ManagingDensityFor

AsphaltPavement

1

Densityvs.

PavementPerformance

2

CostofCompactionCostofCompaction

Leastexpensivepartoftheprocess

Compactionaddslittletothecostofatonofasphalt

ImportanceofCompactionImportanceofCompaction

Nf = -1361.88*AV2 + 15723.35*AV + 88162R2 = 0.98

60,000 70,000 80,000 90,000

100,000 110,000 120,000 130,000 140,000 150,000 160,000

0.0 5.0 10.0 15.0

Fatig

ue L

ife, c

ycle

s

Air Voids, %

Effect of Percentage of Air Voids on Fatigue Life20C, 500 microstrain UKAIStudy

1.5%increaseindensityleadsto10%increaseinfatiguelife.

FieldDensityTesting

5

QualityControl&AcceptanceofJointDensity

DensityGauge 6inchCore

CompactionofHMAPavements

Coresdeterminedensity Qualitycontrol Payment Differentfromnuclear Correlatereadings

25mm(1")

CompactionofHMAPavementsNucleargauges Setuprollingpattern Usedforqualitycontrol Adjustrollingwhen

Mix Conditionschange

FactorsAffectingCompaction

9

FactorsAffectingCompactionFactorsAffectingCompaction

MixProperties Aggregate Asphalt Air(Volumetrics) MixTemperature

LiftThickness

Subgrade&BaseSupport

EnvironmentalFactors

TypeandSizeofRoller,#ofPasses

EffectofAggregateEffectofAggregate

Gradation Continuouslygraded,gapgraded,etc.

Shape Flat&elongated,cubical,round

SurfaceTexture Smooth,rough

Strength Resistancetobreaking Abrasion

AggregateTypes

Natural Processed Synthetic

Round(uncrushed) SingleCrushedFace MultipleCrushedFaces

Mixtures Compactionvaries Adjustthicknessforrolldown

Matchmatthickness

AsphaltMixtures

PerformanceGradedBinders

PG6422

PerformanceGrade

Average7daymaxpavementtemperature

Minimumpavement

temperature

147.2F 7.6F

LoadingRateofLoading

Example Mainlinepavement

PG6422

TollboothPG7022

WeighStationsPG7622

70mph

Slow

Stopping

EffectofTemperatureMatTooHotEffectofTemperatureMatTooHot

Bulgesinfrontofdrums Mixmoves&willnot

compact RollerleavesdeepmarksSolution Staybackfrompaver Allowmattocool(stiffen)

EffectofTemperatureMatTooColdEffectofTemperatureMatTooCold

Lowerlimit180o F Noadditionalcompaction

Noaggregatemovement Crushingaggregate

Solutions Closertopaver

Slowpaver Addrollers

Increasemixtemp

EffectofLiftThicknessEffectofLiftThickness

Optimumliftthickness 4xNominalMaximumAggregateSize(NMAS)

Acceptableliftthickness=3xto5xNMAS ProblemsCompacting

2xNMASorless 6xNMASormore

Especiallycriticalpavingonunevensurfaces

Superpave MaxSize,Designation mm

37.5mm 50.025.0mm 37.519.0mm 25.012.5mm 19.09.5mm 12.54.75mm 9.5

Remember:

AsphaltMixDesignation

30

20

10

01 2 3 4

TimeforC

ompa

ction,m

in

CompactedThickness,in

30F60F90F

MS22QualityConstructionTable6.03(b))

Increasingtheliftthicknessbyinchadds67minutestoavailablecompaction

time.

LiftThickness

EffectofSubgrade&BaseSupportEffectofSubgrade&BaseSupport

Goodsupportcriticaltoobtainproperdensity

Spongyorunstablesupport

Provideslittleresistancetotherollers

Mixturenotconfined,energydisipated

Mixturemoves&cracksratherthancompacts.

EffectofEnvironmentalFactorsEffectofEnvironmentalFactors

Factorsaffectinghowfastthemixcools Affectstimeavailableforcompaction

Ambientairtemperature Temperatureoftheexistingsurface Windspeed Liftthickness Asdeliveredmixtemperature Overcastconditions

EffectofEnvironmentalFactorsEffectofEnvironmentalFactors

MinnesotaDOTsPaveCool

Excellenttooltodeterminecompactiontime

Basedallfactors Freedownload

http://www.dot.state.mn.us/app/pavecool/index.html

ForcesofCompaction&RollerTypes

24

EffectofRollerType,Size,PassesEffectofRollerType,Size,Passes

Rollertypeandsizeaffects:

