highway maintenance course · · 2016-04-04the repair of the functional pavement defects . 2. ......

Al- Mustansiryah University, Faculty of Engineering, Department of Highways and Transportation Engineering

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Highway Maintenance Course

Course No.: 506060406 Course Name: Highways Maintenance Academic Year: 2015-2016 Time Division: 3hr. 2-Theoretical 1-Tutorial Course Description ( 2 credit hours) Teaching maintenance of highways "techniques and methods". Teaching students causes of highways pavement distress and repairs. Highway maintenance has the following objectives:

1. The repair of the functional pavement defects 2. Prolonging the functional and structural life of the pavement 3. Maintaining road safety and signage 4. Keeping the road reserve in an acceptable condition 5. Management of the above activities

This course will include: General-Objectives-Definitions-Types of Maintenance, Maintenance of Flexible Pavements, Unique Properties of Flexible Pavements, Type of flexible pavement distress, Description of Defects and Distresses, Causes of Failure and Distinguishing Features Pavement Condition Survey, Maintenance Planning and Management ,Maintenance Criteria, Design and Construction of Surface Dressings, Design and Construction of a Slurry Seal, Winter Maintenance, Execution of Highway Maintenance , Performance Based Specifications, Labor Based Techniques, Other Considerations, Traffic Control and Safety + Environment, Repair of Defects in Flexible Pavements , Sustainability and Recycling of Pavements, Repair of Defects in Rigid Pavements , Repairs of Traffic Signal Maintenance, Street Lighting and Illuminated Traffic Sign, Maintenance Of HWY Structures, and Sustainability. Course Intended Outcomes: At the end of the course, students are expected to learn: � Understand the basics of highway maintenance system, � Understand the types, causes and repair of pavement distress., � Understand the methods to prolonging the functional and structural life of highway pavement. � Understand the sustainability and recycling techniques of highway pavement. � Understand the management of above activities.


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Course Outline:

Week Description depends on the Timing table(Theoretical & Practical)

1

General- Objectives-Definitions-Types of Maintenance

2 Maintenance of Flexible Pavements

3 Unique Properties of Flexible Pavements

4 Type of flexible pavement distress

5 Type of flexible pavement distress

6 Description of Defects and Distresses

7 Description of Defects and Distresses

8

Causes of Failure and Distinguishing Features

9 Causes of Failure and Distinguishing Features

10 Causes of Failure and Distinguishing Features

11 Pavement Condition Survey



14

Repair of Defects in Flexible Pavements

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16



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17 Maintenance Planning and Management

18 Design and Construction of Surface Dressings

19 Design and Construction of a Slurry Seal

20 Winter Maintenance

21 Execution of Highway Maintenance

22 Performance Based Specifications

23 Labor Based Techniques

24 Other Considerations

25 Traffic Control and Safety + Environment

26 Repair of Defects in Rigid Pavements

27 Repair of Defects in Rigid Pavements

28 Repairs of Traffic Signal Maintenance

29 Highway Maintenance and Sustainability

30

Pavement Recycling

31 Maintenance Of HWY Structures

32 Pavement Management System

Textbooks:

1. Huang, Yang H., "Pavement analysis and design", 2nd edition, Prentice Hall, Inc., New Jersey, USA, 2004.

2. Nikolaides Athanassios, "Highway Engineering, Pavements, Materials and Control of Quality", 1st ed , USA, CRC Press (2014)


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Suggested references:

1. Yoder, E. J., and Witczak, M. W., "Principles of pavement design ", 2nd edition, John Wiley and Sons, Inc., New York, 1975.

2. Y. Shahin and S.D.Kohn, "Pavement Maintenance management for Roads and Parking Lots, "Construction Engineering Research Laboratory (CERL), United States Army Corps of Engineers, Technical Report M-294.2004. 3. Asphalt Institute, "Asphalt in Pavement Maintenance," manual Series No.16

(MS-16).1999 4. Roads and Transportation Association of Canada, "Pavement Management

Guide."2014

5. http://www.dot.gov

Marking: First Semester Second Semester Final Exam

1st exam

Project 2nd exam

1st exam

Project Final Practical

Activity

5 5 10 5 5 10 - Exam 60

Assignments and/or Projects: Assignment/Project Description Due Date Marking

Case study There are many case study in the 2 semesters

During the course

5

Instructor information: Lecture Room: [ Group A:301, Group B:301 ] Time: Sun., Mon. 8:30-11:30 Wed., Thr.. 8:30-11:30. Instructor's Name: Dr. Saud A. Sultan Office No.: - E-Mail: [email protected] NOTES: � Office Hours: Other office hours are available by appointment. � The content of this syllabus not be changed during the current semester.


