PAVEMENT MAINTENANCE 1Part 3: Potholes and Cracks

Objectives

Explore alternatives for repairing potholes,Review options for extensive patching,Investigate methods and materials for treating pavement cracking.

HOW A POTHOLE DEVELOPS

HOW A POTHOLEDEVELOPS

Elements of Successful Pothole PatchingUse high-quality patching materials, which are cost-effective compared to less expensive products.Place--do not throw--material in the patch area. Compact every patch.

High Quality Cold Mixes Include:Carefully selected aggregate types and gradationsVery clean, durable aggregatesVery little sand-mixtures are porousPolymer modified binderAdditives that promote adhesion in wet conditions

Asphalt Cold Patch MaterialsStandard Spec 00745.00 Asphalt Cold Patch-High PerformanceQualified Products List available describing suitable materials

Theres a gentleman here to see you about potholes.

Permanent Repairs

Dig Out and RepairIdentify area affectedRemove to sound materialClean, tack edgesPlace patching mixtureCompactCheck level

Mark Area to be PatchedMark patch area, extending at least 1 foot outside of distressed area.

Remove Failed Materials

Place Patching Mixture

Spread Mixture Carefully

Compact Each Lift Thoroughly

Straight-edge the Patch

Blown-in Pothole Filler

Blown-In FillerSPRAY INJECTION The hole is cleaned with a high volume blower.

A tack coat of asphalt is applied to the area.A mixture of aggregate and hot asphalt fills the hole.

A finish coat of aggregate, and traffic flows.

Patching Rules of ThumbDig out 1 foot beyond the visible crackingDont rock the jackhammerDig out at least 1 1/2 times the thickness of the failed ACCompaction, compaction, compaction.

Questions?Potholes and Cracks

Crack TreatmentsPurpose Used to prevent water and debris from entering individual cracks in the asphalt pavement surfaceCrack treatments are both a corrective and preventative maintenance treatment.

Crack SealingDistress TypeFatigue CrackingLinear & Block CrackingStable RuttingRavelingFlushing/BleedingRoughnessFriction LossMoisture DamageShovingExtent of ProblemMinorMajorFeasibleNot AppropriateFeasibility

Crack SealingDistress TypeFatigue CrackingLinear & Block Crack Stable RuttingRavelingFlushing/BleedingRoughnessFriction LossMoisture DamageShovingExtent of ProblemMinorMajor

Crack Repair Guidelines

Dont do this!

Or this!

Proper Crack Sealing Technique

For Effective Crack Sealing:Perform sealing during late fall/early spring when cracks are open.Sealing does not proceed if rain is imminent.Ambient or surface temperature should meet manufacturers requirementsusually 40F and rising for routing and sealing.Use appropriate materials.

Preparation is Key!Spray the weeds in advanceClean the pavement surface.Provide for traffic control.Clean the crack, removing any moss or grass out of crack.Dry the crack if necessary. (Hot air lance)Fill it with crack seal material.Apply something to surface of seal to minimize the tackiness.

Pavement PreparationCleaning and DryingBroomCompressed AirSandblastingHot Air Blasting (Heat Lance)

Cracks Must Be Clean & DryUse Compressed Air

Note: Be Sure Compressor Is Equipped With A Moisture Trap

...Or Clean with a Hot Air LanceUp to 3000F> 2000 ft/sec blast velocityPropane burner-no flameConducted immediately ahead of sealant installation (5 mins or 50 yards max)Comments:For wet conditions, lance can improve performanceOtherwise, compressed air may be more effective (Qubec study)

Rout and SealCut the pavement to a prescribed width and depthImproves sealant performanceBetter adhesionReduced tensile stress on materialCrafco, Inc

Crack SealingWDW = 0.5 to 0.75D = 0.5 to 0.75Typical Dimensions:

Traffic ControlDetour traffic until seal curesCover sealant with sand for quick openingBegin filling at pavement centerline

Blotting MaterialsDry sandToilet paper (proven effective in SHRP research!)

