Stretching Pavement Maintenance Dollars Through

Pavement Preservation

By R. Gary Hicks and Ding Cheng

CP2 Center, CSU, Chico for the

Fall Asphalt Pavement ConferenceOctober 24, 2013

• Types of TreatmentsTypes of Treatments– Materials UsedMaterials Used– Design & Construction Design & Construction

ConsiderationsConsiderations– Causes of problemsCauses of problems

• Factors Affecting Factors Affecting PerformancePerformance

• Strategy Selection ProcessStrategy Selection Process

Most of this work has been supported by Caltrans

Overview of Presentation

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http://www.dot.ca.gov/hq/maint/MTA_GuideVolume1Flexible.html

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Co

nd

itio

n

Time

$1-3 for preventive

maintenance here

Costs $10-20 or more

when it’s done as rehab

Cost Effectiveness Pavement Preservation

• Fog and Rejuvenating Fog and Rejuvenating SealsSeals

• Chip SealsChip Seals• Slurry SealsSlurry Seals• MicrosurfacingMicrosurfacing• Cape SealsCape Seals• Bonded Wearing CoursesBonded Wearing Courses• Thin HMA overlaysThin HMA overlays• CIR and HIRCIR and HIR

Types of Preservation Treatments

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• Purpose- enriches dry pavement Purpose- enriches dry pavement surfaces, reduces raveling, and surfaces, reduces raveling, and locks in chips on chip sealslocks in chips on chip seals

• Materials- generally diluted asphalt Materials- generally diluted asphalt emulsions or a specialty productemulsions or a specialty product

• Design considerations- application Design considerations- application rate a function of surface condition rate a function of surface condition

• Construction- applied using a Construction- applied using a distributor truck in diluted formdistributor truck in diluted form

• Expected life - 1 to 3 years or moreExpected life - 1 to 3 years or more

Fog and Rejuvenating Seals

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• Using excess emulsion for the Using excess emulsion for the existing pavement surfaceexisting pavement surface

• Placing in wet and/or cool weatherPlacing in wet and/or cool weather• Over or under dilutionOver or under dilution• Incompatible water for dilutionIncompatible water for dilution

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• Purpose- waterproof the existing Purpose- waterproof the existing surface and improve texture. Can surface and improve texture. Can also serve as an interlayeralso serve as an interlayer

• Materials- application of emulsions Materials- application of emulsions or hot binders followed by clean or hot binders followed by clean aggregate aggregate

• Design- application rates need to Design- application rates need to be determined be determined

• Construction-asphalt is applied Construction-asphalt is applied followed by an application of followed by an application of aggregate. May be used in multiple aggregate. May be used in multiple layerslayers

• Expected life- 5-7 years or moreExpected life- 5-7 years or more

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Sweeping (before and after)Sweeping (before and after)

RollingRollingAggregate Aggregate ApplicationApplication

Binder Binder ApplicationApplication

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• Improper surface preparationImproper surface preparation• Applying in cool and/or wet weatherApplying in cool and/or wet weather• Using dirty rockUsing dirty rock• Not accounting for new patches or flushed Not accounting for new patches or flushed

surfacessurfaces• Not taking traffic into accountNot taking traffic into account• Over spreading or under spreading binder or Over spreading or under spreading binder or

aggregate aggregate • Application on unsound pavementsApplication on unsound pavements

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Loose Chips

Bleeding Streaking

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• Chip seal with a polymer modified rejuvenating emulsion (PMRE)

• A scrub broom is used to push the emulsion into the cracks

• Rejuvenates as it seals the pavement surface

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The size of wave is a function of the number and severity of cracks.

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Existing pavementExisting pavement

After emulsion After emulsion applied with the applied with the scrub broomscrub broom

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• Purpose- Seals minor cracks, restores Purpose- Seals minor cracks, restores surface texture, mitigates ravelingsurface texture, mitigates raveling

• Materials- a mixture of graded Materials- a mixture of graded aggregate, asphalt emulsion (generally aggregate, asphalt emulsion (generally polymer modified), and setting agentspolymer modified), and setting agents

• Design considerations- special mix Design considerations- special mix design is neededdesign is needed

• Construction-applied using a special Construction-applied using a special paver mounted on a truckpaver mounted on a truck

• Expected life- 5 to 7 years or more if Expected life- 5 to 7 years or more if placed on sound pavementsplaced on sound pavements

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SweepingSweeping Manhole CoveringManhole Covering

ApplicationApplication HandworkHandwork 17

Type

I II III

Crack Filling

Fine Seal

General Seal

Medium-Textured Surface

Rough -Textured Surface

Parking Lots Residential

Streets

Airfield Runway

Urban Streets

Primary Highways

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• Improper surface preparation or Improper surface preparation or placing on unsound pavementsplacing on unsound pavements

• Place in cool and/or wet weatherPlace in cool and/or wet weather• Not requiring a mix design or Not requiring a mix design or

calibrating the equipmentcalibrating the equipment• Aggregate grading out, especially Aggregate grading out, especially

in fines contentin fines content• Too much or too little additiveToo much or too little additive• Improper maintenance of spreader Improper maintenance of spreader

box and dragbox and drag• Adding too much waterAdding too much water

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Unsound Pavement Unsound Pavement

