Pavement MaintenanceM A N U A L

Mike JohannsGovernor

John CraigDirector

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Pavement Maintenance ManualAcknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Chapter 1: Types of Pavement Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Preventive MaintenanceRoutine/Corrective MaintenanceEmergency Maintenance

Chapter 2: Pavement Management Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Chapter 3: Distress Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Flexible Pavement

Alligator CrackingEdge CrackingLongitudinal CrackingRandom/Block CrackingTransverse CrackingRaveling/WeatheringDistortionRuttingExcess Asphalt

Rigid PavementFaultingTransverse CracksPattern CrackingSurface DistressSlab Cracking

Chapter 4: Pavement Maintenance Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Rigid Pavement Maintenance Decision MatrixFlexible Pavement Maintenance Decision Matrix

Chapter 5: Recommended Treatment Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Preventive Maintenance Tracking FormPreventive Maintenance

Crack RepairJoint Resealing-Concrete PavementsSeal Coats

Fog SealScrub SealSlurry SealChip Seal/Armor Coat

MicrosurfacingShoulder Maintenance

Corrective MaintenanceFull Depth Asphalt RepairFull Depth Concrete PatchingSpray-Injection PatchingMachine Patch Using Cold-Mix AsphaltCold Mix ProductionHot Mix Asphalt PatchProfile Milling

Emergency MaintenanceHand Patching

Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60

Acknowledgements

This manual was prepared with the assistance of many people.The following Nebraska Department of Roads employees and/or Divisions were involved:

District Engineers, District Maintenance Superintendents, District 1 Maintenance Supervisors,Transportation Planning Division1, Materials and Research Division,

Information Systems Division, and Communication Division.Recommended Practices were submitted by

District 3, District 5, District 6, District 7, and District 8.

Outside assistance on Preventive Maintenance was provided by Dean Testa, Kansas DOT,Larry Galehouse, Michigan DOT, Dick Clark, Montana DOT and Tom Lorfeld, Wisconsin DOT.

The AASHTO Subcommittee on Maintenance provided the Glossary of Terms.

Wayne Teten

Assistant to the Director(402) 471-0850 Ext. 1072

1Transportation Planning Division has since been eliminated but their previous responsibilitiesare being performed in various reorganized Divisions. The Pavement Management Section,formerly in Transportation Planning Division, is now part of Materials & Research Division.

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Introduction

Nebraska has approximately 10,000 miles ofState Highways. With few exceptions, ourroads are something to be proud of. Sinceour beginning in 1895, we have beenconcentrating on new construction andupgrading our standards. We have reached apoint where pavement preservation mustshare the funding spotlight.

Pavement preservation is a program of activitiesaimed at preserving our highway system wheremillions of dollars have been invested. It isnow apparent that additional emphasis must beplaced on maintenance if we are to preserveand prolong the life of the system that hasevolved over the last 100+ years.

The purpose of this manual is to assist thoseresponsible, in making good decisions relatedto the maintenance and preservation ofpavement surfaces. Obviously, there are manyfactors such as traffic, weather, soil type,availability of equipment and crews, etc. thatmake it difficult to identify the correcttreatment, the service life and the cost for everycase. Hopefully, this manual will help in theselection of consistent, effective and efficientstrategies and will provide guidance to ensureuniform, quality maintenance practices.

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Chapter 1: Types of Pavement Maintenance

Pavement maintenance is the key topavement preservation. An effectivepavement preservation program integratesmany maintenance strategies and treatments.There are three types of pavementmaintenance:

Preventive Maintenance: Plannedstrategy of cost-effective treatments to anexisting roadway system and itsappurtenances that preserves the system,retards future deterioration, andmaintains or improves the functionalcondition of the system (withoutincreasing the structural capacity).Surface treatments that are less thantwo inches in thickness are notconsidered as adding structural capacity.

Corrective Maintenance: Performedafter a deficiency occurs in the pavement,such as moderate to severe rutting,raveling or extensive cracking. This mayalso be referred to as “reactive”maintenance.

Emergency Maintenance: Performedduring an emergency situation, such asa blowup or severe pothole that needsrepair immediately. This could alsoinclude temporary treatments thathold the surface together until a morepermanent treatment can be performed.

There are no clear boundaries between whena treatment is preventive versus corrective,or corrective versus emergency. All types ofmaintenance are needed in a completepavement preservation program. However,emphasizing preventive maintenance mayprevent or prolong the need for correctivemaintenance.

Preventive maintenance is completing theright repair on the right road at the right time.

Although all three types of maintenance areimportant for pavement preservation, thismanual will primarily focus on preventivemaintenance since it is the most cost-effective. However, as stated earlier, due tothe overlap in maintenance types, there willbe some limited discussion of the others.The following figures and explanations areprovided to help the reader better understandthe differences and importance of each type.

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Preventive

Corrective

Emergency

Time or Traffic Figure 1.1 Categories of Pavement Maintenance

Pav

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Preventive Maintenance

Rehabilitation

Time or Traffic Figure 1.2 Performance of Preventive Maintenance Treatments

Pav

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Preventive Maintenance

A preventive maintenance program has beenshown to often be six to ten times morecost-effective than a “do nothing” strategy.Conservatively, $1.00 spent for preventivemaintenance will provide the same pavementcondition that costs $4-5.00 if rehabilitationis needed. By extending the life of apavement until it needs rehabilitation,preventive maintenance allows theDepartment to even out its budget forboth maintenance and construction.

Preventive maintenance should be planned.The intent is to repair early pavementdeterioration, delay failures and reduce theneed for corrective or emergency treatments.Although preventive maintenance does notinclude activities that are intended to increasethe structural or load carrying ability of apavement, it does extend the useful life andlevel of service (e.g. ride). Performingpreventive maintenance activities onpavements in good condition will be veryeffective in extending the life. Theeffectiveness of the treatment is directlyrelated to the condition of the pavement.A discussion of the tools from the PavementManagement System that are available fordetermining the right time to do preventivemaintenance can be found in Chapter 2.

Preventive maintenance treatments include:dowel bar retrofitting, crack sealing, armorcoating/chip sealing, fog sealing, broom orscrub seals, rut filling (in some cases), andthin overlays.

For the Department to have an effectivepreventive maintenance program, allpersonnel associated with the care of ourhighways must understand the basis for sucha program and then be prepared to educatethe public. It is quite likely that motorists willquestion why work is being done on roadsthat appear to be in good shape. We must beable to explain the timing needs and benefits.Finally, for the Department to have aneffective preventive maintenance program,adequate funding must be set aside toprovide the treatments that are needed.

Corrective Maintenance

The differences between preventive andcorrective maintenance occur in the timingand cost. Corrective maintenance is reactive,i.e., it is done after a road is in need of repairso the cost is greater. Delays in correctivemaintenance result in even larger costs sincedefects and their severity continue to increase.

Corrective maintenance treatments include:structural overlays (3 inches or greater),milling, patching and crack repair.

Emergency Maintenance

Emergency maintenance is often related tosafety and time, with cost not being a primaryconsideration. Likewise, materials that maynot be acceptable for preventive or correctivemaintenance may be the best choice foremergency situations.

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Chapter 2: Pavement Management Information

Introduction

Since 1984, personnel in the PavementManagement Section have been collectingdata on the surface condition of Nebraska’shighways. This data is just a small part of theinformation that is available on the NebraskaPavement Management System (NPMS).The Pavement Management System wasdeveloped as a tool for the Department’sadministration to more efficiently manage thehighways.

There are two main parts to the system: 1) a computer master file, and 2) interpretingprograms. The master file is the realfoundation to the system and contains thefollowing data for all rural and urban highwaysby highway number and reference post:

✔ Length, width and other layergeometric data

✔ Pavement structure, layer types, anddesign thickness

✔ Pavement distress condition data forbituminous and concrete pavement,Present Serviceability Index (PSI) andInternational Roughness Index (IRI)data

✔ Skid resistance data

✔ Traffic volume data (ADT), equivalent18-kip axle load information, loads,frequencies, and vehicle classifications

✔ Pavement temperature and variationranges during skid testing

✔ Regional weather data, highs, lows,precipitation amounts, and othermiscellaneous items.

✔ Construction and maintenancerehabilitation costs by activity

✔ Bridge deficiency

✔ Safety records (fatalities and propertydamage data)

✔ Nebraska Highway Program data forthe next six fiscal years

Deflection data, which is considered avaluable tool, is available on a limited projectby project basis.

All historical information will be kept for a50-year time period.

The master file is then used to: 1) reportexisting pavement conditions, 2) trackprogression of distress over the service life ofa pavement, 3) list pavement section surfacedeficiencies, the extent of deficiencies, andvalid rehabilitation repairs, and 4) reportsections programmed for construction

Procedures

Pavement Management personnel gatherpavement condition data annually.Inspections are made of the pavement surfaceat sample locations. For rigid pavements, testsections of ten panels and joints at each mileor reference post are rated. Bituminouspavements are done by taking one-tenth mile

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test sections every mile as near to thereference post as practical. An overall“windshield” survey is done at highwayspeeds to verify the sample sections arerepresentative of the entire segment.

Chapter 3 of this manual providesdescriptions and illustrations of the variousdistresses. Results of the condition survey aregenerally available by September of the yearin which they are taken.

The various distress factors are combined toprovide an overall rating of each section.Ratings of greater than 70 are consideredgood and ratings of below 50 are consideredpoor, indicating the need for rehabilitation.Ratings of 50-70 are considered fair andindicate only a few years of service liferemain.

On the average, the rating of a bituminousroad decreases three points per year for thefirst ten years and two points per year afterthat. In other words, a new asphalt road willrate 70 after ten years and rate 50 aftertwenty years. Ratings on concrete roads (>8")decrease at the rate of 1.25 points per year,so in forty years, a new concrete surfacereaches a rating of 50.

More details on ratings may be found inNebraska Department of Roads PavementManagement System dated January 1996.

Measurements of the roughness, or ridequality, are also taken each year. Themeasurements are expressed in terms ofmillimeters per meter (mm/m). Surfaces with

ratings greater than 2.00 are considered roughand greater than 3.00 are very rough.Maps showing the overall surface conditionrating, referred to as the Nebraska Service-ability Index (NSI), the amount of rutting, andthe roughness (IRI) for each highway areavailable from Materials & Research Division.

Uses of Pavement Management Data

The amount of data available is enormous.Interpreting programs are used to summarizethe information and provide reports listingcandidate sections of pavement suitable forrehabilitation. A list of pavement conditions isprovided to the District Engineer each year toassist in establishing the six-year rehabilitationprogram. Another list is generated fromwhich the Pavement Extension Program (PEP)projects are selected.

On a statewide basis, the PavementManagement data is used in preparation ofthe Department’s annual 20-year NeedsAssessment. In turn, the Needs Assessment isused to determine the amount of fundingallocated to each District for highwayimprovements.

At the project level, life cycle cost analysis isavailable for rehabilitation strategies. Work isunderway to develop life cycle cost analysisfor maintenance strategies.

A review of the surface condition rating byMaintenance decision makers may help inselection of the proper preventivemaintenance treatments.

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The following section provides a detaileddescription of how to access the materialavailable from the Pavement ManagementSection.

How to Access Pavement Management Data

Shown below is a step-by-step procedure youmay use to obtain current and historical datafor highways in your area.

1. Open a Mainframe Session.2. Type C1, press enter.3. A “Production CICS1 Region” screen

will appear, press enter.4. Type in your User ID: (if your number is

DOR 26002 use DR26002).5. Type in your Password, press enter.6. Next screen choose selection “8” (IHI1)

IHI Integrated Highway InventorySystem, press enter.

7. On the Main Menu screen choose “18”Roadway Condition, press enter.

8. On the Roadway Condition Menuchoose “02” Query, press enter.

9. On the Roadway Condition QueryMenu choose what data you want toreview. For example: choose “03”Bituminous Condition Ratings, pressenter.

10. Enter highway Number: Example“002”a. Enter Beg Ref Post, if desired.b. Enter End Ref Post, if desired.c. Enter Lane Dir Cde, if desired.d. Enter Lane Typ Cde, if desired.

e. Enter Lane Num, if desired.f. Enter Start/End Dates, if you want

to see more than the current data.g. Enter Restrn Idx Low/Hi, select

range of Restoration Index values,if desired.

h. Enter Crking Idx Low/Hi, selectrange of Cracking Index values, ifdesired.

11. Press enter.12. Follow the directions on the lower

portion of the screen in reference tothe “PF” keys (“F” keys on thekeyboard, the upper row of keys).The “PF” keys 13 and above can beaccessed by pressing the “Shift” + “F”key. Example: “PF19” = Shift + F7;“PF20” = Shift + F8; etc.

If at step # 9 above, you chose to look at “01”Roadway Condition Summary Query;Pavement Management Data can also beaccessed there. However, it will only be forthe section being summarized. The processwould then be Steps 1 thru 8 as above, then:

9. Choose “01” Roadway ConditionSummary Query, press enter.

10. Enter District number on this screen,press enter.

11. Scroll down list (F8) and choose asection and place an “X” in the “Sel”column on the line of your selection,press enter.

12. Press enter on the next screen.

13. The next screen is the “NebraskaPavement Management SystemSummary Query” screen. If you place

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the cursor in front of the IRI data onthe lower portion of the screen orRutting data, if this is a bituminoussection or Faulting if this is a PCCsection and press “F4”, the profilerdata for this section will be displayed.If the cursor is placed in front of theCracking Index, Trans. Cracking, NSI orHist Low NSI, if bituminous and press“F4”, the bituminous ratings for thissection will be displayed. Likewise, ifthe cursor is placed in front of thePCC rating elements and “F4” ispressed, the PCC ratings for thissection will be displayed.

14. There are other types of data that arealso accessible from this screen. “F7” calls up all the Crew CardTransactions for this section. “F9” shows the Maintenance Costsand various activities for the last 5years. “F10” shows the conditionhistory and the ratings for this sectionfor the last 10 years.

Additional information may be accessed fromthose locations that have high-speed T1 lines.These locations include the District offices,about 90% of the MaintenanceSuperintendents’ offices and a few others.The following procedures apply to informationthat may be accessed if served by a T1 line.

Pavement Management System, Version 1.0,Procedure for Access

1. When your computer is booted up,there will be an icon that is a greenbox with a red car in it, double click onthis icon or highlight it and press enter.

2. A short movie is displayed while theprogram loads.

3. The next screen shows a file folderwith several tabs on it and the optionof Current Pavement ManagementData or Historic PavementManagement Data. Choose selectionfrom the Current PavementManagement Data.

a. Statewide Data displays allhighway data.

b. District Data displays only thechosen district.

c. Highway Data displays only thechosen highway.

d. Other displays only Interstate,Priority Commercial or Expresswayby District and/or Highway.

4. You may select data by the entire roadsystem, district, highway, district andhighway, or other. A number must beadded in the dropdown box next tothe District Data and the Highway Databuttons if those selections are used.To continue, just single click on one ofthese four buttons. The data will thenbe displayed.

5. The top half of the screen shows theselected statistics for the segmenthighlighted in yellow on the lowerportion of the screen. You maynavigate this screen by one of severalmethods.

a. Using the four buttons on theupper right corner of the screen,you can to go to the top of the file,next record, previous record or goto the bottom of the file.