Magnitudeoftheload Howtheloadisapplied

Numberofpasses: Increasesthedensity Tobreakoverpointaftera#ofpasses

Lowerscompaction Ifcontinued,damagesmat

ForcesofCompactionForcesofCompaction

Compactionforces Lowforce

Staticpressure Manipulation

Higherforces Impact Vibration

RollerTypesRollerTypes

SteelWheeled Pneumatic Vibratory

StaticSteelWheeledRollersStaticSteelWheeledRollers

414tonrollersappliesstaticforce 3Wheel Vibratoryrollersinstaticmode Lighterrollersforfinishrolling Drivewheelmustfacepaver

Climbsuncompactedmix Tillerwheelpushesmix

Drumsmustbesmoothandclean Waterspray&scraperbars Criticalforpolymermodifiers Avoidrollersusedonagg base

PneumaticRollersPneumaticRollers

Kneadingactionreorientsaggregate Tirepressures:

~80psi(cold)forcompaction ~50psi(cold)forfinishrolling Rangenottoexceed10psi

Tiresmustbehottoavoidpickup Tiresmustbesmooth notread Notusedfor

Porousfriction SMA Polymermodifiedmixes

PneumaticRollersPneumaticRollers

Forceis: Weightontiredividedcontactarea ExpressedasPSI

ChangePSIbychanging: Tirepressure Ballast

Lowtirepressure Lowforce

Hightirepressure Highforce

PneumaticRollersPneumaticRollers

Frontrearaxlesoffset Manipulatesmix Under&betweentires

Tightenfinish Toresistmoisture

Loweringpressure Increasesmanipulation

Increasingpressure Increasesstaticforce

PneumaticRollersPneumaticRollersKeeptireshotandclean: Driveback&forthoncoldmat

Upto30minutes Internallyheattires

Keepmovingtokeeptireshot Skirtsmaybeneededtoretainheat Scrubbersmustbeused

Knockoffanyaccumulation Onlyusereleaseagent

Oncepickupstarts Markswillnotcomeout Tiresdifficulttoclean

VibratoryRollersVibratoryRollers

Commonlyusedforinitialrolling Breakdown Largestcompactionincrease

Heavy rollers Heavydutycomponents&frames 818.5tons,5784inwide 50200lbs/linearinch(PLI)

Frequency:27004200impacts/min Amplitude:0.0160.032in

Thinoverlays(2in) Lowamplitudeorstaticmode

Operateatleast10impacts/foot 24mph

VibratoryRollersVibratoryRollers

Effectiveness Movementofdruminitiatesparticlemotion Whenparticlesaremoving

Resistancetodeformationisreduced Forceappliedbyweightofdrumplusinertia

Producesagreatercompactiveeffect Achievingmorecompactionperpassthanstaticrollers

VibratoryRollers AmplitudeVibratoryRollers Amplitude

Spinningeccentricweightcausesdrummovement

Fallingdrumaddstocompactiveforce

Distancedrummovesiscalledamplitude

Amplitudedeterminesimpactforce

HighAmplitudeLowAmplitude

VibratoryRollers AmplitudeVibratoryRollers Amplitude

Amplitudetoohigh Travelspeedtoofast Vibratingcoolmat

Rollclosertopaver Finishrollingtoocool

Rollclosertointermediateroller

Finishrollertoolight

VibratoryRollers FrequencyVibratoryRollers Frequency

Frequency Drumimpacts

perminute Matchtravelspeed

tofrequency Bestresultswhen

impactspacingis1014perfoot

VibratoryRollers FrequencyVibratoryRollers Frequency

VibratingReedTachometer Checkstheaccuracyoftherollersfrequencyreading Containsagroupofreedswithaspecificnaturalfrequency AsasinglevibratingdrumpassesVRT

Observewhichreedisvibrating Checkvalueoffthemachinetachometer

VibratoryRollers FrequencyVibratoryRollers Frequency

DrumImpactsperFootDrumImpactsperFootFrequency 2 MPH 3 MPH 4 MPH 5 MPH2000 vpm 11.36 7.58 5.68 4.552200 vpm 12.50 8.33 6.25 5.002400 vpm 13.64 9.09 6.82 5.452600 vpm 14.77 9.84 7.39 5.912800 vpm 15.91 10.61 7.95 6.363000 vpm 17.05 11.36 8.52 6.823200 vpm 18.18 12.12 9.09 7.273400 vpm 19.32 12.88 9.66 7.723600 vpm 20.45 13.64 10.22 8.183800 vpm 21.59 14.39 10.80 8.634000 vpm 22.72 15.16 11.36 9.10

SequenceofRollerOperations&

RollerProcedures

41

SequenceofRollerOperationsSequenceofRollerOperations

BreakdownRolling IntermediateRolling FinishRolling

RollerOperations TemperatureZonesRollerOperations TemperatureZones

CompactiveForce

PressureImpactVibration

PressureManipulation Pressure

TemperatureRanges

300 260F 250 220 F 200 180 F

BreakdownRollingBreakdownRolling

Initialcompactionoperation Getsmostofthedensity Beginathighesttempwithoutmatdistortion

