Large Stone Asphalt Mixes: Design and Construction

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    LARGESTONEASPHALTMIXES:DESIGNANDCONSTRUCTIONBy

    PrithviS.Kandhal

    PaperpublishedintheJournaloftheAssociationofAsphaltPavingTechnologists,AsphaltPavingTechnology,Volume59,1990

    277TechnologyParkway Auburn,AL36830

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    LARGESTONEASPHALTMIXES:DESIGNANDCONSTRUCTION

    By

    PrithviS.KandhalAssistantDirector

    NationalCenterforAsphaltTechnologyAuburnUniversity,Alabama

    PaperpublishedintheJournaloftheAssociationofAsphaltPavingTechnologists,AsphaltPavingTechnology,Volume59,1990

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    DISCLAIMER

    Thecontentsofthisreportreflecttheviewsoftheauthorswhoaresolelyresponsibleforthefactsandtheaccuracyofthedatapresentedherein.ThecontentsdonotnecessarilyreflecttheofficialviewsandpoliciesoftheNationalCenterforAsphaltTechnologyofAuburnUniversity.Thisreportdoesnotconstituteastandard,specification,orregulation.

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    ABSTRACT

    Prematureruttingofheavydutyasphaltpavementshasbeenincreasinglyexperiencedinrecentyearsprimarilyduetohighpressuretrucktiresandincreasedwheelloads.Manyasphalttechnologistsbelievethattheuseoflargesizestone(maximumsizeofmorethanoneinch)inthebinderandbasecourseswillminimizeoreliminatetheruttingofheavydutypavements.

    TheequipmentspecifiedintheMarshallprocedure(ASTMD1559)usedby76percentofthe

    statesintheUnitedStatesconsistsofa4-inchdiametercompactionmoldintendedformixescontainingaggregateuptol-inchmaximumsizeonly.Thishasinhibitedtheuseoflargestonemixes.

    Astandardmethodforpreparingandtesting6-inchdiameterspecimenshasbeenpresented.The

    proposedmethodhasthefollowingsignificantdifferencesfromASTMD1559:(a)hammer

    weighs22.5pounds,(b)specimensizeis6-inchdiameterand3-3/4inchheight,(c)specimenweighsabout4,050grams,and(d)thenumberofblowsneededis1-1/2timesthenumberofblowsneededforastandardMarshallspecimentoobtainequivalentcompactionlevels.

    Comparativetestdata(4-inchversus6-inchdiameterspecimens)obtainedfromvarioushighway

    agenciesandproducersindicatesthatthecompactionlevelsarereasonablyclose.Theaveragestabilityratio(stabilityof6-inchspecimen/stabilityof4-inchspecimen)andflowratio(flowof6-inchspecimen/flowof4-inchspecimen)weredeterminedtobeveryclosetothetheoreticallyderivedvaluesof2.25and1.50,respectively.

    Atypicalmixdesignusing6-inchspecimensisalsogiven.Constructiondataandexperience

    gainedfromsixfieldprojectsinKentuckyandPennsylvaniaisalsoincluded.Itisbelievedthattheproposedtestmethodwillbeusefulindeterminingtheoptimumasphaltcontentoflargestoneasphaltmixes.

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    LARGESTONEASPHALTMIXES:DESIGNANDCONSTRUCTION

    PrithviS.Kandhal

    INTRODUCTIONPrematureruttingofheavydutyasphaltpavementshasbeenincreasinglyexperiencedinrecentyears.Thisphenomenonisprimarilyresultingfromhighpressuretrucktiresandincreasedwheelloads.ThedesignofHotMixAsphalt(HMA)whichservedreasonablywellinthepastneedstobere-examinedtowithstandtheincreasedstresses.VariousasphaltadditivesarebeingpromotedtoincreasethestabilityofHMApavementsathightemperatures.However,mostasphalttechnologistsbelievethatfundamentalchangesintheaggregatecomponentoftheHMA(suchas,size,shape,textureandgradation)mustbemadefirst.Thereisageneralagreementthattheuseoflargesizestoneinthebinderandbasecourseswillminimizeoreliminatetheruttingofheavydutyasphaltpavements.

    Theuseoflargestonemixesisnotnew.WarrenBrothersCompanyhadapatentissuedin1903whichspecifiedatopsizeaggregateofthreeinches( 1).Mostpavingcompaniesstartedtousesmallstonemixestoavoidinfringementofthepatent,andsuchuseisstillprevalenttoday.

    Marshallmixdesignproceduresareusedby76percentofthestatesintheUnitedStates

    accordingtoasurveyconductedin1984( 2).TheequipmentspecifiedintheMarshallprocedure(ASTMD1559)consistsofa4-inchdiametercompactionmoldwhichisintendedformixturescontainingaggregateuptol-inchmaximumsizeonly.ThishasalsoinhibitedtheuseofHMAcontainingaggregatelargerthanoneinchbecauseitcannotbetestedbythestandardMarshallmixdesignprocedures.Thereareothertestproceduressuchas,gyratorycompaction,TRRLrefusaltestandMinnesotaDOTvibratinghammerwhichuse6-inchdiametermoldsaccommodating1-1/2-2inchmaximumaggregatesize( 3).However,mostagenciesare

    reluctanttobuynewequipmentbecauseofcostand/orcomplexity.Theytendtopreferandutilizetheexistingequipmentand/ormethodology(suchasMarshalltest)withsomemodifications.TherearepreliminaryindicationsfromtheNCHRP'sAAMAS(Asphalt-AggregateMixAnalysisSystem)researchstudythatalaboratorygyratorycompactorbettersimulatestheaggregateparticleorientationobtainedinthefieldcomparedtoanimpacttypecompactorusedintheMarshallprocedure(4).However,itwillbeafewyearsbeforemanyagenciesstarttoimplementAAMASstudy'srecommendationsandusegyratorycompactors.InthemeantimethereisanurgentneedtostartdesigninglargestonehotmixasphaltusingmodifiedMarshalldesignproceduresbasedonthecurrentknowledgeandexperience.Itisexpectedthattheseprocedureswillbecontinuallymodifiedasmoreexperienceisgainedinthefield.

    Theterm"largestone"isarelativeone.Forthepurposeofthisreportlargestoneisdefinedasan

    aggregatewithamaximumsizeofmorethanoneinchwhichcannotbeusedinpreparingstandard4-inchdiameterMarshallspecimens.

    BACKGROUNDOFDEVELOPMENTPennsylvaniaDepartmentofTransportation(PennDOT)implementedMarshallmixdesignproceduresintheearly1960s.TheMarshallmethodwasgenerallybasedonASTMD1559(StandardTestMethodforResistancetoPlasticFlowofBituminousMixturesUsingMarshallApparatus).ASTMD1559specifiestheuseof4-inchdiameterspecimenmoldformixescontainingaggregateuptol-inchmaximumsize.Thecompactionhammerweighs10poundsandafreefallof18inchesisused.ItbecameapparentthatASTMD1559couldnotbeusedfordesigningPennsylvaniaID-2bindercoursemixandbasecoursemixwhichspecifiedmaximum

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    permissiblesizesof1-1/2inchesand2inches,respectively.Therefore,astudywasundertakenbyPennDOTin1969todeveloptheequipmentandprocedurefortesting6-inchdiameterspecimens(5)sinceitisgenerallyrecognizedthatthediameterofthemoldshouldbeatleastfourtimesthemaximumnominaldiameterofthecoarsestaggregateinthemixturetobemolded

    (6).Aseriesofcompactiontestswererunusing4-inchand6-inchdiameterspecimensofwearingandbindermixes.Thenominalheightofthe6-inchdiameterspecimenwasincreasedto3-3/4inchtoprovidethesamediameter/heightratiothatisusedfora4-inchdiameterx2-1/2inchhighspecimen.Whenthe6-inchcompactorwasdesigneditwasassumedthattheweightofthehammershouldbeincreasedinproportiontothefaceareaoftheMarshallspecimen,andtheheightofhammerdropandthenumberofblowsonthefaceofthespecimenshouldremainthesameasthatusedforthe4-inchdiameterspecimens.Theweightofthehammer,therefore,wasincreasedfrom10lbs.to22.5lbs.,andthehammerdropwasmaintainedat18-incheswith50blowsoneachface.However,theinitialtestdataindicatedthattheenergyinputtothespecimenduringcompactionshouldhavebeenbasedonftlb/cuinchofspecimeninsteadofftlb/sqinchofthespecimenface.Therefore,toobtainthesameamountofenergyinputperunitvolumeina6-inchby3-3/4inchspecimenthenumberofblowshadtobeincreasedfrom50to75.ThecomparativecompactiondatagiveninTable1substantiatesthis.Basedonthisdata,itwasspecifiedthata6-inchdiameter,3-3/4inchhighspecimenshouldbecompactedwitha22.5lb.hammer,freefallof18-inchesand75blowsperface.Thedetailsofequipment,suchasmold,hammerandbreakingheadaregiveninPennsylvaniaTestMethod705developedbyKandhalandWenger(7)