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Lectures

1- Highway maintenance has the following objectives:

6. The repair of the functional pavement defects 7. Prolonging the functional and structural life of the pavement 8. Maintaining road safety and signage 9. Keeping the road reserve in an acceptable condition

2- Definitions: Road maintenance has been defined by the Permanent International Association of Road Congresses, (PIARC) as “Suitable routine, periodic and urgent activities to keep pavement, shoulders, slopes, drainage facilities and all other structures and property within the road margins as near as possible to their as-constructed or renewed condition. Maintenance includes minor repairs and improvements to eliminate the cause of defects and avoid excessive repetition of maintenance efforts.” PIARC further defined periodic maintenance as “Operations that are occasionally required on a section of road after a period of a number of years. They are normally large scale and require specialist equipment and skilled resources to implement, and usually necessitate the temporary deployment of those resources on the road section. These operations are costly and require specific identification and planning for implementation, and often require design.” Periodic maintenance is akin to preventive maintenance defined by the American Association of State Highway and Transportation Officials (AASHTO) as follows “…preventive maintenance is a planned strategy of cost-effective treatments that preserves and maintains or improves a roadway system and its appurtenances and retards deterioration, but without substantially increasing structural capacity.” The U.S. Federal Highway Administration, FHWA defines pavement preservation as: “all activities undertaken to provide and maintain serviceable roadways; this includes corrective maintenance and preventive maintenance, as well as minor rehabilitation projects.” Periodic or preventive maintenance is non-structural and is applied to extend the life of the pavement, to enhance the performance and to reduce user delays. Examples of preventative (or periodic) maintenance are re-graveling of unpaved roads, resealing (with surface dressing, ultra thin asphalt, etc.) of paved roads, and re-graveling of shoulders.


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Routine maintenance is defined by PIARC as “Operations required to be carried out once or more/year on a section of road. These operations are typically small-scale or simple, but widely dispersed, and require skilled or unskilled manpower. The need for some of these can be estimated and planned on a regular basis e.g., vegetation control.” Non-preventive maintenance can also be described as routine, recurrent and urgent where routine refers to the “fixed-cost” activities such as grass cutting, drainage maintenance and road sign maintenance; recurrent to activities required throughout the year such as pothole patching, crack sealing, and grading, and urgent to the repair of defects caused by disasters (e.g., floods) or accidents. Routine maintenance activities are not influenced by the traffic, while the recurrent maintenance activities are. Both these sets of activities can also be defined as reactive maintenance, where activities are unscheduled and immediate response sometimes required. The urgent maintenance is required to keep the highways open, protect property and road users. This has also been referred to as emergency maintenance and includes repair of washouts, rigid pavement blow-ups, and earth slides. AUSTROADS divides road maintenance into preventive and remedial maintenance, with preventative maintenance involving actions to prevent the roads from deteriorating and remedial maintenance involving the repair of defects. The following classification of highway maintenance activities will be used : Preventive maintenance refers to actions associated with restoring the condition of the highway, reducing the rate of deterioration and increasing the life of the pavement. The restoration of the condition of the pavement is primarily related to the functional, i.e., skid resistance and riding quality, properties of the pavement. These activities are normally planned based on an assessment and processing of information in a pavement or bridge management system. All maintenance should include attention to drainage as water is the single most important factor affecting pavement performance. Remedial maintenance refers to actions associated with the rectification of defects on the carriageway or the road reserve. Emergency maintenances refer to activities associated with the urgent repair of defects caused by natural disasters or accidents. The highway maintenance types and activities are summarized below :


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3- Unique Properties of Flexible Pavements:

Pavement is unique when compared to other civil engineering structures. Some of the unique properties of flexible pavement are discussed below.

