IRC : 95-1987

SPECIFICATIONFOR

SEMI-DENSE BITUMINOUSCONCRETE

THE INDIAN ROADS CONGRESS

1989

TRC 95-1987

SPECIFICATIONFOR

SEMI-DENSE BITUMINOUSCONCRETE

Publishedby

THE INDIAN ROADS CONGRESSJaninagar House,ShabjahanRoad,

NewDelhi-lID 011

1989

Price RsIII. 24(Plus packing& postage)

IRC 95-1987

First published July, 1987

Reprinted: September,1989

(RightsofPublicationandof Translationare Reserved)

Printed at PRINTAID, New Delhi-20(2000 Copies)

IRC : 95~987

CONTENTS

Clause No. Page No.

1. Introduction ... I

2. Scope .~ 2

3. DesignCriteria . ~. 2

4. Materi&s ... 3

5. JobMix Formula ,. 5

6. Construction .. 5

7. Controls 7

8. WeatherandSeasonalLimitations 9

IRC 95-iqg~

SPECIFICATION FOR SEMI-DENSEBIT MINOUS CONCRETE

1. INTRODUCTION

1.1, The formulationof the draft of the Specification forSemi-DenseBituminous Concrete hadbeenunderthe considera-tion of the BituminousPavementsCommittee.This Committeeintheir meetingheldat Madrason the 12th December,1985 discus-sedthe abovementionedSpecificationandauthorisedS/Skill K.?.Nair andR.S,Shukia to modify andredraft the Specification inlight of the commentsreceived. Accordingly, the draft Specific-ation was revisedby thisGroupandconsidered~bythe Specifica-tions & Standards~Committee. The draft Specification wasmodified by Shri P Bhaskaran,Member-Secretary,BituminousPavementsCommittee on the basis of the comments of theSpecifications& StandardsCommitteeand it was again placedbefore the Bituminous PavementsCommittee (personnelgivenbelow) in their meetingheldat Madrason the 13th March, 1987.

Prof.C,G. SwamiriathanP. Bhaskaran

G.R.AmbwaniR.C. AroraDr. ArunKuntarR.T. AtreAS. BhattaeharyaS.F. BhargavaP.C.BhasznG.C. GuptaR.A. GodY.C. Gokhaie0.1’, Gupta8.5.DasGuptaM.D. JayawantV.P. KamdarUK, AggarwalP.K. LauriaV. Krishna Murthy

• . .C’onvnwr• .. Member-Secretary

MembersBK. MailiotraK.P. NairA.N. NandaT.H. Pestiorii.t. Cot. icamieshPrakashR.K. SaxenaSneonandanPrasadN. SivaguruG.M. ShonthLIA. SankaranS.K. MaihocraA. VeniratarangarajuCD. Thattei3aibir SinghR.K. SamanraA.K. RoyA Rep.of Ke~ala Higlw.a}ResearchinstiLuteN.S. Rama.Sttarina

The President,IndianRoadsCongressandDirector General(RoadDevelopment)& Addi, Secretaryto theGovt. of India

(K.K. Sarin) -Ex-officloTheSecretary,IndianRoadsCongress (NainanKoshi) -Es-officio

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1RC 95-1981

1.2. The Committee authorisedShri P. Bhaskaranto fina-Ike the draft Specificationandtorward for further considerationof the Specifications& StandardsCommittee. The revised draftSp~ci&cationwas considered by the Specifications& StandardsCommitteein their meetingheld at New Delhi on the 23rd April,1987. Lateron the Specificationwas approvedby the ExecutiveCommittee on 28th April, 1987 and by the Council in theirmeetingheld at Udaipur on 22nd May, 1987 for being publishedby the Indian Roads Congress.

2. SCOPE2.1. This draftSpecification dealswith the basic outline

for the design, construction and controls neededwhile laying•semi.densebituminous concretewearing course mixes for high-ways. it only highlights the essentialsso asto be of usewhilepreparingthe contractualdocumentsfor specificjobs of this type,and is not intendedto be adetailedcodeof practice.

2.2. Semi-densebituminousconcrete shall be used as awearing courseand shall notbe laid directly overWBM or anygranularbase. The item shallconsistof mineral aggregatesandappropriate binder mixed in a hot-mix plant andlaid with apaver on a previously prepared base in accordancewith theSpecifications and conforming to the lines, gradesand cross-sections.

3. DESIGN CRITERIA

3.1. Beinghigh cost specification, semi-densebituminousconcretemixesshouldbe properlydesignedso asto satisfy cer-tain criteria needed to assure satisfactory performance anddurability. The mix asdesignedand laid should satisfy the re-quirements given in Table1 basedon Marshallmethodwhich issuggestedfor the presentfor the sake ofsimplicity and uniformity.

