5. EQUIPMENTS

5.1. Batchingand mixing Equipmentfor Lime-Fly AshConcrete

Batching of materialsfor lime-fly ashconcreteshould be doneby weight,andvolume batchingmaybe permittedonly whenun-avoidable. Mixing shouldbe donein powerdriven concretemixersof adequatecapacity. The stipulationsof IRC: 43-1972 “Recom-mendedPracticefor. Tools,Equipmentand Appliancesfor ConcretePavementConstruction”in respectof weigh-batchersand mixersfor concretepavementsshould be followed in this casealso.

5.2. Compacting EquipmentCompactionof lime-fly ash concretelayer in the field should

bedone by meansof an 8 to 10 tonnesmoothwheelroller forharderaggregatesand 6 to 8 tonneroller for softer aggregates. Alternati-vely, vibratory roller of equivalentcapacitymayalso be used.

6. PREPARATIONOFTHE SUBGRADEJSUBBASE

The subgradeor subbase over which lime-fly ashconcrete,layer is to be laid, should be checkedfor line, grade and cross-section,as per provisionsof Chapter7 of IRC SP~l973:Handbookof Quality Control for Constructionof Roadsand Runways. Allirregularitiesbeyondthe permittedtoleranceshouldbe rectified. Itshouldbe ensuredthat thereareno soft spotstherein. Soft andyielding spotsandruts shouldbe corrected androlied until firm.The checkingand rectificationof the underlyinglayer should bedoneat least2 days in advanceof laying lime-fly ash concretethereon.

To prevent absorption of water from lime-fly ashconcrete,the underlying layer should either be covered with waterproofpaperor broughtto moist conditionwithout free wateratthe surfacebefore laying lime-fly ash concrete. For thispurpose,it may besaturatedwith waternot less than6 hoursnor morethan20 hoursin advanceof laying lime-fly ash concrete, if necessary~followed

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IRC : 60-1976

by light sprinkling prior to concreting,if any areashave becomedry.

7.. CONSTRUCTION

7.! Storage and Handling of Lime

Limc should be stacked under cover in a dry place. Whenslaking of quick lime is carried out at site, the lime shouldbele.ft over,night for slaking to completeandfor cooling down. Thelime soslakedshouldhe usedwithin abouta week’s time to avoidcarbonation by aerittion, If slaked lime is supplied in airtightbags in dry hydratedform, the periodof storage canbe longer (upto3 months).

7.2. Storageand Handling of Fly Ash

fly ash,beinga very fine material,gets easily air-borne. Forprotection againstthis, fly ash may beeitherbaggedor soakedwithwater at the top during transport, as welt as storage. Whennotbagged,it may hestoredin regular trapezoidalpits dug [hrthe pur-pose. The lop surfacemay be either kept wet or covered withta.rpauhns.

7.3. Storageand Handling of Aggregates

The provisionsof IRC: 15.1970:Standard SpecificationsandCode of Practice for Constructionof ConcreteRoads, Clause8.2should be followed in respect of storage and handling ofaggregates.

7.4 Batching andMixing of Materials

The materials formaking lime-fly ash concretemix shouldhehatchedby weight, usinga.pproved weigh-batching equipment, andvolume hatchingmay bepermittedonly when unavoidable, Watermay be measuredby volume using calibrated containers.. Propor-tion ing of the constituent materials shouldbe asspecifiedon thebasis of designed in ix proportions, making due allowancefOr freemoisture absorptionin aggregatesand moisturepresentin lime andfly ash. It hasbeenfound that moist fly ashfacilitateseasy mixingto obtai’n the desired compa.ctibility.

Mixing should be done in powerdriven mixers of approvedtype, and uniform homogeneousmixing of all the ingredientsshouldbe ensured. Themixer should not be overloaded,andadequatemixing time (1-2 mm.) shouldbe given to ensureuniform mixing.

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IRC 60-1976

7.5. Transportation and Placementof Lime-fly Ash Concrete

The lime-fly ash concreteshouldbe transportedandplaced onthe preparedsuhgrade/suhbaseso that the compactedlayerhas therequireddepth, slopeandcamber, The amountof surchargerequ-ired is about 20-25 per cent of the thicknessof layer to be laid.The actualamount of surchargemay be determined through fieldtrial. Transportationand placementshouldbe sodone as to avoidsegregation. Any portion of the batchwhich becomessegregatedduring placingshouldbe thoroughlymixed with the mainbody of thebatchduring the processof spreading.