    Table1.ComparativeData(4"Versus6"-DiameterSpecimens)-1969Data

    WEARINGMIX BINDERMIX

    SpecimenDiameter,in. 4 6 6 6 4 6 6

    SpecimenHeight,in. 2.50 3.75 2.50 3.75 2.50 3.75 3.75

    HamerWeight.lbs. 10 22.5 22.5 22.5 10 22.5 22.5HammerDrop,in. 18 18 18 18 18 18 18

    No.ofBlows/Face 50 50 50 75 50 50 75

    EnergyInput:

    Ft.lb/sq.in.ofSpecimenFace119.4119.4 119.4 179.1 119.4 119.4179.1

    Ft.lb/cu.in.ofSpecimen 47.7 31.8 47.7 47.7 47.7 31.8 47.7

    PercentCompactionofTheor. 94.2 92.9 93.9 94.0 97.5 96.4 97.4Max.SpecificGravity

    PercentVoidContent 5.8 7.1 6.1 6.0 2.5 3.6 2.6

    Stability,lbs. 20495316 -- -- 1622 3785 3440Flow,Units 10.0 20.4 -- -- 10.8 20.8 17.5

    Preliminarytestdataobtainedin1969duringthedevelopmentalstageisgiveninTables2and3forID-2wearingcourse(maximumaggregatesize1/2inch)andID-2bindercourse(maximumaggregatesize1-1/2inches)mixtures,respectively.Thedataindicatesthatreasonablyclosecompactionlevelsareachievedin4-inchand6-inchdiametermoldswhenthenumberofblowsfor6-inchspecimenis1-1/2timesthatusedfor4-inchspecimen.Marshallvoidparameterssuchas,%airvoids,%VMAand?%VFAarealsoreasonablyclose.Table3showsthatapreliminarystabilityratio(stabilityof6-inchspecimen/stabilityof4-inchspecimen)of2.12,and

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    ThenextsteptakenbyPennDOTin1970wastoevaluatetherepeatabilityofthetestresultsusing6-inchequipment.Abindercoursemixsimilartotheonetestedin1969wasusedtocompactnine4-inchdiameterspecimensandten6-inchdiameterspecimens.Statisticalanalysisofstability,flowandairvoidsdatagiveninTables4and5indicatesbetterrepeatabilityof6-

    inchspecimenscomparedwith4-inchspecimenswhentestingalargestonemix.Thisisevidentfromlowervaluesofthecoefficientofvariationobtainedon6-inchspecimens.

    ASTMSubcommitteeD04.20onMechanicalTestsofBituminousMixesappointedataskforce

    inDecember1988todevelopanASTMstandardtestforpreparingandtesting6-inchdiameterMarshallspecimens.TheauthorwhoischairmanofthistaskforcehaspreparedadraftforthisproposedstandardwhichisgiveninAppendix"A."TheproposedstandardfollowsASTMD1559-82(8)whichisintendedfor4-inchdiameterspecimensexceptthefollowingsignificantdifferences:

    1.Equipmentforcompactingandtesting6-inchdiameterspecimenssuchas,moldsandbreakinghead(Section3).

    2.Sincethehammerweighs22.5pounds,onlyamechanicallyoperatedhammerisspecified(Section3.3).

    3.About4,050gramsofmixisrequiredtoprepareone6-inchMarshallspecimencomparedtoabout1,200gramsfora4-inchspecimen.

    4.Themixisplacedinthemoldintwoapproximatelyequalincrements,spadingisspecifiedaftereachincrement(Section4.5.1).Pastexperiencehasindicatedthatthisisnecessarytoavoidhoney-combingontheoutsidesurfaceofthespecimenandtoobtainthedesireddensity.

    5.Thenumberofblowsneededfor6-inchdiameterand3-3/4incheshighspecimenis1-1/2timesthenumberofblowsneededfor4-inchdiameterand2-1/2incheshighspecimentoobtainequivalentcompactionlevel(Note4).

    Table4.RepeatibilityofMarshallTest(4"DiameterSpecimens)BinderCourseMix

    (1970Data)StabilityPounds

    1290

    1750

    1635

    2035

    1540

    2090

    1975

    2200

    1620

    Flow0.01Inch

    9.0

    13.5

    17.0

    10.0

    22.0

    13.5

    19.0

    14.0

    11.5

    VoidsPercent

    3.23.4

    2.83.0

    3.22.8

    2.32.6

    2.6

    N 9.0 9.0 9.0

    Mean 1793 14.4 2.9

    StdDev 300 4.2 0.4

    CoeffofVar.(%) 16.7 29.2 13.8

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    Table5.RepeatibilityofMarshallTest(6"DiameterSpecimens)BinderCourseMix (1970Data)

    StabilityPounds

    4850

    4653

    4605

    5428

    5188

    4960

    5232

    5886

    -

    -

    Flow0.01Inch

    13.0

    18.0

    19.0

    15.0

    15.0

    15.5

    18.0

    19.0

    -

    -

    VoidsPercent

    3.23.0

    2.52.7

    2.72.7

    2.72.4

    2.82.2

    N 88 10Mean

    5100 16.6 2.7

    StdDev 427 2.2 0.3

    CoeffofVar.(%) 8.4 13.2

    11.1Note:Stabilityratioandflowratio(6"versus4"diameter)intheserepeatabilityexperimentsweredeterminedtobe2.81and1.15,respectively.

    Thecompleteassemblyofequipmentforcompacting6-inchdiameterspecimensisshowninFigure1.

    Sincethehammerweighs22.5poundsandthenumberofblowsoneachsideis75or112

    dependingontheanticipatedtraffic,somecrushingoftheaggregateatthesurfacehasbeenobserved.However,itisbelievedthatitseffectonMarshallpropertiesisminimal.

    Vigorousspadinginthemoldisnecessarytopreventvoidsnearthelargestones.Themixshould

    notbeallowedtocoolbelowtheintendedcompactiontemperature.Therearetwoknownsuppliersof6-inchMarshalltestingequipment:

    1.PineInstrumentCompany(Attention:TimKnauff)

    101IndustrialDriveGroveCity,PA16127Phone(412)628-6391

    2.RainhartCompany(Attention:LarryHart)

    P.O.Box4533Austin,TX78765Phone(512)452-8848

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    Figure1.CompactionAssemblyfor6-inchMarshallSpecimens

    Thesamemechanicalcompactorisusedforcompacting4-inchand6-inchdiameterMarshallspecimens.Therefore,ifamechanicalcompactorisalreadyonhand,oneneedstobuythefollowingadditionalequipment(estimatedcost$1,800):

    1.6"completemoldassemblyconsistingofcompactionmold,baseplateandcollar(3arerecommended);

    2.6"additionalcompactionmolds(6arerecommended);3.6"compactionhammer(2arerecommended);4.6"moldholder(ensurethatthespringisstrong);5.6"breakingheadassembly;

    6.Specimenextractorfor6"specimen;and7.6"paperdiscs(boxof500).

    Althoughnotincludedintheproposedtestmethod,theautomaticrecordingequipmentfor

    stabilityandflowcurveisrecommendedforreasonableinterpretationofMarshalldata.Flattoppedcurvesareverycommoninlargestonemixes.Frequently,aseatingloadalsooccurspriortoactualspecimenloading.Thiscanbereadilyobservedandcorrectedwhenrecordingequipmentisused.Ifnotcorrectedexcessiveflowmayberecorded.PennDOTrequirestheuseofrecordingequipmentforboth4-inchand6-inchdiameterMarshallspecimens.

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    4-INCHVERSUS6-INCHDIAMETERSPECIMENSAfterthepreliminarydevelopmentalworkdonebyPennDOTduring1969and1970therewasminimaluseof6-inchMarshallequipmentuntil1987.Interestinthisequipmentwasrevived

    becausevariousagenciesandproducerswantedtotestlargestonemixesforminimizingoreliminatingruttingofHMApavementsasdiscussedearlier.Theseagencies(includingPennDOT)andproducerswhoprocuredthe6-inchMarshalltestingequipmentranalimitednumberofteststoverifythedegreeofcompactionobtainedin6-inchmoldcomparedto4-inchmold.Also,aneedwasfelttoverifythestabilityratio(stabilityof6-inchspecimen/stabilityof4-inchspecimen)andtheflowratio(flowof6-inchspecimen/flowof4-inchspecimen)obtainedinPennDOT'spreliminarywork.Thiswasnecessarysothatminimumstabilityvalues,andtherangeofflowfor6-inchspecimenscouldbederivedfromthevaluesspecifiedfor4-inchspecimens.

    Personalcontactsweremadewithvariousagenciesandproducers,andthecomparativedata(4-

    inchversus6-inchdiameterspecimens)wasobtained.Thediscussionofdatafollows.

    KentuckyDepartmentofHighways(KYDOH)KYDOHdevelopedalargestonebasecoursemix(TypeKBase)containinga2-inchmaximumsizeaggregateforheaviercoalhaulroads.Thismixisdesignedandcontrolledusing6-inchMarshalltestingequipment.Thismixwastriedinthefieldduring1987constructionseason.KYDOHobtainedcomparativetestdata(4"versus6")ontheirconventionalClassIBasemixasshowninTable6.Thelevelsofcompactionobtainedin4-inchand6-inchmoldsusing75and112blows,respectivelyarereasonablyclose.Stabilityandflowratiosare2.08and1.34,respectively.