1- Fast deterioration with time Each traffic load application contributes to some extent to pavement distresses. Different types of distress could happen and accumulate over the years such as rutting, fatigue cracking, material disintegration, roughness and bleeding. When one or more of these distresses arrives to a certain unacceptable level, the pavement is considered as failed. The typical life of a flexible pavement varies from case to case,


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with an average value of 10 to 15 years. A good method of pavement design should including the designed life, or how long the pavement is expected to last before failure.

2- Repeated loads When a traffic wheel moves on the pavement surface it creates a stress pulse. This stress pulse creates a dynamic pavement response. Which is harder to analyze as compared to static response.

3- Variable load magnitude Traffic loads vary from light to heavy for passenger cars and loaded trucks respectively. Increasing the load magnitude exponentially increases the rate of pavement deterioration

4-Traffic growth Pavement is design to carry future traffic. Which usually increases over the years. Predicating future traffic growth is not always accurate. This inaccuracy in predicting future traffic affects the accuracy of predicting pavement performance and consequently pavement designed life.

5-Change of material properties with environmental conditions Environmental conditions have large effect on the properties of pavement materials. For example, HMA gets softer at high temperatures resulting in rutting and harder at low temperatures resulting in thermal cracking. Also, rain and freeze–thaw cycles weaken the HMA materials and reduce the load carrying capacity of base, subbase and subgrade. In addition, HMA ages with time resulting in increasing its stiffness and its susceptibility to cracking.

Multi – layer system-6

The pavement structure consists of several layers built over the subgrade. These layers have different materials with different properties. The distribution of stresses and strains within the multi-layer pavement system depends on the thickness and material properties of these layers.

4- Types of flexible pavement distress:

The early detection and repair of defects in the pavement will prevent minor distresses from developing into a pavement failure. The identification of the distress aids the engineer or maintenance professional in identifying what caused the distress and the required approach in repairing it. Cracks and other defects start appearing very small and are usually only detectable when walking along the pavement. Water pooling in select areas of the pavement is identification of potential problems in the


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pavement later on. It is important that the water quickly drains away from the pavement surface. Inspection and cleaning of drainage systems ensures that they are working properly and will eliminate some of the major causes of pavement damage.

Distress is an important criterion of pavement design. Many of the distresses are caused by the deficiencies in construction, materials, and maintenance and not related directly to design. The knowledge of the various types of distress is important to identify the causes of the distress and then how to remedy them. By using specific design of pavement that may decrease the distress and to have long life for the road or least the maintenance cost. There are two types of pavement failure namely structural and functional. The structural failure indicates a breakdown of one or more of the pavement components. The functional failure wherein the pavement can no longer carry out its intended function. The two types of failure do not necessarily go together. Distress is an important criterion of pavement design. Many of the distresses are caused by the deficiencies in construction, materials, and maintenance and not related directly to design. The knowledge of the various types of distress is important to identify the causes of the distress and then how to remedy them. Structural failures in flexible pavements may result from surface fatigue, consolidation, or shear, developing in the subgrade, subbase, base course, or surface. Functional failure depends primarily upon the degree of surface roughness. In general the typical pattern of deterioration in asphalt pavement is rutting, which develops rapidly during the early stages. The width of rut indicates in a general way the depth of the failed layer. Subgrade shear failures exhibit surface up heaval at some distance from the depressed rut, whereas shear failures in the surface result in upheavals relatively close to the tire track. It is important that a more exact analysis be made before conclusions are drawn regarding the component of the pavement that has failed. Surface movement can be caused by consolidation of one or more of the pavement layers. Upheaval does not accompany this type of depression. Lateral shoving can also cause surface irregularities. Distress may be caused by too little or too great an amount of asphalt. Table (1) shows the general types of pavement distress and their contributing causes and distinguishing features. 5- Description of Defects The purpose of highway maintenance is to rectify defects and preserve the pavement. It is necessary to define and record the defects, as well as to understand the mechanism of failure in order to select the most appropriate action. The commonly occurring defects are defined in this section and related to appropriate maintenance activities. It is important to emphasize that drainage should always be addressed as part of all maintenance actions.