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b. Use the find button to search for ahighway.

c. You may also use the scroll bar onthe right side of the lower half ofthe screen to locate a highwaysegment, and then use the mouseto select a segment by clicking onit once.

d. You may also use the up anddown arrows to locate a segment.

e. The return button takes you backto the previous screen.

f. Below the return button is a buttonwith a camera on it. When youclick on it, thumbnail images of theroad surface will be displayed.Single click on the Slide Showbutton at the next screen and theslide show will begin. If youdouble click on an image, thatimage will be enlarged. That imagewill also be enlarged when yousingle click on the small buttonwith the square in it next to thebutton with the “X” in the upperright corner of that window. Usethe “X” in the top right corner ofthe screen to return to the previousscreen.

6. The bottom half of the screen lists thecomplete information on each highwaysegment. You can view this data byusing the left and right arrow keys orusing the scroll bar on the bottom ofthe screen. A definition of the columnof data is displayed if the mousebutton hovers over the column for afew seconds.

7. When you finish viewing the data,single click on the Return button or the“X” in the top right corner of the screento exit.

8. Single click on the Exit button to quitthe program.

If any problems are encountered or if youhave any questions regarding the use of eitherof these data sources, contact Gary Brhel at(402) 479-3620.

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Chapter 3: Distress Identification

The purpose of this chapter is to help the userrecognize the distresses typically found onpavements in Nebraska and understand thepossible causes.

Distress is defined as a condition of pavementstructure that reduces serviceability or leads to areduction in serviceability. Serviceability isdefined as the ability of a pavement to provide asafe and comfortable ride to its users.

Distresses may be treated with a range of repairs,each having a varying degree of success. Some ofthe treatments shown for the distresses willprovide only a short term solution, which may beall that is needed.

Selection of the best treatment is complicatedand the decision on which to use should not bemade until you review the material in Chapter 4.

Flexible Pavement Distresses

Flexible pavement surface distresses include awide variety of pavement defects that generallyfall into the following categories:

I. CrackingA. AlligatorB. EdgeC. LongitudinalD. Random/BlockE. Transverse

II. Raveling/WeatheringIII. DistortionIV. RuttingV. Excess Asphalt

Rigid Pavement Distresses The most significant and severe distresses in rigidpavements generally occur along joints. Jointdeterioration reduces pavement performancesubstantially and increases the need formaintenance. Other distresses occur within aconcrete slab away from joints, leading to a lossof ride quality and structural failure of thepavement.

Types of distresses in portland cement concrete(PCC) pavements include:

A. Joint DistressB. FaultingC. Transverse CracksD. Pattern CrackingE. Surface DistressF. Slab Cracking

Each of these distresses is described in thefollowing pages along with photographs andpossible causes. Similar photographs are used asguides by Pavement Management personnelwhen doing the annual rating of the highways.For each distress a number of possiblemaintenance treatments are also shown. Itmust be emphasized that the treatmentsshown here are those that could be applied bymaintenance forces, that may be effective intreating the distresses. Treatments appliedunder contract work are included in the tablesin Chapter 4. Note that under certaincircumstances, the Do Nothing strategy may bethe most appropriate.

Two important points should be remembered: (1) in many instances, multiple types ofdistress occur, so the treatment selected mustbe appropriate for all distress that is present. (2) the appropriate treatment may require acombination of treatments. Again beforeselecting any strategy, the decision matrix inChapter 4 should be reviewed, since some ofthe treatments shown will only provide atemporary fix. In some cases, total reconstruc-tion may be the most appropriate strategy.

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FLEXIBLE PAVEMENT

I. Cracking

A. Alligator Cracking

1. Description

Alligator cracking is a series ofinterconnected cracks in an asphalt layerforming a pattern, which resembles analligator’s hide or chicken wire. The cracksindicate fatigue failure of the asphalt layergenerally caused by repeated trafficloadings and this distress allows water topenetrate the surfacing materials andsubgrade, which furthers the damage.Alligator cracking, also called fatiguecracking, usually first begins as a singlelongitudinal crack in the wheel path.

2. Possible Causes

✔ Insufficient pavement structure✔ Inadequate base support✔ Poor base drainage✔ Aging and traffic loading

3. Maintenance Treatments1

✔ Do Nothing✔ Fog Seal✔ Scrub Seal✔ Slurry Seal✔ Chip Seal/Armor Coat✔ Thin Cold Mix Overlay✔ Thin Hot Mix Overlay✔ Patching

1 Except for patching, most of these treatments willprobably fail rapidly, since additional structure isneeded.

Low - Longitudinal disconnected hairlinecracks no greater than 1⁄8- inch wide.

Moderate - Longitudinal cracks in wheel pathsforming an alligator pattern; cracks may belightly spalled and about 1⁄8- to 1⁄4-inch wide.

High - Pieces appear loose with severelyspalled edges; cracks are 1⁄4-inch or greaterand pumped fines may appear on the surface.

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B. Edge Cracking

1. Description

Edge cracking is similar to alligator crackingonly located within 1 to 2 feet of the edgeof the pavement. Failure begins at the edgeof the pavement and progresses towardthe wheel path. Pavement edge distresscan result in worsening of the wheel pathcondition and allow moisture into thesubgrade soils and base materials. Edgecracking also includes the longitudinalcracking associated with concrete basecourse widening.

2. Possible Causes

✔ Traffic Loading✔ Environmental ✔ Construction Related✔ Low Shoulder✔ High Shoulder Holding Water

3. Maintenance Treatments

✔ Do Nothing✔ Crack Fill✔ Thin Cold Mix Overlay✔ Shoulder Maintenance

Low - Hairline cracks just beginning to show;random with no pattern; may be up to 1⁄8-inch wide.

Moderate - Cracks 1⁄8- to 1⁄4-inch located 1 to2 feet from the edge of the road; may havean alligator pattern.

High - Cracks greater than 1⁄4-inch; may haveloose or missing pieces or potholes oralligator cracking.

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C. Longitudinal Cracking

1. Description

Longitudinal cracking denotes cracks thatrun predominantly parallel to thecenterline. These cracks may be in thewheel paths, between wheel paths and/orat lane joints such as centerline orshoulder/surface.

2. Possible Causes

✔ Traffic Loading (wheel path cracks)✔ Environmental (frost action)✔ Improper Construction Practices

(joint cracks)✔ Poor Drainage✔ Reflection Cracks

3. Maintenance Treatments

✔ Do Nothing✔ Crack Seal/Fill✔ Scrub Seal✔ Chip Seal/Armor Coat✔ Patching

Low - Hairline crack(s) running parallel tocenterline.

Moderate - Cracks parallel to centerline areabout 1⁄8-inch wide.

High - Single cracks are wider than 1⁄8-inch.

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D. Random/Block Cracking

1. Description

Random or block cracks divide thepavement into rough, approximatelyrectangular pieces and typically occurs atuniformly spaced intervals.

2. Possible Causes

✔ Environmental (thermal)✔ Aging

3. Maintenance Treatments

✔ Do Nothing✔ Crack Seal/Fill✔ Fog Seal✔ Scrub Seal✔ Slurry Seal✔ Chip Seal/Armor Coat✔ Thin Cold Mix Overlay✔ Thin Hot Mix Overlay

Low - Hairline cracks, essentially transverse but mayconnect to longitudinal; spacing of 50 to 100 feet.

Moderate - Cracks range from hairline to1⁄8-inch wide and may be slightly spalled.

High - Cracks greater than 1⁄8-inch wide thatare random or have a block pattern, similar toa turtle shell.

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E. Transverse Cracking

1. Description

Transverse cracks are those considered toextend three-fourths of the width of thepavement or more, generallyperpendicular to centerline.

2. Possible Causes

✔ Environmental (thermal)✔ Swelling or shrinkage of the subgrade✔ Reflection cracks✔ Settlement (trench, backfill)

3. Maintenance Treatments

✔ Do Nothing✔ Crack Seal/Fill✔ Fog Seal✔ Scrub Seal✔ Slurry Seal✔ Chip Seal/Armor Coat✔ Mill✔ Patching

Low - Hairline to 1⁄4-inch wide cracksperpendicular to centerline with no distortion.

Moderate - Cracks 1⁄4- to 1⁄2-inch in width,perpendicular to centerline and the full widthof the pavement; slight distortion.

High - Cracks 1⁄2- to 2-inch wide; larger cracks oftenare spalled and/or have noticeable distortions nearthem. Cracks greater than 2 inches wide andcausing extremely rough ride are rated “X”.

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II. Raveling/Weathering

A. Description

Raveling is the progressive wearing awayof the pavement from the surfacedownward caused by the loss of asphaltbinder and the dislodging of aggregateparticles.

B. Possible Causes

✔ Poor mixture quality✔ Asphalt hardening due to aging✔ Insufficient asphalt content✔ Improper construction methods

C. Maintenance Treatments

✔ Do Nothing✔ Fog Seal✔ Scrub Seal✔ Slurry Seal✔ Chip Seal/Armor Coat✔ Thin Cold Mix Overlay✔ Thin Hot Mix Overlay

Low - Minimal loss of aggregate or binder.

Moderate - Some aggregate loss; small areasmay be stripped away.

High - Sections greater than one square footmay be pitted, stripped or eroded away.

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III. Distortion2

A. Description

Distortion is defined as that distress in thepavement caused by densification,consolidation, swelling, heave, creep orslipping of the surface or foundation.

B. Possible Causes

✔ Inadequate support or overloading✔ Thermal and moisture stresses

(freeze-thaw)✔ Loss of bonding between base layer

and surface layer✔ Static load (depressions)✔ Soft AC (shoving)

C. Maintenance Treatments

✔ Do Nothing✔ Crack Seal✔ Chip Seal/Armor Coat✔ Mill✔ Thin Cold Mix Overlay✔ Thin Hot Mix Overlay✔ Patching

2 No longer rated separately byPavement Management personnel.

Low - Slight waves, sags, humps, corrugationsor wash boarding of the pavement.

Moderate - Similar to low except distortionscan be felt while riding in a vehicle.

High - Shoving and major changes inpavement profile that require vehicles to slowfrom normal speeds.

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IV. Rutting

A. Description

A rut is a surface depression in the wheelpath after pavement layers or subgradedeform from traffic load applications.

B. Possible Causes

✔ Poor mixture quality✔ Insufficient support✔ Improper construction procedures

C. Maintenance Treatments3

✔ Do Nothing✔ Chip Seal/Armor Coat✔ Mill✔ Thin Cold Mix Overlay✔ Thin Hot Mix Overlay

3 No preventive applications available.

Low - Depressions in the wheel path less than1⁄8-inch.

Moderate - Wheel path depressions of 1⁄4- to 1⁄2-inch.

High - Wheel path depressions greater than 1⁄2-inch.

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V. Excess Asphalt

A. Description

Excess asphalt, also called bleeding orflushing, is used to describe a free film ofasphalt on the surface of the pavementthat creates a smooth, shiny, greasy, andreflective surface. It is usually found in thewheel paths and becomes quite stickywhen hot.

B. Possible Causes

✔ Mixture problems (bad oil, stripping aggregate, low air voids, high ACcontent, etc.)

✔ Improper construction practices✔ Paving over excess asphalt

C. Maintenance Treatments

✔ Do Nothing✔ Chip Seal/Armor Coat✔ Mill✔ Thin Cold Mix Overlay✔ Thin Hot Mix Overlay

Low - Intermittent films of bituminousmaterial create a shining, reflective surface.

Moderate - Large areas or continuous strips ofbituminous films where little, if any, aggregatecan be seen.

High - Excess bituminous material appearswet and actually liquefies during hot weather.

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RIGID PAVEMENT

A. Joint Distress

1. Description

Joint distress reflects the deterioration ofthe concrete within 2 feet on either sideof a joint. Breaking or chipping of thepavement joints usually results infragments with feathered edges.

2. Possible Causes

✔ Expansive internal pressure due toalkali -aggregate reactivity between thecement and aggregates.

✔ Expansive internal pressure due tocorrosion and deterioration of dowelbars.4

✔ Seized dowel bars combined withthermal expansion (freeze-thaw).

✔ Misaligned dowel bars.4

✔ Lack of support at joint due to pumpingaction and voids.5

✔ Overloading.5

3. Maintenance Treatments

✔ Partial/Full Depth Slab/Joint Repair✔ Crack & Joint Seal/Fill✔ Thin Hot Mix Overlay

4 Causes spalling5 Causes corner cracks

Low - A few hairline cracks from the jointand/or discoloration at the joint.

Moderate - Frequent hairline to 1⁄8-inch cracksradiating from the joint forming a web like pattern.

High - Cracks 1⁄8-inch or larger forming multiplepatterns and often having a white appearance.

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B. Faulting

1. Description

Faulting is a differential vertical displace-ment of a slab or other member adjacentto a joint or crack. Faulting may be eitherlongitudinal or transverse and creates a“step” deformation of the pavement sur-face. Faulting commonly occurs in trans-verse joints of portland cement concretepavements that do not have load transferdevices (dowels). Usually the “upstream”slab is higher than the “downstream” slab.

2. Possible Causes✔ Uneven roadbed support.✔ Thermal and moisture stresses (frost

action).✔ Pumping of slabs due to lack of load

transfer (dowel) devices✔ Insufficient pavement structure

3. Maintenance Treatments✔ Mudjacking✔ Slab replacement✔ Thin Hot Mix overlay

Low - Less than 1⁄8-inch vertical displacementbetween adjacent panels.

Moderate - Displacement of 1⁄8- to 1⁄4-inchbetween adjacent panels.

High - Displacement greater than 1⁄4-inchbetween adjacent panels.

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C. Transverse Cracks

1. Description

Transverse cracks are cracks that run perpendicular to centerline, resulting in apanel that is broken into two or morepieces. Panels broken into two pieces arerated as Class I and panels broken intomore than two pieces are rated as Class II.

2. Possible Causes

✔ Thermal contractions✔ Over-long joint spacing✔ Overloading✔ Swelling/shrinkage/settlement of

subgrade

3. Maintenance Treatments✔ Crack & Joint Seal/Fill✔ Partial/Full Depth Slab Repair✔ Thin Hot Mix Overlay

Low - Hairline to 1⁄4-inch wide cracks extendingthe full width of a panel.

High - Transverse cracks greater than 1⁄4-inch wide extending the full width of panel.

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D. Pattern Cracking

1. Description

Pattern cracking refers to occasional toextensive interconnected cracks that mayappear anywhere within a panel but donot extend throughout the entire depth ofthe slab.

2. Possible Causes✔ Shrinkage cracks✔ Materials: related distress

(including alkali -aggregate reactivity)

3. Maintenance Treatments✔ Do Nothing✔ Thin Hot Mix Overlay

Low - Negligible or occasional interconnecting1⁄16-inch wide or less cracks.

Moderate - Interconnected cracks between 1⁄16- to 1⁄8-inch wide throughout the panel.

High - Occasional to extensive interconnectingcracks 1⁄8-inch wide or greater. Spacingbetween cracks is usually only a few inches.

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E. Surface Distress

1. Description

Surface distress is the scaling, spalling,chipping or disintegration of the concretewearing surface that leads to roughnessand poor durability. It is measured insquare feet per panel but does not includeany distresses within 2 feet of the joint.

2. Possible Causes

✔ Poor materials or construction (e.g. too much water, overworking ofsurface, etc.)

