eoftheresearchersadoptedorsuggestedthelowerlevelsoftheMarshallcompaction,forcharacterizingthePFCmixes[–]...ObjectiveandscopeThemainobjectiveofthisinvestigationwastocharacterizethePFCmixesforthreelevelsoftheMarshallcompaction.Thecompactionlevelsinvestigatedinclude,,andblowsappliedoneachendofthespecimen.TheeffectofeachcompactionlevelwasstudiedoneightdifferentPFCmixes,whichcorrespondedtofourdifferentquentlypooradhesionbetweenthemasticandaggregateresultsinravelling.Experienceswiththeuseofopen-gradedmixesintheUSAindicatedthatravellingwasoneofthemajorissuestobetackled[].Thus,structuraldurabilityofPFCsneedstobeensuredbasedontheresistancetoravelling[].SomeoftheexperienceswithPFCsinJapan,thepoorperformancewasrelatedtothelackofcompaction,orcompactionatlowertemper-aturesthanthespecified[].PermeabilityandsoundattenuationcharacteristicsarethemainmeasuresofperformancelifeofPFCs[].StudiesperformedontestsectionsinDenmark,indicatedthatdeterioratedmasticmaterialscloggedthelarge-sizedairvoidsinPFCs,whichledtotheformationofhigherpercentageofsmall-sizedvoids[].Clog-gingwasfoundtobemorepronouncedonolderpavement,especiallyalongthewheelpath,andalsointheemergencylanes[].Although,PFCsarecomposedofrelativelyuniformly-gradedaggregate[],theuseofthickerPFCsmayundergosecondarydensificationduringservice,resultinginlossofpermeability.Thus,thelossofpermeabilitycanbedirectlyrelatedtocloggingofvoidsduetointernalandexternalmaterials,anddensificationundertraffic[].Anoptimaldesignmixshouldensurehighairvoidscontentandgoodresistancetoravelling.ProcedureformixdesignofPFCsrecommendedbyvariousagenciesincludetheevaluationofdrain-downlossesinloosehotmixes,airvoidscontent,stone-on-stonecontactcondition,permeability,andtheabrasionresistanceusingtheCantabroabrasiontestmethod[,,,].Oneofthemajordifferencesobservedinthespecificationsbyvariousagenciesisthatoftheconsiderationoftrafficvolumeintheoptimummixselectioncriteria.Theminimumairvoidscontentandthemaximumabrasionlossspecifiedbysomeoftheagenciesweredependentonthetrafficvolume[,,],whereas,thisdependencywasnotconsideredbymanyagenciesintheUSA[,,,].ThelevelofMarshallcompactionsuggestedbymanyagencieswerefoundtobeblowsperface,irrespectiveofthetrafficvolume.Inaddition,intherecentpastmanyresearchersadoptedthesameleveloftheMarshallcompactionforthedesignofPFCmixes[–].However,someoftheresearchersadoptedorsuggestedthelowerlevelsoftheMarshallcompaction,forcharacterizingthePFCmixes[–]...ObjectiveandscopeThemainobjectiveofthisinvestigationwastocharacterizethePFCmixesforthreelevelsoftheMarshallcompaction.Thecompactionlevelsinvestigatedinclude,,andblowsappliedoneachendofthespecimen.TheeffectofeachcompactionlevelwasstudiedoneightdifferentPFCmixes,whichcorrespondedtofourdifferent件下平均间接抗拉强度比值,试验要求温度为_C。按照ASTMD[]规定要求,.每种混合料需要准备个一样试件,然后从每组选出三个试件分别作干燥和潮湿条件下ITS试验。潮湿条件下试验按AASHTOT[]规定,主要做如下修改:所有压实混合料不论空隙率如何都经过潮湿条件处理。根据印度公路协会建议石质基沥青设计(方法),可以得到冻融循环次数。但是这与沃森等人建议不相符。例如,只有一个冻融循环值满足PFC混合料水分条件要求。图显示了种混合料在干燥条件下间接抗拉强度平均值(ITSd)。在所有混合料(ITSd)值中,对应G和G集料等级混合料表现出较高和较低两个极端。在对应G(M–M)六组混合料中,(ITSd)平均值没有超过Kpa。另一种对应集料等级为G(M–M)情况下,人们发下(ITSd)平均值最小值也超过了Kpa。