Improved Rice Method for Determining Theoritical Maximum Density of Asphalt Paving Mixtures

8/9/2019 Improved Rice Method for Determining Theoritical Maximum Density of Asphalt Paving Mixtures

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IMPROVEDRICEMETHODFORDETERMININGTHEORETICALMAXIMUMGRAVITYOFASPHALT PAVINGMIXTURES

By

PrithviS.Kandhal

MaqboolA.Khatri

PaperpublishedinTransportationResearchBoard,TransportationResearchRecord1353,1992

277TechnologyParkway •Auburn,AL36830



IMPROVEDRICEMETHODFORDETERMININGTHEORETICALMAXIMUMSPECIFICGRAVITYOFASPHALTPAVINGMIXTURES

By

PrithviS.Kandhal

AssistantDirectorNationalCenterforAsphaltTechnology

AuburnUniversity,Alabama

MaqboolA.Khatri

ResearchEngineerSouthwesternLaboratories

PaperpublishedinTransportationResearchBoard,TransportationResearchRecord1353,1992



DISCLAIMER

Thecontentsofthisreportreflecttheviewsoftheauthorswhoaresolelyresponsibleforthefactsandtheaccuracyofthedatapresentedherein.ThecontentsdonotnecessarilyreflecttheofficialviewsandpoliciesoftheNationalCenterforAsphaltTechnologyofAuburnUniversity.Thisreportdoesnotconstituteastandard,specification,orregulation.

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ABSTRACT

Ricemethod(ASTMD2041)isusedfordeterminingthetheoreticalmaximumspecificgravity

ofasphaltpavingmixtureswhichisoneofthemaintestparametersusedformixdesignandconstructionqualitycontrol.TherepeatabilityandreproducibilityoftheRicemethodisnotconsideredsatisfactoryespeciallywhenhighlyabsorptiveaggregatesareusedinthemixture.SuchaggregatescanabsorbwaterduringthevacuumingphaseoftheRicemethod.Thisnecessitatestheuseofasupplementary(dry-back)procedurewhichisevenmorepronetotestingerrors.ThereisaneedtoimprovetheRicemethodtoavoidtheaforementionedproblems.

Twodensegradedasphaltpavingmixtures(representinglowandhighabsorptionaggregates)

andoneAC-20asphaltcementwereusedinthisstudy.Threefactors(temperature,residualpressure,andvacuumingtime)affectingtheresultsfromtheRicemethodwereinvestigatedatthreelevelseach,involvingsome108tests.

Basedonthetestdata,optimumlevelshavebeenrecommendedfortemperature(77°F),residual

pressure(30mmHg),andvacuumingtime(15minutes).UseoftheseoptimumlevelsbyalllaboratoriesisexpectedtoimprovethereproducibilityoftheRicemethod,especiallywhenhighlyabsorptiveaggregatesareusedintheasphaltpavingmixtures.TheimprovedRicemethodisalsolikelytominimizethenecessityofusingthesupplementary(dry-back)procedure.

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Kandhal&Khatri

EVALUATIONOFPARTICLESHAPEANDTEXTUREOFMINERALAGGREGATES

ANDTHEIRBLENDS

PrithviS.Kandhal,MaqboolA.Khatri,andJohnB.Motter

INTRODUCTION

TheoreticalmaximumspecificgravityofHotMixAsphalt(HMA)mixturesisusedinallstagesofHMAdesign,construction,andevaluation.TheprocedurefordeterminingthetheoreticalmaximumspecificgravityofHMAmixtureswasoriginallydevelopedbyRice(7 ,2)andisstandardizedasASTMD2041-TheoreticalMaximumSpecificGravityandDensityofBituminousPavingMixtures.Itisoneofthemaintestparametersusedformixdesignandconstructionqualitycontrol.BesidesthevoidparametersofanHMAmixture,theamountofasphaltcementabsorbedbytheaggregateisalsocomputedbytheuseoftheoreticalmaximumspecificgravityisdeterminedbyASTMD2041.