✔ Thermal and moisture stresses (freeze-thaw)

✔ Corrosion of reinforcing steel✔ Reinforcing steel too close to surface

3. Maintenance Treatments

✔ Partial/Full Depth Patching✔ Slab Replacement✔ Thin Hot Mix Overlay

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F. Slab Cracking

1. Description

Slab cracking is used to describe anyunplanned longitudinal or diagonal struc-tural crack(s) that extend through thedepth of the slab

2. Possible Causes✔ Overloading✔ Long joint-spacing✔ Shallow or late joint sawing✔ Pumping of the subgrade✔ Curling or warping of slab✔ Culvert or utility trench subsidence

3. Maintenance Treatments✔ Crack & Joint Seal/Fill✔ Full Depth Slab Repair✔ Thin Hot Mix Overlay

Low - Hairline, single structural cracks in apanel that may be longitudinal or diagonal innature and extend from joint to joint.

Moderate - Two or three major structuralcracks with no faulting or displacement.

High - Multiple structural cracks or cracks withevidence of faulting, displacement or spalls.

25

Chapter 4:Pavement Maintenance Treatments

The selection of the right maintenancestrategy at the right time is of utmostimportance for an effective management ofhighway pavements. The appropriatemaintenance strategy will be influenced bythe type, severity, and extent of the pavementsurface distresses and the structural androughness condition of the pavement. Thephotos in Chapter 3 depict the type andseverity of various distresses. Choosing theright treatment also depends on the extent orfrequency that the distress occurs. Some ofthe treatments may be most applicable whenvery little distress is present. The photos onthe following pages may be used to helpidentify the extent when using the FlexiblePavement Decision Matrix shown as Table 4.1later in this chapter.

Where the extent of the distress is describedas a “Trace” or “Occasional”, it may also beregarded as occurring in localized areas onlyand affecting less than 30% of the pavementsurface. If the extent is described as“Frequent”, “Extensive”, or “Complete”, thedistress affects more than 30% of thepavement surface and occurs more or lessevenly throughout the section.

Application of the extent rating is generallythe same for Flexible and Rigid pavements.However, the Rigid Pavement Decision Matrixshown as Table 4.2, points out someexceptions; i.e., in the rating of TransverseCracks and Surface Distress.

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A. Extent-Environmental Related

Some of the flexible pavement distresses thatare normally environmental related include:transverse cracking, random/block cracking,and raveling/weathering. Others such as edgecracking, longitudinal cracking, and distortionmay be due to either environmental orloading influences.

Trace - less than 10%

Occasional - 10% to 30%

Frequent - 30% to 50%

Extensive - 50% to 80%

Complete - greater than 80%

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B. Extent - Load Related

Some of the distresses commonly associatedwith loading include: alligator cracking,longitudinal cracking in wheel paths andrutting. Preventive maintenance will notcorrect most load-related distresses. Percentsrelate only to wheelpaths and not to theentire pavement surface.

Trace - less than 10%

Occasional - 10% to 30%

Frequent - 30% to 50%

Extensive - 50% to 80%

Complete - greater than 80%

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Table 4.1: Flexible Pavement Maintenance Decision Matrix1

Flexible Pavement Low Moderate High

Distresses Occasional Frequent Occasional Frequent Occasional Frequent

Alligator Cracking2 3,1 3,6 6,3,11,4 6,5 13,6,11 15,13

Edge Cracking 1,2 2,1 2,13 2,13 13 13

Longitudinal Cracking 2,1 2,6,1 2,6 2,6 13,2,6 6,2,13

Random/Block Cracking 2,1 2,3 2,6 2,6 6,11,12 12,6,14

Raveling/Weathering 3,1,6 3,6,5 6,4 6,7 6,11,5 6,12,11

Distortion 1,8,13 13,1,8 8,13,2 8,13,6,2 8,11,6,13 8,14,13

Rutting 1 1 8 + 6 8 + 6 8 + 6, 12 8,14,12

Excess Asphalt 1 1,6 6,1,8 6,8 8 + 6 8 + 6 or 12

Transverse Cracking 2,1 2 2,6 2,6 2,6 2,6,13

Pavement Treatments

1 Based on recommendations of the eight District Maintenance Superintendents andMaterials & Research Division. Treatments are listed based on the frequency with which theywere selected. Only treatments shown are those which were selected by more than two ofthe group. Other possible treatments are listed on the pages showing the distresses.

2 Effectiveness of treatments other than 13, 14 & 15 will be minimal and short-lived.3 Pavement Extension Program (PEP) projects are typically 2 inches thick and are considered

the maximum thickness of this treatment.

29

1 Do Nothing2 Crack Seal/Fill3 Fog Seal4 Scrub Seal (Broom Seal)5 Slurry Seal6 Chip Seal/Armor Coat7 Micro Surfacing8 Mill

9 Cold-in-place Recycle10 Hot-in-place Recycle11 Thin Cold Mix Overlay12 Thin Hot Mix Overlay3

13 Patching14 Thick Overlay15 Total Reconstruction

Table 4.2: Rigid Pavement Maintenance Decision MatrixRigid Pavement Low Moderate High

Distresses Occasional Frequent Occasional Frequent Occasional Frequent

Joint Distress 1,2 1,2 2,3 2,3 3,4 3,4

Faulting 1 1 1 6,4,1 6,4 6,4

Transverse Cracks 1,2 1,2 NR* NR* 2,8,4 2,4,8

Pattern Cracking 1 1 1 1 1,4 1,4

Surface Distress** 3,8,4

Slab Cracking 2 2,4 2,7 2,7,4 3,9 3,9

* Not Rated

** Measured as square feet/panel

Pavement Treatments

1 Do Nothing2 Crack & Joint Seal/Fill3 Partial/Full Depth Slab/Joint Repair4 Thin Hot Mix Overlay (11⁄2")5 Mudjacking6 Diamond Grinding (may include dowel bar retrofit)7 Cross Stitching8 Slab Replacement9 Thick Hot Mix Overlay

30

31

Table 4.3: Flexible Pavement Maintenance Treatment Cost and Expected Life

Treatment Average Cost 1 (Mile) Expected Life (Years)

Crack Seal/Fill $0.55 - $0.60/lin.ft. 2 3 - 5

Fog Seal $1,750 - $2,500 1 - 4

Scrub Seal $7,000 - $8,000 2 - 5

Slurry Seal 3 $40,000 - $45,000 3 - 8

Chip Seal / Armor Coat $8,000 - $9,000 3 - 6

Microsurfacing $41,000 - $43,000 3 - 8

Mill (1") $7,500 - $8,500 1 - 4

Cold-in-Place Recycle $100,000 - $115,000 8 - 12

Hot-in-Place Recycle $22,000 - $25,000 3 - 6

Thin Cold Mix Overlay $18,000 - $25,000 3 - 5

Thin Hot Mix Overlay (1") $45,000 - $55,000 5 - 8

Pavement Extension Program $80,000 - $120,000 7 - 9(2" PEP)

Thick Overlay (5") $195,000 - $215,000 8 - 15

Total Reconstruction $525,000 - $550,000 20+

1 Costs shown are for a 24' roadway unless otherwise noted.

2 Varies depending on extent of cracking. Amounts to $7,000 - $9,000/mi. assumingtransverse crack spacing of 30' and two full-length longitudinal cracks.

3 Includes a 1⁄2" surface treatment over a leveling course. Cost for leveling course alone = $9,000 - $12,000.

Table 4.4: Rigid Pavement Maintenance Treatment Cost and Expected Life

Treatment Average Cost 1 Expected Life (Years)

Crack & Joint Seal/Fill $1.00 - $1.75/ lin.ft. 2 4 - 7

Partial/Full DepthSlab/Joint Repair $95 - $110/sq.yd. 10 - 15

Thin Hot Mix Overlay (11⁄2") $65,000 - $75,000 6 - 10

Mudjacking $80 - $120/sq.yd. 10 - 15

Diamond Grinding $38,700 - $115,400 3 12 - 15

Cross Stitching $9 - $10/bar 4 10 - 15

Slab Replacement $50 - $100/sq.yd. 5 20+

Thick Hot Mix Overlay (5") $195,000 - $215,000 8 - 12

1 Since some treatments are often limited to one lane, costs shown are per lane-mile, unless otherwisenoted.

2 Varies but ranges from $25,000 - $35,000 per two-lane mile with surfaced shoulders. Random, workingcracks on high end of estimate.

3 Diamond grinding = $38,700/ lane-mile; diamond grinding + dowel bar retrofit = $115,400/ lane-mile.Both figures include all associated repairs and sealing.

4 Cross Stitching bars placed at 2' intervals.

5 Smaller per unit cost for large quantities ($700,000/ two-lane mile).

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Chapter 5:Recommended Treatment Practices

As stated in the Introduction, there are manyvariables that influence the selection of theright treatment. After the treatment isselected, there are still many choices as to theproper procedures and materials to use.

The information presented in this Chapter isbelieved to represent “good, sound practice”for a number of the treatments that havebeen previously identified. Various Districtsprepared this information based on what hasbeen found to work best in their areas underthe circumstances where they were tried.Nothing being presented is intended to keepsupervisors and superintendents from usinghis/her own methods, if previous performancehas been satisfactory. However, Districts areencouraged to try the practices described inthis Chapter, if your current efforts are notproducing the desired results. The detailedtracking system being implemented byMaterials and Research Division will helpdetermine the effectiveness of the variousmethods and will provide guidance for futuredecision making. A copy of the electronicform that is to be completed by the Districts isshown on the following page.

The Materials and Research Division shouldbe contacted for information regardingstrategies not described in this Chapter.

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PREVENTIVE MAINTENANCE TRACKING FORM

The following section of highway has recieved a Preventive Maintenance treatment:(Do not submit unless both lanes of a 2-lane or at least two lanes of a 4-lane

and the section length is equal to or greater than 1/2-mile.)

Submitted by:

Date:

Highway:

Reference Posts: Beg End

(Provide lane direction for 4-lane roads)

Type of Work:

■■ Crack Seal/Asphalt ■■ Milling ■■ Joint Sealing/PCC

■■ Fog Seal ■■ Cold-in-place Recycle* ■■ Dowel Bar Retrofit / Grinding

■■ Scrub Seal ■■ Hot-in-place Recycle* ■■ Microsurfacing

■■ Slurry Seal ■■ Thin Cold Mix Overlay* ■■ Diamond Grinding

■■ Armor Coat/Chip Seal* ■■ Thin Hot Mix Overlay*

Work Done By:

●● State Forces ●● Contractor

Control Number Project Number

Date Started: Date Completed:

Optional Data

Surface Temperature Range: to

Air Temperature Range: to

Vendors:

Aggregate Information (washed /crushed / limestone, etc.):

Type of Oil:

Crack or Joint Sealant Information (brand / variety, etc.):

Comments:

INFORMATION TO BE COMPLETED BY TRANSPORTATION PLANNING / PROJECTDEVELOPMENT:

NSI prior to Preventive Maintenance Treatment: ________ Date: _____⁄_____⁄________

Preventive Maintenance

Crack Filling and Sealing Procedures-Asphalt Pavements

In the past, there has been little distinctionbetween Crack Sealing and Crack Filling. Inaddition to the definitions provided in theGlossary, remember that the working cracksrequiring sealing are usually transverse. Non-working cracks, that may be filled, are usuallydiagonal, longitudinal, or some block cracks.

Crack filling and sealing is probably the mostimportant and cost effective preventivemaintenance strategy. Because of thisimportance, detailed information is providedfor your use. Procedures used by Districts 7and 8 are listed below, as are some of theguidelines supplied by Materials and ResearchDivision. Suggested personnel and equipmentneeds are also included.

Crack filling and sealing is our first line ofdefense in roadway maintenance. Cracksealing should be done within 2 years afteran asphalt overlay. Cracks 1⁄4-inch or widershould be filled or sealed before rainfallseasons or before maintenance surfacetreatments, such as fog seals, scrub seals,slurry seals, chip seals, maintenanceoverlays, etc., are applied.

Cracks should be routed and cleaned beforefilling or sealing. When moisture is present orsuspected, it is recommended hotcompressed air (heat lance) be used toprepare cracks immediately before filling orsealing materials are applied. All cracks should

be squeegeed during filling and sealing (ifproduct is left above the surface) to savematerials, prevent road noise, improve ridequality, prevent bleeding or masking throughfuture surface treatments, and preventcompaction problems on future overlays.

Crack sealing operations can be very laborintensive. A value engineering studyconcluded that 66 percent of the total cost forthese projects was for labor, 22 percent forequipment, and 12 percent for materials.Because crack sealing takes a lot of time,workers are exposed to traffic and motoristsencounter delays. Therefore, it is safer andusually more cost-effective to use a productthat will last longer, even if it is moreexpensive.

Figure 5.1 Heat Lance

35

Filling or sealing pavement cracks to preventwater from entering the base and subbase likelywill extend the pavement life by 3 to 5 years.

Sealing the cracks with flexible rubberizedasphalt that bonds to the crack walls and moveswith the pavement will prevent water intrusion.Because fillers do not expand or contract, wecan conclude that sealing is the better option.Sealing will last longer and cost less.

Sealing prior to surface treatments enhancesthe treatment and further extends thepavement life. At a time when highway crewmanpower is shrinking, along with the funds tosupport road maintenance, crack sealing standsout as an economical maintenance technique.

The overall success of pavement maintenancesystems that include crack sealing, combinedwith their generally low cost, make cracksealing a desired maintenance treatment.Crack sealing provides the most cost-effectiveuse of dollars over time compared to otherpavement maintenance techniques.

Equipment

Using the right equipment is an importantpart of any crack sealing program. There aretwo major areas of consideration: crackpreparation and sealant application. In thesame way that a dentist prepares a toothbefore filling a cavity, crews must preparecracks to receive sealants. The better thepreparation, the better the chance that thesealant will last and perform. Cracks must befree of all dirt, dust and debris. The sealantmust have a clean, dry bonding surface.

Surface preparation can be accomplished withcompressed air and a simple blowpipe. Thistechnique works well when the dirt is dry andnot packed hard. If the cracks are filled withwet dirt, the dirt needs to be removed andthe crack must be completely dried. An aircompressor or a hot air lance generatingtemperatures of approximately 2,500 degreesFahrenheit is the best tool. In simple terms, aheat lance uses hot, compressed air thatblows cracks clean while drying them out. Results from the Strategic HighwayResearch Program (SHRP) study showedthere is almost a 40 percent greater chanceof sealant success if cracks are routed priorto sealing. Cutting a reservoir above the crackallows adequate sealant expansion andcontraction. The reservoir also ensures thatthe proper amount of sealant penetrates thecrack. An operator passes the pavement cutteror router over the crack and cuts a reservoirinto the crack. Modern routers can followeven the most random pavement cracks.Once the routing is complete, simply use

Figure 5.2 Router

36

compressed air (hot or cold) to remove thedust created by the router. Engine-poweredsteel wire brushes also can be used to cleanrouted and non-routed cracks. (Note: Older-aged asphalt pavements and thin asphaltpavements may not be suitable for routing.)

Although tar pots are still used for applyingmineral-filled materials, they will burn ordestroy crack and joint sealants that utilizepolymers or rubbers. Melters eliminate thisproblem by using a high-temperature heat-transfer medium, such as oil. These types ofmelters are known as “oil jacketed” melters or“double boilers.” Hot pour sealants areeffectively applied through a delivery hose andwand. These materials are commonly appliedat 375 degrees Fahrenheit To prevent sealantcooling, set up, and clog, the hose is placedunder constant pressure and the sealantconstantly circulates back into the main tank.Crew members, therefore, must be trainednot only in proper safety procedures, but alsoin proper operation of the melter. Recentinnovations in melter designs have greatly

improved melter safety. Melters with “ondemand” pumping and thermostaticallycontrolled delivery hoses reduce the chancesof mistakes and improve productivity. Thesenewly designed melters also reduce operatorconfusion. Digital temperature controls, theabsence of flush clean up systems andperplexing timing of valves and rapid heat uptimes have given operators more precisecontrol over sealing. This ease reduces costs,increases productivity and greatly improvessafety. Many melter manufacturers claimsuperior features and benefits for theirequipment.