Workcloselytopaver Dualdrumvibratoryworksbest

Bothdrumspowered Pressure Impact Vibration

BreakdownRollingBreakdownRolling

Traditionally3wheelsteel D/Dvibratorymostcommon Vibrationmostproductive

duringbreakdown Pneumatics

Usedonbasecourses Levelingcourses

Forcesmixintocracks Compactswithoutbridgingminorruts

Leavedeepmarks hardtorollout

IntermediateRollingIntermediateRolling

Finalstepingettingdensityandinitialsmoothness Mathotenoughtoallowaggregatemovement Matalreadyclosetofinaldensity Toomuchforcewillfractureaggregate Typicalrollertype:

Traditionallypneumatic Vibratoryatlowamplitudeand/orstaticmode

FinishRollingFinishRolling

Mainpurpose Minimalcompaction Smoothness Removalofanymarks Oncesmooth,stoprolling

Typicalrollertypes: Tandemsteelwheel Pneumaticw/lowerpressure Vibratorystaticmodeonly

Den

sity

0 1 2 3 4 5# Passes

EstablishingRollingPattern

RollingPattern

Speed&lappatternforeachroller Numberofpassesforeachroller

Onetripacrossapointonthemat Setminimumtemperatureeachrollerfinishespattern

IMPORTANT: Paverspeedmustnotexceedcompactionoperation!!!

Pavermakessinglepass Rollerpatternrequires37passes

GeneralRollingProcedures

ReversingDirections Avoidstraightstops Turntowardcenterofmat Dontturndrumwhilestopped Nextpassshouldrolloutanymarkscreatedbyreversing

GeneralRollingProceduresGeneralRollingProcedures

Forbestresults Rollathighesttemperaturewithoutexcessivedisplacement

Stayclosetopaver Monitorweather

Keepupbutnottoofast Adj paverspeed

GeneralRollingProceduresGeneralRollingProcedures

152 mm (6")

Overlaps 6 overlapassuresuniformcompaction

Includeoverlapwhenselectingdrumwidth

Rollershouldcovermatin3overlappingpasses

GeneralRollingProceduresGeneralRollingProcedures

Rolldown Paverlaysthickerlift Rollercompactstothedesignthickness

Superpavemixesrolldown~25%

SMA,PFC&otheropengradedmixesrolldown~15%

GeneralRollingProceduresGeneralRollingProcedures

RollingaCrown Neverstraddlecrown Workfrombottomtowardcrownbothsides

Strengthensmattosupportrolleronslope

Overlapcrown6 onlastpass

GeneralRollingProceduresGeneralRollingProcedures

Parking Neverparkonahotmat Leavesatransversebumpthatcannotberolledout

Whenservicing: Rollbacktocoolermat Servicevehiclesonmat

AchievingDensityonHMAJoints

56

LongitudinalJointTypes

NotchedWedge

Butt

ButtJoint(paverconstruction)

ButtJoint(milledorcutback)

NotchedWedgeJoint

LongitudinalJointTypes

ProperOverlap: 1.0+ 0.5inches

Exception:Milledorsawedjointshouldbe0.5inches

Rolldown 1525%basedonmix

Roller

6

4 6

4 6

Option1Hangover46

Roller

Roller

Option21st Pass46inside

2nd Passhangover46

RollingUnsupportedEdge?

Option11stPassHangsOver46inches

Option2:StayBack46incheson1st pass,thenroll

2nd passw/slightoverhang

Concern: Developingstresscrack?

Merit: Minlateralmovement?

DontStarvetheJoint

1st passoffthejointapprox68inches

2nd passoverlapsoncoldmat36inches

RollingtheSupportedEdge

Roller

Rollerinvibratorymodewithedgeofdrumoverhanging2to4inchesoncoldside.

AlternateMethod1st PassovertheSupportedEdge

ConcernwiththismethodisifinsufficientHMAlaidatjoint,thenbridgingoccurs(rollersupportedbycoldmat)

Overlap

TransverseJointStartingaLaneTransverseJointStartingaLane

Paver

New Old

150mm(6") Rolltransverse Rollstatic Startdrumoncoldside Moveoverin6 8

incrementsuntildrumisallonhotside

TransverseJointStartingaLaneTransverseJointStartingaLane

RollingTransverseJoint

CheckingTransverseJoint

SafetyandTrafficControlConcernsSafetyandTrafficControlConcerns

ReferenceMaterialsontheTopic:

MS2: MixDesignMethods

SP2:Superpave MixDesign

MS4: TheAsphaltHandbook

MS22: HMAConstruction

http://www.asphaltinstitute.org

ThankYou

WayneJones,P.E.AsphaltInstitute6148551905wjones@asphaltinstitute.org

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