TABLa”i. REQUIREMENT OF THE Mix(i) Numberof compactionblowson eachendof

Marshallspecimen 50(ii) Marshallstability in kg (Minimum) 340

(iii) Marshall flow (‘,~,,,) 2-4(iv) Percentvoids in mix 5-b(v) Percentvoids in mineral aggregatefilled with bitumen 55-75(vi) Binder contentaspercentby weight of total mix

(to be decidedbased_onMarshalidesignmethod) 4.5-6.0

Notes 1. it is suggestedthathigherstability values consistentwith otherrequirementsshouldbeachievedasfar as possible.

2, At busstops,parkingareasandroundabouts,nearminimum flowvalueshouldbeadopted.

3. The attemptshould be tohavewell gradedaggregateandthe percentvoidsin themix closerto thelower limit.

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IRC: 954987

4. MATERIALS

4 1 In order to satisfythe requirements speltout u~para3,the semi-densebituminousconcrete mix shall consist of coarseaggregatefine aggregateand filler in suitable proportions andmixed with sufficient binder content. Trueand representativesamplesof the aggregatesproposedto be usedon thespecific jobshall be tested in the designlaboratory andproperblendof thcaggregatesshallbe workedout so that the gradationof the finalcomposition will satisfy either of the three Urnits set forth inTable 2.

T&sL~2. GRADATION OF AGGREGATE IN Tue FINAL Mix

GradingNumber: ~: 1 2 3

Sievesize (percentpassingby weight)

22A mm — 101) 10013.2mm 100 85— tOO 79— 100

11.2mm 88—100 70—92 68—905.6mm 42—64 42—64 33—55

2.8mm 22—38 22—38 22—38710~im 11—24 II —24 6—22355pm 7—18 7—18 4—14180 ~ 5—13 5—13 2—99OLm 3—9 3—9 0—5

GradingNo. 1 is suggestedfor compactedthicknessof 25mmandGradingNos. 2 and3 for compactedthicknessof 25-40mm.

The exact bitumencontent required shall be arrived at asper Marshall procedurefoi the aggregategradationworkedoutin the laboratory andby usingthe samepavingbitumenproposedto be used in the field.

4.2, The materialshall furthersatisfythe following physicalrequirements.

42.1 Bitumen: The bitumenshall be paving bitumenofsuitablepenetration gradewithin the range of S 35 to S 90 orA. 35 to A.90 (30(40 to 80/100)~as perIS: 73 Paving Bitumen’.The actualgradeof bitumen to beused shaJi be decided by theEngineer-in-charge,appropriateto the region, traffic, rainfall andotherenvironmentalconditions.

3

IRC 95-1987

4.2,2. Coarseaggregate:The coarseaggregateshall be crush-ed material retainedo:n 2.8 mm sieve andshall be crushedstone,crushedslag, crushedgravel(shingle)andshall consistof angular,clean, tough and durablefragments, free fromdisintegratedpiecesandorganicor deleteriousmatter and adherentcoatings. Theaggregate shall preferablybe hydrophobic arid of low porosity.When thehydrophilli~aggregatesareused,the bitumen shall betreatedwith anti-strippingagentsof approvedquality in suitabledoses. The aggregate,shall satisfy the physical requirementsasgiven in Table3.

TABLE 3. PHYsICAL REQUIREMENTS or COARsE AGGREGATE

Test Requirement(percent

maximum)

Test Method

Aggregate Impact Value 30 IS 2386 (Part IV)

or Los,.AngelesAbrasionValue 40 —do—

FlakinessIndex 30 iS: 2386 (PartI)

StrippingValue 25 15: 6241

Water Absorption 1 is : 2386 (Part Iii)

SoundnessLosswith Sodium sulphate,

Loss with MagnesiumsulphS cyclesate, S cycles

1218

iS : 2386 (PartV)—do

Notes: I * For slag,the unit weightshall not be lessthan 1120 kg/&2 Water absorption upto2 per centmaybe permittedin exceptional

cases.

4.2.3. Fine aggregate The fine aggregateshall be thefraction passing2.8 mm sieve and retained on 90 &m sieve,andshall consist of crushedscreenings,naturalsandora mixture ofboth, It shall be clean, hard, durable, uncoated,dry and freefrom injurious, soft or flaky pieces and organicor deleteriousmatter.

4.2.4. Filler The requirementof filler in semi-densebitu-minious mixesshall normallybe met by the material passing90p.m sieve in fine aggregate.In casethe fine aggregateis deficientinmaterialpassing90 .‘ni sieve, extrafiller shall beadded.The fillershall be an inertmaterial,the whole of which passes710p.m sieve,atLeast90 percent passesISO p.m sieve and not less than 70 percent passes90 pm sieve. The filler shall be stone dust, cement

4

1RC : 95-19*7

hydrated lime, flyash or other approved non-plastic mineralmatter.