It is in your best interest to fully examineindividual features and keep in mind not onlythe manufacturer’s general reputation but alsothe availability of parts and services. Productand service support often is important toon-time job completion.

Sealant Application

Sealant application can be accomplished in avariety of ways. Twelve methods are outlinedin the Strategic Highway Research Program

37

RESERVOIR RESERVOIRRESERVOIR

Configuration A. Standard Reservoir-

and-Flush

Configuration B. Standard Recessed

Band-Aid

Configuration C. Shallow Recessed

Band-Aid

Configuration D. Overband

Configuration E. Flush Fill

The combination of reservoir and an overband helps to maximize sealant performance. Life cycle costs show that by utilizing either crack sealing configuration B or C, the cost of crack sealing is 50% less than that of using configuration D.

Figure 5.3 Sealing & Filling Diagram

(SHRP) publication Materials and Proceduresfor Sealing and Filling Cracks in Asphalt-Surfaced Pavements. (SHRP-H-348). Thesuccess of each method is not onlydetermined by configuration but also bycleaning technique and sealant selection.Sealants applied in routed cracks performlonger. A recessed configuration dispensesmaterial into the confines of a routed crack.The sealant can be placed flush with thepavement, slightly below the surface of thepavement or slightly overfilled on the surface.

Pavement Selection

Pavement selection is often a forgottenelement in determining the success or failureof a crack sealing program. If the road hasalligator cracking, high-density multiplecracking, poor subbase drainage or structuraldamage, crack sealing will not solve theproblem. In these cases, the damage is toosevere. If you try to save a pavement with toomuch cracking, you will be disappointed withyour efforts. The best candidates for cracksealing are newer pavements that arebeginning to form cracks. You certainly canextend the life of these roads. More sealant isnot always better. The new sealants are notdesigned to be “road glue.” They are verysticky and have tremendous bonding power,but they are not made to “hold the roadtogether.” Crack sealing has one objective: toprevent water from further damaging roads.Sealing buys time and saves money bydelaying the expense of major reconstructivepavement work.

Priority

Crack filling and sealing operations are to beperformed as part of a comprehensivemaintenance program. This will take time toaccomplish and a greater dedication ofresources until we achieve the goal of makingthese operations a routine maintenancefunction throughout the State.

Criteria for Crack Filling and Sealing

Crack filling and sealing on newer pavementsshould be considered a high priority item andcracks should be filled as soon as possibleafter detection, preferably in the first fall crackfilling period after they initially appear.

Priority for crack filling and sealing on olderpavement should be based on the conditionof the pavement and on the condition of thecracks. The potential for moisture relatedpavement damage must be evaluated in orderto establish both the need and urgency forresealing.

The factors that should be considered inestablishing the priority for crack filling onolder pavements include:

✔ Weather✔ Age of pavement✔ General pavement condition✔ Type and condition of crack

On existing pavements, cracking may be sosevere that crack filling or sealing may not beappropriate and other repair methods mustbe considered.

38

When to Fill Cracks

Crack maintenance at the proper time withthe proper material and methods will reduceoverall maintenance costs and prolong the lifeof pavements. Crack filling and sealing shouldbe a high maintenance priority, whether it iscorrective or preventive. Crack filling andsealing can correct the problem of moistureintrusion and help prevent or slow thedevelopment of more serious problemsthereby extending the life of the pavement.

The optimum environment for performing thecrack filling and sealing operations are as follows:

✔ Temperature above freezing✔ Minimal moisture present in the pavement✔ Cracks open to approximately the midpoint

It is important to remember that, althoughcrack filling and sealing is not totallydependent on the size of the opening andthat the operation can be performed at anytime of the year, moisture in the crack is thecritical factor in preventing a quality seal.The fall of the year usually provides the bestconditions because of the moderatetemperatures, minimal rainfall, and the cracksare reaching their midpoint in width. Thistime-frame also prevents the intrusion ofwater and chemicals during the wintermonths. During the summer, crack openingswould be too small to seal. During the spring,although temperatures are often moderate,crack filling crews may have to contend withthe moisture in the pavement.

Since moisture has been identified as aleading cause of failure, additional effortswould be necessary to ensure the crack was

dry enough to fill. During the winter, crewswould be faced with temperature fluctuations,frozen moisture, and wide crackconsiderations.

These many considerations do not preclude aquality seal, but would require extra work onthe part of the crew to ensure properpreparation of the crack.

It is important to remember that eventhough crack filling and sealing is nottotally dependent upon the crack openingand can be done at all times of the year,the critical factor is moisture.

To minimize the problem of moisture incracks, a commercial heating unit (heat lance)should be used. Heat lances capable ofproducing approximately 2,500 degreesFahrenheit air, with operating velocities ofapproximately 3000 FPS at the nozzle orifice,have produced good results.

Material

To obtain a good seal, it is important to use aquality product. For cracks 1" wide or less, anASTM D5078-90 sealant should be used.Application should be made under pressureusing a 1⁄8" diameter nozzle. The use of pourpots is discouraged because very littlematerial gets into the crack and a lot iswasted on the surface. Asphalt with crumbrubber has been shown to work satisfactorilyon cracks over 1” wide and up to 11⁄2", butcaution must be used. With rubber asphaltproducts, it is very important to follow themanufacturer’s recommended specificationsfor handling and placing the sealant.

39

Procedures

Before crack filling and sealing, a pavementanalysis should be made to determine thetype and scope of work. This analysis is madeto determine if crack filling or sealing will becost effective for the particular pavementbeing evaluated. See paragraph 2.1 of theSHRP Materials and Procedures For Sealingand Filling Cracks In Asphalt-SurfacedPavements manual of practice.

Crack filling and sealing can only be effectiveas long as the sealant prevents the intrusionof water. It cannot be effective when theintegrity has failed due to extensive cracking.The pavement analysis may indicate that achip seal, slurry seal, or an overlay may beneeded with badly deteriorated areas beingappropriately patched.

Cleanliness and dryness are important factorswhen crack filling and sealing. Usingcompressed air with a heat lance is a goodmethod for removing dust, sand and otherforeign matter from the crack and will usuallyprovide a clean face for bonding. In additionto drying the crack, the asphalt surface isheated and the asphalt binder softened,which helps bond the sealant.

Crack Filling Prior to Overlay Operations

Crack filling and sealing should be performedwell in advance (at least 1 year) andindependent of any type of overlay operationin order to allow sufficient cure time for thesealant. This is particularly important onoverlays 2 inches or less in thickness, where

tearing, shoving, and/or wash boarding canoccur during rolling due to the influence ofcrack filler material expanding up into thefresh hot asphalt pavement.

When traffic picks up or pulls out fillermaterial, sand should be used for blotting. Ingeneral, this situation can be avoided by notoverfilling and by using squeegees on thefreshly filled cracks and confining any excessto a 4” band over the crack.

Training Requirements

Prior to beginning crack filling and sealingoperations, all personnel involved shouldreceive the following training:

A 1-hour session covering the following items:

✔ Importance of crack filling and sealingoperations

✔ Equipment requirements

✔ Manpower requirements

✔ Safety requirements and equipment

✔ *Specialized equipment

*Melter operations

*Hot compressed air lance operations

*Air compressor operations

*Router operations

*Use/operation of each piece of specializedequipment should be demonstrated topeople that may operate such equipmentprior to use on the job site. New operatorsshould demonstrate proficiency prior tobeing required to operate specializedequipment.

40

Equipment and Manpower Requirements

Equipment and personnel requirements arelisted below. As stated previously, crack fillingand sealing is very labor intensive.Approximately 3 to 5 people are needed for arouting operation (depending on flaggingneeds). An additional eight people arerequired for efficient and safe crack fillingoperations.

✔ One person to drive melter truck

✔ One to operate melter

✔ One to pour/fill cracks

✔ One to squeegee cracks

✔ One to drive air compressor vehicle

✔ One to operate HCL (hot compressedair lance)

✔ Two flaggers for safety

Not routing reduces personnel needs by about4 people, which represents about 33% lowerlabor costs. A supervisor must weigh thatagainst the increased performance of routedand sealed cracks.

For example, if routed and sealed cracks havea service life of 5 years and non-routed andsealed cracks have a service life of 3 years, itis still more cost effective to rout and seal.However, not all surfaces are candidates forrouting and if the necessary life of thetreatment is relatively short, routing may notbe appropriate.

Equipment needs for the sealing operation are:

✔ One towed air compressor✔ One pickup or other truck to tow air

compressor✔ One propane bottle mounted in bed of

pickup✔ One hot compressed air lance✔ One melter✔ One pickup or other truck to tow

melter and haul material to be addedto melter

✔ Two flagging vehicles for transportationof flaggers, barricades and traffic controlsigns as per the Maintenance Manualand Section 900 of the Standard Planfor traffic control.

✔ Two hand-held two-way radios forflaggers

✔ One squeegee

Equipment and flagging needs for the routingoperation is dependent on whether it is doneseparately, ahead of the sealing, or as part ofthe sealing operation.

Normal productivity is 3800 lineal feet of crackfilling per day, which represents treatment ofapproximately 1 mile of 2-lane pavement.

Safety Considerations

In addition to the recommended flaggingoperation and warning signs, the followingequipment and safety considerations arenecessary:

✔ One type 4A4OBC 10-pound fireextinguisher to be mounted in the bedof the vehicle towing the air compressor

41

✔ One type 4A4OBC 10-pound fireextinguisher mounted on the melter

✔ One first aid kit in each of the aircompressor and melter vehicles

✔ Suitable eye protection (goggles or faceshield) for HCL operator, cracksealer/pourer and router operator

✔ Gloves for HCL operator, cracksealer/pourer and router operator

✔ Safety vests and caps for each person✔ Steel toed boots for all people

Care should be taken when using the heatlance. Burns may be possible from superheated air and flying debris. Care should betaken around dry or flammable material. Careshould be used when using the melter, wandor squeegee. Burns may be possible from thehot tar. Propane bottles should have approvedvalve protection and be secured in the pickup.

References

The crack sealing and filling informationpresented above, was gathered from anumber of sources. District 7 personnelconducted interviews with highway personnelfrom Colorado, Kansas and Nebraska. Currentcrack filling procedures from these states werealso reviewed. Finally, two additionaldocuments, the SHRP Materials andProcedures For Sealing and Filling Cracks InAsphalt-Surfaced Pavements and The U.S.Army Corps Of Engineers, Cold RegionsResearch and Engineering Laboratory (CRREL)Report 92-18 were extensively consulted.

The information in this manual should be usedin conjunction with those two documents.

There are no hard and fast rules to follow incrack filling and sealing. One has to consider:1) traffic volume, 2) age of surface, 3) densityof cracks, 4) deterioration of cracks, 5) whenis next rehabilitation project scheduled, 6)personnel resources, 7) equipment resources,8) safety of personnel, 9) other maintenanceproblems, etc.

Sealing materials that are currently being usedare ranked as follows:

✔ Crafco AR-2, the lowest quality we areusing, is recommended for Sealing(possibly Filling). For FILLING wider, non-working cracks this material is mostpractical in either flush or overbandedinstallation when not routing. Thepresence of crumb rubber chunks limits itsplacement in very narrow cracks.

✔ Type I, contains recycled rubber, being alittle softer for cold weather locations andit is recommended for Sealing (possiblyFilling). Whether FILLING or SEALING,flush or overbanded installation, werecommend routing which will increaselength of time of good performance.

✔ Type II, contains recycled or virgin rubber,and is more resilient than Type I and it isrecommended for Sealing. Again, werecommend routing cracks, with flush oroverbanded material installations. Theyshould perform TWICE as long as non-routed cracks. It is also VERY importantthat the cracks are clean and dry.

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✔ Crafco 231 Low-modulus, very goodcold temperature properties and it isrecommended for Sealing. Routing isrequired to insure the sealant is belowthe surface. It is also VERY importantthat the cracks are clean and dry.

Note: Do not use Low-Modulus material inlongitudinal cracks which are anywhere near thewheel path because it will track and pull out!

Cracks less than 1⁄4--inch wide have littlemovement during temperature variations. It isrecommended that these cracks be routedand filled with a material such as AR-2. If notrouted and filled, a hot kettle of PG58-28 leftover from an asphalt project may be the mostpractical to use. It’s quick and easy to place(pour), it has a short cure time, and any PGBinder has good adhesion properties.

The most successful crack treatments consistof at least three and up to five steps,depending on the type of treatment (sealingor filling). These steps are:

1. Crack routing or sawing2. Crack cleaning and drying3. Material preparation and application4. Material finishing/shaping5. Blotting

Steps 4 and 5 are considered optional.Concentrate on 1, 2 and 3 at all times toinsure the greatest success. Crack routing orsawing isn’t as critical in filling operations, butneeds to be done in sealing operations. WithNebraska’s significant annual temperature

variations, crack routing or sawing in sealingoperations is even more important to achieveshape factors that provide added flexibility forwithstanding high crack movements.

Note: When routing, insure that you routthrough any surface treatments down into thehot mix asphalt. You may lose the sealant andthe surface treatment adjacent to the crack, ifthe sealant is bonded only to the surfacetreatment. This can get very ugly and be causefor added maintenance problems.

Joint Resealing-Concrete Pavements

Many of the recommendations presented inthis section are the result of 5 years ofresearch done through the Federal HighwayAdministration, Long Term PavementPerformance Program (LTPP). This researchvalidated earlier research done as part of theStrategic Highway Research Program(SHRP-H-349) and is presented in detail in amanual of practice (FHWA-RD-99-146).

Joint sealants serve two primary purposes;prevention of incompressible materials andwater from entering the joint. To be effective,the sealant must resist the embedment ofincompressible material. It must alsomaintain adhesion to the concrete sidewalls.

Since joints in concrete pavement are sealedas part of new construction, the issuebecomes “When is resealing appropriate?”Excessive delay in resealing can result in amore rapid deterioration of the pavement.Spending money to replace the sealant tooearly is not cost-effective either.

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Four things should be considered when decidingwhether to reseal joints: 1) climatic conditions,2) sealant condition, 3) pavement condition, and4) traffic. Since Nebraska is in a Wet/Freeze region,sealants are very important. Also, since most of theconcrete pavements have medium to high trafficvolumes (>5000ADT), good sealants are againimportant. A sealant such as the Low ModulusRubberized Asphalt meeting a modified ASTM D3405 specification that we use (Crafco 231),should last for 5 years.

If pavement condition dictates the need for asurface treatment in fewer years than that, thejoints should still be sealed but a less expensive,temporary seal such as a Rubberized Asphalt,Type II may be used.

In general, the FHWA manual recommends thatunder Nebraska climatic and traffic conditions,joints should be resealed when the sealantcondition rating is Fair to Poor.

A sealant condition is rated Fair when water cannotenter in more than 10-30% of the length, and stoneintrusion is limited to mostly being stuck to the top ofthe sealant with very little being deeply embedded. Itis recommended that 10 or more joints, that areconsidered representative of the section, be inspectedcarefully and rated before making a decision.

Once the decision has been made to reseal, otherrepairs such as corner breaks, spalls, grinding, etc.should be done before resealing begins. Also,evaluate the sealing needs of the longitudinaljoints, lane-shoulder joints, and transverse crackssince considerable water can enter through these ifopen.

