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1、OverviewConstructionqualityiscrucialtothelong-termpavementperformance.Constructionfactorssuchassurfacepreparation,placement,jointconstructionandcompaction/consolidationhaveanoverwhelmingeffectonpavementperformance,whichcannotbeignoredorcompensatedforinmixorstructuraldesign.CompactionCompactioni
2、stheprocessbywhichthevolumeofairinanHMAmixtureisreducedbyusingexternalforcestoreorienttheconstituentaggregateparticlesintoamorecloselyspacedarrangement.ThisreductionofairvolumeproducesacorrespondingincreaseinHMAdensity(Robertsetal.,1996[1]).Figure1:ASteelWheelandaPneumaticTireRollerWorkingSide-
3、by-Side.Compactionisthegreatestdeterminingfactorindensegradedpavementperformance(ScherocmanandMartenson,1984[2];Scherocman,1984[3];Geller,1984[4];Brown,1984[5];Bellet.al.,1984[6];Hughes,1984[7];Hughes,1989[8]).Inadequatecompactionresultsinapavementwithdecreasedstiffness,reducedfatiguelife,accel
4、eratedaging/decreaseddurability,rutting,raveling,andmoisturesusceptibility(Hughes,1984[7];Hughes,1989[8]).CompactionMeasurementandReportingCompactionreducesthevolumeofairinHMA.Therefore,thecharacteristicofconcernisthevolumeofairwithinthecompactedpavement,whichistypicallyquantifiedasapercentageo
5、fairvoidsinrelationtototalvolumeandexpressedas“percentairvoids”.Percentairvoidsiscalculatedbycomparingatestspecimen’sdensitywiththedensityitwouldtheoreticallyhaveifalltheairvoidswereremoved,knownas“theoreticalmaximumdensity”(TMD)or“Ricedensity”afterthetestprocedureinventor.Althoughpercentairvoi
6、dsistheHMAcharacteristicofinterest,measurementsareusuallyreportedasameasureddensityinrelationtoareferencedensity.Thisisdonebyreportingdensityas:·PercentageofTMD(or“percentRice”).Thisexpressionofdensityiseasytoconverttoairvoidsbecauseanyvolumethatisnotasphaltbinderoraggregateisassumedtobeair.For
7、example,adensityreportedas93percentRicemeansthatthereare7percentairvoids(100%–93%=7%).·Percentageofalaboratory-determineddensity.Thelaboratorydensityisusuallyadensityobtainedduringmixdesign.·Percentageofacontrolstripdensity.Acontr
