英翻中.docx

英翻中.docx

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英翻中

EnglishLiterature

1MAINTENANCE

MaintenanceisafundamentalaspecttoconsiderinanyprojectinvolvingOGFCorPA,sincetheseactivitiescannotbeperformedinthesamewayasforconventionalDGHMA.ThefirstpartofthissectionreviewsthemainissuesassociatedwithwintermaintenanceinbothOGFCandEuropeanPAmaterials.Next,surfacemaintenanceisdiscussed,followedbyasummaryofcurrentrehabilitationpracticesforOGFCandPA.

1.1WinterMaintenance

Ingeneral,open-gradedmixturesexhibitlowerthermalconductivityandreducedheatcapacitycomparedwithDGHMA（18）.ElevatedairvoidscontentsinOGFCreducetheflowrateofheatthroughthematerial.Infact,thethermalconductivityofOGFCcanbe40to70percentthemagnitudeofthatforDGHMA,makingOGFCoperateasan“insulatingcourse”atthesurface（16）.

Asaresultofthesethermalproperties,thesurfaceofOGFCcanexhibittemperatures1to2°C（1.8to3.6°F）lowerthanthesurfacetemperatureofadjacentDGHMA,producingearlierandmorefrequentfrostandiceformation（6,16）.Longerperiodsundersuchconditions,comparedwithDGHMA,arethusexpected.TheoccurrenceofthisphenomenoninPAhasbeenidentifiedinEurope（3,16）,intheUnitedStates12,andspecificallyinTexas13.Thus,thetimetoreachadequatepavementfrictionvaluesaftericeformationhasoccurredislongerinporouspavement（16）.Infact,formationofblackiceandextendedfrozenperiodsarecurrentlyconsideredthemainproblemsassociatedwithOGFCmaintenanceintheUnitedStates12.

Consequently,OGFCrequiresspecificwintermaintenancepractices.Forexample,inadditiontoconventionalpracticesforwintermaintenance,theuseofpavementconditionsensors,meteorologicalinstrumentation,andconnectinghardwareandsoftwareissuggestedtomonitortheroadsystemandsupportthedecisionprocessinvolvingwhenandhowtotreatanOGFCsurface（5）.

Moresalt（ordeicingagents）andmorefrequentapplicationsthanonDGHMAarerequiredtoperformwintermaintenanceonOGFCandPA（15,16,18,32）.InTexas13,deicingagentsarecurrentlyconsideredthemosteffectivewintertreatment,followedbyliquiddeiceragentsandsand.However,FHWArecommendsdevelopingsnowandicecontrolusingchemicaldeicersandplowingandavoidingtheuseofabrasivematerialstoimprovetraction（20）.

Spreadingofsandtoenhancefrictionandhastendeicingcontributestothecloggingofvoids,causingadecreaseindrainageandnoisereductioncapabilities,whichareconsideredtwoofthemainOGFCadvantages（5）.

SincethedeicercanflowintoanOGFCinsteadofremainingatthesurface,OregonDOThassuggestedresearchonorganicdeicerswithhigherviscosityandelectrostaticchargetechnology（similartothatemployedinemulsifiedasphalt）toimprovebondingofdeicersonthesurface（15）.

IntensiveapplicationofliquiddeicingsaltshasallowedBelgiumtoobtainsimilarconditionsbetweendenseandporousmixturessubjectedtosnowyweather.Further,higherfrequencyofapplicationand25percentmoreliquidsaltingarereportedinTheNetherlandstoaddresswintermaintenancedifficultiesinPA（3,6）.Furthermore,theuseofliquidchloridesolutionswasreportedinthecoldAlpineregionsofItaly,Austria,andSwitzerlandasmoreeffectivethantheuseofsolidsalt（5）.Onthecontrary,aJapanesestudyconcludedthatfundamentalmodificationsarenotrequiredtopracticewintermaintenanceinPAsurfaces,sinceconsiderabledifferencesbetweenthesemixturesandDGHMAwerenotfound（33）.

BritainpracticespreventivesaltingjustbeforesnowfallandmorefrequentapplicationofsaltincomparisonwithDGHMA（18）.TheyrecommendincreasingtheamountofsaltappliedonDGHMAsectionsthatareadjacenttoPAsegments.ThisrecommendationisduetothereductioninthetransferofsaltfromthePAtotheDGHMAandthedifferencesinresponseofeachmaterial.Additionally,theyproposepromptplowingofsnowusingplowsfittedwithrubberedgesontheblades（topreventsurfacedamage）.Finally,greatercontrolinthehomogeneousapplicationofdeicingchemicalisrequiredinOGFC,asthetraffichasminimalcontributioninitsdistributionovertheOGFCsurface（5）.

1.2SurfaceMaintenance

AccordingtoasurveyconductedaspartoftheNationalCooperativeHighwayResearchProgram（NCHRP）Synthesis284,therearenoreportsintheUnitedStatesontheapplicationofmajormaintenanceforOGFC.From17statesthatreportedtheuseofOGFC,onlyNewMexico,Wyoming,SouthCarolina,andOregonemployfogsealstoperformpreventivemaintenance.

AlthoughquantitativeinformationaboutthesignificanceofthesetreatmentswhenappliedtoPAisnotavailable,itisexpectedthatfogsealsextendthelifeofporousmixturessincetheyprovideasmallfilmofunagedasphaltatthesurface（15）.FHWArecommendsfogsealapplicationintwopasses（atarateof0.05gal/yd2foreachpass）usinga50percentdilutionofasphaltemulsionwithoutanyrejuvenatingagents（20）.

