Technology Transfer Specialist - Michigan LTAP

Seminar on Maintenance of Asphalt Pavements

Crack Sealing

Alan L. Gesford, P.E.Technology Transfer Specialist

Michigan’s Local TechnicalAssistance Program

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Agenda1. Importance of Crack Sealing

Road Enemy #1 - ‘Water’2. FHWA/SHRP/LTPP

Studies & Results Manual of PracticeLTPPBind Software

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Agenda3. Crack Sealing Program

MaterialsEquipmentPreparationSealingSafety

4. Saw and Seal Program

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Video

US Army Corps of EngineersCold Regions Research &

Engineering Laboratory (CRREL) Hanover, NH

“Crack Sealing Flexible Asphalt Pavement”

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Importance of Crack Sealing

One of the best early Preventive Maintenance Techniques to prolong the life of your roadsCost Effective!

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Factors Affecting Road Life

Traffic Loads

Subgrade Quality

Water

Quality of

MaintenanceProgram

Construction &Road Materials

Road Life

Water

Age

Traffic Loads

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4 8 12 16YEARS

VERYGOOD

GOOD

FAIR

POOR

VERYPOOR

40% Quality Drop

40% Quality Drop

75% Time

17% Time

Deterioration / RehabilitationRelationship

If left go, a single crack will only continue to deteriorate, resulting in more severe distress with more work to repair along with additional costs.

Crack Sealing

Types of Cracks

BlockReflection

EdgeLongitudinalTransverse

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Caution!Alligator/Fatigue Cracking

Recommended Treatment: Base Repair

DO NOT CRACK SEAL

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Caution!Alligator/Fatigue Cracking

Recommended Treatment: Base Repair

DO NOT CRACK SEAL

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FHWA / SHRP / LTPP

Strategic Highway Research Program

SS

RRHH

PP

Long Term Pavement Performance

LLTTPPPP

Federal Highway Administration

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SHRP Studies

H-105 Innovative Materials & Equipment for Pavement surface RepairH-106 Innovative Materials Development & TestingFHWA Long-Term Monitoring (LTM) of Pavement Maintenance Materials Test Sites

Final Report: LTPP Pavement Maintenance Materials: SHRP Crack Treatment Experiment, Final Report. FHWA-RD-99-142

TechBrief: Sealing and Filling Cracks in Asphalt Pavements

http://www.fhwa.dot.gov/pavement/pub_listing.cfm?areas=LTPP

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SHRPManual of Practice

Materials and Procedures for Sealing and Filling

Cracks in Asphalt-Surfaced

Pavements

FHWA Report No. FHWA-RD-99-147http://www.fhwa.dot.gov/pavement/pub_listing.cfm?areas=LTPP

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Crack Treatment

Method depends on crack density and edge deterioration

Surface TreatmentRepairSealingFilling

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Crack Sealing vs Filling

Crack Sealing: Placement of specialized materials above or into working cracks using unique configurations to prevent water intrusion.Crack Filling: Placement of ordinary treatment materials into non-workingcracks to prevent water intrusion

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Working vs Non-working Cracks

Working Cracks: Horizontal movement of 0.1 inches or greater, usually transverseNon-working Cracks: Horizontal movement less than 0.1 inch, usually longitudinal

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Materials for Sealing vs Filling

Minimal movement permits use of less expensive, less specialized crack-filler materialsIf existing cracks are both working and non-working, using a material appropriate for the most demanding crack type may be desirable

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Factors Effecting Sealants

ClimateTrafficWeather Conditions during SealingPavement DesignPavement AgeDrainage Profile

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Factors Effecting Sealants

Material Preparation Material Type (& manufacturer)Material ConfigurationCrack MovementCrack DeteriorationCrack Preparation

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Sealant Distresses

Adhesion Failure*Cohesion FailureWeathering/AgingExtrusion, Tracking, PulloutsIntrusion of Incompressibles

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*Adhesion Failure

Sealant MaterialImproper ConfigurationInadequate Crack PreparationIncorrect Installation Procedures

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Desirable Sealant Characteristics

Short preparation timeQuick & easy to placeShort cure timeAdhesivenessCohesiveness

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Desirable Sealant Characteristics

Resistance to softening & flowFlexibilityElasticityResistance to aging & weatheringAbrasion resistance

