多孔磨耗层外文翻译.docx

多孔磨耗层外文翻译.docx

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多孔磨耗层外文翻译

Characterizationofporousfrictioncoursemixesfordifferent

Marshallcompactionefforts

DepartmentofCviliEngnieernig,NatoinalInsttiuteofTechnologyKarnataka,Surathka,lMangaolre575025,India

ABSTRACT

Porousfrictioncourses（PFCs）aremainlyrecommendedassurfacedrainagelayersonhigh-speedroadcorridorsandrunwaypavements.PermeabilityandsoundattenuationcharacteristicsareconsideredtobetheindicesforperformanceassessmentofPFCs.OneofthereasonsforthelossofpermeabilityinPFCsisdensificationunderheavytraffic.But,resistancetoravellingtoo,isofmainconcerninthecaseofunder-compactedPFCs.ThispapersummarisesthedetailsoflaboratoryinvestigationonthecharacterizationofPFCmixescorrespondingtofourdifferentgradationsandtwobindercontents,forthreelevelsoftheMarshallcompaction.ThefindingsoftheinvestigationsuggestthattheselectionofthecompactionlevelforPFCmixdesignshouldbebasedonthedesigntrafficlevel,andthegradationselected.

2009ElsevierLtd.Allrightsreserved.

Keywords:

PorousfrictioncoursePorousasphaltMarshallcompactionAirvoidsVoidsincoarseaggregatePermeabilityMoisturesusceptibility

Abrasionloss

1.Introduction

Porousfrictioncourses（PFCs）aretypicalopen-gradedasphalticmixes,composedofrelativelyuniformly-gradedaggregateandasphaltcementormodifiedbinders,andaremainlyusedtoserveasdrainagelayers,eitheratthepavementsurfaceorwithinthepavementstructure[1].Pavementssurfacedwithopen-gradedasphalticmixeswerefoundtoimprovewetweatherskid-resistance,minimizehydroplaning,reducesplashandspray,improvenightvisibilityduringwetweatherconditions,andreducetraffictyrenoise[2,3].IncountriesliketheUnitedStatesofAmerica,Japan,theUnitedKingdom,Malaysia,Australia,NewZealand,andSouthAfrica,open-gradedmixesareinuseassurfacelayersoverhigh-speedandheavilytraffickedhighwaypavements[2–8].Thesearealsorecommendedforsurfacingrunwaypavements[9-10].Manyagenciesaroundtheworldusedifferentterminologiesforopen-gradedmixes,andspecificationsthatareslightlydifferent.Thevariousterminologiesusedincludeopen-gradedasphalt（OGA）,porousasphalt（PA）,open-gradedfrictioncourse（OGFC）,andporousfrictioncourse（PFC）.

.1.1Background

ThehighairvoidscontentinPFCscontributetowardspavementsurfacedrainageandinattainingnoisereduction.But,acceleratedasphalt-filmaging,maysubsequentlyleadtolossofcohesioninthemastic,consequentlypooradhesionbetweenthemasticandaggregateresultsinravelling.Experienceswiththeuseofopen-gradedmixesintheUSAindicatedthatravellingwasoneofthemajorissuestobetackled[11].Thus,structuraldurabilityofPFCsneedstobeensuredbasedontheresistancetoravelling[12].SomeoftheexperienceswithPFCsinJapan,thepoorperformancewasrelatedtothelackofcompaction,orcompactionatlowertemper-aturesthanthespecified[6].PermeabilityandsoundattenuationcharacteristicsarethemainmeasuresofperformancelifeofPFCs[2].StudiesperformedontestsectionsinDenmark,indicatedthatdeterioratedmasticmaterialscloggedthelarge-sizedairvoidsinPFCs,whichledtotheformationofhigherpercentageofsmall-sizedvoids[12].Clog-gingwasfoundtobemorepronouncedonolderpavement,especiallyalongthewheelpath,andalsointheemergencylanes[13].Although,PFCsarecomposedofrelativelyuniformly-gradedaggregate[1],theuseofthickerPFCsmayundergosecondarydensificationduringservice,resultinginlossofpermeability.Thus,thelossofpermeabilitycanbedirectlyrelatedtocloggingofvoidsduetointernalandexternalmaterials,anddensificationundertraffic[2].

Anoptimaldesignmixshouldensurehighairvoidscontentandgoodresistancetoravelling.ProcedureformixdesignofPFCsrecommendedbyvariousagenciesincludetheevaluationofdrain-downlossesinloosehotmixes,airvoidscontent,stone-on-stonecontactcondition,permeability,andtheabrasionresistanceusingtheCantabroabrasiontestmethod[4,7,8,15].Oneofthemajordifferencesobservedinthespecificationsbyvariousagenciesisthatoftheconsiderationoftrafficvolumeintheoptimummixselectioncriteria.Theminimumairvoidscontentandthemaximumabrasionlossspecifiedbysomeoftheagenciesweredependentonthetrafficvolume[4,7,8],whereas,thisdependencywasnotconsideredbymanyagenciesintheUSA[2,10,15,16].ThelevelofMarshallcompactionsuggestedbymanyagencieswerefoundtobe50blowsperface,irrespectiveofthetrafficvolume.Inaddition,intherecentpastmanyresearchersadoptedthesameleveloftheMarshallcompactionforthedesignofPFCmixes[17–20].However,someoftheresearchersadoptedorsuggestedthelowerlevelsoftheMarshallcompaction,forcharacterizingthePFCmixes[21–24].