Although,thisisoneofthemostcriticaltestparametersinthedesignofHMAmixtures,its

repeatabilityandreproducibilityhasgenerallybeenunacceptable.InJuly1983,thetaskforceonrevisionofASTMD2041(theRicespecificgravitymethod)recommendedthatthewaterbemadetoboil(throughsuitablecombinationsofsaturationtemperatureandpressure)inthevesselwhensubjectingthespecimentovacuumforremovalofair.However,notestdatawasreportedto justifytherecommendationanditwasnotmadeapartofthetestmethod.

ThesituationisfurthercomplicatedwhenhighlyabsorptiveaggregatesareusedinHMA

mixturesandthereisapotentialofwaterbeingabsorbedbytheaggregateduringthevacuumingphase.ThecurrentASTMmethodspecifiesaminimumvacuumlevel(maximumresidualpressureof30mmofHgorless).Therefore,onecanuseahighvacuumlevelandincreasethepotentialforwaterabsorption.ThecurrentASTMtestmethodsuggeststheuseofasupplementalproceduretocorrectforthissituation.However,thisprocedureisquitetime

consuminganditsrepeatabilityandreproducibilityhavenotbeenestablished.

Alternativetechniquesfordeterminingthetheoreticalmaximumspecificgravityhavealsobeen

proposedandareinuse.TheU.S.ArmyCorpsofEngineers(3,4)developedandhasusedthebulkimpregnatedspecificgravityinthedesignandcontrolofasphaltpavingmixtures.Onelimitationofthismethod,however,isthepossibledifficultyofremovingairbubblesentrappedintheasphaltcementwhenbothcoarseandfineaggregatesareaddedtomoltenasphalt.FrancoandLee(5)haverecentlyevaluatedtheviabilityofusinganairmeterfordeterminingthemaximumspecificgravityofHMAmixtures.Theairmeterhasnormallybeenusedfordeterminingthepercentofairentrainedinportlandcementconcrete.Theso-calledpressuremethodworksontheprincipleofBoyle'slaw.AweighedsampleofHMAmixisintroducedintothebowloftheairmeter(TypeBairmeterasspecifiedinAASHTOT152)andwateris

introducedtofillthemetertothecapacity(noattemptismadetoremovetheentrappedair).Thefilledairmeterisweighedandtheweightofwaterobtained.TheaircontentofthemeteristhendeterminedinaccordancewithAASHTOT152.BackcalculationsarethenperformedandthevolumeoftheHMAmixisdetermined.Furtherworkisneededtoimprovethedesignoftheairmetersothatitsconsistencyandsensitivityisacceptable.

ThisstudywasaimedatrefiningthecurrentRicemethod(ASTMD2041).Twodifferent

aggregatesandoneasphaltcementwereusedinthisstudy.Threefactors,namely,temperature,residualpressure,andvacuumingtimewereinvestigatedtodeterminetheiroptimumlevels.Thematerialsusedinthestudy,theexperimentalplan,testresults,andconclusionsarepresentedbelow.

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Kandhal&Khatri

MATERIALSUSED

Aggregates

AllthematerialsusedinthisstudywereobtainedfromtheStrategicHighwayResearchProgram(SHRP)'sMaterialsReferenceLibrary(MRL).Thefollowingtwodifferentaggregateswereused:

RD-FrederickLimestone(BulkSpecificGravity=2.713,WaterAbsorption=0.38%)

RB-WatsonvilleGranite(BulkSpecificGravity=2.692,WaterAbsorption=1.68%)

AggregateRDwasusedinthefirstphaseofthestudywherethreefactors,temperature,residualpressureandvacuumingtime,wereinvestigatedfortheiroptimumlevels.ThisaggregatewasselectedbecauseithadthelowestwaterabsorptionofalltheSHRPMRLaggregatesanditsusewouldreducethevariationoftestresultsduetowaterabsorptionduringthevacuumingoperation.AggregateRB,whichwasusedinphase2ofthisstudy,wasselectedtorepresenta

highabsorptionaggregate.Initially,thehighestabsorptionSHRPMRLaggregateRCwastried.However,duringvacuumingatlowresidualpressures(highvacuum)whilerunningtheRicemethod,thewaterintheflaskbecamemuddyduetosuctionoffinesfromthematedaggregateparticles.Asaresult,thesupplementalprocedurewasinerror.UseofahighabsorptionaggregatelikeRBwasnecessitatedtoamplifythedifferenceinthevaluesofthetheoreticalmaximumspecificgravitybeforeandafterrunningthesupplementalprocedure.ThewashedgradationsofthemixesusedaregiveninTable1.