压实程度比较高混合料具有较高ITS值,比较之下粘合剂含量较高混合料ITS值则相对较低。ITS值升高主要由于混合料压实度提高引起空隙率降低。然而,沥青含量升高会形成较厚沥青层,导致骨料颗粒之间摩擦力减少,进而引起(混合料)强度降低。图显示了每种混合料抗拉强度比(TSR)。M(G--.)和M(G--.)混合料抗拉强度在摄氏度潮湿条件下下降很大,因此,这些混合料潮湿条件实验温度降到了摄氏度。一般来说,TSR最小值能到达时候,人们认为这种材料拥有良好抗水敏感性。但是TNZ推荐TSR最小值为.在目前研究种,不满足上述要求混合料要么是对应最低压实水平(次),要么是最低BC值(.)。所有压实次数为混合料都满足TSR最小值要求。很显然,Va值高混合料更容易受到因为受潮引起病害,与此同时,BC值最低混合料对应更薄沥青层,从而导致抵抗受潮引起病害能力相对降低。.未老化磨耗损失Cantabro磨损试验方法用于检验未老化PFC试件磨耗损失。试验试件放在没有任何磨损物洛杉矶磨耗试验机中,机器以每分钟–转转速转动圈。试件损失质量与试件初始质量相比得到百分比定义未未老化磨耗损失(UAL)。按照ASTMD相关规定,试验过程中温度要保持在_C范围之内。G等级混合料经过了UAL试验。试验证明该等级混合料更容易受到磨耗损失影响,因为这种混合料有较高Va和K值,以及较低ITS值。图显示了UAL试验结果。按照规定,未老化试件磨耗损失最大值不得超过。在目前调查中,M混合料个体和平均UAL值均满足要求。压实水平低(次)试件平均UAL值低于,试验中没有任何试件UAL值超过。UAL平均值上限远远小于(置信度)。压实度和沥青使用量增加,都会引起UAL平均值显著下降。结论和建议为了表征PFC特征,我们用不同马歇尔压实度进行实验室试验。PFC混合料对应四种集料级配和两种沥青含量(分别站混合料总体积.和.),压实度对应三个等级,次,次和次。通过评价作用于PFC混合料多种特性各种(作用)效果,我们可以得出以下结论:——G和G等级混合料各自特性表现出两个极端。G等级混合料有较高毛体积比重,较低空隙率和渗透性。该种混合料VCAm和ITSd值相对较高,——采用最低压实度G和G等级之间PFC混合料,粗骨料之间石料与石料连结,因此人们认为这种混合料使用性能是最好。——很显然,在经过最高压实水平(次)所有混合料中,只有G等级混合料Va最小平均值为,最小K值为m/day.。——从统计中分析,压实水平和集料等级对PFC混合料设计性质有重大影响,然而粘合剂含量改变对VCAm.没有显著影响。在相似集料混合料中,压实水平对Va和VCAm值变化起主要作用。并且,K值变化也主要与集料等级和压实水平变化相关联。——干燥条件下PFC混合料间接抗拉强度在-Kpa范围内变化。TSR最小值达不到混合料对应较低粘合剂含量和较低压实水平。不过,在所有试件中没有任何试件TSR值小于。——基于混合料多种特性试验得出结果,可以推测G和G等级混合料在各种反映特性中发生变化不大。各种组织机构制定规范中一般推荐PFC混合料压实水平为次。然而,上述试验结果显示,压实度对空隙率,渗透性以及抗磨损性都有重要影响。为了满足最小空隙率要求,推荐PFC混合料设计压实水平采用次。次水平马歇尔压实试验可以用来检验过分压实PFC混合料特性。另外我们还推荐G等级集料于PFC混合料可以用来做重交通行车道路面,相对细小G和G等级集料也推荐用于PFC混合料——用于相对和缓轻交通行车道路面。(上述)这些(建议)除了进行实验室比较之外,还需要在实地进行检验。鸣谢:所有作者非常感谢(印度)科学技术部在FIST–中对该研究资金支持,以及卡纳塔克邦国家技术学院提供基础试验设施,人力资源及其它及时帮助。quentlypooradhesionbetweenthemasticandaggregateresultsinravelling.Experienceswiththeuseofopen-gradedmixesintheUSAindicatedthatravellingwasoneofthemajorissuestobetackled[].Thus,structuraldurabilityofPFCsneedstobeensuredbasedontheresistancetoravelling[].SomeoftheexperienceswithPFCsinJapan,thepoorperformancewasrelatedtothelackofcompaction,orcompactionatlowertemper-aturesthanthespecified[].PermeabilitCharacterizationofporousfrictioncoursemixesfordifferentMarshallcompactioneffortsDepartmentofCviliEngnieernig,NatoinalInsttiuteofTechnologyKarnataka,Surathka,lMangaolre,IndiaABSTRACTPorousfrictioncourses(PFCs)aremainlyrecommendedassurfacedrainagelayersonhigh-speedroadcorridorsandrunwaypavements.PermeabilityandsoundattenuationcharacteristicsareconsideredtobetheindicesforperformanceassessmentofPFCs.OneofthereasonsforthelossofpermeabilityinPFCsisdensificationunderheavytraffic.But,resistancetoravellingtoo,isofmainconcerninthecaseofunder-compactedPFCs.ThispapersummarisesthedetailsoflaboratoryinvestigationonthecharacterizationofPFCmixescorrespondingtofourdifferentgradationsandtwobindercontents,forthreelevelsoftheMarshallcompaction.ThefindingsoftheinvestigationsuggestthattheselectionofthecompactionlevelforPFCmixdesignshouldbebasedonthedesigntrafficlevel,andthegradationselected.ElsevierLtd.Allrightsreserved.Keywords:PorousfrictioncoursePorousasphaltMarshallcompactionAirvoidsVoidsincoarseaggregatePermeabilityMoisturesusceptibilityAbrasionloss.IntroductionPorousfrictioncourses(PFCs)aretypicalopen