    PennsylvaniaDepartmentofTransportation(PennDOT)

    Comparativetestdataobtainedin1988ontwobindercoursemixesaregiveninTables7and8.Thelevelsofcompactionobtainedin4-inchand6-inchmoldsusing50and75blows,respectivelyarereasonablyclose.Surprisingly,thecoefficientofvariation(measureofrepeatability)ofthespecimenbulkspecificgravityofthe6-inchspecimenswasgreaterthan4-inchspecimens.However,6-inchspecimensgavebetterrepeatabilityonstabilityandflowcomparedto4-inchspecimenswhenlargestoneisused.Stabilityandflowratiosrangedfrom1.95to2.17and1.39to1.58,respectively.Table9givesthecomparativetestdataobtainedinearly1989alsoonabindermix.Sixspecimenseachwerecompactedin4-inchand6-inchmoldsusing50and75blows,respectively.Thelevelsofcompactionobtainedinbothmoldswasreasonablyclose.Thetestdataindicatessignificantlybetterrepeatability(lowercoefficientofvariation)ofspecimenspecificgravity,stabilityandflowwhen6-inchmoldisusedinlieuof4-inchmoldforlargestonemixes.

    Stabilityandflowratiosweredeterminedtobe1.68and1.40,respectively.

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    Table6.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:KentuckyDept.ofHighways(JohnsonCounty) Mixtype:ClassIBase

    Aggregates:Limestone#57(50%),limestone#8(10%),andlimestonesand(40%).

    DesignGradation(%Passing):2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200

    100 100 -- 91 -- 64 44 34 24 18 14 7 3.5

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.1 4.1Stability,pounds(1) 2898 --

    No.ofBlows 75 112 (2) 2998 6430BulkSp.Gr.

    (1) 2.439 2.441 (3) 2798 5629

    (2) 2.428 2.450 Mean 2898 6030

    (3) 2.430 2.437Flow,units (1) 13.0 --

    Mean 2.432 2.443 (2) 14.0 18.0Max.Sp.Gr. 2.517 2.517 (3) 14.0 18.5

    %AirVoids 3.4 3.0 Mean 13.7 18.3

    %VMA 14.0 13.6StabilityRatio 2.08

    %VFA 76.0 78.3FlowRatio 1.34Remarks:AASHTOgradations#57(1"to#4)and#8(3/8"to#8)used.

    Stabilityvaluesadjustedforspecimenthickness.Table7.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:PennsylvaniaDept.ofTransportation(1988Data) Mixtype:ID-2BinderCourse(InterstateAmiesite)

    Aggregates:Dolomitecoarseaggregates#467(48%),#8(9%),andDolomitefineaggregate(43%)DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200100 100 90 -- 65 59 47 35 20 12 7 5 4

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.6 4.6Stability,pounds --

    No.ofBlows 50 75 Mean 2650 5169

    BulkSp.Gr. Std.Dev. 319 530

    Mean 2.541 2.549 Coeff.of 12.0 10.3

    Variation(%)Std.Dev. 0.009 0.013 Flow,units

    Coeff.ofVar.(%) 0.35 0.51 Mean 21.0 29.1

    Max.Sp.Gr. 2.606 2.606 Std.Dev. 3.2 0.9

    %AirVoids 2.5 2.2 Coeff.ofVar.(%) 15.2 3.1

    %VMA 13.5 13.1 StabilityRatio 1.95

    %VFA 81.4 83.4 FlowRatio 1.39Remarks:Five(5)sampleseachof4"and6"diameterspecimenswereanalyzed.

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    Table8.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:PennsylvaniaDept.ofTransportation(1988Data) Mixtype:ID-2BinderCourse(EasternIndustries)

    Aggregates:Limestonecoarseaggregate#467(60%),andlimestonefineaggregate(40%).

    DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200100 100 90 73 63 54 44 30 17 10 7 5 4

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.3 4.3Stability,pounds --

    No.ofBlows 50 75 Mean 2524 5477

    BulkSp.Gr. Std.Dev. 530 363

    Mean 2.461 2.455 Coeff.of 21.0 6.6Variation(%)

    Std.Dev. 0.009 0.031Flow,unitsCoeff.ofVar.(%) 0.37 1.27 Mean 16.7 26.4

    Max.Sp.Gr. 2.551 2.551 Std.Dev. 2.2 2.5

    %AirVoids 3.5 3.8 Coeff.ofVar.(%) 13.2 9.5

    %VMA 13.9 14.1StabilityRatio 2.17

    %VFA 74.5 73.6FlowRatio 1.58Remarks:Seven(7)sampleseachof4"and6"diameterspecimenswereanalyzed. JamestownMacadamInc.

    JamestownMacadam,Inc.ofJamestown,NYtestedabindercoursemixconsistingofcrushedgravelaggregate.Thecompactionlevelsachievedin4-inchand6-inchmoldsusing50and75blows,respectivelyareveryclose(Table10).Stabilityandflowratiosweredeterminedtobe1.89and1.24,respectively.

    AmericanAsphaltPavingCompany

    AmericanAsphaltPavingCompanyofChase,PAtestedfour(4)bindercoursemixes.AUmixeshadthesamegradation,onlytheasphaltcontentand/ortheproportionofmanufacturedsandwerevariedasshowninTables11,12,13,and14.Thecompactionlevelsachievedin4-inchand6-inchmoldsusing75and112blows,respectivelyarereasonablycloseexceptthemixinTable14.Stabilityandflowratiosrangedfrom1.98to2.58and1.27to1.68,respectively.

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    Table9.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:PennsylvaniaDept.ofTransportation(1989Data) Mixtype:ID-2BinderCourse

    Aggregates:DolomitecoarseandDolomitefineaggregate.

    DesignGradation(%Passing):2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200

    100 100 92 -- 62 -- 40 30 19 13 9 7 4.3

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.4 4.4Stability,pounds(1) 2730 5350

    No.ofBlows 50 75(2) 3640 5450BulkSp.Gr. (1)

    2.494 2.494 (3)2975 5500

    (2) 2.504 2.491 (4)3430 5550(3) 2.514

    2.492 (5) 2870 4700(4) 2.530 2.502

    (6) 3185 5100(5) 2.506 2.495 Mean 3138 5275(6) 2.511 2.483

    Std.Dev. 348 324

    Mean 2.510 2.493 Coeff.ofVar.(%) 11.1 6.1

    Std.Dev. 0.012 0.006Flow,units (1) 13.3 25.0

    Coeff.ofVar.(%) 0.5 0.2 (2) 19.3 21.6

    Max.Sp.Gr. 2.613 2.613 (3) 13.7 22.0

    %AirVoids 3.9 4.6 (4) 16.3 24.0

    %VMA 13.4 14.0 (5) 15.0 22.3

    %VFA 70.8 67.3 (6) 22.5 25.3

    Mean 16.7 23.4

    Std.Dev. 3.7 1.6

    Coeff.ofVar.(%)

    StabilityRatio

    FlowRatioRemarks:AASHTOgradations#57(1"to#4)and#8(3/8"to#8)used.

    Stabilityvaluesadjustedforspecimenthickness.

    21.6

    1.68

    1.40

    6.8

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    Table10.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:JamestownMacadam,Inc.,Jamestown,NY Mixtype:ID-2BinderCourse

    Aggregates:Crushedgravelcoarseaggregate(76%),gravelfineaggregate(12%),andconcretesand(12%).DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200

    100 100 98 -- 62 -- 24 20 16 11 7 5 3

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.5 4.5Stability,pounds(1) -- 2900

    No.ofBlows 50 75(2) -- 3200BulkSp.Gr. (1) 2.357 2.369

    (3) -- 3400

    (2) 2.350 2.340 Mean 1675 3167

    (3) 2.346 2.355Flow,units (1) -- 18.0

    Mean 2.351 2.355 (2) -- 20.0

    Max.Sp.Gr. 2.430 2.439 (3) -- 18.5

    %AirVoids 3.3 3.4 Mean 15.2 18.8

    %VMA 13.5 12.9StabilityRatio 1.89

    %VFA 76.0 73.3FlowRatio 1.24Remarks:Max.Sp.Gr.valuesofthemixesusedin4"and6"specimensaredifferentbecausethespecimenswere

    compactedindifferentyears.Table11.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:AmericanAsphaltPavingCo.,Chase,PA Mixtype:ID-2BinderCourse(Special)Design#2

    Aggregates:Siltstonecoarseaggregate(64%),manufacturedsand(27%)andnaturalsand(9%).DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200100 100 90 -- 61 -- 40 30 18 15 12 7 4.5

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.0 4.0Stability,pounds 2723 6450

    No.ofBlows 75 112

    BulkSp.Gr. 2.450 2.457Flow,units 9.8 16.0

    Max.Sp.Gr. 2.565 2.565%AirVoids 4.5 4.3

    %VMA 12.9 12.7StabilityRatio 2.37

    %VFA 65.1 66.6FlowRatio 1.63Remarks:4"dataisaverageof3specimenswhereas6"dataisaverageof2specimensonly.

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    Table12.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:AmericanAsphaltPavingCo.,Chase,PA Mixtype:ID-2BinderCourse(Special)Design#5

    Aggregates:Siltstonecoarseaggregate(64%),manufacturedsand(27%)andnaturalsand(9%).

    DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200100 100 90 -- 61 -- 40 30 18 15 12 7 4.5

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 3.8 3.8Stability,pounds 2416 6225

    No.ofBlows 75 112

    BulkSp.Gr. 2.444 2.446Flow,units 10.0 15.2

    Max.Sp.Gr. 2.573 2.573

    %AirVoids 5.0 5.0

    %VMA 13.0 12.9StabilityRatio 2.58%VFA 60.3 61.5FlowRatio 1.52Remarks:4"dataisaverageof3specimenswhereas6"dataisaverageof2specimensonly.

    Table13.ComparativeTestData(4"Versus6"-DiameterSpecimens)Source:AmericanAsphaltPavingCo.,Chase,PA Mixtype:ID-2BinderCourse

    (Special)Design#3

    Aggregates:Siltstonecoarseaggregate(64%),manufacturedsand(36%).DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200

    100 100 90 -- 61 -- 40 30 18 15 12 7 4.54" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.2 4.2Stability,pounds 2961 5850

    No.ofBlows 75 112

    BulkSp.Gr. 2.435 2.448Flow,units 11.3 19.0

    Max.Sp.Gr. 2.551 2.551

    %AirVoids 4.5 4.1

    %VMA 13.5 13.1StabilityRatio 1.98

    %VFA 66.6 69.2FlowRatio 1.68

    Remarks:4"dataisaverageof3specimenswhereas6"dataisaverageof2specimensonly.

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    Table14.ComparativeTestData(4"Versus6"-DiameterSpecimens)

    Source:AmericanAsphaltPavingCo.,Chase,PA Mixtype:ID-2BinderCourse(Special)Design#6

    Aggregates:Siltstonecoarseaggregate(64%),manufacturedsand(36%).

    DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200

    100 100 90 -- 61 -- 40 30 18 15 12 7 4.5

    4" 6" 4" 6"Specimen Specimen Specimen Specimen

    %AsphaltContent 4.0 4.0Stability,pounds 2791 6700

    No.ofBlows 75 112

    BulkSp.Gr. 2.432 2.559Flow,units 14.0 17.8

    Max.Sp.Gr. 2.559 2.559

    %AirVoids 5.0 3.9

    %VMA 13.5 12.6StabilityRatio 2.40%VFA 63.3 68.9FlowRatio 1.27Remarks:4"dataisaverageof3specimenswhereas6"dataisaverageof2specimensonly. AnalysisofAllComparativeDataTheprecedingdiscussionofcomparativedata(4-inchversus6-inchspecimens)obtainedbyvarioushighwayagenciesandproducersindicatesthatthecompactionlevelsobtainedin4-inchand6-inchmolds(usingtheappropriatehammerandnumberofblows)arereasonablyclose.Asexpected,therepeatabilityofstabilityandflowtestissignificantlybetterwhen6-inchdiameterspecimensareusedforlargestonemixes.Therefore,itisrecommendedthat6-inchdiameter

    specimensbeusedfordesigningsuchmixes.

    Table15summarizesthestabilityandflowratiovaluesobtainedbyvariousagenciesand

    producersonlargestonebaseorbindermixes(maximumaggregatesize1-1/2-2inches).Theaverageof11stabilityratiosis2.18,andtheaverageof11flowratiosis1.44.Thesevaluesareveryclosetotheoreticallyderivedvaluesasfollows.

    Fromatheoreticalviewpoint,anexternalloadappliedtothecircumferenceofacylindermaybe

    consideredasactingdirectlyonthediametricalcrosssectionofthecylinder.Thispermitscalculationofthestressinpoundspersquareinch.Thestandard6-inchspecimenis3-3/4incheshigh,whichgivesadiametricalcrosssectionof22.5squareinches.Thestandard4-inchspecimenis2-1/2incheshighandithasadiametricalcrosssectionof10.0squareinches.Therefore,onthebasisofunitstress,thetotalloadona6-inchspecimenshouldbe2.25times

    theloadappliedtoa4-inchspecimenofthesamemix.Thismeansthestabilityratioshouldbe2.25.

    Flowunitsmeasuredbythetestingmachinearethevaluesforthetotalmovementofthe

    breakingheadstothepointofmaximumstability.Whenflowisconsideredonaunitbasis(inchesperinchofdiameter),theflowvaluefora6-inchspecimenwillbe1.5timesthatofa4-inchdiameterspecimen.Thismeanstheflowratioshouldbe1.5.

    Surprisingly,theaveragestabilityandflowratioofspecimenscompactedwith75and112blows

    (4-inchand6-inchmold,respectively)are2.28and1.49whichareveryclosetothetheoreticallyderivedvaluesof2.25and1.50,respectively.

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    Table15.SummaryofStabilityandFlowRatiosforLargeStoneMixes

    Agency(Yeardataobtained) No.ofBlows Ratio

    4" 6" Stability Flow

    Penn.DOT(1969) 50 75 2.12 1.62Penn.DOT(1970) 50 75 2.81 1.15

    Penn.DOT(1988) 50 75 1.95 1.39

    Penn.DOT(1988) 50 75 2.17 1.58

    Penn.DOT(1989) 50 75 1.68 1.40

    JamestownMacadam(1989) 50 75 1.89 1.24

    KentuckyDOH(1988)* 75 112 2.08 1.34

    AmericanAsphaltPaving(1989)* 75 112 2.37 1.63

    AmericanAsphaltPaving(1989)* 75 112 2.58 1.52

    AmericanAsphaltPaving(1989)* 75 112 1.98 1.68

    AmericanAsphaltPaving(1989)* 75 112 2.40 1.27

    No.ofMixes(N) 11 11

    Mean 2.18 1.44

    Std.Dev. 0.33 0.18*Note:Theaveragestabilityandflowratioforthesefivemixescompactedwith75/112blowsare2.28and1.49, respectively.ItisrecommendedthattheminimumMarshallstabilityrequirementfor6-inchdiameterspecimensshouldbe2.25timestherequirementfor4-inchdiameterspecimens.Forexample,if1000poundsminimumstabilityiscurrentlybeingspecifiedusingASTMD1559(4-inchspecimen),then2,250poundsminimumstabilityshouldbespecifiedforlargestonemixesusingthe6-inchMarshalltestingequipment.

    Similarly,therangeofflowvaluesfor6-inchspecimensshouldbeadjustedto1-1/2timesthe

    valuesrequiredfor4-inchspecimens.Forexample,ifthespecifiedrangefor4-inchis8-18,itshouldbeadjustedto12-27for6-inchspecimens.

    ItshouldbenotedthatPennsylvaniaDOTrequirestheflowvaluetobemeasuredatthepoint

    wherethestabilitycurveonthechartbeginstoleveloff,whereasotheragenciesmeasuretheflowatthepointwherethestabilitystartstodecrease.However,thesedifferencesinmeasuring

    methodswillnotsignificantlyaffecttheflowratiosbecausethesamemethodisemployedbothfor4-inchand6-inchspecimensbyanagency.

    TYPICALMIXDESIGNUSING6-INCHSPECIMENS

    KentuckyDOHhascompletedasubstantialnumberoflargestonemixdesignsusingthe6-inchMarshalltestingequipment.Theyrequirethecontractortobuythetestingequipmentfortheprojectsothatproperqualitycontrolismaintained.KentuckyDOHClassKBasemixhasbeenusedoncoalhaulroadscarryingveryheavytrucks(grossloadsvaryingfrom90,000to150,000poundsormore).Tirepressuresarealsohigherthangenerallyencountered,rangingfrom100to130psi(9).

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    Table16givesthetypicalMarshallmixdesigndataforoneprojectalongwiththegradationusedforClassKBase.Themixcontainslimestoneaggregatesandamaximumaggregatesizeof2incheswithasubstantialamountofmaterialretainedonl-inchsieve.Thisresultsinsubstantialamountofl-inch-3/4inchmaterialinthemix.Themixdesignwasdevelopedusing6-inch

    moldand112blowsoneachside.Asphaltcontentwasvariedfrom3.2to4.0percentin0.4percentincrements.EitherAASHTOGradation#467(1-1/2inchtoNo.4)or#4(1-1/2inchto3/4inch)isusedforcoarseaggregatetoincorporate+l-inchmaterialinthemix.ThefollowingdesigncriteriahasbeenusedbyKentuckyDOH:

    Stability 3000lbs.minimum

    Flow 28maximumAirVoids 4.51.0percentVMA 11.5percentminimum

    Table16.TypicalMarshallMixDesignData(6"-DiameterSpecimens)Source:KentuckyDept.ofHighways Mixtype:ClassKBase

    (LawrenceCo.-LouisaBypass)

    Aggregates:Limestone#467(55%),limestone#8(20%),limestonesand(25%).