Table1.WashedGradationsofMixesUsed

SieveSize PercentPassingforAggregate

RB RD

1/2in. 100.0 100.0

3/8in. 81.1 95.8

No.4 54.1 50.3

No.8 48.6 40.4

No.16 35.0 28.7

No.30 26.8 20.0

No.50 18.5 14.7

No.100 11.0 11.5

No.200 6.1 9.5

AsphaltCementsOnlyoneasphaltcement(AAM-1,WestTexas)wasusedinthisstudyanditwasanAC-20.ItwasselectedbecauseAC-20isthemostwidelyusedviscositygradedasphaltcementinUnitedStates.

TESTINGPLAN

Thisstudywasdividedintwophases.Phase1involvedtheuseoftheleastwaterabsorptionSHRPMRLaggregateRDinordertoavoidthesupplementalprocedureoftheRicemethod.Threefactors,temperature,residualpressureandvacuumingtime,wereallinvestigatedatthreelevelseach.Thelevelsofthefactorstestedwere:

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Kandhal&Khatri

Temperature - 69,77,and85°F.ResidualPressure - 16,23,and30mmHg.VacuumingTime - 5,10,and15min.

Therespectivecombinationsoftemperatureandresidualpressure,namely,69°Fand16mmHg,77°Fand23mmHg,and85°Fand30mmHg,wereselectedtoensurecontinuousboilingofwaterduringthevacuumingphaseoftheRiceprocedure.Threereplicateswererunateachtreatmentcombination.Thedesignwasa33designwiththreereplicatesgivingatotalof81tests.Thereplicateswereconsideredasblocks.

Forphase2,thefactortemperaturewasdroppedbasedontheresultsfromphase1.Theother

twofactors,i.e.,residualpressureandvacuumingtime,wereincludedatthreelevelseach.Thelevelsusedforthesefactorswerethesameasforphase1.Threereplicateswererunforeachtreatmentcombinationandweretreatedasblocks.Thedesignwasa32designwiththreereplicatesgivingatotalof27tests.

DISCUSSIONOFRESULTSTheresultsforphase1ofthestudyarereportedinTable2.AnanalysisofvariancewascarriedoutandANOVAisreportedinTable3.Allthreefactors,temperature(A),residualpressure(B),andvacuumingtime(C),werefoundtobesignificantata=0.05.OnlyoneinteractionA×C(temperature×vacuumingtime)wasfoundtobesignificantat"=0.05.BylookingattheaveragesreportedinTable2foreachfactor,itcanbeseenthataveragetheoreticalmaximumspecificgravitydoesnotvarymuchatthevariouslevelsofailfactors.Theerrorvarianceisfoundtobe0.00001givingastandarddeviationof0.00228.Thisgivesasingleoperatorprecisionfortheexperimentas0.007whichislessthanthecurrentASTMvalueof0.011.Moreover,therangeofthevaluesfortheentireexperimentis2.490-2.502=0.012whichisaboutthesameasthecurrentASTMsingleoperatorprecision.

Forphase1ofthestudy,theobjectivewastomaximizethevalueofthetheoreticalmaximum

specificgravity.Theoptimalconditionsforallthefactorsareselectedasfollows.

WithoutConsideringInteractions

Thecumulativeaverages(averageof27observations)forallthefactorsaretabulatedbelow:

1.Temperature:

2.ResidualPressure:

3.VacuumingTime:

Level

69°F

77°F

85°F

Level

16mmHg

23mmHg

30mmHg

Level

5min.

10min.

15min.

