Technology Transfer Specialist - Michigan LTAP
Transcript of 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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SHRP Crack Treatment Experiment, Final Report Recommendations
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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SHRP Crack Treatment Experiment, Final Report Recommendations
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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SHRP Crack Treatment Experiment, Final Report Recommendations
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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SHRP Crack Treatment Experiment, Final Report Recommendations
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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Crack Sealing ProgramMaterials
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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Crack Sealing ProgramMaterials
Problems with field mixing:Proper KettleProper proportionsUniform mix
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Prepackaged Materials: Right proportions, uniform mix
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Crack Sealing ProgramMaterials
Temperature of sealant is critical Follow manufacturer’s recommendations
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Crack Sealing ProgramMaterials
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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Crack Sealing ProgramEquipment
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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Crack Sealing ProgramEquipment
Air CompressorTo clean dust & debrisPressure: 100 psi minFlow: 150 cfm minVelocity: 3250 fps min
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Crack Sealing ProgramEquipment
Hot LanceHeats & dries crackVelocity: 2000 fps minTemperature: 2500o F min
Hot lance heats and dries crack
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Crack Sealing ProgramEquipment
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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Crack Sealing ProgramSealing
SealingKettle with pump & wand preferred
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Crack Sealing ProgramSealing
Pour pots & buckets» Higher safety
risks» Difficult to
maintain temperature
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Crack Sealing ProgramSealing
Apply the sealant INTO the cracks with the sealant wand.
Slightly overfill to squeegee for bandaidconfiguration
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Crack Sealing ProgramSealing
Band-aid configurations» Squeegee or special nozzle head» Keep squeegee free of material buildup
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Crack Sealing ProgramSealing
Band-aid configurations» Keep squeegee or special head
centered over crack» Operate squeegee closely behind wand
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Crack Sealing ProgramSealing
Sealant Configuration:» Standard Reservoir
with band-aid
» Width = 3”
» No build-up!
A “Wipe”
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Crack Sealing ProgramSealing
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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Crack Sealing ProgramSealing
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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Crack Sealing ProgramSafety
SafetyFace shield and/or gogglesHeat resistant coveralls & glovesNo direct heat applied to hosesTraining for entire crew
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Crack Sealing ProgramSafety
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