Like sealing cracks in asphalt, the proper jointpreparation and final cleanliness of the concretejoint walls prior to installation and the properinstallation procedures are critical for a long-lasting, successful sealant operation.

Procedures found to be effective are as follows:✔ Plow or saw the joint to remove as much of the

existing sealant as possible. If the existingsealant does not gum-up the blades, then saw.If it does gum-up the saw blades, plowing is theway to go.

✔ Next, consider water washing when you feeladditional cleanliness of the joint is needed.This will seldom, if ever, be needed.

✔ Give the joints a good initial air blasting toremove loose material in the joint.

✔ Next, Sand Blast the Joints! This procedurehas been found to be a MUST if the seal is toperform to our expectations. Using thisprocedure and the Low Modulus materialshould provide a joint seal that will last at least5 years.

✔ Give the joints another air blast to remove anydebris left after the sand blasting.

✔ Properly install the Backer Rod. Correct sizebacker rod will be at least 25 percent largerthan the joint width. The backer rod should beplace at such a depth so the “shape factor” ofthe sealant is proper for the sealant materialbeing used. The shape factor for the LowModulus and the Type II sealants mentionedabove is 1:1, width to thickness. When figuringthe depth for placement of the backer rod, keepin mind an allowance for the sealant to berecessed below the pavement surface.

✔ Installation of the sealant is the final step in thesealing operation. Make sure Low Modulusmaterial is recessed below the pavementsurface, it will track and pull out if exposedto traffic contact. Although not as critical withthe Type II, it is recommended that it also berecessed.

Joint resealing will not perform as intended ifthe surfaces are not completely clean (no dustwhen running a finger along the joint wall).The surface must also be dry.

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Seal Coats Asphalt roadway surfaces tend to deteriorateover time as the elements of nature cause theasphalt to become hard and brittle. This oftenoccurs in the form of raveling or surface cracks.Application of a seal coat can restore the resilientproperties of the asphalt surface and preventfurther deterioration. Seal coats will not helpthe load carrying ability of a roadway.

Experience has shown when proper preparationhas been done in areas scheduled for seal coattype surface treatments, the life of the surfacetreatments can be greatly extended and help inreducing life-cycle cost. It is critical that allnecessary preparation work such as crack filling,pothole repair, patching, leveling, core outs, etc.,be done prior to surface treatments being placed.

Seal coats commonly used in roadwaymaintenance are fog seals, scrub seals, slurryseals, and chip seals. Seal coats should not beplaced over AC mixes with a history of moisturesensitivity or stripping problems.

The type of seal coat selected should bedictated by the following guidelines and site-specific field conditions.

A. Fog SealA fog seal is a light application (0.12 gal./sq.yd.)of a slow-setting asphalt emulsion diluted withwater, similar to a tack coat, to an existingsurface. It can be diluted in varying proportionsup to one part emulsion to five parts water, butin most cases a one to one dilution is used.Grades of asphalt emulsion normally used forthis purpose are SS-1, SS-1h, CSS-1, or CSS-1h.

A fog seal should be considered forapplication, 4 years after an asphalt overlay,and be completed by August 31st. It isimportant that fog seal not be applied untilsealed cracks have undergone at least 2 seasons

of oxidation. Also, a fog seal should not beapplied to any pavement with existing low skidnumbers (signed slippery when wet).

A fog seal can be a valuable maintenance aidwhen used for its intended purpose. It is neithera substitute for an asphalt surface treatment norother types of seal coats. It is used to renew oldasphalt surfaces that have become dry andembrittled with age and to seal very smallcracks and surface voids. Open-graded asphaltsurfaces such as the MQ mix require fog sealson a two to three year basis to prevent raveling.The fairly low viscosity diluted emulsion flowseasily into the cracks and surface voids. It alsocoats aggregate particles on the surface. Thiscorrective action will prolong pavement life andmay delay the time when major maintenance orreconstruction is needed.

Typically, fog seals are used to seal shouldersand dikes, dig outs, blankets, and patches.Also, they are used as a flush coat (with goodsuccess) on newly applied chip seals to providebetter rock retention, which can assist inpreventing broken windshields and otherdamages to vehicles. Normally, sand is used asa cover material after applying a flush coat.

Care should be taken to keep traffic off of thenewly sealed surface until the emulsion hasbroken which usually occurs in one to two hours.Even though the application is light, special caremust be used when going around curves to keeptraffic away from the oil that has a tendency toflow because of the super elevation.

Normal crew size for fog sealing is five. Unlessspecial traffic control is required, equipmentneeds are a distributor truck and a pickup.The operation proceeds rapidly and dailyproductivity is approximately 25,000 squareyards on non-Interstate and 20,000 square yardson Interstate highways.

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B. Scrub Seal (Broom Seal)

A scrub seal may be used effectively tofill cracks in cases of low to moderatenon-working cracks, as long as the roadwayprofile is good.

A scrub seal is normally an application of apolymer modified asphalt that is broomedinto the pavement surface followed by a coverof fine aggregate (sand), and a secondbrooming. The seal should then be rolled witha pneumatic roller. These seals may be used toimprove skid resistance, prevent oxidation, andto seal hairline cracks against water infiltration.

C. Slurry Seal

A slurry seal is a mixture of slow settingemulsified asphalt, well-graded fine aggregate,mineral filler, and water. It will fill fine cracksin the pavement surface, fill in slight imperfec-tions and give a uniform color and texture. Itslows down the rate of surface oxidation butmost importantly it seals the highway, thuspreventing the infiltration of water, which isthe most frequent cause of pavement failure.Generally, this strategy performs best whenten percent or less alligator cracking ispresent (i.e. when extent rating = trace).

The product may beused as a substitutefor our traditional“chip seal” and“hot mix” pavingmethods. Unlike“chip seal,” there areno loose stones ordust to contend with.

There is a residue (sandy grit) that remainsloose on the finished surface, but it dissipatesin a short time. Slurry seals can be placed in areas withpavement and ambient temperatures as lowas 50 degrees Fahrenheit when approved bythe Maintenance Superintendent. Normally,slurry seals are not placed if the wheel pathson the surface to be treated have depressionsgreater than 1⁄2-inch, or if the treatment mustbe placed at night. If these two conditionsexist, the use of a slurry seal should beevaluated on a case-by-case basis.It is suggested that if a slurry seal is believedto be the appropriate treatment, contactMaterials and Research Division for verifica-tion. Although some of this type of work hasbeen done with State forces, contracting withfirms that specialize in this type of work maybe more cost effective.

Figure 5.4 Apply asphalt Figure 5.5 Apply fine aggregate

Figure 5.6 Drag broom Figure 5.7 Drag broom

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Figure 5.8 Slurry Seal

D. Chip Seal (Armor Coat)

Chip seal should be used in cases wherelight to moderate cracking, light tomoderate “raveling”, or light to moderatepolishing or flushing is occurring.Additionally chip seal should be used toseal “machine patches”.

Chip seals provide skid resistance andimprove ride quality, as well as seal theroadway. This work should be scheduled soit can be completed by September 30th.

Chip seals generally consist of applyingasphaltic emulsions or liquid paving gradeasphalts (with additives) and then coveringthem with aggregate and rolling. Chip sealsare a very good surface treatment if they areplaced correctly. Consideration should begiven not to place them at politically sensitiveareas (e.g., high ADT due to special events),high percentage of truck traffic, or whereextremely heavy snow and ice removaloperations are common.

All cracks should be sealed prior to chipsealing, as chip sealing is not a substitute forcrack sealing. Also, centerline tabs must beplaced before chip sealing.

It is recommended that sand/gravel aggregatebe crushed to provide the gradation shown inthe table below.

The use of crushed material should providebetter performance and the smaller, “onesize” gradation should provide a quieter ride.Where crushed limestone is available, it isrecommended that 1⁄4" chips be specified.Regardless of which crushed material isused, it is important that clean material beused. With too much #200 sieve material, theemulsion may not stick to the aggregate.

The use of non-crushed aggregate should belimited to only the very lowest volume roads(if used at all).

Figure 5.10 Apply

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Figure 5.9 Armor Coat Placement

ALD2⁄3 ALD

Table 5.1 Chip Seal Aggregate Gradation Limits

Percent PassingSieve Size Target Tolerance

3⁄8 inch 100% ---

No. 4 70% ±10%

No. 10 30% +5% *

No. 50 5% ±5%

No. 200 2% ±2%

* Pay penalty for value > 35% passing

There is also a tendency to apply moreaggregate than is required, which ultimatelyjust gets swept off the road and wasted.With the correct amount, trucks backing onthe aggregate will give the appearance ofnearly bleeding and a sweep of the hand willbrush very little excess aggregate off thesurface. Application rates should be about200 tons/mile (24’ wide), or approximately28 lbs/sq. yd.

The emulsion should be applied at a rate of0.27 gal./sq.yd. and at a temperature of160-170 degrees Fahrenheit. Although thereare many choices of oils to use, the bestsuccess has come from using CRS-2P, CRS-2Land CRS-2, with the CRS-2P being used forhigher ADT’s and CRS-2 for low ADT’s.

Nozzles on the distributor bar should be setat 12 inches above the pavement surfaceand angled so all areas are covered.

The distributor truck should be operatedimmediately ahead of the trucks applying theaggregate (no more than 20 seconds ahead).When necessary to switch trucks hauling theaggregate, the distributor must stop to preventapplied oil from becoming cool.

After the oil and aggregate have been placed,the surface should be rolled two to threetimes with a pneumatic roller(s). Excessaggregate may be lightly swept from the roadat the end of the day or no later than the nextmorning.

During the chip sealing operation, at aminimum, traffic should be controlled byflaggers. If traffic volumes are high, the useof a pilot vehicle is recommended.

Proper warning signs and reduced speedsigns should remain in place until allexcess material has been removed.

The chip sealing operation may be done witha crew of 8 people and the followingequipment: 1 Distributor Truck, 4 TandemTrucks, 1 Roller, 1 Chip Spreader, 2 Pickups,1 Rotary Broom, and possibly a Loader andPortable Traffic Control Device.

An operation such as described above canaccomplish about 10,000 square yards orroughly 3⁄4 mile of two-lane highway in a day.

Since this represents only about one-half theamount of oil on a normal semi-load, someDistricts combine forces in order to use one,two or even three loads in a day. For example,a District 7 chip seal operation consists of5 Tandem Trucks, 2 Distributors, 1 Loader,2 Rubber-tired Rollers, 1 Chip Spreader(2 people to operate), 2 Flaggers and a pilotcar, 2 people to set tabs and move signs and2 supervisors for a total of 19 people. Thebroom crew consists of 3 Brooms, 2 Flaggersand a pilot car, and 1 Water Truck (to controldust while brooming). An operation such asthis can expect to chip seal two to three milesper day.

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Microsurfacing

Microsurfacing refers to a mixture of polymermodified asphalt emulsion, mineral aggregate,mineral filler, water, and other additives,properly proportioned, mixed, and spread ona paved surface. Microsurfacing differs fromslurry seal in that it can be used on highvolume roads to correct wheel path ruttingand provide a skid resistant pavement surface.

Although Nebraska has limited experiencewith the use of Microsurfacing, literature suchas FHWA – SA-94-051, State of the PracticeDesign, Construction, and Performance ofMicro-surfacing and from the InternationalSlurry Surfacing Association (ISSA) providedmuch of the following insight.

Using various design mixes, techniques, andequipment, Microsurfacing can be usedsuccessfully in these situations:

✔ Capable of filling wheel ruts up to11⁄2 inches deep when the pavement hasstabilized and is not subject to plasticdeformation. Microsurfacing creates anew, stable surface that is resistant torutting and shoving in summer and tocracking in winter. Microsurfacing hasthe unique ability to solve this problemwithout milling.

✔ In quick-traffic applications as thin as3⁄8-inch, Microsurfacing can increase skidresistance, color contrast, surfacerestoration, and service life to highways.Such projects are often reopened to trafficwithin an hour.

✔ Modern, continuous-load pavers can lay500 tons of Microsurfacing per day, withno long traffic delays. This equates to anaverage 6.6-lane miles per day forsurfacing applications.

✔ As a thin, restorative surface source onheavy traffic intersections, Microsurfacingdoes not alter drainage; there is no lossof curb reveal.

✔ Because Microsurfacing can be effectivelyapplied to most surfaces at 3⁄8-inch orless, more area per ton of mix is covered,resulting in cost-effective surfacing.

✔ Applied to both asphalt and portlandcement concrete surfaces (usually precededby a tack coat on concrete), Microsurfacingis often used to restore a skid-resistantsurface to slick bridge decking withminimum added dead weight.

Figure 5.11 Microsurfacing RutsFigure 5.12 Surface

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Finer Stones Finer StonesLarger Stones

Cross section of a rut

✔ Because of its quick-traffic properties,Microsurfacing can be applied in a broadrange of temperature and weatherconditions, effectively lengthening thepaving season. Applied at ambienttemperatures, Microsurfacing has lowenergy requirements and it isenvironmentally safe, emitting nopollutants.

✔ Microsurfacing’s life expectancy usuallyexceeds 7 years.

How is Microsurfacing Made and Applied?

Microsurfacing is made and applied to existingpavements by a specialized machine, whichcarries all components, mixes them on site, andspreads the mixture onto the road surface.

Materials are continuously and accuratelymeasured, and then thoroughly combined inthe Microsurfacing machine's mixer.

As the machine moves forward, the mixture iscontinuously fed into a full-width “surfacing”box, which spreads the width of a traffic lanein a single pass. Specially engineered “rut”boxes, designed to deliver the largestaggregate particles into the deepest part ofthe rut to give maximum stability in the wheelpath, may also be used. Edges of theMicrosurfacing are automatically feathered.

The new surface is initially a dark brown colorand changes to the finished black surface asthe water is chemically ejected and thesurface cures, permitting traffic within onehour in most cases.

Continuous-load pavers utilize support units,which bring the materials to the job site andload the machine while it is working, thusmaximizing production and minimizingtransverse joints.

A Product of Quality

Successful Microsurfacing incorporatescarefully selected materials, scientific mixdesigns, and advanced technicalspecifications.

Microsurfacing begins with the selection ofhigh-quality materials—asphalt, aggregate,emulsifiers, water, and additives—which mustpass special laboratory tests, both individualand when combined, as a Microsurfacingsystem.

The ISSA’s broad range of specialized mixdesign tests help to insure that the mixturehas these Microsurfacing characteristics:

Figure 5.13Microsurfacing

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1. Is capable of being spread in various thick cross-sections (wedges, ruts, scratchcourse), which

2. After initial traffic consolidation, does notfurther compact (i.e. resists compaction)throughout the entire design tolerancerange of bitumen content and variablethicknesses to be encountered, and

3. Maintains good macro-texture (high wetcoefficient of friction) in variable thicksections throughout the service life of theMicrosurfacing.

Successful Microsurfacing projects dependon strict adherence to technical specifications.Many users find it helpful to design theirindividual job specifications around thoserecommended by ISSA (Technical BulletinA-143).

The resulting “mix design” and jobspecifications are carefully adhered to in thefield, where ISSA member contractors usespecialized job-calibrated equipment andthoroughly trained crews to maintainconsistent quality control.

Shoulder Maintenance

Every maintenance supervisor is well aware ofthe liability associated with shoulder drop-offs.