CumulativeAverage

2.497

2.495

2.496

CumulativeAverage

2.495

2.496

2.497

CumulativeAverage

2.495

2.496

2.498

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Kandhal&Khatri

Table2.RiceSpecificGravitiesUsingAggregateRD

Temperature,°F 69 77 85

Res.Pressure,mmHG 16 23 30 16 23 30 16 23 30

v 2.501 2.495 2.503 2.492 2.495 2.499 2.495 2.495 2.500acuum

T

ime,

m

in

51015

2.493

2.492

2.495

2.495

2.4962.497

2.496

2.496

2.496

2.497

2.496

2.498

2.493

2.495

2.496

2.4982.499

2.498

2.501

2.499

2.498

2.499

2.501

2.500

2.501

2.496

2.4962.499

2.497

2.500

2.500

2.497

2.499

2.491

2.491

2.491

2.496

2.4932.499

2.496

2.502

2.497

2.498

2.499

2.495

2.490

2.493

2.491

2.4902.493

2.491

2.499

2.495

2.496

2.497

2.492

2.492

2.494

2.493

2.4962.491

2.493

2.502

2.500

2.495

2.499

2.491

2.493

2.493

2.495

2.4972.494

2.495

2.497

2.497

2.495

2.496

2.494

2.495

2.495

2.495

2.4942.493

2.494

2.500

2.497

2.497

2.498

2.493

2.494

2.496

2.495

2.5012.502

2.499

2.499

2.496

2.494

2.496

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Kandhal&Khatri

Table3.ANOVAForRiceGravitiesUsingAggregateRD

Total

Source df

80

SS

0.00081

MS

---

Fo

---

FCrit.

---

Temperature(A) 2 0.00009 0.00005 8.72 3.18*

Res.Pressure(B) 2 0.00006 0.00003 5.42 3.18*

VacuumTime(C) 2 0.00012 0.00006 11.69 3.18*

A×B 4 0.00003 0.00001 1.53 2.56

A×C 4 0.00006 0.00002 3.08 2.56*

B×C 4 0.00004 0.00001 2.03 2.56

A×B×C 8 0.00008 0.00001 1.99 2.13

Error 52 0.00027 0.00001 --- ---*=Significantat "=0.05.

Observingthecumulativeaveragevaluesofthetheoreticalmaximumspecificgravity,the

optimallevelsoffactors,basedonthehighestvalue,areselectedas:

Temperature - 69°F.

ResidualPressure - 30mmHg.VacuumingTime - 15min.

ConsideringInteractionA×C

ThecellaveragesforinteractionA×C(temperature×vacuumingtime)areasfollows:

VacuumingTime,min.(C)

Temperature,°F(A) 5 10 15

69 2.497 2.497 2.498

77 2.493 2.494 2.498

85 2.494 2.496 2.497

Observingthecellaverages,theoptimallevelforfactorC(vacuumingtime)isconfirmedtobe15minutes.However,forfactorA(Temperature),twolevelsareindicated.Theselevelsare69°F

and77°F.Sincethereisnotmuchvariationinresults,andmoreover,since77°Fisarepresentativeindoortemperatureandisquitecommonlyusedformostoftheindoortesting,itwasselectedastheoptimaltemperature.

Theoptimallevelsforthefactorsselectedonthebasisofphase1ofthestudy,therefore,are:



Asaconsequenceoftheresultsfromphase1,itwasdecidedtodropthefactortemperaturefrom

thedesignforphase2ofthestudy.Forphase2,itwasdecidedtousethehighwaterabsorptionaggregateRB.

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Kandhal&Khatri

Theresultsfromphase2experimentsarereportedinTable4.Therepottedresultsincludethe

valuesfortheoreticalmaximumspecificgravitybothbeforeandafterrunningthesupplementaryprocedure.TheANOVAforthisphasearereportedinTables5and6,respectively,for:

a.differenceintheoreticalmaximumspecificgravityvaluesbeforeandafterrunning

thesupplementaryprocedure,and,b.theoreticalmaximumspecificgravityvaluesbeforerunningthesupplementary

procedure.

Theresultsareindividuallydiscussednowfora)andb)above.

Table4.RiceSpecificGravitiesUsingAggregateRB

ResidualPressure(A),mm

5

VacuumingTime(B),min.

10

15

Hg

16Avg.

23

Avg.