Crack Seal MaterialsStandard Spec 00746.00 Poured Filler/ Hot PouredQualified Products List available describing suitable materials

Crack SealThe most common product used: D1190Cost per pound: $0.26Cost per linear foot to crack seal: $0.40Should reseal after 5 years?

Crack Sealing

Crack Sealing Rules of ThumbFor linear cracks only (not intended form alligator cracking)Clean cracks with forced air or heat lanceDont over-fill crack with sealant; avoid surface smearsSweep up excess sanding

Review

Investigate methods and materials for treating pavement cracking, Explore alternatives for repairing potholes,Review options for extensive patching.

Questions?Potholes and Cracks

Small Group ActivityIdentify the distressDescribe the causeOutline the optimum maintenance repair 10 Minutes

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AI 38: Use for GroupPhoto No. 4:

AI 30: Use for GroupPhoto No. 5:

AI 47: Use for GroupPhoto No. 6:

AI 47: Use for GroupPhoto No. 7:

Water: Typically, water seeps in the subbase either through cracks in the surface or from standing water along the side.If the water is improperly drained, it can soften the subbase and the soft material underneath may shift or ooze to the size leaving nothing to support the pavement above it. After awhile, repeated beatings from traffic cause the pavement to weaken, seriously crack and ultimately cave in.

Traffic: heavier loads than the pavement is designed to carry.Lower cost materials end up costing more because they dont last.

Compact every patch--even if you compact the patch by driving over it with a truck.

When using cold mix, allow at least 6 months for mixture to cure before placing overlay or seal coat

The procedure for semi-permanent patching is similar to permanent patching, but the pavement is not cut and the resulting patched area is not rectangular.

Temporary patching is done when there could be damage to vehicles and it is not realistic to close the roadway. Temporary patching can also be used on a road that is in generally poor condition or is scheduled for an overlay or reconstruction soon.

Maintenance staff should consider pavement life expectancy, and overall resource availablity when determining the type of pothole patch to place.

Watch temperatures in heated hoppers. Do not heat this material over 100F which may cause binder to harden.We identified what material properties work best and then required suppliers to meet those minimum requirements. Wanted material to be on the coarse side so it didnt move around in the hole; required the material to be workable in cold temperatures.

See handouts for available information...What about bigger problems?Mark the area to be patched, extending at least 1 foot outside the distressed area. The outline should be rectangular with two sides at right angels to the direction of traffic. Cut the outline of the patch with a saw or jackhammer.Remove as much material as necessary to reach firm support, using a milling machine, backhoe, or front-end loader. For alligator cracking and potholes, remove weak granular base and subgrade materials before replacing the asphalt surface course.

Cut faces should be straight, vertical, and solid. Trim and compact the granular base or subgrade to establish a firm foundation.

Apply tack to the vertical edges of the excavated area, and a prime or tack coat to the base of the excavation.Backfill the excavation with asphalt mixture. Shove the patching mixture directly from the truck, and place the mix against the edges first.

Spread the mix carefully to avoid segregation.Avoid pulling material from the center of the patch to the edges.After compaction, the patch surface should be flush with the adjacent pavement, not humped or depressed.System that uses air pressure to apply asphalt emulsion and aggregate into large cracks and potholes.Four steps:Blow water and debris from the pothole.Spray a tack coat on the sides and bottom of the pothole.Blow asphalt and aggregate into the pothole.Cover the patched area with a layer of aggregate.Crack treatments are used to prevent water and debris from entering cracks in an HMA pavement. Limiting water infiltration protects the underlying pavement layers and reduces the detrimental effects of freeze thaw cycling.