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Distresses and Defects (i) Cracking occurring in flexible pavements can be classified in one of three types, i.e. surfacing, fatigue and others. Surfacing cracks are associated with the aging and deterioration of the surface bituminous layer due to shrinking and hardening of the bituminous binder with a loss of volatiles. These cracks are in general not load-related. One type of surfacing cracks is cracking in an irregular pattern. These cracks are also referred to as map cracks, star cracks and amorphous cracks. Another type is block cracking with cracks in well-defined rectangular blocks. Surfacing cracks occur across the full-width of the pavement. Block cracks divide the asphalt surface into approximately rectangular pieces. The blocks range in size from approximately 0.1 to 10m². Cracking into larger blocks is generally rated as longitudinal and transverse cracking. Block cracking is caused mainly by the shrinkage of hot mix asphalt and daily temperature cycling, which results in cyclic stress and strain. It is not load associated, although loads can increase the severity of the cracks. The occurrence of block cracking usually indicates that the asphalt has hardened significantly. Block cracking normally occurs over a large portion of pavement area, but sometimes will occur only in nontraffic areas. Block cracking is measured in square feet or square meters of surface area. The surface cracks are more prominent on thin surfacings such as slurries, sand seals, and the block cracking more pronounced on asphalt concrete surfacings. In the latter the cracks start from the top and progress to the bottom asphalt layer. Fatigue cracks (commonly called alligator or crocodile cracks) are a series of interconnected cracks in a chicken-wire pattern. The cracks are caused by traffic loading, occur only in wheel-paths and are often associated with deformation. Early signs of fatigue cracks are fine parallel longitudinal cracks in the wheel-path. Fatigue cracking is a series of interconnecting cracks caused by the fatigue failure of asphalt surface or stabilized base under repeated traffic loading. The cracking initiates at the bottom of the asphalt surface or stabilized base where the tensile stress or strain is highest under a wheel load. The cracks propagate to the surface initially as one or more longitudinal parallel cracks. After repeated traffic loading, the cracks connect and form many-sided, sharp-angled pieces that develop a pattern resembling chicken wire or the skin of an alligator. The pieces are usually less than 30cm on the longest side. Alligator cracking occurs only in areas that are subjected to repeated traffic loadings. It would not occur over an entire area unless the entire area was subjected to traffic loading. Alligator cracking does not occur in asphalt overlays over concrete slabs. Pattern-type cracking, which occurs over an entire area that is not subjected to loading, is rated as block cracking, which is not a load-associated distress. Alligator cracking is considered a major structural distress. Alligator cracking is measured in square feet or square meters of surface area


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Other types of cracks in flexible pavements are longitudinal, edge, transverse, reflection and stabilization cracks. Longitudinal cracks are parallel to the pavement centerline, while transfer cracks extend across the centerline. They may be caused by the shrinkage of asphalt surface due to low temperature or asphalt hardening or result from reflective cracks caused by cracks beneath the asphalt surface, including cracks in concrete slabs but not at the joints. Longitudinal cracks may also be caused by a poorly constructed paving lane joint. These types of cracks are not usually load associated. Longitudinal and transverse cracks are measured in linear feet or linear meters. These are well-defined fairly continuous cracks. Longitudinal and edge cracks are normally associated with the differential movement of the subgrade due to moisture variations (i.e. at embankments or on clays), and discontinuities in the pavement. Transverse cracks occurring in isolation are caused by movements under the surfacing such as at a culvert or bridge joint. When these cracks appear at regular intervals they are classified as reflection cracks where joints of an overlaid concrete pavement reflect through the asphaltic concrete surfacing. Cracking on longitudinal joints would also be present in such cases. Reflection cracks follow the dimensions of the concrete slabs beneath the asphalt concrete surfacing. A further type of cracking is stabilization cracks, which are rectangular blocks from 0.5 to 3 m in size and formed by the reflection of the cracked stabilized layer through the surfacing. Pumping, i.e., the movement of fine material from the stabilized layer through the cracks can occur as stabilization cracks. Closely spaced stabilization cracking (i.e., small blocks) is an indication that the stabilized layer has broken up into small pieces and is close to the end of its functional life. Stabilization cracks should not be confused with block cracks. Stabilization cracks develop from the bottom of the surfacing and block cracks from the top. Stabilization cracks tend to be more prominent in the wheel tracks, than between the wheel tracks, especially when the block sizes are small. Isolated and well-defined cracks, such as transverse, longitudinal and reflection cracks can be sealed with a penetration grade or polymer modified bitumen (PMB). Where cracks are active the application of a thin (150 to 300 mm) strip of geo-textile on the crack is appropriate. Extensive cracking cannot be sealed individually cost-effectively and the application of a membrane of bitumen, or PMB or geo-textile is more feasible (AUSTROADS, 1998a).Low severity surface cracking can be addressed with the application of a rejuvenator to the surface. Extensive and severe surface cracking can be rectified by removal and replacement of the defective portion of the layer or by hot in-place recycling (HIPR) depending on the thickness which is affected. Where fatigue cracking is extensive and associated with deformation, the appropriate action is to remove the defective material and replace it with new material.