    No.ofBlows:112 Asphalt:AC-20

    DesignGradation(%Passing):

    2" 1-1/2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100#200

    100 99 86 75 58 50 29 21 15 10 8 5 3.5

    %AsphaltContent %AsphaltContent

    3.2 3.6 4.0 3.2 3.6 4.0

    BulkSp.Gr.(1) 2.424 2.410 2.440Stability,pounds(1) 5037 4980 4915

    (2) 2.428 2.430 2.440 (2) 5663 5326 4627

    (3) 2.419 2.434 2.437 (3) 5625 5236 5376

    Mean 2.424 2.425 2.439 Mean 5448 5181 4973

    Max.Sp.Gr. 2.546 2.530 2.515Flow,units (1) 17.5 14.5 14.0

    %AirVoids 4.8 4.2 3.0 (2) 19.0 19.5 17.0

    %VMA 11.4 11.7 11.6 (3) 17.0 14.5 15.0

    %VFA 57.8 64.5 73.8 Mean 17.8 16.2 15.3Remarks:AASHTOGradations#467(1-1/2"to#4)and#8(3/8"to#8)wereused.

    Stabilityvaluesadjustedforspecimenthickness.

    FIELDCONSTRUCTIONDATAThevalidityofanylaboratorycompactionmethod(suchas,applying112blowstocompact6-inchMarshallspecimensforheavydutypavements)mustbeverifiedinthefield.Usuallyitisnotpossibletoachievethelaboratorydensityinthefieldatthetimeofconstruction.ItisassumedintheMarshallmixdesignproceduresthatthelaboratorydensity(ifproperlyobtained)willbeachievedinthefieldaftertwo-threeyears'densificationbytraffic.Althoughithasbeenshowninthelaboratorythat112blowsfor6-inchspecimenand75blowsfor4-inchspecimenyieldcomparabledensities,itisrecommendedtomeasuretheactualdensitiesachievedaftertwo-threeyears'service.Thiswouldrequirecollectionoffieldcompactiondatajustafterconstructionandperiodicallythereafterfortheprojectsutilizinglargestonemixes.AdiscussionofpreliminaryconstructiondataobtainedfromKentuckyDOHandPennDOTfollows.

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    KentuckyKentuckyDOH'Sexperimentalspecificationsrequireconstructionofacontrolstrip(atleast500ft.longand12ft.wide)atthebeginningofconstructionofClassKbase.Constructionofthe

    controlstripisaccomplishedusingthesamecompactionequipmentandprocedurestobeusedintheremainderoftheClassKbasecourse.Afterinitialbreakdownrollingandtwocompletecoveragesofthepneumatic-tiredintermediateroller,threedensitymeasurementsaremadeatrandomlyselectedsites.Measurementsarerepeatedatthesamesitesaftereachtwosubsequentcompletecoveragesbythepneumatic-tiredrolleruntilnofurtherincreaseindensityisobtained.Afterthecompletionofthecontrolstriptenfielddensitymeasurementsareperformedatrandomlocations.ThetargetdensityforthecompactionoftheremainderClassKbaseistheaverageofthesetenmeasurements.Thetargetdensityobtainedfromthecontrolstripshouldbenogreaterthan97.0%norlessthan93.0%ofthemeasuredmaximumspecificgravity(RiceSpecificgravity)asdeterminedbyAASHTOT209.Theminimumacceptabledensityfortheprojectis:

    SingleTest: 96.0percentofthetargetdensity.

    Movingaverageoflast10tests: 98.0percentofthetargetdensity.

    Fourheavilytraffickedsectionswereconstructedduring1988inKentuckyforfieldtestingTypeKBase.TheseprojectscomprisedtheLouisaBypassinLawrenceCounty,theMountainParkwayinPowellCounty,RouteNo.3inJohnsonCounty,andthePennyrileParkwayinHendersonCounty.Table17givesthemixdesigndataandaveragefieldcompactiondataforthefirstthreeprojects.Itshouldbenotedthatthebottomlifthashigherasphaltcontentthanthetoplift(s)andistypicallydesignedforabout3percentvoids.Thisisdoneforfulldepthpavementsorverythickasphaltlayers(forexample,LouisaBypasshadtwelveinchesofTypeKBaseplacedinthreeliftsandone-inchthicksurfacecourse).Theobjectiveistoreducewaterorvaporentryfromthesubgrade.Thesecondandthirdtopliftsareusuallydesignedforabout4.5percentvoids.

    Someliftshadmorethanonecontrolstripwhichwereusedfordeterminingtargetdensitiesforacceptingthecorrespondingfielddensities.AUprojectsgenerallyexceededtheminimumspecifieddensitybasedonthecontrolstriptargetdensity.Table17givethein-placevoidsjustafterconstructionforthreeprojects.Thedataindicatesthatachievingthedesireddensity(compaction)inthefielddoesnotappeartobeaproblemifthecompactionprocessisoptimized.Theaveragevoidcontentofallthreeprojects(bothbottomandtoplifts)wasabout6.5percent.Duetothecoarsesurfacetexture,nucleardensitieswereconsistentlylowerthancoredensitiestakenatthesamespot.Theaveragenucleardensitywasaboutonepoundpercubicfootlessthancoredensity,indicatingthatcalibrationisnecessaryfordeterminationofactualvalues.Limitedcrushingofcoarsesurfaceparticlesoccurred.Itshouldbenotedthatadoubledrumvibratoryrolleranda25-tonpneumatic-tiredroller(tirepressureupto125psi)wereusedforprincipal

    compactiononLouisaBypass(9).

    Carefulattentiontodetailswasneededtoassureuniformdeliveryandlaydownoflargestone

    mixwithoutanysignificantsegregation.Thefollowingfactors( 9)wereconsideredimportant:1.Uniformcomponentaggregategradationsandgoodstockpilingpractices.2.Increasedsamplingandtestingisdesirabletoassuregoodqualitycontrol.Usual

    extractiontestsforcontrolofgradationandasphaltcontentprovedtobeaproblemduetodifficultyinobtainingarepresentativesamplefortesting.Binsamples,recombinedattheproperpercentages,weremorerepresentativeofgradation.Printoutdatawasrelieduponforasphaltcontentcontrol.

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    Table17.FieldCompactionDataSummary(KentuckyProjects)

    Project Lift Asphalt Design FieldCompactionContent,% Lab Max. PercentControl Avg. %of %

    DensityDensity Voids StripNo.*

    FieldDensity

    Max.Density

    Voids

    LawrenceCounty Bottom 4.0 152.2 156.9 3.0 (1) 149.9 95.5 4.5

    (LouisaBypass) (2) 149.2 95.1 4.9

    (3) 149.2 93.8 6.2

    Top 3.6 151.3 157.9 4.2 (1) 148.9 94.3 5.7

    (2) 149.2 94.5 5.5PowellCounty Bottom 4.0 152.5 157.1 2.9 -- 148.4 94.5 5.5

    (MountainPkwy)

    Top 3.5 150.9 158.2 4.6 (1) 148.9 94.1 5.9

    (2) 144.5 91.3 8.7

    (3) 145.2 91.8 8.2

    JohnsonCounty Bottom 4.1 151.8 157.1 3.4 -- 148.4 94.5 5.5

    (RouteNo.3)

    Top 3.7 152.1 158.9 4.3 (1) 146.4 92.1 7.9

    (2) 143.7 90.4 9.6*Someliftshadmorethanonecontrolstripwhichwereusedfordeterminingtargetdensitiesforacceptingthecorrespondingfielddensities.Note:Alldensityvaluesarereportedinpoundspercubicfoot.

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    3.Segregationinthesurgebinwasmoredifficulttocontrol.Thistendencytosegregate

    extendedtotruckloading.However,segregationduetoloadingwasovercomebyusingafront,back,centerloadingschemeforsingleunittrucks.Afivedroploadingsequence(front,rear,center,forthefirstthreedropswiththelasttwodropsbetween

    thefront/centerandtherear/center)wasusedforsemi-trailertrucks.4.Coarseparticlesaccumulateinthereceivinghopperwings.Thiseffectwasreduced

    bynotclearingcoarsematerialfromthehopperuntiltheendofeachday'spaving.Theaccumulatedcoarseparticleswerewasted.

    5.Mixtureinthereceivinghoppershouldbemaintainedataminimumdepthof18to24inchesovertheslatconveyortopreventcoarseparticlescollectedinthewingsfromrecenteringthemixandproducingconcentrationsofcoarseparticles.

    6.Receivinghoppergatesshouldbesettoprovideasnearlycontinuousoperationoftheslatconveyoraspossible.Further,tosupplymixtothescreedattherequiredrate,continuousoperationofthedistributionaugersisdesirable.

    7.Depthofmixtureinfrontofthescreedmustbemaintainedataconstantlevelforthefullscreedwidthtoassureauniformspread.Augerextensions,asneeded,supplymaterialuniformlytotheendplates.Ifextensionsarenotused,coarseparticlestendtorolltotheouteredgeofthespread,creatingalowdensity,porousarea.

    8.Paverspeedisveryimportant.Thelowestrateoftravelthatwillaccommodateproductionshouldalwaysbeused.Slowerrateofmovementpermitsmoreuniformfeedingofmixtureunderthescreedandsuppliesmorevibratingcompactionbythescreed.Bothpermitbetterpositioningofcoarseparticles.Avoiding"stopandgo"pavingreducessegregation,improvesthetextureofthespread,andeliminatesanytendencyforscreedsettlement.

