縱向接縫密度的實踐狀態.pdf

《縱向接縫密度的實踐狀態.pdf》由會員分享，可在線閱讀，更多相關《縱向接縫密度的實踐狀態.pdf（31頁珍藏版）》請在三個皮匠報告上搜索。

1、Longitudinal Joint Density State of PracticeDave Johnson,P.E.Alaska Asphalt Pavement SummitAnchorage AlaskaNovember 6,2023Background InformationCase StudiesBest PracticesQuestionsOutlineBackgroundWhat we“know”Asphalt Institute study(2012)showed that longitudinal joint construction is an area where c

2、onsensus is nearly unachievable,but that with attention to detail,we can produce good joints with differing techniques.Longitudinal Joints are most pavements weakest pointTypically,joint density is 2%less than mat densityUnsupported edge will usually have the lowest densityJoint density specificatio

3、ns typically 89-92%of TMDFor each 1%loss in density=about 10%loss of lifeAreas of General AgreementCase Studies August 2021 26-Mile Project State Highway#8 3”CIR Two 1.5”12.5 mm Superpave Lifts 58S-28(MSCR)Mix Temperatures 250-280F at Paver 90.5 Joint Density RequiredNorth DakotaND Highway 8Notched

4、Wedge ConfigurationWillow Design DevisePaveScan RMD 2.0Unique FeaturesPhotos and graphics from Asphalt Pro Magazine and Willow DesignUnique FeaturesBreakdown Roller CAT OscillatoryIntermediate Roller(s)CAT Vibratory(Primarily used)Sakai Vibratory Pneumatic(Used on hot days when tenderness appeared)F

5、inish Roller CAT Vibratory in Static Mode Results94.8%Joint Density(93.9%Matt Density)Courtesy of Asphalt Pro MagazineState Trunk Highway 237.5-Mile Project 22,230 T 19 mm 2.25”1st lift 18,289 T 12.5 mm 1.75”2nd lift 58-28S(MSCR)290F at Breakdown Roller90.5 Joint Density RequiredWisconsinSTH 23Uniqu

6、e FeaturesPaving Speed Set as 22ft/minBreakdown Roller Sakai High Frequency VibratoryIntermediate Roller(s)BOMAG PneumaticFinish Roller BOMAG SteelCourtesy of Asphalt Pro MagazineUnconfined Joints206 Nuclear TestsAveraged 93.3%Confined Joints 224 Nuclear TestsAveraged 94.5%+95%of joints received max

7、imum bonusesResultsVoid Reducing Asphalt Membrane Heavy application of modified binder 18 inches in total Material wicks up to fill voidsOther TechnologyExisting Pavement1.5”final depth of mixLJScalculated 63%of mix final heightCross Sectional View at Longitudinal Joint15Materials Solution to Longit

8、udinal Joint IssuesVRAM Application MethodsPlaced by pressure distributor with mechanical agitation in tankManual strike off box fed from melting kettle Tow behind melter applicator16Materials Solution to Longitudinal Joint IssuesStates implementing specs or have had demos(2021)Best PracticesCommon

9、on AirportsNo cold jointCreates the best possible jointNot practical for all projects Traffic Production EquipmentEchelon Paving Courtesy of Gohkan Alay Required on most airports Eliminates low density material“Waists”material Avoid tearing Must do when mix still warm(temperature sweet spot)Critical

10、 to cut straight(stringline)Easier with long wheelbase vehicleCutting Back the JointJackson MS AirportNo guideline!No cutting wheel or guideline!Unacceptable Cutting Cutting wheel,but no guideline.Not straight.Joint Construction MethodsReference Knik Construction Infrared Joint HeaterPros:Can achiev

11、e good density and aggregate interlockNo additional labor requiredNo waste asphalt or edge cleanup“pretty”joint no bridging/stackingCons:Limits paving productionAdditional aging of asphaltWill not work well with any moisture in the pavementDoes not heat full depth First Pass Must Be Straight!String-

12、line should be used to assure first pass is straightStringline for reference,and/or Skip Paint,Guide for followingIf not straight,impossible to get consistent overlap with next passBest Way to Roll an Asphalt Joint6”4”-6”4”-6”Option 1Hang over 4-6”RollerRollerOption 21st Pass 4”-6”inside2nd Pass han

13、g over 4”-6”Rolling Unconfined Side?50-50 on Where to Put 1st PassRollerWhen Closing Joint,Set Paver Automation to Never Starve the Joint of Material Target final height difference of+0.1”on hot-side versus cold side NH spec requires 1/8”higher If hot-side is starved,roller drum will“bridge”onto col

14、d mat and no further densification occurs at jointProper Overlap:Cutback or milled:.5”+0.5”If not cutback:then 1.0”+0.5”Bumping the Joint?1st pass entire drum on hot mat with roller edge off joint approx.6-12”2nd pass overlaps on cold mat 3-6”Rolling Confined Side Kneading action helps provide tight

15、er surface that is more dense and less permeable compared to drum rollers.Keep these away from unsupported edge to avoid excessive lateral movement of mat Use during intermediate rolling of supported edge Not finish rollingConsider Pneumatic Rubber Tired RollersQuestions?AI Longitudinal Joint Webpage