30

Avg.

Before

2.529

2.527

2.529

2.528

2.518

2.520

2.523

2.520

2.529

2.522

2.524

2.525

After

2.524

2.520

2.519

2.521

2.508

2.510

2.513

2.510

2.527

2.518

2.521

2.522

Difference

0.005

0.007

0.010

0.007

0.010

0.010

0.010

0.010

0.002

0.004

0.003

0.003

Before

2.533

2.524

2.524

2.527

2.532

2.526

2.526

2.528

2.524

2.527

2.520

2.524

After

2.523

2.514

2.515

2.517

2.529

2.524

2.522

2.525

2.519

2.519

2.516

2.518

Difference

0.010

0.010

0.009

0.010

0.003

0.002

0.004

0.003

0.005

0.008

0.004

0.006

Before

2.534

2.531

2.532

2.532

2.530

2.531

2.536

2.532

2.532

2.528

2.527

2.529

After

2.528

2.524

2.521

2.524

2.521

2.523

2.525

2.523

2.530

2.526

2.523

2.526

Difference

0.006

0.007

0.011

0.008

0.009

0.008

0.011

0.009

0.002

0.002

0.004

0.003Notes:Before,After,andDifferencerefertobeforedry-back,afterdry-back,andthedifferenceofthetwo.

Table5.ANOVAForRiceGravitiesUsingAggregateRB

Total

Source df

26

SS

0.00026674

MS

---

Fo

---

FCrit.

---

Res.Pressure(A) 2 0.00010496 0.00005248 23.09 3.63*

VacuumTime(B) 2 0.00000230 0.00000115 0.51 3.63A×B 4 0.00011215 0.00002804 12.33 3.01*

Blocks 2 0.00001096 --- --- ---

Error 16 0.00003637 0.00000227 --- ---*=Significantat "=0.05.

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Kandhal&Khatri

Table6.ANOVAForRiceGravityValuesBeforeRunningSupplementaryProcedure

UsingAggregateRB

Total

Source df

26

SS

0.00055000

MS

---

Fo

---

FCrit.

---

Res.Pressure(A) 2 0.00005267 0.00002633 2.92 3.63

VacuumTime(B) 2 0.00021667 0.00010833 12.00 3.63*

A×B 4 0.00009733 0.00002433 2.70 3.01

Blocks 2 0.00003889 --- --- ---

Error 16 0.00014444 0.00000903 --- ---*=Significantat "=0.05.DifferencesHerethefactorA(residualpressure),andtheinteractionA×B(residualpressurexvacuumingtime)arefoundtobesignificantata=0.05.Theobjectiveinthiscasewastominimizethedifferences.Todeterminetheoptimallevels,thecumulativeaveragesforfactorAarereportedbelow:

Level CumulativeAverage

16mmHg 0.008

23mmHg 0.007

30mmHg 0.004Theoptimallevelsoffactors,withoutconsideringinteractions,areselectedas:

ResidualPressure - 30mmHg.

VacuumingTime - Anylevel

Now,sincetheinteractionA×Bwasalsosignificant,weshouldtakealookatthecellaverages:

VacuumingTime,min.(B)

ResidualPressure,mmHg(A) 5 10 15

16 0.007 0.010 0.008

23 0.010 0.003 0.009

30 0.003 0.006 0.003

Thefactorlevel30mmHgforfactorAappearstobesupportedonthebasisofinteractionA×Baswell.ForfactorsB,however,wecouldselectanylevel.Theoptimallevelsbasedonthedifferences,therefore,are:

ResidualPressure - 30mmHg.

VacuumingTime - Anylevel

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Kandhal&Khatri

ValuesBeforeRunningSupplementaryProcedure

HereonlyfactorB(VacuumingTime)isfoundtobesignificantata=0.05.Theobjectiveinthiscasewastomaximizethevalueofthetheoreticalmaximumspecificgravitybeforerunningthe

supplementaryprocedureortoeliminatetheneedforrunningthesupplementaryprocedurewhichistimeconsumingandpronetotestingerrors.Todecidetheoptimallevels,thecumulativeaveragesforfactorBarereportedbelow:

Level5

min.

