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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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