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Types of Sealants

1. Cold-Applied Thermoplastic2. Hot-Applied Thermoplastic3. Thermosetting Chemically

Cured

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Types of Sealants

Cold-Applied Thermoplastic»Set by release of solvents

(cutbacks) or breaking of emulsions

»Applied at ambient temps or heated to 120-140o F

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Types of Sealants

Hot-Applied Thermoplastic»Soft upon heating»Harden on cooling»No change in chemical

composition

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Types of Sealants

Thermosetting Chemically-Cured»Cure through chemical reaction»High cost

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Sealant UsesNon-working cracks (crack filling)» asphalt emulsions» asphalt cement» fiberized asphaltWorking cracks (crack sealing)» polymer-modified liquid asphalt » asphalt rubber» rubberized asphalt» low-modulus rubberized asphalt» self-leveling silicone

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Configurations

Flush FillReservoir (routed)Overband (band-aid)Combination

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p13-14See Figure 6: Material Placement Configurations

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SHRP Crack Treatment Experiment, Final Report Recommendations

1. Establishing a Program» Assessment prior to action

–Type & orientation of cracks –Climatic conditions, pavement structure,

traffic, future rehabilitation plans» Determine crack movement expected» Determine appropriateness of short,

medium, or long-term treatment

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2. Working Cracks» Short-term 1-3 years

–Rubberized asphalt in simple band-aid configuration

» Medium-term 3-5 years–Rubberized asphalt in standard

recessed band-aid configuration–Modified rubberized asphalt in simple

band-aid configuration

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2. Working Cracks (continued)» Long-term 5-8 years

–Modified rubberized asphalt in standard recessed band-aid configuration

–Modified rubberized asphalt in shallow recessed band-aid configuration

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3. Non-working Cracks» Short-term 1-3 years

–Asphalt cement in flush fill configuration» Long-term 5-8 years

–Asphalt rubber or rubberized asphalt in flush fill or overband configuration

–Fiberized asphalt in overband configuration

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4. Other considerations» Use of hot-lance to clean, dry and

warm cracks appears cost effective» Self-leveling silicone looks

promising, more study needed

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Innovation! LTPPBindLTPPBind: A Software Tool for Selecting Cost-Effective Superpave Asphalt Binder Performance Grades» Database of high & low temps for 7,835 U.S. &

Canandian weather stations» Allows user to select PGs based on actual

temperature conditions at their siteProduct Brief in Handout

So why is this important to crack sealing?????

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Using LTPPBind to Improve Crack Sealing

Sealants with different properties are needed in different climatesWarm climates require stiff sealants, colder climates require softer, more flexible sealantsSealants must function over the range of temperatures from summer to winterInstallation methods also vary by climateThe same pavement temperatures identified by LTPPBind can be used in selecting crack sealant materials and procedures

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Using LTPPBind to Improve Crack Sealing

Using LTPPBind, sealant properties at anticipated high and low temperatures can be evaluated or comparedThe LTPPBind temperature range also indicates expected crack movement aiding in reservoir-widening (routing) decisionsSee Handout: Using LTPPBind V2.1 to Improve Crack Sealing in Asphalt Concrete Pavements FHWA-RD-03-080

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Crack Sealing Program

MaterialsEquipmentPreparation

SealingSafety

Basic Elements of Crack Sealing

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Crack Sealing ProgramMaterials

Materials:Recommend Prepackaged MaterialsDo not recommend field mixingnot

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If you are field mixing:

» Asphalt & PDR : 2 lbs rubber per gallon asphalt

» Asphalt & fibers: 5% fibers by weight of asphalt (10 lb bag per 25 gallons asphalt)

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Problems with field mixing:Proper KettleProper proportionsUniform mix

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Prepackaged Materials: Right proportions, uniform mix

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Temperature of sealant is critical Follow manufacturer’s recommendations

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Two important temperatures»Recommended application

temperature»Safe Heating Temperature

(generally 20o-30oF higher than application temp)

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Crack Sealing ProgramEquipment

EquipmentRouterAir CompressorHot LanceHeating Kettle with pump & agitator

(See Table 7: Types & Recommendations)

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Routing/CuttingVertical-spindle routerRotary-impact routerRandom-crack saw

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Routing Caution!