Sealing cracks is one of the highest priorities you should have for maintaining pavements. The first cracks will usually show up on meet lines and cold joints. A crack in your pavement allows for water to enter your base. A wet base softens your sub-grade and alligatoring will soon develop. The end result is you receive extensive damage to the pavement and the base.GENERAL NOTES ON EXPLAINING THE CONTENTS OF THE BAR CHARTS:These charts mainly identify when a given treatment is NOT and option. That is, these charts collectively do not give you the answer, but they do help identify your feasible treatment options. Engineering judgment must be used in selecting the most appropriate treatment for a given project. Feasibility ChartThis chart illustrates the maximum allowable distress types and levels that may be present when applying the current treatment. If the extent of problem for any one distress is outside of the feasible range, this particular treatment should be excluded from consideration (i.e., excluded from the feasible list). These are general SUBJECTIVE guidelines. Most likely, every State will differ from the ranges shown.These feasibility charts do not necessarily take multiple distresses into consideration, it ONLY shows the maximum allowable extent of problem for any given distress. For example, if a pavement has a medium linear cracking problem and a medium roughness problem, individual crack sealing activities would most likely NOT be used. Rather, a surface treatment would likely be used. Again, these charts are not intended to give you the answer, but instead, focus on eliminating treatments from consideration.GENERAL NOTES ON EXPLAINING THE CONTENTS OF THE BAR CHARTS:These charts mainly identify when a given treatment is NOT and option. That is, these charts collectively do not give you the answer, but they do help identify your feasible treatment options. Engineering judgment must be used in selecting the most appropriate treatment for a given project. Feasibility ChartThis chart illustrates the maximum allowable distress types and levels that may be present when applying the current treatment. If the extent of problem for any one distress is outside of the feasible range, this particular treatment should be excluded from consideration (i.e., excluded from the feasible list). These are general SUBJECTIVE guidelines. Most likely, every State will differ from the ranges shown.These feasibility charts do not necessarily take multiple distresses into consideration, it ONLY shows the maximum allowable extent of problem for any given distress. For example, if a pavement has a medium linear cracking problem and a medium roughness problem, individual crack sealing activities would most likely NOT be used. Rather, a surface treatment would likely be used. Again, these charts are not intended to give you the answer, but instead, focus on eliminating treatments from consideration.Ideally, crack sealing should be conducted shortly after working cracks have developed to an adequate extendt and at a time of year when temperatures are moderately cool--45 to 65 degrees F, such as in the spring or fall.

The next step is to clean and dry the crack. For best results, the crack should be cleaned with a stiff-bristled broom, compressed air, or. Sand blasting. Hot air blasting uses a heat lance to dry the crack. Moisture will inhibit bonding of the crack sealer to the wall of the crack. The slide shows cleaning a crack with compressed air

The second slide shows hot air blasting (using a heat lance) dries the crack before sealing. Take care not to burn the asphalt around the crack by moving the heat lance too slowly.Used on transverse and longitudinal crack, involves using a pavement saw or router to create a reservoir centered over existing cracks, then filling with a sealant. Note when longitudinal cracks are sealed, especially on curves, tires may slip when traveling over the overband material. This can be very dangerous and should be avoided when sealing longitudinal cracks on curves.Reroute traffic until material cures.Traffic should be rerouted until the sealant material cures. If the pavement is to be opened to traffic immediately after sealing, the sealant must be protected against pick-up by tires, which can be accomplished by dusting the cracks with fine sand, mineral dust, or similar material. It is good practice to work from the centerline to the edge of the pavement to avoid backing into the stream of

Bumps in overlays do not have to happen. Perform crack sealing 6 to 12 months prior to an overlay. Proper sealant application procedures and roller operation techniques can eliminate bumps caused by too much sealant or roller slippage.Here a crew member sprinkels the surface of the sealed crack with dry sand to prevent sealant pick-up by traffic.

See handouts for available information...About 18 minutes.Pieces we will be covering in the entire course (Part 1: Road surface, materials, pavement engineering; Part 2: Traffic side of things and into safety aspects; Part 3: Road management.

We will start with a discussion of materials, In this piece, we will talk about why pavements are important.What are the key parts to good pavement performance?Then how pavements are designed in terms of thickness and materials?Ask questions...