    Pennsylvania

    Tables18through20givemixcompositionandcompactiondataobtainedonthreeprojectsusinglargestonemixesforthebindercourse.Mixcompositionwasdeterminedbyrunning

    extractiontestsonmixsamplesobtainedatrandombehindthepaver.Compactiondataisbasedon6-inchdiameterroadwaycorestakenjustafterconstruction.Nosignificantproblemsinobtainingauniformmixandachievingspecifiedcompactionlevels(92percentminimumofmaximumspecificgravity)areindicatedbythefielddata.Theaveragevoidcontentofallthreeprojectswasabout6.5percent.

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    Table18.FieldData(PennsylvaniaDOTProjectNo.1)

    Test JMF AveragesforLotNumbers*

    1 2 3 4 5 6 7 8

    Gradation:%Passing

    2" 100100 100 100 100 100 100 100 100

    1-1/2" 95 100 100 100 100 100 98 100100

    1" 90 98 94 92 95 95 90 92 92

    1/2" 64 76 73 68 73 72 68 68 61

    #4 37 39 37 36 39 36 35 34 33

    #8 25 28 27 27 28 28 26 26 25

    #16 20 23 21 21 22 22 20 20 20

    #30 18 19 17 18 18 18 17 17 16#50 12 12 10 10 11 11 12 11 10

    #100 78 67 77 77 6#200 4.0 5.2 4.3 5.0

    4.5 4.3 4.5 4.8 4.2

    AsphaltContent,% 4.5 4.6 4.5 4.6 4.7 4.6 4.5 4.4 4.4

    Density,pcf --147.9147.8147.7148.1146.3146.1144.9147.0Std.Dev.

    --1.711.641.741.791.861.932.382.50Max.Sp.Gr.,pcf

    156.0157.1157.1157.1157.1157.1157.1157.1157.1

    %ofMax.Sp.Gr. 92+ 94 94 94 94 93 93 92 94

    *Eachlotconsistsof4subplots.Mixcompositionisbasedonextractiontestsrunonloosemixsamplestaken behindthepaver.Densityresultswereobtainedonroadwaycores.

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    Table19.FieldData(PennsylvaniaDOTProjectNo.2)

    Test JMF AveragesforLotNumbers*

    1 2 3 4 5 6 7 8 9 10

    Gradation:%Passing

    2" 100 100 100 100 100 100 100 100 100 100 100

    1-1/2" 95 100 100 100 100 98 100 100 99 98 98

    1" 90 98 97 95 94 94 97 94 83 87 88

    1/2" 64 77 74 68 68 69 67 68 58 64 63

    #4 37 39 39 34 35 36 35 37 30 32 33

    #8 25 28 28 25 26 28 26 27 23 24 25

    #16 20 23 22 20 21 21 21 21 17 18 19

    #30 18 19 18 17 17 18 17 17 14 15 16

    #50 12 10 10 10 10 13 11 11 910 10#100 77

    67 68 77 66 7#200 4.0 4.4 3.9 4.3 4.0 5.1

    4.6 4.5 3.4 3.8 4.4

    AsphaltContent,% 4.5 4.7 4.64.3 4.54.5 4.44.4 4.24.2 4.4Density,pcf -- 145.5143.7 147.2 145.2

    147.5 146.7 145.5 146.0 147.2 147.6Std.Dev. -- 2.27 1.69 1.19 1.88

    1.35 2.11 0.75 1.98 0.92 2.31Max.Sp.Gr.,pcf 156.0 155.9 155.9

    155.9 155.9 156.8 156.8 156.8 156.8 156.8 156.8%ofMax.Sp.Gr. 92+

    9392 9493 9494 9393 9494

    *Eachlotconsistsof4-5subplots.Mixcompositionisbasedonextractiontestsrunonloosemixsamplestakenbehindthepaver.Densityresultswereobtainedonroadwaycores.

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    Table20.FieldData(PennsylvaniaDOTProjectNo.3)

    Test JMF AveragesforLotNumbers*

    1 2 3

    Gradation:%Passing

    2" 100 100 100 100

    1-1/2" 99 98 99 100

    1" 88 82 81 78

    1/2" 64 63 59 60

    #4 45 43 40 41

    #8 30 30 28 29

    #16 18 20 18 18

    #30 13 13 12 12#50 99 99#100 66 6

    6#200 4.5 5.2 5.0

    5.0

    AsphaltContent,% 4.0 4.0 3.7 3.8

    Density,pcf --151.6 150.8 150.1Std.Dev.--

    1.37 2.81 2.54Max.Sp.Gr.,

    pcf 158.9 158.9 158.9 158.9

    %ofMax.Sp.Gr. 92+95 9594

    *Eachlotconsistsof4subplots.Mixcompositionisbasedonextractiontestsrunonloosemixsamplestaken behindthepaver.Densityresultswereobtainedonroadwaycores.SUMMARY,CONCLUSIONSANDRECOMMENDATIONS

    1.SincelargestonemixeswillbeincreasinglyusedtominimizeruttingpotentialofHMApavementsthereisaneedtostandardizeaMarshalldesignprocedurewhichcantest6-inchdiameterspecimens.Forthepurposeofthisreport"largestone"isdefinedasanaggregatewithamaximumsizeofmorethanl-inchwhichcannotbeusedinpreparingstandard4-inchdiameterMarshallspecimens.

    2.BackgroundandpreliminarydataobtainedduringthedevelopmentofMarshalldesignproceduresforpreparingandtesting6-inchdiameterspecimenhasbeen

    discussed.3.AdraftstandardmethodhasbeenpreparedandisincludedinAppendixA.Thetestingequipmentisavailablecommerciallyfromtwosuppliers.

    4.Statisticalanalysisofstability,flowandairvoidsdataindicatesbetterrepeatabilityof6-inchspecimenscomparedto4-inchspecimenswhentestingalargestonemix.

    5.TheproposedmethodhasthefollowingsignificantdifferencesfromASTMD1559-82intendedfortesting4-inchspecimens.(a)Hammerweighs22.5pounds.Onlyamechanicallyoperatedhammerisspecified.(b)Thespecimensizeis6-inchdiameterand3-3/4inchheight.(c)Thespecimenusuallyweighsabout4050grams.(d)Themixisplacedinthemoldintwoapproximatelyequalincrements,spadingis

    specifiedaftereachincrement.

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    (e)Thenumberofblowsneededfor6-inchdiameterand3-3/4inchhighspecimens

    is1-1/2timesthenumberofblowsneededfor4-inchdiameterand2-1/2inchhighspecimentoobtainequivalentcompactionlevels.

    6.Comparativetestdata(4-inchversus6-inchdiameterspecimens)obtainedfrom

    varioushighwayagenciesandproducersindicatesthatthecompactionlevelsarereasonablyclose.

    7.Dataobtainedonstabilityratio(stabilityof6-inchspecimen/stabilityof4-inchspecimen)andflowratio(flowof6-inchspecimen/flowof4-inchspecimen)byvariousagencieswasobtainedandanalyzed.Theaveragestabilityandflowratiosweredeterminedtobeveryclosetothetheoreticallyderivedvaluesof2.25and1.50,respectively.Therefore,ithasbeenrecommendedthattheminimumstabilityrequirementfor6-inchdiameterspecimensshouldbe2.25timestherequirementfor4-inchdiameterspecimens.Similarly,therangeofflowvaluesfor6-inchspecimensshouldbeadjustedto1-1/2timesthevaluesrequiredfor4-inchspecimen.

    8.Atypicalmixdesignusing6-inchspecimensisgiven.9.TheuseoflargestonemixinfieldtrialsinKentuckyandPennsylvaniahasbeen

    describedalongwithfieldconstructiondata.10.Thereisaneedtocorrelatethecompactionlevelsachievedin6-inchmoldwiththe

    fielddensitiesobtainedatthetimeofconstructionandsubsequentlyundertrafficduringthefirst2-3years.

    ACKNOWLEDGMENTS

    Cooperationofthefollowingpersonsinsupplyingtherelevantdataandinformationisgratefullyacknowledged:

    Messrs.LarryEpleyandMikeAnderson,KentuckyDepartmentofHighways

    Mr.DavidAllen,TransportationCenter,UniversityofKentuckyMessrs.DeanMaurerandJohnMotter,PennsylvaniaDepartmentofTransportation

    Mr.EllisG.Williams,ConsultingEngineerMr.ThomasKerestes,AmericanAsphaltPavingCompanyMr.ThomasOlson,JamestownMacadam,Inc.

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    REFERENCES

    1.

    2.3.

    4.

    5.6.

    7.

    8.

    9.

    David,RichardL.,"LargeStoneMixes:AHistoricalInsight,"NationalAsphaltPavementAssociationReportIS103/88,1988.

    Kandhal,P.S.,"MarshallMixDesignMethods:CurrentPractices,"Proceedings,AssociationofAsphaltPavingTechnologists,Vol.54,1985.Acott,Mike,"TheDesignofHotMixAsphaltforHeavyDutyPavements,"NationalAsphaltPavementAssociation,QIS111/86,October1987.Quintus,HaroldVon,"AAMASMixpropertiesRelatedtoPavementPerformance,"ProceedingsoftheAssociationofAsphaltPavingTechnologistsinNashville,TN,February1989."Comparisonof4and6-InchDiameterMoldedSpecimens,"PennsylvaniaDepartmentofTransportation,BureauofMaterials,TestingandResearch,StatusReport,February21,1969."CompressiveStrengthofBituminousMixtures,"ASTMD1074-84,AmericanSocietyforTestingandMaterials,Vol.04.03,1984."MarshallCriteriaforCompactedBituminousSpecimens,"PennsylvaniaTestMethod705,PennsylvaniaDepartmentofTransportation,FieldTestManual,March1983."ResistancetoPlasticFlowofBituminousMixturesUsingMarshallApparatus,"ASTMD1559-82,AmericanSocietyforTestingandMaterials,Vol.04.03,1988.Williams,EllisG.,"DesignandConstructionofLargeStoneHMABasesinKentucky,"HotMixAsphaltTechnology,Winter1988.