Since the primary purpose of this manual is toprovide information that will aid in pavementpreservation, it would not be complete withouta reminder that proper shoulder maintenancealso plays a major role in how a pavementperforms whether it be asphalt or concrete.

It is important to keep the earth shoulders ofthe roadway graded to the pavement edgewith sufficient vegetation. The shouldersprovide an escape for run-off.

If water is allowed to stand next to thesurfaced roadway, the subgrade may becompromised and major surfacing problemswill be the result. This is most likely to occurat the bottom of hills as build-up fromsanding operations, natural silting, etc. Thisproblem is not limited to roads with earthshoulders. Often surfaced shoulders trapwater on the pavement.

If the shoulders are too high on grades,run-off will be directed along the roadway,causing concentrated flow resulting inshoulder erosion and subgrade failure.

Immediate action to resolve these problems is vital.

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Corrective Maintenance

Figure 1.1 on Page 3 shows the overlapbetween preventive and correctivemaintenance. Corrective maintenance isreactive, i.e. it is done after a road is in needof repair.

As the Department proceeds with a moreaggressive preventive maintenance program,the need for corrective maintenance willdecrease but will never be eliminated. Forthe last 5 years, nearly 60% of the surfacemaintenance budget has been spent onvarious forms of patching (e.g. spot patching,full depth asphalt and concrete repair,hot mix asphalt skin patching, cold mixasphalt patching, and spray-injectionpatching). The following sections provide abrief description of some correctivemaintenance methods used by the identifiedDistricts.

Full Depth Asphalt Repair

Full depth asphalt repair should be consideredanytime you have rutting greater than 3⁄4 ",corrugations and shoving, surface depressions,or a series of potholes. Work shouldnormally be planned between May 1 andSeptember 30 unless frost boils or otherproblems dictate emergency repair.

The first step of full depth patching is to cutan area, 1-2 feet larger than the distressedarea needing repair, by using a wheel cutteror pavement saw. Use a backhoe, millingmachine, or front-end loader to remove asmuch of the pavement as needed, makingsure the subgrade is stable. If the subgradeis unstable, remove it also. Restabilize andcompact the subgrade to proper depth, usinga plate packer. Clean all edges and apply atack coat to all vertical edges and to the base,if desired. Dump hot-mix asphalt directly intothe excavated area, making sure to useenough to allow for compaction. Compactthe edges first, then compact from the low tothe high side, overlapping about 6-10 incheswith each pass. When finished, the patchshould match the existing surface.

Equipment required for the above describedoperation: small milling machine, backhoe,front-end loader, self-propelled roller,pavement cutter, plate packer, oil distributor,power broom, dump truck(s).

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Full Depth Concrete Patching

Full depth concrete patching should beconsidered anytime there is considerabledisplacement, settlement, spalling, or crackingof panels. The easiest time to handlepavement repair (PR) concrete (i.e. finishing,etc.) is during the spring and fall. Workingwith PR concrete in the summer is difficultdue to its rapid-set properties. In the winter,or any season when the air temperatures arecool, the concrete will not set sufficiently toallow traffic to use it in the normal 4-hourcure time.

It is important to remember that PR concreterequires the use of 799 pounds of Type IIIcement and the addition of calcium chloride.Temperatures should be 40 degrees Fahren-heit and rising. The patch must be coveredwith black jack boards for 4 hours to achievestrength, if air temperatures are above60 degrees Fahrenheit, and for 8 hours iftemperatures are between 40 and60 degrees. If Type I cement is used insteadof Type III, the patch should not be openedto traffic for 24 hours.

Since most of Nebraska’s concrete highwaysare located where traffic volumes aresignificant, it is recommended that effortsshould be made to accurately calculate andonly remove the amount of distressed areathat can be replaced and cured during a day.Also, keep in mind the distance betweenrepair locations, since all concrete shouldbe removed from the truck within 30minutes after adding the calcium chloride.

If less than a full panel is to be repaired, startby making a diamond saw blade cut, 2” deep± 1⁄4 " along the area to be removed. Move in2" ± 1⁄2 " towards the area to be patched andmake a full depth cut with a wheel cutter.Use a bobcat with a breaker on it to break upthe concrete and to remove the brokenconcrete (or a loader if a large area). Whenthe concrete is removed, use a chippinghammer to chip the face of the hole at anangle downward to make a wedge.

Fine grade the hole to a depth 2" more thanthe existing concrete depth. Compact thesubgrade with a walk behind vibratorcompactor. Install either bond breaker or tiebars along centerline joint, as applicable.

Add calcium chloride to the concrete, pourconcrete, vibrate and finish, cure with curingcompound, and cover with black jack boardsfor a minimum of 4 hours. Do not overvibrate, as this will cause segregation.

Do not add water to the mix or spray wateron the concrete when finishing. Addingwater lowers the strength and sprayingwater on concrete brings the cement to thetop and will result in scaling.

Saw and seal appropriate joints the followingday.

Equipment needed for doing full-depthconcrete repair includes: Walk behind sawwith diamond blade, wheel saw for bobcat,air compressor and chipping hammer, bobcatwith breaker & bucket, dump truck, walkbehind plate tamper, concrete vibrator, loader,water supply (truck), generator for power

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source, concrete power screed (if large area)or strike off board (if small area), cureapplicator (sprayer), concrete forms(steel and/or wood), concrete tools such asfloats, edgers, shovels,etc., chalk line andblack jack insulation boards with plasticprotection (bottom).

Production is often limited to one panel perday for a six-person crew due to spacingbetween panels needing repair and the desireto restore traffic operations before dark.

Spray Injection Patching

Spray injection patching is a quick and safemethod that can be used to repair alligatorcracking, transverse cracking, edge breaks,depressions, rutting and potholes.

Asphalt mixes basically consist of twocomponents – the aggregate, which providesthe structure for the mix, and the asphaltbinder, which “glues” it all together. The spray-injection pothole patcher has two separatestorage tanks – one for the aggregate and theother for the asphalt binder. The asphalt andaggregate are mixed as they travel underpressure through the machine's spray hose;the mix is then sprayed into the pothole,filling it. A layer of aggregate is then placedon top of the patched area.

This procedure is fast, simple, and efficient.Work crews spend less time toilingdangerously close to traffic, and motoristsspend less time waiting for the patch to beapplied. The pavement can be opened totraffic almost immediately after patching.

Figure 5.14 Spray Injection (AMZ)

Figure 5.15 Spray Injection (AMZ)

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Machine Patch Using Cold-Mix Asphalt

There are numerous types of distress that maybe encountered in our highways. The reasonfor the distress should be determined andaction taken to correct the condition thatcaused the problem.

Some of the surface evidence of various typesof pavement distress are: weathering, raveling,longitudinal cracks, alligator cracks, chuckholes, bleeding and instability, depressions,wheel rutting and edge breaking. Frequentlythere will be more than one of these surfacecharacteristics that will be in evidence at thesame time. Sometimes one type of distressmay progress to a more serious type ofdistress.

Alligator cracks are usually caused by a basefailure and should be repaired prior torepairing the surfacing. Depressions usually

occur because of subgrade settlement ortraffic rutting. They may be in the form of ratruns, long swales or may have sheared sidesbecause of sudden earth movement.

These types of distresses may be corrected bymachine patching of the roadway surface withmaintenance cold mix using a motor grader toeliminate potential surface hazards.

Cold-mix asphalt is a combination ofunheated aggregates, fillers, and asphaltic oils.Although gravel and/or sand are the mostcommonly used aggregates, asphalt millingsand crushed concrete have also been usedsuccessfully. Clay is the most commonly usedfiller. Emulsified asphaltic oil is recommendedbut cutbacks can also be used.

If properly tested and controlled, quality coldmix can be produced from a wide variety ofmaterials as described in the next section.

Figure 5.16 Machine Patching55

Cold-Mix Production

The first step is to determine the neededquantity of mix. As a “rule of thumb”, 400 tonsof cold mix will patch 1⁄2 to 1 mile of roadway,depending on the condition of the surface,e.g. a severely rutted road will take about400 tons per 1⁄2-mile or 800 tons per mile.

Second, sample the materials and submitthe sample to a Testing Lab for performanceof gradation tests, pulverization tests, P.I.determination, and mix design.

Using the mix design, compute the windrowquantities for oil, aggregate, and filler. Thewindrow site should then be staked fordelivery of individual loads of aggregate.Prior to hauling gravel and filler, checkgradations to make sure they are the sameas the mix design. A change in materialscan create major problems. After allaggregate has been hauled and evenlydistributed, place the gravel in a windrow onone side of the mixing platform. The fillershould then be computed and staked in asimilar manner.

Before hauling the filler to the windrow site,spread a portion of the gravel to a uniformdepth, and then dump the filler directly ontothe gravel, placing one load between each setof flags. A motor grader can be used to spreadthe filler uniformly. After all the gravel andfiller are in place, mix thoroughly, beingcareful to not overwork the mixture. At thecompletion of the mixing, sample the mixtureand do a gradation test and a moisture test.The gradation should be close to the mix

design or adjustments must be made prior toapplication of the oil. The desired moisturecontent of the mixture prior to oil applicationis 5 to 9%. If too dry, it may be necessary toadd water; if too wet, additional mixing willbe needed. The moisture content andgradation are very critical to producing aquality, consistent mix.

When the oil tanker arrives, verify that thecorrect oil has been delivered and that thetemperature of the oil is between 105 and220 degrees Fahrenheit. Always use safetygear when working with oil, includinggloves, eye protection and protectiveclothing.

Although the oil can be applied directly fromthe tanker, a distributor with a meter is therecommended method of oil application.This will provide the desired, uniform oilapplication on any windrow site, whether hillyor flat. Determine the number of passesneeded to add the entire quantity of oil to thewindrow. The application rate when using adistributor can be adjusted by the truckspeed and pump pressure. (Consult themanufacturer’s recommendations for theproper settings). Pull out the appropriateportion of the windrow needed for one passof the distributor and spread into a uniformlayer. Apply the oil and immediately move thematerial to the opposite side of the mixingsurface. Repeat this process until all of therequired oil has been applied.

Mixing should continue with any combinationof equipment available, such as blades androtovaters. The heat in the oil will enhance

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the mixing operation, speed uniform mixing,and allow proper aggregate coating. Whenusing motor graders, the proper vertical andhorizontal angle of the blade should create arolling action of the cold mix material whichspeeds the mixing and aggregate coatingprocess. When using emulsified oil, thematerial should be ready to use as soon as allaggregates are thoroughly coated and the mixis uniform. An experienced operator can tellwhen the material is ready. The material willappear to crawl when being moved. There isa tendency on the part of operators used toworking with cutbacks, to mix emulsifiedwindrows too long, as cutbacks requiremore time for mixing and aerating.

Generally, if the moisture content is correctwhen the oil is applied and no additionalmoisture is received, an emulsified windrowis ready as soon as it is thoroughly mixed.A sample can be taken to a testing lab todetermine the actual moisture content.A moisture content of 2 to 5% is optimumfor laydown operations.

When the mixing process has been determinedto be complete, sample the material andsubmit to a testing lab for gradation tests anddetermination of asphalt content. These testresults can be useful in determining why a mixwas “good” or “not so good”.

The residual oil content with an emulsified oilshould be approximately 67% of your target;e.g. if the target is 6%, residual asphalt should be 4%.

A flow chart showing the cold mix processis illustrated above. To obtain additionalinformation regarding cold mix preparation,contact Roger Klasna, District MaintenanceSuperintendent, (308) 535-8031.

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START

PROCESS COMPLETE

DETERMINE WINDROW TONNAGE

DETERMINE AGGREGATE, OIL & FILLER

COMPUTE QUANTITY OF OIL NEEDED

COMPUTE QUANTITY OF AGGREGATE & FILLER

HAUL AGGREGATE AND FILLER TO SITE

MIX MATERIALS & TEST MOISTURE & GRADATION

MAKE NECESSARY CORRECTIONS

SAMPLE & SUBMIT TO LAB

SAMPLE & TEST AGGREGATE & FILLER

DETERMINE MIX DESIGN

DETERMINE TRUCK CAPACITY

COMPUTE & STAKE LOAD DISTANCE

DO SAMPLES MEET REQUIREMENTS

DETERMINE RATE & APPLY OIL

MIX UNTIL READY

YES NO

Cold Mix Process Flow Chart

Figure 5.17 Cold Mix Process Flow Chart

Hot Mix Asphalt Patch

When hot mix asphaltic concrete (HMAC) isavailable, this is often the material of choicefor repairing ruts, corrugations, depressionsor raveling. This practice is commonly referredto as skin patching or surface patching.Most skin patches are 1 to 4 inches deepdepending on what distress is beingremedied. Skin patches may be feathered atthe ends to meet an existing grade, the gradeat the ends of the patch may be milled to geta better transition, or a portion or the entiredistressed pavement may be milled.

After milling, broom the surface and apply atack coat, waiting until the oil breaks beforestarting to lay the hot mix. Use enough trucksto assure material can be supplied to keepfrom having a cold joint in a lane. The laydown machine speed should be consistentand the use of the vibratory screed is recom-mended since about 80% of the densityoccurs as a result of its use.

The breakdown roller should stay as closeas possible to the lay down machine. Thespeed should be consistent and no faster than4 mph. One pass with the breakdown roller(vibratory) and two passes with a finish roller(static) should provide adequate compaction.The finish roller needs to make the final passbefore the asphalt cools to 185 degreesFahrenheit. On small jobs, all compactioncan be accomplished with one roller.

The material should cool to around100 degrees Fahrenheit before allowingtraffic to drive on it.

Never allow the use of diesel as a releaseagent in truck boxes, the lay down machine,or on hand tools. Always use commercialrelease agents from the Approved ProductsList that are available locally.

Equipment required for hot mix patching:small milling machine, large milling machine,self-propelled roller (2), lay down machine,trucks, oil distributor, power broom.

Profile Milling

Profile milling may be considered as apossible treatment to restore roadway cross-sections, when wheel rutting is greater than1⁄2”. This may be followed up with either a chipseal or machine patch. Milling may also beused to treat roads with excess asphalt orextreme cases of raveling.

If rutting is caused by poor materials or weakbase, milling should be considered as a“temporary fix”, since the ruts will likelyreappear in 1 to 3 years. Also, caution mustbe used if the surface thickness is marginal forthe traffic loading.

Determining whether milling is the propertreatment is often a judgment call, consideringthe severity of the ruts, the cause of the rutsand the overall condition of the road.

When wheel rutting is greater than 1⁄2" deepand the asphalt pavement has sufficientthickness, profile milling may be performed torestore roadway cross-sections.

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Emergency Maintenance

Safety and time are often the differencesbetween corrective and emergency mainte-nance. Emergency maintenance needs areunique and specific procedures cannot bedefined. However, never take short cuts thatsacrifice the safety of the workers performingthe emergency maintenance!

One of the most common emergencymaintenance needs is patching. Informationfollows on various patching methods.

Hand Patching

The Strategic Highway Research Programlooked at three methods of repairing potholes:

✔ The throw-and-roll method, in which thecrew simply fills the pothole withpatching material, then compacts thepatch by driving over it.

✔ The semi-permanent method, whichinvolves squaring up the edges of thepothole with a saw or other equipment,placing the repair material, andcompacting it with a small vibratorycompactor. The technique is effective butvery labor-intensive.

✔ The spray-injection method, whichemploys special truck- or trailer-mountedequipment that shoots asphalt andaggregate into the pothole. Although thespray-injection equipment is expensive,the technique is extremely fast and canbe done by a crew of just one or twoworkers. (See detailed description undercorrective maintenance).