-gradedasphalticmixes,composedofrelativelyuniformly-gradedaggregateandasphaltcementormodifiedbinders,andaremainlyusedtoserveasdrainagelayers,eitheratthepavementsurfaceorwithinthepavementstructure[].Pavementssurfacedwithopen-gradedasphalticmixeswerefoundtoimprovewetweatherskid-resistance,minimizehydroplaning,reducesplashandspray,improvenightvisibilityduringwetweatherconditions,andreducetraffictyrenoise[,].IncountriesliketheUnitedStatesofAmerica,Japan,theUnitedKingdom,Malaysia,Australia,NewZealand,andSouthAfrica,open-gradedmixesareinuseassurfacelayersoverhigh-speedandheavilytraffickedhighwaypavements[–].Thesearealsorecommendedforsurfacingrunwaypavements[-].Manyagenciesaroundtheworldusedifferentterminologiesforopen-gradedmixes,andspecificationsthatareslightlydifferent.Thevariousterminologiesusedincludeopen-gradedasphalt(OGA),porousasphalt(PA),open-gradedfrictioncourse(OGFC),andporousfrictioncourse(PFC)...BackgroundThehighairvoidscontentinPFCscontributetowardspavementsurfacedrainageandinattainingnoisereduction.But,acceleratedasphalt-filmaging,maysubsequentlyleadtolossofcohesioninthemastic,consequentlypooradhesionbetweenthemasticandaggregateresultsinravelling.Experienceswiththeuseofopen-gradedmixesintheUSAindicatedthatravellingwasoneofthemajorissuestobetackled[].Thus,structuraldurabilityofPFCsneedstobeensuredbasedontheresistancetoravelling[].SomeoftheexperienceswithPFCsinJapan,thepoorperformancewasrelatedtothelackofcompaction,orcompactionatlowertemper-aturesthanthespecified[].PermeabilityandsoundattenuationcharacteristicsarethemainmeasuresofperformancelifeofPFCs[].StudiesperformedontestsectionsinDenmark,indicatedthatdeterioratedmasticmaterialscloggedthelarge-sizedairvoidsinPFCs,whichledtotheformationofhigherpercentageofsmall-sizedvoids[].Clog-gingwasfoundtobemorepronouncedonolderpavement,especiallyalongthewheelpath,andalsointheemergencylanes[].Although,PFCsarecomposedofrelativelyuniformly-gradedaggregate[],theuseofthickerPFCsmayundergosecondarydensificationduringservice,resultinginlossofpermeability.Thus,thelossofpermeabilitycanbedirectlyrelatedtocloggingofvoidsduetointernalandexternalmaterials,anddensificationundertraffic[].Anoptimaldesignmixshouldensurehighairvoidscontentandgoodresistancetoravelling.ProcedureformixdesignofPFCsrecommendedbyvariousagenciesincludetheevaluationofdrain-downlossesinloosehotmixes,airvoidscontent,stone-on-stonecontactcondition,permeability,andtheabrasionresistanceusingtheCantabroabrasiontestmethod[,,,].Oneofthemajordifferencesobservedinthespecificationsbyvariousagenciesisthatoftheconsiderationoftrafficvolumeintheoptimummixselectioncriteria.Theminimumairvoidscontentandthemaximumabrasionlossspecifiedbysomeoftheagenciesweredependentonthetra CharacterizationofporousfrictioncoursemixesfordifferentMarshallcompactioneffortsDepartmentofCviliEngnieernig,NatoinalInsttiuteofTechnologyKarnataka,Surathka,lMangaolre575025,IndiaABSTRACTPorousfrictioncourses(PFCs)aremainlyrecommendedassurfacedrainagelayersonhigh-speedroadcorridorsandrunwaypavements.Permeabilityandsoundattenuationcharacteristicsareco