Improper Surface Preparation Improper Mix design 20

• Purpose- seal the surface, fill wheel ruts and minor Purpose- seal the surface, fill wheel ruts and minor surface irregularities, and can be placed at nightsurface irregularities, and can be placed at night

• Materials- a mixture of graded aggregates, polymer Materials- a mixture of graded aggregates, polymer modified emulsion, and set additivesmodified emulsion, and set additives

• Design considerations- requires a mix design to Design considerations- requires a mix design to determine the proportion of componentsdetermine the proportion of components

• Construction- applied using a special truck mounted Construction- applied using a special truck mounted mixing/paving machine. For long straight jobs a mixing/paving machine. For long straight jobs a continuous machine is recommendedcontinuous machine is recommended

• Expected life-last 8-12 years depending on the surface it Expected life-last 8-12 years depending on the surface it is applied toois applied too

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Continuous Machine

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Quick Traffic Cool Climates

Placed at Night

Interstates

Arterials

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• Improper surface preparation or placing on Improper surface preparation or placing on badly cracked pavementsbadly cracked pavements

• No mix designNo mix design• Construction in wet weatherConstruction in wet weather• Truck mounted equipment placing improper Truck mounted equipment placing improper

jointsjoints• Too much hand workToo much hand work• Too much overlap on jointsToo much overlap on joints• Too much water in the mix causing segregationToo much water in the mix causing segregation

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Placed on Unsound

Pavements

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• Purpose- seal the surface and provide a Purpose- seal the surface and provide a smooth hard wearing surfacesmooth hard wearing surface

• Materials- a chip seal followed by a slurry Materials- a chip seal followed by a slurry sealseal

• Design considerations- mix designs for Design considerations- mix designs for both productsboth products

• Construction- application of a chip seal Construction- application of a chip seal followed by a slurry sealfollowed by a slurry seal

• Expected life- 8-12 years or moreExpected life- 8-12 years or more

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Chip Seal Followed by a SlurryChip Seal Followed by a Slurry

Slurry

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Chip Seal

Slurry SealFinished Surface

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• Improper surface preparationImproper surface preparation• No mix designsNo mix designs• Applying in cool and/or wet Applying in cool and/or wet

weatherweather• Over application of binder in Over application of binder in

either courseeither course• Using conventional chip seal Using conventional chip seal

or polymer modified chip or polymer modified chip seals over cracked surfaces.seals over cracked surfaces.

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Thin Bonded Overlays

• Application of Application of polymer modified polymer modified binder immediately binder immediately followed by a thin hot followed by a thin hot mix overlaymix overlay

• Total thickness has Total thickness has been about 25 mmbeen about 25 mm

• Applied with a spray Applied with a spray paverpaver

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Thin HMA Overlays

• TypesTypes– ConventionalConventional

– Polymer modified Polymer modified asphaltasphalt

– Asphalt rubberAsphalt rubber

– Terminal BlendTerminal Blend

• Thickness 1-1.5 Thickness 1-1.5 inchinch

• Used with warm Used with warm mix additivesmix additives

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• Existing pavement Existing pavement conditioncondition

• Construction process Construction process and workmanshipand workmanship

• Materials quality and Materials quality and selectionselection

• Climate and TrafficClimate and Traffic

Factors Affecting the Performance of Pavement Preservation Treatments

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Treatment Life Reduction Percentage, % AverageStandard Deviation

Pretreatment Pavement ConditionFair 36% 18%Poor 64% 18%

Materials Selection and QualityMarginal 36% 22%

Poor 57% 20%

Construction and WorkmanshipMarginal 45% 21%

Poor 61% 21%

Mix and Structural DesignMarginal 35% 19%

Poor 57% 20%

Traffic LevelMedium 22% 22%

Poor 45% 25%

Climate during and immediately after construction

Marginal 33% 24%Poor 50% 24% 33

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Strategy Selection Process

• Assess Pavement Conditions

• Determine Feasible Treatment Options

• Analyze and Compare Feasible Options

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User Interface – Main Page

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•Treatment Life•Treatment Cost•Interest Rate

Equivalent Annual Cost

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Advantage of the Preliminary Developed Expert System

• Uses Caltrans MTAG existing decision matrix

• Can deal with more complex scenarios

• Knowledge is retained to the system

• New treatments can be added

http://ceresearch.ecst.csuchico.edu/TreatmentSelection2.0/View/LoginPage.aspx

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• Types of Surface TreatmentsTypes of Surface Treatments– Design and construction considerationsDesign and construction considerations– Expected performanceExpected performance– Causes of problemsCauses of problems

• Factors Affecting the Performance of Factors Affecting the Performance of Preservation Treatments-FHWA studyPreservation Treatments-FHWA study

• Strategy Selection Process Using Life Strategy Selection Process Using Life Cycle Cost Cycle Cost

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Any Questions?

rghicks@csuchico.edu

530-588-4446

and

dxcheng@csuchico.edu

530-588-0155

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