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    APPENDIXA

    STANDARDTESTMETHODFORRESISTANCETOPLASTICFLOWOFBITUMINOUSMIXTURESUSING

    MARSHALLAPPARATUS(6INCH-DIAMETERSPECIMEN)

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    DRAFTNO.4(July26,1989)

    STANDARDTESTMETHODFOR

    RESISTANCETOPLASTICFLOWOFBITUMINOUSMIXTURESUSINGMARSHALLAPPARATUS(6INCH-DIAMETERSPECIMEN)

    1.Scope

    1.11.2

    ThismethodcoversthemeasurementoftheresistancetoplasticflowofcylindricalspecimensofbituminouspavingmixtureloadedonthelateralsurfacebymeansoftheMarshallapparatus.Thismethodisforusewithmixturescontainingasphaltcementandaggregateupto2in.(50.8mm)maximumnominalsize.

    Thisstandardmayinvolvehazardousmaterials,operations,andequipment.This

    standarddoesnotpurporttoaddressallofthesafetyproblemsassociatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.

    2.SignificanceandUse

    2.1

    Thismethodisusedinthelaboratorymixdesignofbituminousmixtures.Specimensarepreparedinaccordancewiththemethodandtestedformaximumloadandflow.Densityandvoidspropertiesmayalsobedeterminedonspecimenspreparedinaccordancewiththemethod.Thetestingsectionofthismethodcanalsobeusedtoobtainmaximumloadandflowforbituminouspavingspecimenscoredfrompavementsorpreparedbyothermethods.Theseresultsmaydifferfromvaluesobtainedonspecimenspreparedbythismethod.

    3.Apparatus

    3.13.2

    3.33.4

    SpecimenMoldAssembly-Moldcylindersnominal6.5in.(165.1mm)outsidediametersteeltubingwith6.0000.008in.(152.40.2mm)insidediameterby4.5in.(114.3mm)inheight,baseplates,andextensioncollarsshallconformtothedetailsshowninFigureA-1(a).Allshallbeplated.Ninemoldcylindersarerecommended.

    SpecimenExtractor,steel,intheformofadiskwithadiameterfrom5.950to5.990in.

    (151.1to152.1mm)and0.5in.(13mm)thickforextractingthecompactedspecimenfromthespecimenmoldwiththeuseofthemoldcollar.Asuitablebarisrequiredtotransfertheloadfromtheringdynamometeradaptertotheextensioncollarwhileextractingthespecimen.

    MechanicalCompactorandCompactionHammer-Compactorwith1/3hp(250W)minimummotor,chainlift,frameandautomaticslidingweightrelease.Thecompactionhammer(FigureA-2)shallhaveaflat,circulartampingface5.88in.(149.4mm)indiameteranda22.500.02lb(10.210.01kg)slidingweightwithafreefallof18.00.1in.(457.22.5mm).Twocompactionhammersarerecommended.

    CompactionPedestal-Thecompactionpedestalshallconsistofan8by8by18-in.

    (203.2by203.2by457.2-mm)woodenpostcappedwitha12by12byl-in.(304.8by304.8by25.4-mm)steelplate.Thewoodenpostshallbeoak,pine,orotherwoodhavinganaveragedryweightof42to48lb/ft3(0.67to0.77g/cm3).Thewoodenpostshallbesecuredbyfouranglebracketstoasolidconcreteslab.Thesteelcapshallbefirmlyfastenedtothepost.Thepedestalassemblyshallbeinstalledsothatthepostis

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    FigureA-1(a).CompactionMold

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    3.5

    3.63.7

    plumbandthecapislevel.

    SpecimenMoldHolder,mountedonthecompactionpedestalsoastocenterthe

    compactionmoldoverthecenterofthepost.FigureA-1(b)orequivalentarrangement.

    Itshallholdthecompactionmold,collar,andbaseplatesecurelyinpositionduringcompactionofthespecimen.

    BreakingHead-Thebreakinghead(FigureA-3)shallconsistofupperandlower

    cylindricalsegmentsortestheadshavinganinsideradiusofcurvatureof3in.(76.2mm)accuratelymachined.Thelowersegmentshallbemountedonabasehavingtwoperpendicularguiderodsorpostsextendingupward.Guidesleevesintheuppersegmentsshallbeinsuchapositionastodirectthetwosegmentstogetherwithoutappreciablebindingorloosemotionontheguiderods.Whena6.000in.(152.4mm)diameterby4in.(100mm)thickmetalblockisplacedbetweenthetwosegments,theinsidediametersandthegapsbetweenthesegmentsshallconformtoFigureA-3.Allsteelcomponentsshallbeplated.

    LoadingJack-Theloadingjack(FigureA-4)shallconsistofascrewjackmountedinatestframeandshallproduceauniformverticalmovementof2in.(50.8mm)/min.Anelectricmotormaybeattachedtothejackingmechanism.

    NOTE1-Insteadoftheloadingjack,amechanicalorhydraulictestingmachinemaybeused

    providedtherateofmovementcanbemaintainedat2in.(50.8mm)/minwhiletheloadisapplied.

    3.8

    RingDynamometerAssembly-Oneringdynamometer(FigureA-4)of10,000-lb.(4536-kg)capacityandsensitivityof10lb(4.536kg)upto1000lb(453.6kg)and25lb(11.340kg)between1000and10,000lb(453.6and4536kg)shallbeequippedwithamicrometerdial.Themicrometerdialshallbegraduatedon0.0001in(0.0025mm).

    Upperandlowerringdynamometerattachmentsarerequiredforfasteningtheringdynamometertothetestingframeandtransmittingtheloadtothebreakinghead.

    NOTE2-Insteadoftheringdynamometerassembly,anysuitableload-measuringdevice

    maybeusedprovidedthecapacityandsensitivitymeettheaboverequirements.

    3.9 Flowmeter-Theflowmetershallconsistofaguidesleeveandagage.Theactivating

    pinofthegageshallslideinsidetheguidesleevewithaslightamountoffrictionalresistance.Theguidesleeveshallslidefreelyovertheguiderodofthebreakinghead.Theflowmetergageshallbeadjustedtozerowhenplacedinpositiononthebreakingheadwheneachindividualtestspecimenisinsertedbetweenthebreakingheadsegments.Graduationsoftheflowmetergageshallbein0.0l-in(0.25-mm)divisions.

    NOTE3-Insteadoftheflowmeter,amicrometerdialorstress-strainrecordergraduatedin0.001in(0.025-mm)maybeusedtomeasureflow.

    3.10OvensorHotPlates-Ovensorhotplatesshallbeprovidedforheatingaggregates,

    bituminousmaterial,specimenmolds,compactionhammers,andotherequipmenttotherequiredmixingandmoldingtemperatures.Itisrecommendedthattheheatingunitsbethermostaticallycontrolledsoastomaintaintherequiredtemperaturewithin5F(2.8C).Suitableshields,baffleplatesorsandbathsshallbeusedonthesurfacesofthehotplatestominimizelocalizedoverheating.

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    FigureA-1(b).SpecimenMoldHolder

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    FigureA-2.CompactionHammer

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    FigureA-3.BreakingHead

    FigureA-4.CompressionTestingMachine30

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    3.11MixingApparatus-Mechanicalmixingisrecommended.Anytypeofmechanicalmixermaybeusedprovideditcanbemaintainedattherequiredmixingtemperatureandwillprovideawell-coated,homogeneousmixtureoftherequiredamountintheallowabletime,andfurtherprovidedthatessentiallyallofthebatchcanberecovered.

    Ametalpanorbowlofsufficientcapacity(suchas,standard13qt.sizeapproximately6-1/4inchdeep)andhandmixingmayalsobeused.

    3.12WaterBath-Thewaterbathshallbeatleast9in.(228.6mm)deepandshallbe

    thermostaticallycontrolledsoastomaintainthebathat1401.8F(601.0C)or1001.8F(37.81C).Thetankshallhaveaperforatedfalsebottomorbeequippedwithashelfforsupportingspecimens2in(50.8mm)abovethebottomofthebath.

    3.13MiscellaneousEquipment:

    3.13.1Containersforheatingaggregates,flat-bottommetalpansorothersuitablecontainers.

    3.13.2Containersforheatingbituminousmaterial,eithergill-typetins,beakers,pouringpots,orsaucepansmaybeused.

    3.13.3MixingTool,eitherasteeltrowel(gardentype)orspatula,forspadingandhandmixing.

    3.13.4Thermometersfordeterminingtemperaturesofaggregates,bitumen,andbituminousmixtures.Armored-glassordial-typethermometerswithmetalstemsarerecommended.Arangefrom50to400F(9.9to204C),withsensitivityof5F(2.8C)isrequired.