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(ii) Potholes are bowl-shaped holes of various sizes on the pavement surface. A pothole is normallyonly considered significant if the diameter of the hole is more than 150 mm and the depth more than25 mm. Potholes are secondary forms of distress that develop from cracks. The ingress of moisture into the pavement layers reduces the structural capacity of the layers and thereby accelerates the progression of the pothole. The condition of patches must be recorded and repaired. Repair of the potholes entails patching which is the removal of the defective layers and the replacement with, normally, a bituminous mixture. Patch deterioration refers to the condition of the patch and requires the same remedial actions as potholes. (iii) Rutting is the longitudinal surface depression in the wheel-path. Rutting is caused by compaction or shear deformation of the pavement layers through traffic loading. Wide-shaped rutting is normally an indication of deformation of the lower pavement layers or subgrade and narrower and more sharply defined rutting, of deformation in the upper layers (i.e., surfacing or base). Rutting can be repaired by the filling of the ruts with a slurry or thin asphalt or milling and replacement. A resurfacing will rectify rutting, and if properly designed, reduce further rutting. If rutting is severe more than one application of the resurfacing layer may be required. A rut is a surface depression in the wheel paths. Pavement uplift may occur along the sides of the rut. However, in many instances ruts are noticeable only after a rainfall, when the wheel paths are filled with water. Rutting stems from the permanent deformation in any of the pavement layers or the subgrade, usually caused by the consolidation or lateral movement of the materials due to traffic loads. Rutting may be caused by plastic movement of the asphalt mix in hot weather or inadequate compaction during construction. Significant rutting can lead to major structural failures and hydroplaning potentials. Rutting is measured in square feet or square meters of surface area for a given severity level based on rut depth (iv) Shoving refers to the longitudinal displacement of localized areas of the pavement caused by shear forces induced by traffic loading. Shoving is most evident where vehicles stop and start. The repair is similar to that of rutting. (v) Other defects associated with the surfacing are bleeding, polished aggregate, raveling (aggregate loss), weathering and the binder condition. Bleeding is the condition where a film of bituminous binder is present on the surface which creates a shiny, reflective surface which may be tacky in hot weather. Polished aggregate refers to the smoothness of the exposed aggregate. Bleeding and polished aggregate reduce the skid resistance of the pavement with resulting safety consequences. Bleeding is a film of bituminous material on the pavement surface, which creates a shiny, glass-like, reflecting surface that usually becomes sticky. It is caused by high asphalt content or low air void content. Since the bleeding process is not reversible during cold months, asphalt will accumulate on the surface and lower the skid resistance.


