Development and Use of High Performance Thin Overlays - neaupg

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Development and Use of High Performance Thin Overlays - neaupg

The Development and Use of HighPerformance Thin OverlaySystemsNEAUPG 2009 Annual MeetingPortland, MaineOctober 8, 2009Ronald CorunManager - Asphalt Technical ServicesNuStar Asphalt Refining LLC


HMA Thin Surface Mixes• Not New – in usesince the early1900’s• Originally all fineaggregate – plus AC– Could work well inlow stressapplication– But tended to rutand crack underhigher traffic /stress


HMA Thin Surface Mixes• City of Rockville,Maryland – 1960’s– Fine graded Marshallmix with AC-10– Named it“Smoothseal”


HMA Thin Surface Mixes• Ohio DOT– Borrowed Rockvilleidea and product name– First use in 1973– Added polymers in1990’s– Type A – 5/8” thick• Sand mix with 8.5% AC– Type B – ¾” thick• 4.75 mm mix with 6.4%AC


HPTO Design• Requirements– Improve Durability• Higher AC/ filmthickness mix (VMA)• Dense / nonsegregatingmix (inplacedensity)– Rut & CrackResistant• PMA Binder• High qualityaggregates• Mix performance test


HPTO – Developed to meetTwo ApplicationsLocal & Secondary Roads• Suburban development– Higher traffic and stresson pavement– Intolerance of trafficinterruption (get-in &get-out and don’t comeback)– Usual maintenancetreatments no longeracceptablePrimary & Interstate Hwy• Budget shortfallsrequire delays in somenormal rehabilitations• Need to provide a“maintenance”application until nextmajor rehab• HPTO can provide asolution


HPTO ApplicationsLocal UseDOT Use


Development of theFlexGard System• Achieving ResearchObjectives– Fatigue cracking• Increased asphalt content– Slightly gap-graded mix– Mix design at 3% air voidtarget (SGC = 50 gyrations)– Minimum 7% asphaltcontent• Specifically designed toincrease fatigue life– Thicker asphalt filmcoatings – min. VMA = 18%– Greater resistance to aging


HPTO & 9.5 mm Mix Gradation Plot100.090.080.070.0Percent Passing60.050.040.030.020.010.00.0Sieve Size (mm) Raised to 0.45 PowerMD FlexGardNJ I-5.07 .15 .30 .60 1.1 2.3 4.79.5 12.5


Development of theFlexGard System• Achieving ResearchObjectives– Balanced Performance• NCAT test track• Higher binder contentpossible with no ruttingwhen PMA used• National study - PMA– National study –increased pavementlife of 5-7 years– Significant fatigue lifeimprovement


Initial Installation of theHPTO for Local Roads• NuStar AsphaltRefinery in Paulsboro,NJ– Main entrance road– 20 year old existingHMA pavement– Approximately 5 loadedtanker trucks per day– Substantial fatiguecracking– Rutting not an issue– Minimal pavementdeflection under loads


Initial Installation of theFlexGard System• NuStar AsphaltRefinery inPaulsboro, NJ– Full depth HMApatching section inone lane– Compareperformance


Initial Installation of theFlexGard• Construction objectives– Adhesion to underlyingpavement• Require clean and drypavement• Use PG 64-22 as tack coatmaterial• Require complete and evencoverage


Initial Installation of theFlexGard System• NuStar AsphaltRefinery inPaulsboro, NJ– Constructability• Specificationdensity achievedeasily– 7% AC contentand 3% designair voids makescompactioneasier


Initial Installation of theFlexGard System• NuStar AsphaltRefinery inPaulsboro, NJ– Constructability• Transverse andlongitudinaljoints areexcellent• Projectappearance isvery good


Paulsboro FlexGard –Pavement Evaluation• Evaluation eachyear– Rut & cracksurvey– Pavement coring


Paulsboro HPTO - Cores


Paulsboro HPTO – after 3 years


Paulsboro HPTO – 3 years oldOriginalAfter 3 years


Harford County FlexGard Project


Harford County FlexGard Project


Harford County FlexGard Project


Harford County FlexGard Project


Performance Testing ofthe FlexGard Mix• Laboratory Testing– Rutting• Asphalt Pavement Analyzer(APA)– Fatigue Cracking• Flexural Beam Fatigue Device– Reflective Cracking• Texas Overlay Tester– Permeability• Flexible Wall PermeabilityTester– Skid Friction• Skid Trailer


Asphalt Pavement AnalyzerResults – Test ProjectLess than 1/3 rutting ofStandard Mix


Performance Testing ofthe FlexGard Mix• FlexuralBeamFatigueTesting– Measurenumber ofcycles tofailure


Flexural Beam Fatigue Results– Harford County Project12 X Fatigue Life of Control Mix


Climatic Loading – HorizontalHot Mix Asphalt Overlaid on PCCMovementPCCPCCHorizontal Tensile Stress due to Expansion/Contraction of PCC from TemperatureHorizontal Stress/Strain is modeled usingOverlay Tester


Overlay Tester Results – HarfordCounty ProjectNumberof CyclestoFailure15001000500077F7 times morecycles thanStandard MixStandard9.5mm MixFlexGardTestTemperatureTexas DOT requires minimum of 300 cycles to pass the test


Flexible Wall PermeabilityTesting• For PavementPreservation, importantto “seal” pavement tolimit moisture• Permeability on orderof a silt/clay, requiredtesting in “FlexibleWall” Permeability SetupSamples cored from 6-inchdiameter gyratory sample


Typical Permeability Values100 times less permeable


Surface (Skid) Friction, SN 40Material Type Skid NumberFlexGard 539.5 mm Mix (New) 51.69.5 mm Mix (4 Yrs) 54.319mm Mix (4 Yrs) 55.719mm Mix (5 Yrs) 47.7


DOT Application forInterstate & Primary Roads• Material needed for‘intermediate’maintenance application(one that extendpavement life but withoutimpact on existingclearances)• Prefer to use a ‘nonproprietary’product• HPTO can be a solution


NJ DOT HPTO Materials• New Jersey requirements– Thin-lift ≤ 25mm thick(Ideally)• eliminate change toexisting infrastructure(bridge clearances,drainage, etc.)– Minimal Impact to Users(Coverage vs. Unit Time)– Re-new and upgraderoad surface (Ride Quality- serviceability)– No “Cure-time”dependent materials– Must withstand highstresses


NJDOT HPTO - SpecificationSieve SizePercent PassingFlexGard NJ HPTO NJ 9.5 mm (I-5)12.5 mm ½” 100 100 1009.5 mm 3/8” 100 100 954.75 mm #4 65-95 65-85 602.36 mm #8 35-55 33-55 421.18 mm #16 20-35 20-35 320.60 mm #30 15-30 15-30 240.30 mm #50 10-20 10-20 150.075 mm #200 4-10 5-8 6.3Binder Type FlexGard XP PG 76-22 (PMA) PG 64-22Minimum AC% 7.0% 7.0% 5.1% Air Voids 3.0% 3.5% 4.0VMA > 18% > 18% 16.3SGC N des 50 50 75APA Rutting Max. 5 mm Max. 4 mm


NJ I-295 HPTO Project


NJ I-295 HPTO Project


NJ I-295 HPTO Project


FlexGard / HPTO SystemSummary• Can be designed for county /municipal roads as well asInterstate highways• Based on lab tests & projectperformance to date –should provide longer lifethan conventional mix(9.5mm)• User friendly - local materialsand contractors• Cost effective alternative to“mill & fill”• Good performance to datefor state agencies with PMA– Ohio DOT– NJ DOT – HPTO– NYSDOT – 6.3 mm mix


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