Routing may NOT be suitable for:Older, aged asphalt pavements (above 6 yrs old)Thin asphalt pavements (less than 2” thick)

Routing not needed if pavement is to be overlayed within 2 years

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Routing

Advantages:Opens small cracks to allow greater penetrationProvides a reservoir for sealantProduces uniform edges for better adhesion

Disadvantages:Very labor intensive, thus extra costCan be difficult to follow meandering crackMay damage older or thin asphalt pavementsLonger exposure of workers to traffic

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Air CompressorTo clean dust & debrisPressure: 100 psi minFlow: 150 cfm minVelocity: 3250 fps min

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Hot LanceHeats & dries crackVelocity: 2000 fps minTemperature: 2500o F min

Hot lance heats and dries crack

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Heating KettleDirect heatingIndirect heating (double boiler)

Type must be correct for material being used!

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Direct Heat Indirect Heat

Indirect Heating KettleDouble boiler with separate temp controls & gauges for oil & melting chamberMechanical full-sweep agitatorHeating range to 450o F

60 gal.capacity

200 gal. capacity

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Crack Sealing ProgramPreparation

PreparationA clean, dry crack is criticalDirt, dust, cold, and dampness can be disastrous

Compressed airor…….

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Hot-Air Lance

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Crack Sealing ProgramPreparation

Routed cracks also need to be clean & dry

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Cracks ¼” to 1"

Crack Sealing

Temperature (air & surface)» 40oF. min» 90oF. max

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Crack Sealing ProgramSealing

SealingTemp above 40o FWait 24 hours after rainfallCracks 1/4” to 1”Material at proper temperature

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Winter & Summer NOT the Right Time for Joint and Crack SealingWinter

Don’t Pour

Spring or Fall

Pour Joint

Summer

Don’t Pour

Compression

Summer

Tension

Winter

Compression (minimum)

Summer

Tension (minimum)

Winter

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SealingKettle with pump & wand preferred

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Pour pots & buckets» Higher safety

risks» Difficult to

maintain temperature

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Apply the sealant INTO the cracks with the sealant wand.

Slightly overfill to squeegee for bandaidconfiguration

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Band-aid configurations» Squeegee or special nozzle head» Keep squeegee free of material buildup

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Band-aid configurations» Keep squeegee or special head

centered over crack» Operate squeegee closely behind wand

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Sealant Configuration:» Standard Reservoir

with band-aid

» Width = 3”

» No build-up!

A “Wipe”

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Consistently maintaining application temperatureMaintaining sufficient supply of heated material in kettleProperly dispensing right amount of material into crack

3 important items:

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Blotting»Prevents tracking»Fine sand, limestone dust,

talcum powder, toilet paper»Apply immediately after

finishing

toilet paper

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Crack Sealing ProgramSafety

SafetyTraffic - Proper work zone traffic controlCompressed airHot materials

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SafetyFace shield and/or gogglesHeat resistant coveralls & glovesNo direct heat applied to hosesTraining for entire crew

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Hot Asphalt First AidDO NOT attempt to remove asphalt from the skinSubmerge affected area in ice waterSeek medical attention

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Crack Sealing ProgramSummary

Cracks Clean & DryProper Material & Configuration

Correct TemperatureProper Equipment

Safety

See Table 8: Crew requirements & production rates

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SAW and SEAL

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Sawing & Sealing Joints in Asphalt Pavement to Control Cracking

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Saw & Seal

An option for controlling cracks»New Asphalt Pavements»Asphalt Overlays on Jointed

Concrete Pavements (JCP)»Asphalt Overlays on Asphalt

Pavement

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Saw & SealShould not be used:» Overlays on JCP with high frequency of

midpanel cracks or badly deteriorated cracks

» Overlays on JCP with badly deteriorated joints or joint patching

» Overlays on asphalt pavements with meandering transverse cracks

» Overlays on asphalt pavements with severe load related distress - alligator cracking, potholes, etc.

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Would you rather have this, …

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...or This!

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RecommendationsJoints spaced 30-50 feet apart. Most recommended is 40 feet.Depth of deep cut to be 1/3 asphalt thickness or 2 ½”, whichever is greater.Sawing done in one pass.Reservoir filled properly to achieve good bond & long sealant lifeSpecification MnDOT 3720

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Thank You!

Alan L. Gesford, P.E. Technology Transfer Specialist

E-mail: [email protected]

Documents

Technology Transfer Specialist - Michigan LTAP