10min.15

min.

Theoptimallevelsoffactorsareselectedas:

CumulativeAverage

2.525

2.526

2.531

ResidualPressure - AnylevelVacuumingTime - 15min.

Combiningtheresultsthen,theoptimallevelsoffactorsforphase2are:

ResidualPressure - 30mmHg

VacuumingTime - 15min.

Finally,asaresultoftheexperimentsconductedduringphase1and2ofthisstudy,the

followinglevelsoffactorsshouldbeusedwhenemployingtheRicemethodtodeterminethetheoreticalmaximumspecificgravityofHMAmixtures:



Theuseoftheseoptimallevelsoffactorsbecomesevenmoreimportantwhendealingwith

absorptiveaggregateswhichtendtoabsorbwaterduringthevacuumingphasethusrequiringtheuseofsupplementaryproceduretocorrectforthis.Theuseoftheselevelswillminimizethedifferencebetweenthevaluesofthetheoreticalmaximumspecificgravityobtainedbeforeandafterrunningthesupplementaryprocedureandmayeveneliminatetheuseofthesupplementaryprocedureforabsorptiveaggregatesiftheseareadequatelycoated.

ThecurrentASTMtestmethodD2041(theRicemethod)doesspecifythetemperaturetobe

77°F.However,thereisnorestrictiononthelowerlimitoftheresidualpressure(or,inotherwords,theupperlimitofthevacuumlevel)whichisimportantwhiledealingwithhighlyabsorptiveaggregates.Thishasprobablyledtothepoorreproducibilityofthetestmethod.Onemoreconclusionthathasemergedoutofthisstudyisthatitisnotnecessarytomakethewaterboilduringvacuumingphaseinordertogetalltheairoutofthesample.Thisisconcludedbasedonthefactthattheinteractionoftemperatureandresidualpressurewasnotfoundtobesignificant.

CONCLUSIONSANDRECOMMENDATIONS

Basedonthedataobtainedusingtwodifferentaggregatesandoneasphaltcement,thefollowingconclusionsaredrawnandrecommendationsmade.

1.Thefollowingoptimumlevelsofthefactors:temperature,residualpressure,andvacuumingtime,arerecommendedforusewhenemployingtheRicemethodfor

determiningthetheoreticalmaximumspecificgravityofanHMAmixture:8



Kandhal&Khatri


Residualpressure - 30mmHg.Vacuumingtime - 15min.

Theuseoftheselevelsoffactorsbecomesevenmoreimportantwhendealingwithabsorptiveaggregateswhichtendtoabsorbwaterduringthevacuumingphasethusrequiringtheuseofsupplementary(dry-back)proceduretocorrectfortheamountofwaterabsorbed.Useoftheseoptimumlevelswillminimizethedifferencebetweenthevaluesofthetheoreticalmaximumspecificgravityobtainedbeforeandafterrunningthesupplementaryprocedureandmayeveneliminatetheuseofthesupplementaryprocedureforabsorptiveaggregatesiftheaggregateisadequatelycoated.UseofthesesamelevelsbyalllaboratoriesisalsoexpectedtoimprovethereproducibilityoftheRicemethod.

2.ItisnotnecessarytomakethewaterboilduringvacuumingphaseoftheRicemethodinordertogetalltheairoutofthesample.Infact,theuseoflowerpartialvacuum(30mmHgresidualpressureinsteadof23mmHgasrequiredforboilingat77°F)is

evenmoreimportantwhenaggregatesofabsorptivenaturearebeingdealtwith.3.ProposedmodificationstotheASTMstandardmethodD2041inviewoftheaboveconclusionsandrevisionstotheprocedureareindicatedinAppendixA.CuringoftheHMAmixat290°FforfourhourspriortorunningtheRicemethodisbasedonpreviousresearchbytheauthorsunderSHRPProjectA-003B.Itshouldbenotedthattheproposedmodificationsarebasedondatafromtwomixesonly.Amultilaboratoryroundrobinstudyinvolvingseveralmixesisrecommended.