5. JOB MiX FORMULA5,1. While theJ*boratory mix design gives the different

proportionsof the Mineral aggregatecombination in termsofindividual sievesizes, for actualoperationalpurposesin the field,blendingof two or more sizes of agg’refltes (eaáh size havingwithin it a range of individual sieve sIzes)would be necessary.This blendingratio is obtainedon a weight basis,giving the percent weight of the coarse aggregate,fine aggregateand fillerneeded to give the ultimateaggregategradation. It can alsobeproportioned on a Volumetric basisbasedon theunit weight orbulk density of the4gregatessupPlied. Thismineralaggregatecombination together with the corresponding optimumbitumencontent as determined in thelaboratorycOnstitutesthe job mixformula for implemen:tatibnduring construction,

5.2. It is emphasisedthat in order that this formulabeadheredto in practice, the niix.design shallbe workedout basedon a correctand truly representativesampleof the materials thatwill actuallybe usedin thespecificconstructionproject.

6. coNSTRurrioN

6.1. PreparatIonof the Base

The base over which the semi-densebituminousconcreteisto be laid shall be completely free from dnst~cáedmud, etc.before laying the surface course. Where the existingbaseispotholed or rutted, the irregularities shall be filled in withpremixedmaterialsand well rammed.

If the existing baseis extremelyirregular andwavy, it maybe considered worthwhile to lay a bituminouslevelling course(Profile Corrective Course) of adequatethickness to avoid anexcessiveuseof the costlysurfacecourse.

A tack coat at the rateof 6 to 7.5 kg of bitumenper 10 m2shallbe given over abituminousbaseor bindercourseif the exis-ting surface is dry and hungry,and 5 to 5.5 kg per 10 mc on anormal bituminousbase.

6 2. Praparatlonof the Mix

It is imperative th:at the semi-densebitnminousconcretemixbe manufacturedbyusinga hot-mix plant Of adequatecapacity

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11W : 95-1987

to yield a mix of properanduniform quality. Theplant maybeeither abatchtype or acontinuousonehavingaco-ordinatedsetof essentialunits such as a dryer for heating theaggregates,arrangementsfor grading andbatching by weightor volume therequired quantities of aggregates,a bitumenheatingandcontrolunit for metering out the correct quantity of heated bitumentogetherwith a paddle mixerfor intimatemixing of bitumen andaggregates. A fines feeder for incorporation of the correctquantity of filler is also a necessaryauxilliary,

6,3. Spreadingof the Mix

The mix shall be transportedfrom the mixer bytippertrucks to the worksite andspreadingdonepreferablyby meansof a self-propelled mechanicalpaverwith suitable screedcapableof spreading,tampingand finishing the mix true to grade,lineandcross-section. Themix should be spreadin suchamannerthatafter compaction,the requiredthicknessof carpetis unifor-mly laid.

Longitudinaljoints andedges shall be constructed truetoline markingparallelto the centre lineof the road. Longitudinaljoints should be offset atleast by 150mm from those inbindercourse,if any, andtransverse jointsor construction jointshall beplaced in the vertical plane after cutting backto the originalthicknessof the previously laid mix. Theverticalcut face shallbe painted with hot bitumen prior to the layingof fresh mixagainst it.

6.4. CompactIon

The mix after spreadingshall be thoroughly anduniformlycompactedby rolling by a set of rollers ata speednot morethan5 km per hour, immediately following the paver. The initial orbreak downrolling shall be with 8-12 tonne three wheelsteelroller and the surfacefinished by final rolling with the 8-10 tonnetandem roller. Before finishing with the tandemroller, break-down rolling shall preferably be followed by an intermediatesmooth wheel pneumaticroller of 15 to 30 tonnehavingatyrepressureof 7 lcg/sq.cm. The joints andedgesshall berolled witha 8-12 tonnethreewheel roller. All the compactionoperationsi.e.breakdownrolling, Intermediaterolling and finish rolling can beaccomplished by using a vibratory roller of 8-10 tonne staticweight. During finish rolling the vibratory system shall beswit-chedoff.

The wheelsof roller shall be kept moist to preventthe mixfrom adhering to them. In no case shallfuelfiubricatingoil be

6

IRC : 95-1987

usedfor this purposenor excessivewaterpoured on the wheels.Rolling shall commencelongitudinally from edge and progresstowardsthe centreexcept on super-elevatedportions where itshallprogressfrom the lower to upperedge,parallelto the centreline of the pavement. The roller should proceed on the freshmaterial with rear fixed wheelleadingsoas to minimisethe push-ing of the mix andeachpassof the roller shall overlap the pre-ceding oneby half the width of the rear wheel. Rolling shall becontinuedtill the desireddensityof not less than 98 per centofthe lab design density is achieved and all roller marks areeliminated.