1.2.Objectiveandscope

ThemainobjectiveofthisinvestigationwastocharacterizethePFCmixesforthreelevelsoftheMarshallcompaction.Thecompactionlevelsinvestigatedinclude35,50,and75blowsappliedoneachendofthespecimen.TheeffectofeachcompactionlevelwasstudiedoneightdifferentPFCmixes,whichcorrespondedtofourdifferentaggregategradations（G）,andtwobindercontents（BC）of4.5and5.0%bymassoftotalmix,usingtheneatbitumenof85–100penetrationgrade.Theselectionofgradation,bindertype,andbindercontentwerebasedonthepreviousstudiesperformedonsimilarmixes[25,26].Fig.1showsthedetailsofthefouraggregategradationsinvestigated.Table1providesdetailsofthecodingmethodadoptedfordesignatingthemixesforvariouscompactionlevelsandmixcompositions.

2.Specimenpreparationandtestplan

Straight-runbitumenandcrushedstoneaggregatesarethemajorconstituentsofPFCmixes.Thestraight-runpavinggradebitumenusedinthepresentinvestigationwassuppliedbyMangaloreRefineryandPetrochemicalsLimited（MRPL）,Manga-

lore.Crushedgranitestoneaggregatesobtainedfromlocalstone-crushingplantswereusedinthisstudy.Table2showssomeofthephysicalpropertiesofbitumenandaggregatestestedinaccordancewiththerequirementsoftheASTMD946[27]andASTMD7064[15],respectively.OrdinaryPortlandCement（OPC）wasusedasapartofthemineralfiller,constituting2%bymassoftotalaggregatesweighing1000g.

TheprocedureadoptedforpreparationofthePFCspecimenswasquitethesameasthatadoptedfordensegradedasphalt,assuggestedinAsphaltInstituteManualSeries-2[28].Thepropertiesofcompactedmixesinvestigatedincludebulkspecificgravity（Gmb）,airvoidscontent（Va）,stone-on-stonecontactcondition,per-

meability（K）,moisturesusceptibility,andunagedabrasionloss.ThesepropertieswereevaluatedinaccordancewiththeguidelinesoftheASTMD7064[15].Table3providesdetailsonthetestsperformedforvariousexperimentalmixes.Threeobservationsweremadeoneachexperimentalmix.

3.CharacterizationofPFCmixes

3.1.Bulkspecificgravityofcompactedmix

Thetestsforbulkspecificgravityofcompactedmixes（Gmb）wereperformedon24mixesasdescribedinTable3,withthreereplicatesforeachmix.TheGmbofeachcompactedmixwasdeterminedusingthegeometricmeasurementsofdiameter,height,andthemassofthespecimeninair,inaccordancewithASTMD7064[15].TheindividualandmeanGmbvalueswerefoundtobeintherangeof1.935–2.249,and1.984–2.226,respectively,asshowninFig.2.Itisevidentthatanincreaseinthecompactioneffortwillleadtodensificationofthemix,resultinginhigherdensities.Further,itisevidentfromthe95%confidenceintervalsthatthereisnosignificantdifferencebetweenthemeanGmbvaluesamongthemixeswithbindercontentsof4.5%and5.0%whencompared,foraparticulargradationandcompactionlevel.ThemixeswithgradationsG1andG4exhibitedhigherandlowerGmbvalues,respectively,especiallysinceG4comprisedofcoarseraggregates.ThemeanGmbvaluesforthemixeswithgradationsG2andG3areapproximatelythesame,astheminordifferencesingradationshavenotaffectedtheGmbvaluessignificantly.

3.2.Airvoids

Theairvoids（Va）contentinacompactedmixisrelatedtotheGmbandthetheoreticalmaximumdensity（Gmm）oftheuncompactedmix,determinedinaccordancewiththeASTMD2041[30].TheincreaseinthecompactioneffortresultsinhigherGmb,resultinginadecreaseinVa.

Fig.3showstheindividualplotofVaforeachmix.ItalsoindicatesthemeanVaoftheindividualmixestested,andthe95%confidenceintervalforthemean.ThelineconnectingthemeanVashowsthetrendinvariationsoftheVawiththecompactioneffort.TheindividualandmeanVavalueswerefoundtobeintherangeof10–22%,and10–20%,respectively.AsperthestandardrequirementsofASTMD7064[15],PFCmixesshouldhaveaminimumVaof18%.ThemeanVacorrespondingtothemixesM19（G4-35-4.5）,M20（G4-35-5.0）,andM21（G4-50-4.5）satisfiedthisrequirement,while,themixesM7（G2-35-4.5）,M8（G2-35-5.0）,M9

（G2-50-4.5）,M13（G3-35-4.5）,andM15（G3-50-4.5）seemtosatisfythisrequirementataconfidencelevelof95%.However,inthemixestestedfor75blows,theindividual,mean,andupperlimitsof95%confidenceintervalofmeanVafailedtosatisfytheminimumVarequirement.AllmixescorrespondingtothegradationG4,i.e.,M19–M24werefoundtohavemeanVaofmorethan15%.ThereductioninthemeanVaduetochangeinthecompactionlevelfrom50blowsto75blowswasfoundtobeintherangeof0.6–3.2%.Similarly,changeincompactionlevelfrom50to35

blows,resultedinanincreaseinmeanVaintherangeof0.2–2.9%.

3.2.Verificationofstone-on-stonecontactcondition

Thepresenceofstone-on-stonecontactconditioninthecoarseaggregateskeletonisconsideredtobemust,forthebestperformanceofPFC[15].InthecompactedPFCmix,stone-on