ACKNOWLEDGMENTS

ThisstudywasconductedbytheNationalCenterforAsphaltTechnology(NCAT)atAuburnUniversityundertheStrategicHighwayResearchProgram(SHRP)ContractA-003BonFundamentalStudiesofAsphaltAggregateInteractionsIncludingAdhesionandAbsorption.The

opinions,findings,andconclusionsexpressedherearethoseoftheauthorsandnotnecessarilythoseofSHRP,NCAT,orAuburnUniversity.REFERENCES1.2.

3.

4.

5.

J.M.Rice,"MaximumSpecificGravityofBituminousMixturesbyVacuumSaturationProcedure,"ASTMSpecialTechnicalPublication,191(1956).J.M.Rice,"NewTestMethodforDirectMeasurementofMaximumDensityofBituminousMixtures,"CrushedStoneJournal(September1953).W.C.Ricketts,J.C.Sprague,D.D.Tabb,andJ.LMcRae,"AnEvaluationoftheSpecificGravityofAggregatesforUseinBituminousMixtures,"Proc.ASTM,Vol.54(1954)."InvestigationofthePenetrationofAsphaltintoPorousAggregatesasRelatedtoand

AffectingtheSpecificGravityoftheAggregate,"U.S.CorpsofEngineersWaterwaysExperimentStation,CorpsofEngineersMisc.PaperNo.4-66(1954).C.A.FrancoandK.W.Lee,"DevelopmentofAPressureMethodtoDetermineTheoreticalSpecificGravityofBituminousPavingMixtures,"TransportationResearchRecord1269(1990).

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Kandhal&Khatri

APPENDIXA

ADDITIONS/REVISIONSTOASTMSTANDARDTESTMETHODD2041-90

Theproposedrevisionsand/oradditionstotheASTMStandardtestmethodD2041-90-TheoreticalMaximumSpecificGravityofBituminousPavingMixtures-basedonthisstudyaregivenbelow.

Section6.1.2

Old:6.1.2Thevacuumcontainersizedependsontheminimumsamplesizerequirementsgivenin8.2.Avoidusingasmallsampleinalargecontainer.

New:6.1.2Thevacuumcontainersizedependsontheminimumsamplesizerequirementsgiven

in7.2.Avoidusingasmallsampleinalargecontainer.

NewSectionandNote

7.3Formixdesignandproductioncontrolpurposes,thesampleshouldbecuredinanovenat290°Fforatleast4hours.

Note5:Curingintheovenatthespecifiedtemperatureisespeciallyimportantwhenabsorptive

aggregatesareused.Thiswillensurethecomputationofrealisticvaluesfortheamountofasphaltabsorbedbytheaggregateandvoidpropertiesofthemix.

Note6:Curingofthemixasrequiredin7.3abovemaynotbenecessaryduringproductionifthe

mixisstoredinasurgeorstoragesiloforatleastthreehours.Curingtimecanalsobereducedoreliminatedduringproductionifitcanbedemonstratedthroughaseriesoftestsconductedafter0,1,2,3,and4hourscuringtime.

Note5

RenumberexistingNote5toNote7.

Section9.4andNewNote

Old:Removeairtrappedinthesamplebyapplyinggraduallyincreasedvacuumuntiltheresidualpressuremanometerreads30mmofHgorless.Maintainthisresidualpressurefor5to15min.Agitatethecontainer....

New:Removeairtrappedinthesamplebyapplyinggraduallyincreasedvacuumuntilthe

residualpressuremanometerreads30mmofHg.Maintainthisresidualpressurewithin+1mmHgfor15min.Agitatethecontainer....

Note8:Ithasbeenfoundthatbyusingthiscombinationofresidualpressure(30mmHg)and

vacuumingtime(15min.),theneedforrunningthesupplementaryprocedure(section11)can

generallybeavoidedwhentestingathoroughlycoatedmix.

Note6

DeleteexistingNote6.

Notes7,8,and9

RenumberexistingNotes7,8,and9toNotes9,10,and11.

Section13

Changeallthereferencesof'Section9'intheprecisionstatementsto'Section11.'

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Improved Rice Method for Determining Theoritical Maximum Density of Asphalt Paving Mixtures

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