improved rice method for determining theoritical maximum density of asphalt paving mixtures
TRANSCRIPT
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
8/9/2019 Improved Rice Method for Determining Theoritical Maximum Density of Asphalt Paving Mixtures
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IMPROVEDRICEMETHODFORDETERMININGTHEORETICALMAXIMUMSPECIFICGRAVITYOFASPHALTPAVINGMIXTURES
By
PrithviS.Kandhal
AssistantDirectorNationalCenterforAsphaltTechnology
AuburnUniversity,Alabama
MaqboolA.Khatri
ResearchEngineerSouthwesternLaboratories
PaperpublishedinTransportationResearchBoard,TransportationResearchRecord1353,1992
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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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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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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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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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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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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:
Temperature - 77°F.
ResidualPressure - 30mmHg.VacuumingTime - 15min.
Asaconsequenceoftheresultsfromphase1,itwasdecidedtodropthefactortemperaturefrom
thedesignforphase2ofthestudy.Forphase2,itwasdecidedtousethehighwaterabsorptionaggregateRB.
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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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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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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:
Temperature - 77°F.
ResidualPressure - 30mmHg.VacuumingTime - 15min.
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
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Temperature - 77°F.
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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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.'
10