7.6. Compaction

Whensufficient length of lime—fly ashconcretehasbeenlaid topermit rolling, compactionshouldbe done by rolling (seepara 5.2).Rolling should sta.rtfrom the outer cdgesof the pavementandpro-ceedtowardsthemiddle exceptat superelevatedportions where itshould commenceat the lower edge and progress towards thehigher. Adequate numberof passesshouldbe given to ensure fullcornpaction.

The gradeand camberof the surfaceshouldbecheckedduringcompaction, anti all irregularitiesshouldhe correctedby removingor addingfreshmaterial.

Compactionshouldhe completedwithin specified.period whichshall not exceed4 hourssincethe time of mixin,g as stipulatedin IS:58i7-1970: Code of Practice for Preparation and Use of Lim.ePozzolanaConcrete in Buildings and Roads. When lime-fly ashconcreteis to be laid in two layers, the secondlayershouldbe laidwithin 2-3 hoursof compactionof the lower layer.

7.7 Joints

No joints may be provided exceptconstructionjoints at theendof the day’s work, andeachsuccessivelength takenup for roll-ing.. Theseshouldbe formedby chamfer.ingt.he edgeof the alreadylaid concrete at an angleof about 30°,andsubsequentlylaying thefresh concretethereon.

7.8. Curing

After laying andcompactionof the total thicknessof lime-flyashconcretebaseor sub-basehasbeencompleted,it shouldbe curedfor the first 48 hoursby coveringit with wet gunny bags or hessianandsubsequentlyby spreadingwet sand or watering frequently inmoderate quantities, but not by ponding as that would leadto

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IRC:60-1976leaching. Curing should be carried out for not less than 7 days, andpreferably 14 days depending on seasonal and other considerations.No traffic should be allowed on the lime-fly ash concrete layerbefore top courses thereon are placed.

7.9. RectificatIon of Surface lrrogularitlss

The finished surface should be checked for line, level, gradeand surface finish. Provisionsof Chapter 7 or IRC SP-li-L973:Hsndbook of Quality Control for Construction of Roads and Run-ways should be followed for this purpose. The checking snd recti -fication should be carried out while the mix is still plastic. Anysurface irregularities left in the hardened layer should be correctedby cutting out sufficiently large patches and relaying to sped-fication.

8. SURFACECOURSE

Lime-fly ash concrete, being a semi-rigid material, may developtransverse cracks on account of thermal’drying shrinkage effects.These cracks are likely to get reflected on the surface if the pavementthickness over lime-fly ash concrete is insufficient. To preventsuch reflection cracking, when lime-fly ash concrete is used as abase course in flexible pavementconstruction, it is recommended thatan intermediate layer of bitumen bound material should be providedthereon before providing tbe wearing course, so as to absorb themovement of cracks In the lime-fly ash concrete base, and to preventtheir reflection on the surface. Water bound macadam may alsobe considered tentatively in lieu of bitumen bound materials. Theminimum thickness of this Intermediate layer plus wearing courseshould not be less than 10 cm.

In case of rigid pavement, where lime-fly ash concrete is usedas a subbase, the cement concrete wearing course can be laid dire -ctly thereon without provision of any intermediate layer, as due togreater rigidity of the cement concrete layer, such cracks from thesemi-rigid subbase do not get reflected thereon.

9. QUALITY CONTROL

Quality control of lime-fly ash concrete construction should bedone as per the provisions of IRC SF1 1-1973: “Handbook of Qua-lity Control for Construction of Roads and Runways”, in respect of

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IRC 60-1976

TABLE 2: QUAUTY CONTROL TESTS FOR LIME-FLY Asis CONCRETE

S. No, Test Test Method Minimum desirablefrequency

Quality of lime IS: 712/1514 Onceinitially forapprovalof thesource of supplyandlater for each con-signment of thematerial

2, Quality of Fly ash IS: 3812 -do-(PartII)

3. Los Angeles AbrasionValue/Aggregate IS: 2386 One testper 200 m

mimpact Value (Part1V)

4. Aggregategradation IS: 2386 One lest per 100 m1(Part I)

5, Aggregatemoisture IS: 2386 As requiredcontent (Part lii)

6, Control of grade, camber, Vide Chapter Regularlythicknessandsurface 7 of IRC 5P:hnish I t-i973

7. Strengthof cubes iS: 2541 Onetest for 50 m~(2specimensfor eachageof 7 and28 days)

Lime-PozzolanaConcrete. Relevantquality control tests andtheirminimum desirablefrequencyas specified therein, arepartly repro-duce~din Table2 for readyreference.

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