    3.13.5Thermometersforwaterandairbathswitharangefrom68to158F(20to70C)sensitiveto0.4F(0.2C).

    3.13.6Balance10-kgcapacity,sensitiveto1.0g.3.13.7Glovesforhandlinghotequipment.3.13.8RubberGlovesforremovingspecimensfromwaterbath.3.13.9MarkingCrayonsforidentifyingspecimens.3.13.10Scoop,

    flatbottom,forbatchingaggregates.3.13.11Spoon,large,forplacingthemixtureinthespecimen

    4.TestSpecimens

    4.14.2

    NumberofSpecimens-Prepareatleastthreespecimensforaggregatesandbitumencontent.

    PreparationofAggregates-Dryaggregatestoconstantweightat221to230F(105to

    110C)andseparatetheaggregatestodrysievingintothedesiredsizefractions.*Thefollowingsizefractionsarerecommended:

    1-1/2to1in.(38.1to25.4mm)

    1to3/4in.(25.4to19.0mm)3/4to3/8in.(19.0to9.5mm)3/8in.toNo.4(9.5mmto4.75mm)No.4toNo.8(4.75mmto2.36mm)PassingNo.8(2.36mm)

    *DetailedrequirementsforthesesievesaregiveninASTMSpecificationE11,forWire-Cloth

    SievesforTestingPurposesseeAnnualBookofASTMStandards,Vol.14.02.

    4.3 DeterminationofMixingandCompactingTemperatures:

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    4.44.5

    4.3.1Thetemperaturestowhichtheasphaltcementandasphaltcut-backmustbe

    heatedtoproduceaviscosityof17020cStshallbethemixingtemperature.

    4.3.2Thetemperaturetowhichasphaltcementmustbeheatedtoproduceaviscosityof

    28030cStshallbethecompactingtemperature.

    PreparationofMixtures:

    4.4.1Weighintoseparatepansforeachtestspecimentheamountofeachsizefraction

    requiredtoproduceabatchthatwillresultinacompactedspecimen3.750.10in(95.22.54mm)inheight(about4050g).Placethepansonthehotplateorintheovenandheattoatemperaturenotexceedingthemixingtemperatureestablishedin4.3bymorethanapproximately50/F(28/C).Chargethemixingbowlwiththeheatedaggregateanddrymixthoroughly.Formacraterinthedryblendedaggregateandweighthepreheatedrequiredamountofbituminousmaterialintothemixture.Caremustbeexercisedtopreventlossofthemixduringmixingandsubsequenthandling.Atthispoint,thetemperatureoftheaggregateandbituminousmaterialshallbewithinthelimitsofthemixingtemperatureestablishedin4.3.Mixtheaggregateandbituminousmaterialrapidlyuntilthoroughlycoated.

    CompactionofSpecimens:

    4.5.1Thoroughlycleanthespecimenmoldassemblyandthefaceofthecompaction

    hammerandheatthemeitherinboilingwateroronthehotplatetoatemperaturebetween200and300/F(93.3and148.9/C).Placeapieceoffilterpaperorpapertowelingcuttosizeinthebottomofthemoldbeforethemixtureisintroduced.Placeapproximatelyonehalfofthebatchinthemold,spadethemixturevigorouslywithaheatedspatulaortrowel15timesaroundtheperimeterand10

    timesovertheinterior.Placethesecondhalfofthebatchinthemoldandrepeattheforegoingprocedure.Removethecollarandsmooththesurfaceofthemixwithatroweltoaslightlyroundedshape.Placeapieceoffilterpaperorpapertowelingcuttosizeontopofthemix.Temperaturesofthemixturesimmediatelypriortocompactionshallbewithinthelimitsofthecompactingtemperatureestablishedin4.3.

    4.5.2Replacethecollar,placethemoldassemblyonthecompactionpedestalinthe

    moldholder,andunlessotherwisespecified,apply75blowswiththecompactionhammerwithafreefallof18in(457.2mm).Removethebaseplateandcollar,andreverseandreassemblethemold.Applythesamenumberofcompactionblowstothefaceofthereversedspecimen.

    NOTE3-Ithasbeendeterminedthat75and112compactionblowsappliedtoa6-inch(38.1mm)diameterspecimenusingtheapparatusandprocedureinthisstandardgivedensitiesequivalentto50and75compactionblows,respectively,appliedtoa4-inch(101.6mm)diameterspecimenusingASTMD1559.

    4.5.3Aftercompaction,removethebaseplateandplacethesampleextractoronthat

    endofthespecimen.Placetheassemblywiththeextensioncollarupinthetestingmachine,applypressuretothecollarbymeansoftheloadtransferbar,andforcethespecimenintotheextensioncollar.Liftthecollarfromthespecimen.Carefullytransferthespecimentoasmooth,flatsurfaceandallowittostandovernightatroomtemperature.Weigh,measure,andtestthespecimen.

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    NOTE4-Ingeneral,specimensshallbecooledasspecifiedin4.5.3.Whenmorerapidcoolingisdesired,tablefansmaybeused.Mixturesthatlacksufficientcohesiontoresultintherequiredcylindricalshapeonremovalfromthemoldimmediatelyaftercompactionmaybecooledinthemoldinairuntilsufficientcohesionhasdevelopedtoresultintheproper

    cylindricalshape.

    5.Procedure

    5.15.2

    Bringthespecimenstothespecifiedtemperaturebyimmersinginthewaterbath30to40min.orplacingintheovenfor2hr.Maintainthebathoroventemperatureat1401.8/F(601.0/C).Thoroughlycleantheguiderodsandtheinsidesurfacesofthetestheadspriortomakingthetest,andlubricatetheguiderodssothattheuppertestheadslidesfreelyoverthem.Thetesting-headtemperatureshallbemaintainedbetween70to100/F(21.1to37.8/C)usingawaterbathwhenrequired.Removethespecimenfromthewaterbath,oven,orairbath,andplaceinthelowersegmentofthebreakinghead.Placetheuppersegmentofthebreakingheadonthespecimen,andplacethecompleteassemblyinpositiononthetestingmachine.Placetheflowmeter,whereused,inpositionoveroneoftheguiderodsandadjusttheflowmetertozerowhileholdingthesleevefirmlyagainsttheuppersegmentofthebreakinghead.Holdtheflowmetersleevefirmlyagainsttheuppersegmentofthebreakingheadwhilethetestloadisbeingapplied.

    Applytheloadtothespecimenbymeansoftheconstantrateofmovementoftheload

    jackortesting-machineheadof2in.(50.8mm)/min.untilthemaximumloadisreachedandtheloaddecreasesasindicatedbythedial.Recordthemaximumloadnotedonthetestingmachineorconvertedfromthemaximummicrometerdialreading.Releasetheflowmetersleeveornotethemicrometerdialreadingwhereused,theinstantthemaximumloadbeginstodecrease.Noteandrecordtheindicatedflowvalueorequivalentunitsinhundredthsofaninch(twenty-fivehundredthsofamillimeter)ifa

    micrometerdialisusedtomeasuretheflow.Theelapsedtimeforthetestfromremovalofthetestspecimenfromthewaterbathtothemaximumloaddeterminationshallnotexceed30s.

    NOTE5-Forcorespecimens,correcttheloadwhenthicknessisotherthan3.75in.(95.2

    mm)byusingthepropermultiplyingfactorfromTableA-1.ThistablehasbeendevelopedafterTable1ofASTMD1559basingthecorrelationratioonthepercentchangeinspecimenvolumefromstandardspecimenvolume.

    6.Report

    6.1 Thereportshallincludethefollowinginformation:

    6.1.1Typeofsampletested(laboratorysampleorpavementcorespecimen).

    NOTE6-Forcorespecimens,theheightofeachtestspecimenininches(ormillimeters)

    shallbereported.

    6.1.2Averagemaximumloadinpounds-force(ornewtons)ofaleastthreespecimens,

    correctedwhenrequired.

    6.1.3Averageflowvalue,inhundredthsofaninch;twenty-fivehundredthsofa

    millimeter,ofthreespecimens,and

    6.1.4Testtemperature.

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    TableA-1.StabilityCorrelationsRatiosA

    ApproximateThicknessofSpecimenB VolumeofSpecimen, CorrelationRatiocm3

    in.3-1/2

    3-9/16

    3-5/8

    3-11/16

    3-3/4

    3-13/16

    3-7/8

    3-15/16

    4

    mm88.9

    90.5

    92.1

    93.7

    95.2

    96.8

    98.4

    100.0

    101.6

    1608to1626

    1637to1665

    1666to1694

    1695to1723

    1724to1752

    1753to1781

    1782to1810

    1811to1839

    1840to1868

    1.12

    1.09

    1.06

    1.03

    1.00

    0.97

    0.95

    0.92

    0.90AThemeasuredstabilityofaspecimenmultipliedbytheratioforthethicknessofthespecimenequalsthecorrectedstabilityfora3-3/4-in.(95.2mm)thickspecimen.BVolume-thicknessrelationshipisbasedonaspecimendiameterof6in.(152.4mm).7.PrecisionandBias

    7.1 Theprecisionandbiasofthistestmethodarebeingdetermined.

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