SHRP found that it is the quality of thematerials rather than the repair method usedthat has the biggest effect on the performanceof the pothole patch.

Materials

Conventional asphalt hot and cold mixestypically use certain percentages of asphaltcement (hot-mix) or emulsion or cutbackasphalts (cold-mix) and strictly gradedaggregate.

Modified/proprietary asphalt materials includethe addition of modifiers (rubber, fiber, sulfur,antistripping agent) and specially employedproduction processes. Examples of the morecommonly used materials are Sylvax UPM,Perma-Patch, Fiber Pave, Bonifibers, OmegaMix and QPR 2000.

Performance

Proprietary materials are designed to improveperformance under cold and wet conditions.

Hot-mix asphalt is still the #1 patch material

“Bituminous hot-mix has shown the longestservice life of all materials when it is placedproperly in a dry hole.”

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Adhesion – Bond between a sealant material and thecrack or joint sidewall.

Agency Costs – See Annual Costs

Aggregate Interlock – The projection of aggregateparticles or portions of aggregate particles from one sideof a joint or crack in concrete into recesses in the otherside of the joint or crack so as to affect load transfer incompression and shear and maintain mutual alignment.

Alligator Cracking – See Fatigue Cracking

Analysis Period – The period of time used in makingeconomic comparisons between rehabilitationalternatives. The analysis period should not be confusedwith the pavement’s design life (performance period).

Annual Costs – Any costs associated with the annualmaintenance and repair of the facility.

Application Temperature - The manufacturer’srecommended temperature to be used when installingsealant. For hot-applied sealants, the applicationtemperature is any temperature between the minimumapplication temperature and safe heating temperature.

Asset Management – A systematic process ofmaintaining, upgrading, and operating physical assetscost-effectively. It combines engineering principles withsound business practices and economic theory, and itprovides tools to facilitate a more organized, logicalapproach to decision-making. Thus, asset managementprovides a frame work for handling both short andlong-range planning.

Backer Rods – A compressible material that is placedin joints or cracks before applying sealant to preventbonding of the sealant on the bottom of the joint,control sealant depth, and prevent sagging of thesealant.

Bituminous Pavement - A pavement comprising anupper layer or layers of aggregate mixed with abituminous binder, such as asphalt, coal tars, andnatural tars for purposes of this terminology; surfacetreatments such as chip seals, slurry seals, sand seals,and cape seals are also included.

Bleeding – Excess asphalt binder occurring on thepavement surface. The bleeding may create a shiny,glass-like surface that may be tacky to the touch.Bleeding is usually found in the wheel paths.

Block Cracking – A rectangular pattern of cracking inasphalt pavements that is caused by hardening andshrinkage of the asphalt. Rectangular blocks range insize from approximately 1 sq. ft. to 100 sq. ft.

Blow-up – Buckling and shattering of PCC pavementresulting from thermal expansion and the resultantcompressive forces exceeding the strength of thematerial. Occurs at transverse joints or cracks.

Bond Breaker – Any material used to prevent bondingor to separate adjacent pavement layers. Thinbituminous layers are often used as bond breakerlayers between a concrete pavement and an unbondedconcrete overlay.

Bonded Concrete Overlay – Increase in the pavementstructure of a concrete pavement by addition ofconcrete thickness in direct contact with and adheringto the existing concrete surface. May be used to correcteither functional or structural deficiencies. (Based onbut not taken verbatim from 1993 AASHTO Guide,p. III-136)

California Profilograph – Rolling straight edge tool usedfor evaluating pavement profile (smoothness) consistingof a 7.5m (25-ft) frame with a sensing wheel located atthe center of the frame that senses and records bumpsand dips on graph paper or in a computer.

Cape Seal – A surface treatment that involves theapplication of slurry seal to a newly constructed surfacetreatment or chip seal. Cape seals are used to provide adense, waterproof surface with improved skidresistance and ride quality.

Carbide Milling – Surface removal or sawing donewith a carbide milling machine. Machine uses a bladeor arbor equipped with carbide-tipped teeth thatimpact and chip concrete or asphalt.

Glossary of Terms

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Chemically Curing Sealant – A material that reaches itfinal properties through the reaction of the componentmaterials when mixed.

Chip Seal – A surface treatment in which the pavement issprayed with asphalt (generally emulsified) and thenimmediately covered with aggregate and rolled. Chipseals are used primarily to seal the surface of a pavementwith non load-associated cracks and to improve surfacefriction, although they also are commonly used as awearing course on low volume roads.

Cohesion – The internal bond within a joint sealantmaterial. Cohesion loss is seen as a noticeable tearalong the surface and through the depth of the sealant.

Cold Applied Sealant – A crack-sealing compound thatis applied in an unheated state (generally at ambienttemperature) and then reaches final properties througha curing process.

Cold In-Place Recycling (CIR) – A process in which aportion of an existing bituminous pavement ispulverized or milled, and then the reclaimed material ismixed with new binder and, when needed, virginaggregates. The binder used most often is emulsifiedasphalt with or without a softening agent. The resultantblend is placed as a base for a subsequent overlay orsurface treatment.

Cold Milling – A process of removing pavement materialfrom the surface of the pavement either to prepare thesurface to receive overlays (by removing rutting, andsurface irregularities) or to restore pavement cross slopesand profile. Also used to remove oxidized asphaltconcrete. [Also see carbide milling.]

Compressible Insert – Material used to separate freshlyplaced concrete (such as from a partial-depth or full-depthrepair) from existing hardened concrete. This usuallyconsists of a 12-mm thick Styrofoam or compressed fibermaterial that is impregnated with asphalt.

Concrete – See Portland Cement Concrete

Construction Joint – A joint constructed in a transversedirection in PCC pavements to control cracking of theslab as it cures. Highway construction joints are createdby sawing the concrete.

Continuously Reinforced Concrete Pavement (CRCP) –PCC pavement constructed with sufficient longitudinal steelreinforcement to control transverse crack spacings andopenings in lieu of transverse contraction joints for accom-modating concrete volume changes and load transfer.

Contract Maintenance – The range of contractingmethods and vehicles used by public transportationagencies to accomplish maintenance programs andsupplement activities which may be performedin-house. Contracts may be activity based where theagency provides specifications and compensation iseither on a lump sum or unit price basis; orperformance based, long term total asset managementcontracting which requires the contractor to provideturn-key maintenance to an established level of service.

Corner Break – A portion of a concrete slab separatedby a crack that intersects the adjacent transverse orlongitudinal joints at about a 45 º angle with thedirection of traffic. The length of the sides is usuallyfrom 0.3 meters (1-ft) to one-half of the slab width oneach side of the crack.

Corrective Maintenance – Maintenance performedonce a deficiency occurs in the pavement; i.e., loss offriction, moderate to severe rutting, extensive cracking,or raveling.

CPR (Concrete Pavement Restoration) – CPR refers to aseries of repair techniques used to preserve or improvethe structural capacity or functional characteristics of aPCC pavement. CPR techniques each have a uniquepurpose to repair or replace a particular distress (kind ofdeterioration) found in PCC pavement and to managethe rate of deterioration. CPR techniques include:

✓ Full-depth repair✓ Partial-depth repair✓ Diamond grinding✓ Joint and crack resealing✓ Slab stabilization✓ Dowel Bar Retrofit✓ Cross-stitching cracks or longitudinal joints✓ Retrofitting concrete shoulders✓ Retrofitting edge drains

Crack – Fissure or discontinuity of the pavement surfacenot necessarily extending through the entire thicknessof the pavement. Cracks generally develop after initialconstruction of the pavement and may be caused bythermal effects, excess loadings, or excess deflections.Also see Alligator Cracking, Block Cracking, LongitudinalCrack, Reflection Cracking, Slippage Cracking, TransverseCrack, and Working Crack.

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Crack Filling – The placement of materials into non-working cracks to substantially reduce the intrusion ofincompressibles and infiltration of water, while alsoreinforcing the adjacent pavement. Crack filling shouldbe distinguished from crack sealing (see below).

Crack Sealing – A maintenance procedure that involvesplacement of specialized materials into working cracksusing unique configurations to reduce the intrusion ofincompressibles into the crack and to preventinfiltration of water into the underlying pavementlayers. (See Working Crack.)

Cross Stitching – A repair method that involves thedrilling of holes diagonally across a crack in PCCpavement into which steel reinforcement bars areinserted and epoxied in place. The holes are alternatedfrom side to side of the crack on a pre-determinedspacing. This technique is generally used forlongitudinal cracks that are in fair condition. Cross-stitching increases load transfer by adding steelreinforcement to hold the crack together.

Cure – A period of time following placement andfinishing of a material such as concrete during whichdesirable engineering properties (such as strength)develop. Improved properties may be achieved bycontrolling temperature or humidity during curing.

Curing – The maintenance of a satisfactory moisturecontent and temperature in concrete during its earlystages so that desired properties may develop.

Curing Blanket – A built-up covering of burlap sacks,matting, straw, waterproof paper, or other suitablematerial placed over freshly finished concrete.

Curing Compound – A liquid that can be applied as acoating to the surface of newly placed concrete toretard the loss of water, or in the case of pigmentedcompounds, also to reflect heat so as to provide anopportunity for the concrete to develop its properties ina favorable temperature and moisture environment.See also Curing.

Dense-Graded Asphalt Pavement – An overlay orsurface course consisting of a mixture of asphalt binderand a well-graded (also called dense-graded)aggregate. A well-graded aggregate is uniformlydistributed throughout a full range of sieve sizes.

Depression - Localized pavement surface areas at alower elevation than the adjacent paved areas.

Design Life – The expected life of a pavement fromits opening to traffic until structural rehabilitation isneeded. The typical reporting of pavement design lifedoes not include the life of the pavement with theapplication of preventive maintenance. (See alsoAnalysis Period and Performance Period.)

Diamond Grinding – A process that uses a series ofdiamond-tipped saw blades mounted on a shaft orarbor to shave the upper surface of a pavement toremove bumps, restore pavement rideability, andimprove surface friction. (See also CPR)

Discount Rate – The rate of interest reflecting theinvestor’s time value of money used to determinediscount factors for converting benefits and costsoccurring at different times to a baseline date. Discountrates can incorporate an inflation rate depending onwhether real discount rates or nominal discount ratesare used. The discount rate is often approximated asthe difference between the interest rate and theinflation rate.

Dowel – Most commonly a plain round steel bar(usually coated, such as with paint or epoxy), whichextends into two adjoining slabs of a PCC pavement ata transverse joint placed perpendicular to the joint soas to transfer shear loads.

Dowel Bar Retrofit – A rehabilitation technique that isused to increase the load transfer capability of existingjointed PCC pavements by placement of dowel barsacross joints and/or cracks that exhibit poor loadtransfer. (See also CPR)

Emulsified Asphalt – A liquid mixture of asphaltbinder, water, and an emulsifying agent. Minuteglobules of asphalt are suspended in water by using anemulsifying agent. These asphalt globules are eitheranionic (negatively charged) or cationic (positivelycharged).

Equivalent Uniform Annual Cost (EUAC) – The netpresent value of all discounted cost and benefits ofan alternative as if they were to occur uniformlythroughout the analysis period. Net Present Value(NPV) is the discounted monetary value of expectedbenefits (i.e., benefits minus costs).

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Fatigue Cracking – A series of small, jaggedinterconnecting cracks caused by failure of the asphaltconcrete surface under repeated traffic loading (also called alligator cracking)

Faulting – Difference in elevation across a joint orcrack. Faulting commonly occurs at transverse joints ofPCC pavements that do not have adequate loadtransfer.

Fiber Modified Sealant – Generally a hot-applied sealantthat is composed of unmodified or modified asphaltcement and heat resistant polymeric fibers and is usedfor sealing cracks in asphalt concrete pavements.

Fog Seal – A light application of slow setting asphaltemulsion diluted with water and without the additionof any aggregate applied to the surface of a bituminouspavement. Fog seals are used to renew aged asphaltsurfaces, seal small cracks and surface voids, or adjustthe quality of binder in newly applied chip seals.

Free edge - An unrestrained pavement boundary.

Fuel Resistant Sealant – A joint or crack sealantcompound that is resistant to and maintainsserviceability after being exposed to jet fuel or otherpetroleum products.

Full-Depth Patching – Removal and replacement of asegment of pavement to the level of the subgrade inorder to restore areas of deterioration. May be eitherflexible or rigid pavement.

Functional Performance – A pavement’s ability toprovide a safe, smooth riding surface. These attributesare typically measured in terms of ride quality (seeInternational Roughness Index) or skid resistance (seeInternational Friction Index).

Grinding Head – Arbor or shaft containing numerousdiamond blades or carbide teeth on diamond grindingor cold milling equipment.

Grooving – The process used to cut slots into apavement surface (usually PCC) to provide channels forwater to escape beneath tires, improving skidresistance and reducing the potential for hydroplaning.

Heater Scarification – The initial phase of a hot in-place recycling (HIPR) process in which the surface ofthe old pavement is heated and mechanically rakedbefore being removed and recycled.

Hot Air Lance – A device that uses heated compressedair to clean, dry, and warm cracks prior to sealing.

Hot Applied Sealant – A crack or joint sealingcompound that is applied in a molten state and curesprimarily by cooling to ambient temperature.

Hot In-Place Recycling (HIPR) – A process whichconsists of softening the existing asphalt surface withheat, mechanically removing the surface material,mixing the material with a recycling agent, adding virginasphalt and aggregate to the material (if required), andthen replacing the material on the pavement.

Hot Mix Asphalt Concrete (HMAC or HMA) – Athoroughly controlled mixture of asphalt binder andwell-graded, high quality aggregate thoroughlycompacted into a uniform dense mass. HMACpavements may also contain additives such as anti-stripping agents and polymers.

Hydroplaning – Loss of contact between vehicle tiresand roadway surface that occurs when vehicles travel athigh speeds on pavement surfaces with standing water.

Initial Costs – All costs associated with the initialdesign and construction of a facility, placement of atreatment, or any other activity with a cost component.

International Friction Index (IFI) – A measure ofpavement macrotexture and wet pavement friction at60 miles per hour determined using measured frictionat some test speed and macrotexture determined usingASTM E-965 or ASTM E-1845. (Based on “Assessmentof LTPP Friction Data”, publ. # FHWA-RD-99-037, p.6)

International Roughness Index (IRI) – A measure of apavement’s longitudinal surface profile as measured inthe wheelpath by a vehicle traveling at typical operatingspeeds. It is calculated as the ratio of the accumulatedsuspension motion to the distance traveled obtainedfrom a mathematical model of a standard quarter cartraversing a measured profile at a speed of 80 km/h(50 mph). The IRI is expressed in units of meters perkilometer (inches per mile) and is a representation ofpavement roughness.

Joint – A pavement discontinuity made necessary bydesign or by interruption of a paving operation.

Joint Depth – The measurement of a saw cut from thetop of the pavement surface to the bottom of the cut.

Joint Deterioration – See Spalling.

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Joint Filler – Compressible material used to fill a jointto prevent the infiltration of debris.

Joint Sealant – Compressible material used tominimize water and solid debris infiltration into thesealant reservoir and joint.

Joint Seal Deterioration - Break down of a joint orcrack sealant, such as by adhesion or cohesion loss,which contributes to the failure of the sealant system.Joint seal deterioration permits incompressiblematerials or water to infiltrate into the pavementsystem.

Joint Shape Factor – Ratio of the vertical to horizontaldimension of the joint sealant reservoir. Factor can varydepending on type of sealant specified.