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Raveling (aggregate loss) describes the process where the aggregate particles are dislodged andweathering where the asphalt binder is removed. Raveling is caused by the abrasive action of traffic. This can be extensive on surface dressings when the binder content is too low, chippings contaminated or bituminous binder too cold to effectively adhere to the chippings during construction. Raveling and weathering are the wearing away of the pavement surface caused by the dislodging of aggregate particles due to stripping and the loss of asphalt binder due to hardening. Binder condition refers to the freshness and the elasticity of the binder. The binder loses its elasticity with time, resulting in raveling and weathering. Repair of these defects comprises milling and replacement where the defects are isolated and resurfacing where the defects are extensive. Poor binder condition can be rectified with the application of a rejuvenator. (vi) Other miscellaneous distresses are edge breaks and lane-to-shoulder drop-off or separation. Edge breaks are the breaking away of the surfacing at the edges of the pavement and often caused by poor unpaved shoulder maintenance. Lane-to-shoulder drop-off or separation describes the difference in elevation or width of joint between the pavement and the shoulder.Edge breaks are repaired by patching and the lane-to-shoulder drop-off by the reinstatement of theshoulder. The defects can be prevented by regular blading of the unpaved shoulder. (vii) Roughness is defined as deviations of the surface from a true plain. It is caused by one or a combination of the preceding defects, e.g., rutting, cracking, and potholes. The roughness can be improved slightly by patching, crack sealing and elimination of rutting, but only completely be rectifiedwith a resurfacing of slurry (normally coarse slurry) or asphalt. (viii) Skid resistance. Skid resistance is affected by the polishing stone value (PSV) of the chippings and the micro-texture. The skid resistance can effectively be improved by resurfacing, while sand blasting techniques have also been successful in some cases. A portion of the aggregates extending above the asphalt surface is either very small or without rough or angular particles to provide good skid resistance. This type of distress occurs mainly in the wheel path due to repeated traffic loads. (ix) Swell is characterized by an upward bulge on the pavement surface. A swell may occur sharply over a small area or as a long, gradual wave. Either type of swell can be accompanied by surface cracking. A swell is usually caused by frost action in the subgrade or by swelling soils, but a swell can also occur on the surface of an asphalt overlay on concrete pavement as a result of blowup in the concrete slab, as shown in


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Figure 8. Swell can often be identified by oil droppings due to the bumpy surface. Swells are measured in square feet or square meters of surface area (x) The macro-texture reflects the drainage capacity of the pavement under wet conditions and is an important safety issue. Resurfacing with the appropriate type will improve the skid resistance.

1- Causes of Failures and Distinguishing Features:

TYPES OF

CAUSES OF FAILURES DISTINGUISHING FEATURES

FAILURE Primary Contributing Specific General

Disintegration

Low cohesion

Soft asphalt “tenderness” “scuffing”

poor aggregate grading “over sanded”

“marking”

low density “under compacted”

“indenting”

“gouging” Low

abrasion Insufficient asphalt “dryness”

resistance brittle asphalt “brittleness” soft aggregate “crushed

aggregate”

chains and studs “grooving” “pitting” “raveling” Debonding

of Hydrophilic aggregate

displacement of “stripping” “washboardi

ng” asphalt

aggregate asphalt by water clay in

aggregate. “potholing”


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displacement of asphalt

by solvent “fuel

spillage”

displacement of asphalt

mix by jet blast “blast

erosion”

Instability Low

Interparticleexcess asphalt “bleeding”

friction smooth, polished aggregate

“lubricated”

clay water present “flowing” “pushing” rounded aggregate “balls

bearings” “shoving”

“ripping” “rutting” Low mass

stiffness Soft binder “tenderness” “corrugating

” poor aggregate grading (insufficient rock) Insufficient fines Low density Insufficient compaction “porous” cold compaction Improper compaction Changing

foundation differential settlement “bird bath” “longitudinal

support differential expansion “dishing” waves” frost heave “mounding” “transverse trenching “frost ball” waves” “trench

settlement” “porpoising”

Fracture Shrinkage absorptive aggregate “right-angle (or

Cracking) aging asphalt cracking”

temperature fluctuations “random cracking”


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volume change of coatings “curl cracking”

(paint, jet seals, mud, etc.) “transverse” “cracking” Brittleness asphalt embrittlement “pattern” “longitudinal burned asphalt “block

cracking” cracking”

brittle base (e.g. cement-treated)

“ladder cracking”

“diagonal

cracking” low-temperature exposure “low

temperature

cracking” Fatigue resilient or “springy” base “alligatoring” “load-

associated“ Inadequate pavement

stiffness “chicken-

wire “non-load

channelized traffic cracking” associated” poor drainage of pavement

section “wheel track

cracking” Slippage Insufficient bond between

layer

low tensile strength of overlay

“Vee-cracking”

thin overlay “crescent cracking”

no lateral support (e.g. shoulders)

Reflection shrinkage forces “reflection

cracking”

shear forces bending stresses/stains Settlement fill settlement (deep) “settlement & Heave expansive soils cracking” “spread

cracks”

“heave cracks”


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highway maintenance course · · 2016-04-04the repair of the functional pavement defects . 2. ......

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