ResearchinOregonregardingpermeabilityreductionandchangesinpavementfrictiononcertainOGFCpavementsgeneratedbyfogsealsconcludedthatthemixturesstillretainporosityandkeeptheroughtexturerelatedtoitscapabilitytoreducethepotentialforhydroplaning（15）.However,quantitativeconclusionsregardingthechangesintheseparametersarenotincluded.Adecreaseinpavementfrictionwasnoticedimmediatelyafterfogsealapplication,butduringthefirstmonth,itincreasedconsiderablybytrafficaction.

SnowplowbladeabrasionhasconsiderableeffectsonthedurabilityoftrafficmarkingsonOGFC.Thermoplasticmarkingsorevensomefragmentsofmixtureimpregnatedwiththermoplasticcanbedisplacedwhensteelsnowplowbladesareusedforwintermaintenance.

FieldtrialsinRhodeIslandshowedthelackofdurabilityofthepermanentinlaidtrafficmarkingtapeonmodifiedOGFCundersuchconditions.Therefore,theyrecommendedsuspensionoftheuseofpermanentinlaidtrafficmarkingtapeuntilcorrectionscanbeimplementedtoimprovedurability（34）.

RhodeIslandfurtherreportedthatrecessedthermoplastictrafficmarkingsprovedcosteffectiveincomparisonwithnon-recessedthermoplasticmarkings.Althoughrecessedthermoplastictrafficmarkingsshowedlowersnowplowbladedamage,fullyandsemi-recessedmarkingsinstalledinatangenthighwaytestsectionfailedtomaintaintherecommendedminimumretroreflectivityinwetnightconditions.Thisresultwasassociatedwiththeeffectofthewaterfilmpresentinthetangentsectionbutwasirrelevantinthesuper-elevatedcurvedtestsectionincludedintheresearch（34）.

HighwayagenciesinBritishColumbia,SouthCarolina,andMarylandreportedthatthermoplasticmarkingmaterialwasthemostappropriateforOGFCapplications（16）.TheBritishlimittheuseofpavementmarkingswiththermoplasticmaterialstocertaindirectionalsignsandarrows,consideringthatonPAthemarkingmaterialhasmoreopportunitytoflowdownwardintothemixture（18）.AlthoughhigherdemandofmarkingmaterialinOGFC（duetohigherporosity）wasreportedbysomeagenciesintheUnitedStates（e.g.,Ohio,NewYork,andOregon）,therewerenospecificrecommendationsregardingmaterialsfortrafficmarking（16）.

CleaningofOGFCintheUnitedStatesisnotcommonpractice.ThisapproachindicatesthatlocalagenciesacceptthatOGFCfunctionalitycanbemaintainedduetoitsauto-cleaningcapacitycreatedinhighwayswithrelativelyhighspeedandhighvolumesoftrafficbythesuctiongeneratedbytiresrollingontheOGFC（5）.

High-pressurewashingiscurrentlyquiteexpensiveandofquestionablevalue.CurrentmaintenanceactivitiesinDenmarkincludecleaningofthevoidsbyhigh-pressurewaterandairsuctiontwiceayearasastrategythatcombinestheconstructionoftwo-layerdrainageasphaltandcleaninginordertomaintainporosityduringthepavementlifetime（11）.Ingeneral,EuropeanpracticelimitsplacingofPAonhighwayswithspeedshigherthan50km/h（31mph）tohelpinkeepingthesurfaceclean（10）.

Ontheotherhand,Japanisapplyingthe“functionmaintenance”conceptthatcomprisesmorefrequentcleaningoperationswithonlypartialdebrisremovalduringeachcleaning（31）.

1.3CorrectiveSurfaceMaintenance

MillandinlayusingOGFCwasrecommendedinOregontorepairOGFCwhenthequantitiesofmaterialwereenoughtojustifytheseactivities.Ifonlyasmallquantityisneeded,DGHMAissuggestedforpatching（15）.FHWAadvisesonetoconsidertheareaandthedrainagecontinuity（20）.Thus,whentheareatoberepairedissmallandtheflowaroundthepatchcanbeensured,DGHMAisrecommendedforpatching.Otherwise,thezoneshouldberepairedbyusingOGFCmixture.Nonetheless,in2000,theuseofDGHMAtorepairdelaminatedareasandpotholeswasindicatedbyallstatesintheUnitedStatesthatreportedtheutilizationofOGFC.CrackfillingwasreportedonlybyWyomingDOT,andaccordingtotheirexperience,drainageproblemscanresultfromcracksealing,sincewaterflowinsidethematerial

isdiminished（16）.

InBritain,theuseofPAoropen-gradedmacadamisrecommendedtorepairbothsmallandlargepotholes.Theuseofdensebitumenmacadamispermitted,ifnecessary,butitsreplacementbypermeablemixtureisrecommended.Finally,theapplicationofhot-rolledasphalt（HRA）islimitedforrepairingsmallareas（i.e.,ontheorderof0.50m×0.50m[1.64feet×1.64feet]maximum）（18）.

TodiminishthewheelimpactonthepatchjointandfacilitatetheflowofwateraroundaDGHMApatch,rotationofthepatchto45degreestoprovideadiamondshapeisrecommended.

Alternatively,theexecutionofmachinepatch,bladepatch,orscreedpatchmaybeused