Jointed Plain Concrete Pavement (JPCP) – PCCpavement constructed with regularly spaced transversejoints to control all natural cracks expected in theconcrete. Dowel bars may be used to enhance loadtransfer at transverse contraction joints (dependingupon the expected traffic), but otherwise there is nomid-slab temperature reinforcement.

Jointed Reinforced Concrete Pavement (JRCP) –Portland cement concrete pavement containingregularly spaced transverse joints and embedded steelmesh reinforcement (sometimes called distributedsteel) to control expected cracks. Steel mesh isdiscontinued at transverse joint locations. Dowel barsare normally used to enhance load transfer attransverse joints. The transverse joint spacing of JRCPis typically longer than the joint spacing of JPCP.

Lane-to-Shoulder Dropoff – (highways, roads andstreets only) Difference in elevation between thetraveled surface and the shoulder surface.

Life Cycle Costing – An economic assessment ofan item, system, or facility and competing designalternatives considering all significant costs ofownership over the economic life, expressed in termsof equivalent dollars.

Life Extension – The extension of the performanceperiod of the pavement through the application ofpavement treatments.

Load-Transfer Assembly – Most commonly, the basketor carriage designed to support or link dowel bars inthe desired alignment during jointed PCC pavementconstruction.

Load Transfer Efficiency – The ability of a joint or crackto transfer a portion of a load applied on one side of ajoint or crack to the other side of the joint or crack.

Longitudinal Crack – A crack or discontinuity in apavement that runs generally parallel to the pavementcenterline. Longitudinal cracks may occur as a resultof poorly constructed paving lane joints, thermalshrinkage, inadequate support, reflection fromunderlying layers, or as a precursor to fatigue cracking.

Longitudinal Joint – A constructed joint in a pavementlayer that is oriented parallel to the pavementcenterline.

Low Modulus Sealant – A joint or crack sealingmaterial, which is less stiff at low temperatures thanstandard grade sealants.

Maximum Heating Temperature – The maximumtemperature, as recommended by the manufacturer,to which a hot-applied joint or crack sealant can beheated while conforming to all specificationrequirements and result in appropriate applicationcharacteristics.

Melter – A piece of equipment designed specifically toheat hot-applied joint or crack sealant accurately andcontrollably to a temperature where it will flow.

Melter Applicator – A piece of equipment designedspecifically to melt, heat accurately and controllably,and apply hot-applied sealants to pavement cracks orjoints.

Microsurfacing – A mixture of polymer modifiedasphalt emulsion, mineral aggregate, mineral filler,water, and other additives, properly proportioned,mixed, and spread on a paved surface. Microsurfacingdiffers from slurry seal in that it can be used on highvolume roadways to correct wheel path rutting andprovide a skid resistant pavement surface.

Minimum Application Temperature – The minimumtemperature, as recommended by the manufacturer,to which a hot-applied sealant for pavement cracksor joints must be heated while conforming to allspecification requirements and result in appropriateapplication characteristics.

Modified Asphalt Chip Seal – A variation onconventional chip seals in which the asphalt binder ismodified with a blend of ground tire or latex rubber,or polymer modifers to enhance the elasticity andadhesion characteristics of the binder.

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Net Present Value – The value of future expendituresor costs discounted to today’s dollars using anappropriate discount rate.

Open-Graded Friction Course (OGFC) – A thin HMAsurface course consisting of a mix of an asphalt binderand open-graded (also called uniformly graded)aggregate. An OGFC helps to eliminate standing wateron a pavement surface, which reduces tire spray andhydroplaning potential.

Overbanding – Overfilling of a joint or crack reservoirso that a thin layer of crack or joint sealant is spreadonto the pavement surface center over the joint orcrack.

Partial-Depth Patching – Repairs of localized areasof surface deterioration of PCC pavements, usually forcompression spalling problems, severe scaling, or othersurface problems that are within the upper one-thirdof the slab depth.

Patch – Placement of a repair material to replace alocalized defect in the pavement surface.

Pavement Distress - External indications of pavementdefects or deterioration.

Pavement Preservation – The sum of all activitiesundertaken to provide and maintain serviceableroadways. This includes corrective maintenance andpreventive maintenance, as well as minor rehabilitationprojects.

Pavement Preventive Maintenance – Planned strategyof cost-effective treatments to an existing roadwaysystem and its appurtenances that preserves thesystem, retards future deterioration, and maintains orimproves the functional condition of the system(without increasing the structural capacity).

Pavement Reconstruction – Replacement of anexisting pavement structure by the placement of theequivalent of a new pavement structure. Reconstructionusually involves complete removal and replacement ofthe existing pavement structure and may include newand/or recycled materials.

Pavement Rehabilitation – Structural enhancementsthat extend the service life of an existing pavementand/or improve its load carrying capability.Rehabilitation techniques include restorationtreatments and structural overlays.

Performance Period – The period of time that aninitially constructed or rehabilitated pavement structurewill perform before reaching its terminal serviceability.

Point Bearing – Concentration of compressive stressedbetween small areas. May occur when a partial-depthpatch in portland cement concrete pavement is madewithout the compressible insert. Also, slab expansionin hot weather forces an adjacent slab to bear directlyagainst a small partial-depth patch and causes thepatch to fail by delaminating and popping out of place.

Polishing – Wearing away of the surface binder,causing exposure of the coarse aggregate particles.A polished pavement surface is smooth and hasreduced skid resistance.

Portland Cement Concrete Pavement—(PCC) Apavement constructed of portland cement concretewith or without reinforcement. Conventional PCCpavements include JPCP, JRCP, and CRCP.

Potholes – Loss of surface material in an HMApavement to the extent that a patch is needed torestore pavement rideability. Exhibits bowl-shapedholes of various sizes. Minimum plan dimension is150 mm (6 inches).

Preformed Compression Sealant – An extruded jointsealing material for PCC pavement that is manufacturedready for installation and is supplied in rolls. Preformedsealants incorporate an internal web design so that thematerial, when compressed and inserted into thesealant reservoir, remains in compression against thesides of the joint.

Present Serviceability Index (PSI) – A subjective ratingof the pavement condition made by a group ofindividuals riding over the pavement. May also bedetermined based on condition survey information.

Present Worth – See Net Present Value.

Pumping – Ejection of fine-grained material and waterfrom beneath the pavement through joints and crackscaused by deflection of the pavement under trafficloadings.

Raveling – Wearing away of the pavement surfacecaused by the dislodging of aggregate particles and lossof asphalt binder. Also see segregation.

Reactive Maintenance – Maintenance activities such aspothole repairs performed to correct random orisolated pavement distresses or failures.

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Recycling Agents – Organic materials with specificchemical and physical characteristics selected toaddress binder deficiencies and to restore aged asphaltmaterial to desired specifications in pavement recycling.

Reflection Cracking – Cracking that appears on thesurface of a pavement above joints and cracks in theunderlying pavement layer due to horizontal andvertical movement of these joints and cracks.

Rejuvenating Agent – Similar to recycling agents inmaterial composition, these products are added toexisting aged or oxidized HMA pavements in order torestore pavement surface flexibility and to retard blockcracking.

Reservoir – The part of a portland cement concretepavement joint that normally holds a sealant material,usually formed by a widening saw cut above the initialsaw cut. Reservoirs may also be found in HMApavements where joints are sawed and sealed aboveexisting PCC pavements.

Retrofit Dowel Bars – Dowels that are installed intoslots cut into the surface of an existing concretepavement to restore load transfer.

Rideability – A measure of the ride quality of apavement as perceived by its users or roughnessmeasuring equipment.

Router – A mechanical device, with a rotary cuttingsystem, that is used to widen, cut, and clean cracks inpavements prior to sealing.

Rubberized Asphalt Sealant – A sealant, generally hotapplied, that is composed of asphalt cement, varioustypes of rubber or polymer modifiers, and othercompounding ingredients used for pavement crack and joint sealing. Many grades and ranges of propertiesare available.

Rutting – Longitudinal surface depressions in thewheel path of an HMA pavement, caused by plasticmovement of the HMA mix, inadequate compaction, orabrasion from studded tires. It may have associatedtransverse displacement.

Sandblasting – A procedure in which sand particles are blown with compressed air at a pavement surfaceto abrade and clean the surface. Sandblasting is aconstruction step in partial-depth patching and jointresealing.

Sand Seal – An application of asphalt binder, normallyan emulsion, covered with a fine aggregate. It may beused to improve the skid resistance of slipperypavements and to seal against air and water intrusion.

Sandwich Seal – A surface treatment that consists ofapplication of asphalt emulsion and a large aggregate,followed by a second application of asphalt emulsionthat is in turn covered with smaller aggregate andcompacted. Sandwich seals are used to seal the surfaceand improve skid resistance, especially on asphaltpavement surfaces that are bleeding or flushing.

Scrub Seal – Application of a polymer modified asphaltto the pavement surface followed by the broomscrubbing of the asphalt into cracks and voids, then theapplication of an even coat of sand or small aggregate,and a second brooming of the aggregate and asphaltmixture. This seal is then rolled with a pneumatic tireroller.

Sealant – A material that has adhesive and cohesiveproperties to seal joints, cracks, or other variousopenings against the entrance or passage of water orother debris in pavements (generally less than 76 mm(3 in) in width. See also: Backer Material, ChemicallyCuring Sealant, Cold Applied Sealant, Fiber ModifiedSealant, Fuel Resistant Sealant, Joint Filler, JointSealant, Low Modulus Sealant, Performed CompressionSealant, Rubberized Asphalt Sealant, Silicone Sealant,Single Component Sealant, and Two ComponentSealant.

Sealant Reservoir – See Reservoir.

Sealing – The process of placing sealant material inprepared joints or cracks to minimize intrusion of waterand incompressible materials. This term is also used todescribe the application of pavement surfacetreatments. See also: Cape Seal, Chip Seal, CrackFilling, Crack Sealing, Fog Seal, Modified Asphalt ChipSeal, Sand Seal, Scrub Seal and Slurry Seal.

Sealing Compound – See Joint Sealant.

Secondary Sawing – The sawing that takes place toestablish shape in the joint. Many times this shape isthe reservoir of the joint.

Segregation – Separation of aggregate component ofasphaltic or portland cement by particle size duringplacement.

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Serviceability – Ability of a pavement to provide a safeand comfortable ride to its users.

Settlement – A depression at the pavement surfacethat is caused by the settling or erosion of one or moreunderlying layers.

Shoving – Localized longitudinal displacement of anHMA pavement surface. Shoving is often caused bybraking or accelerating vehicles. It may have associatedvertical displacement.

Silicone Sealant – A type of joint or crack sealantcompound either self leveling or non-sag in applicationcharacteristics, that is based on polymers ofpolysiloxane structures and cures through a chemicalreaction when exposed to air.

Single Component Sealant – A sealant supplied asone component.

Skid Resistance – A measure of the frictionalcharacteristics of a surface.

Slab Stabilization – Process of injecting grout orbituminous materials beneath PCC pavements in orderto fill voids without raising the pavement.

Slippage cracking - Cracking associated with thehorizontal displacement of a localized area of an HMApavement surface.

Slurry – Mixture of a liquid and fine solid particles thattogether are denser than water.

Slurry Seal – A mixture of slow setting emulsifiedasphalt, well graded fine aggregate, mineral filler, andwater. It is used to fill cracks and seal areas of oldpavements, to restore a uniform surface texture, to sealthe surface to prevent moisture and air intrusion intothe pavement, and to improve skid resistance.

Spalling, Compression – Cracking, breaking, chipping,or fraying of slab edges within 0.6 meter (2-ft) of atransverse crack.

Spalling, Sliver – Chipping of concrete edge along ajoint sealant, usually within 12 mm (1/2 in) of the jointedge.

Spalling, Surface – Cracking, breaking, chipping, orfraying of slab surface, usually within a confined arealess than 0.5 square meters (0.6 sy).

Stone Matrix Asphalt (SMA) – A mixture of asphaltbinder, stabilizer material, mineral filler, and gap-gradedaggregate. SMAs are used as a rut resistant wearingcourse.

Stress-Absorbing Membrane Interlayer (SAMI) –A thin layer that is placed between an underlyingpavement and an HMA overlay for the purpose ofdissipating movements and stresses at a joint or crackin the underlying pavement before they create stressesin the overlay. SAMIs consist of a spray application ofrubber- or polymer-modified asphalt as the stress-relieving material, followed by placing and seatingaggregate chips.

Structural Condition – The condition of a pavementas it pertains to its ability to support repeated trafficloadings.

Structural Overlay – An increase in the pavement loadcarrying capacity by adding additional pavement layers.(Based on but not taken from 1993 AASHTO guide, p. III-79).

Surface Texture – The microscopic and macroscopiccharacteristics of the pavement surface that contributeto surface friction and noise.

Surface Treatment – Any application applied to anasphalt pavement surface to restore or protect thesurface characteristics. Surface treatments include aspray application of asphalt (cement, cutback, oremulsion) and may or may not include the applicationof aggregate cover. Surface treatments are typically lessthan 25 mm thick. They may also be referred to assurface seals, or seal coats or chip seals.

Swell - A hump in the pavement surface that mayoccur over a small area or as a longer, gradual wave;either type of swell can be accompanied by surfacecracking.

Terminal Serviceability – The lowest acceptable levelbefore resurfacing or reconstruction becomes necessaryfor the particular class of highway.

Thin Overlay – A HMA overlay with 1 lift of surfacecourse generally with a thickness of 38 mm (11⁄2-in)or less.

Transverse Crack – A discontinuity in a pavementsurface that runs generally perpendicular to thepavement centerline. In HMA pavements, transversecracks often form as a result of thermal movements ofthe pavement or reflection from underlying layers. InPCC pavements, transverse cracks may be caused byfatigue, loss of support, or thermal movements.

Treatment Life – The period of time during which atreatment application remains effective. Treatment lifeis contrasted with Life Extension.

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Two Component Sealant – A sealant supplied in twocomponents which must be mixed at a specified ratioprior to application in order to cure to final properties.

Ultrathin Overlay – An HMA overlay over an existingHMA or PCC pavement, generally less than 25 mm (1in) in thickness.

Ultra-thin Whitetopping (UTW) – A thin (2 to 4 inch[50 to 100 mm]) PCC overlay over an existing HMApavement. UTW is a functional overlay that provides astable surface that is resistant to deformation fromstatic, slow moving, and turning loads.

Unbonded Overlay – Increase in the pavementstructure of an existing concrete or compositepavement by addition of jointed plain, jointedreinforced or continuously reinforced concretepavement placed on a separator layer (usually anasphalt layer) designed to prevent bonding to theexisting pavement. (Based on but not taken directlyfrom 1993 AASHTO guide, p. III-145).

User Costs – Costs incurred by highway users travelingon the facility, and the excess costs incurred by thosewho cannot use the facility because of either agency orself-imposed detour requirements. User costs typicallyare comprised of vehicle operating costs (VOC), crashcosts, and user delay costs. To be differentiated fromagency costs.

Waterblasting – The use of a high-pressure waterstream (8500 to 10,000 psi) to clean PCC. It may beused in PCC joint resealing to remove sawing laitanceor in patching to produce a clean surface prior toplacement of the sealer or patch material. Also referredto as hydroblasting.

Working Crack – A crack in a pavement that undergoessignificant deflection and thermal opening and closingmovements greater than 2 mm (1/16 in), typicallyoriented transverse to the pavement centerline.

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2002