6.5. Openingto Traffic

Traffic may be allowedafter completionof the final rollingwhen the mix hascoOleddownto the surroundingtemperature.

7. CONTROLS7.1. Adequatequality controlatevery stageof thework is

essentiaLand as sucha field laboratorymustbe setup to ensurethe following controls.

7.1.1. Periodicsieveanalysisof eachtypeof the aggregateat the cold feederendshouldbe madeto see that the gradationof aggregatesreasonablyfollows the originalgradationof the jobmix designed. The number of samplesper daywould dependupon the numberof bulk supplyof the aggregatesmadein a dayat the plant site. The physicalpropertiesas requiredin Table 3shall be determined at the rateof onetesteachfor every50-100m3 of aggregatesor as directedby Engineer-in-charge.

7.1.2. Periodiccheckon penetrationandsofteningpoint ofthe bindershould alsobe donein the mannerspecifiediü IS:l203and 1205.

7.1,3. It shallbe ensuredthat theaggregatesarenot totallywet asotherwiseit would affect the outputof the plant adversely.The aggregatetemperaturemeasuringdevice installedat the endof dryer shouldbe checkedperiodicallyto seethat the aggregatetemperatureneverexceeds163°C. A toleranceupto lOt on thelower sidemaybe permitted.

7.1.4. The bitumentemperatureshouldbe well within thelimits specified. The viscosityof heatedbitumenshallbebetween150 Sd 300 centi stokesfor which the normal temperaturerangefor pavingbitumenis 1500-177°C.

7

IRC 95-1987

7.1.5. At no time, the diiTerence in temperaturebetweenaggregateandbitumen shouldexceed14~C.

7.1.6. Periodic ôheck of the aggregateat the gradationcontrol unit (if the plant is fitted with one) or at the hot bin gatesshouldbe madeto see thatthe proportion of the aggregatesasspecified in the job mix formulais compliedwith.

7.1.7. At least one sample for every100tonnesof bitu-minous mix discharged at the pugmill chuteor aminimum ofonesampleper plant per day shall be collectedandthe followingtests done

(i) Three Marshall specimensshall be compactedandtestedfor theaveragestability, f1ow~voids content anddensity. The valueshouldclosely followtbó laboratory designvalues.

(ii) Bitumen shall be e~ctractedfrom about 1000 gramsof the mix andbitumen content determined.

(iii) A sieve analysis of the aggregatesafter thebitumenis extracted,shall be doneand the gradationdetermined.

7.1.8. The permissiblevariationsof the individual percen-tages of the variousingredients in the actual mix from thejobmix formulashall be within the limitsindicatedin Table4.

TABLE 4. PERMISSIBLE VARIATIONS PROM JoeMix FORMULA

PermissibleSI.No.

Description of Ingredient variation by weightof total mix

(percent)

1. Aggregate passIng13.2or larger sieve ±S2. Aggregate passing11.2mm sieveand 5.6 mm sieve ±73. Aggregate passing2.8 mm sieveand1.4 mm sieve ±64. AggregatepassIng110~msieveand 355 pm sieve ±55. Aggregate passing180~m sieve ±46. Aggregatepassing90pm sieve ±37. Bitumencontent ±0.3

7.1.9. The temperatureof the mix at the time of laying

shall notexceed160°C~nd shall not be lessthan120°C.

7.1.10. Rolling operationsshall be conductedwhen the

8

IRC 95-1987

mix is neither too hot nor too cold so that shoving or hair cracksmaybe eliminated. Rolling operation shall be completed inevery respectbefore the temperatureof the mix falls below 80°C.

7.1.11. After the mix is compactedthe thicknesslaid maybe checkedby noting the depthof penetrationof hot steelscale.This shall alsobe correlatedwith the measuredarea of the sur-facelaid and the total plant output of the mix in tonnes(as givenin the plant scale).

7.1.12. For every 500 m2 or less of compactedsurface,onefield densitytestshouldbe conductedto determinethe densityofthe mix as laid, compactedandfinished. The density shallnotbe lessthan98 per centof the laboratory density.

7.1.13. The longitudinalprofile of the finishedsurfaceshallbe testedwith a straightedge4.5 m long parallel to the centreline and the transverseprofile with a cambertemplate. Anyirregularity greaterthan6 mm shall be corrected. The longitu-dinal profile of the finished surface shall also be tested with aroughometer/profllometerand it should be ensured that theroughnessshallnot exceed2500 mm per kilometre.

8. WEATHER AND SEASONAL LIMITATIONS

Semi-densebituminous concrete carpet shall not be laidduring rainy weatheror whenthe base/bindercourseis damp orwet, and normally when the atmospherictemperaturein theshadeis 15°Cor less.

9