The cost of pavement maintenance keeps escalating upward as refining crude oil technology increases, a shortage of raw materials rises, and mining permits are harder to obtain. As a result, both private and public property owners and homeowners' associations will be spending more on pavement maintenance than ever before.

Thomas and Patrick McDonald rely on nearly sixty years of experience in pavement construction and maintenance as well as years of research as they share practical tools and tips that will help anyone manage a successful pavement maintenance project. Through the included charts that will help determine maintenance strategies, the McDonalds guide others on how to:

• Identify and repair distresses in asphalt pavement
• Develop the proper scope of work, specifications, bids, and contract documents
• Estimate repair costs, manage the project, and monitor job site materials
• Evaluate the return on investment for repairs

Designed specifically to aid in any asphalt projects for commercial properties, shopping centers, industrial properties, apartment buildings, and homeowners' associations or master communities, the Guide to Pavement Maintenance provides step-by-step leadership for anyone ready to tackle a pavement maintenance project.

GUIDE TO PAVEMENT MAINTENANCE

A Comprehensive Guidebook to Understanding Pavement Maintenance for Parking Lots and StreetsBy Thomas McDonald Patrick McDonald

iUniverse, Inc.

Copyright © 2010 Thomas McDonald and Patrick McDonald
All right reserved.
ISBN: 978-1-4502-0869-7

Contents

Illustrations and Figures.............................................................ixForeword..............................................................................xiiiPreface...............................................................................xvIntroduction..........................................................................xviiChapter 1. Pavement Distress Inventory................................................1Chapter 2. Causes of Pavement Deterioration...........................................11Chapter 3. Measuring Distresses and Pavements.........................................15Chapter 4. Maintenance Applications and Policies......................................23Chapter 5. Scopes of Work and Specifications..........................................63Chapter 6. Developing Requests for Bids or Requests for Proposals.....................163Chapter 7. Developing the Proper Contract Documents...................................195Chapter 8. Project Management, Inspection, and Completion.............................259About the Authors.....................................................................293Appendix A. Troubleshooting Guide.....................................................295Appendix B. Geometric Areas...........................................................321Glossary..............................................................................323Resources.............................................................................339References............................................................................341Index.................................................................................343

Chapter One

Pavement Distress Inventory

Several exposures affect the longevity of pavements over their design life. If no maintenance is performed, pavements will deteriorate until they convert back to gravel. Exposures that adversely affect pavements include the following:

Weather conditions (especially snow and ice)

Deicers for colder climates (chemical and salts)

Ultraviolet rays

Water (natural and irrigation)

Vehicle weight, petroleum (gasoline, oil, hydraulic fluids, antifreeze, brake and power steering fluids, and other petroleum-based products)

Aging

These exposures affect the pavement from the moment it is constructed to the end of its useful life. There are two categories for distresses:

Environmental

Structural

Environmental distresses are outside influences that affect the pavement performance. These influences include snow and ice, chemicals, petroleum products, ultraviolet rays, water, and natural aging. These distresses normally occur from the top down and are usually remedied by surface applications, such as a skin patching, crack sealing, seal coating, type II slurry seal, chip seals, and in some instances, thin hot mixed overlays.

Structural distresses are physical failures in the pavement and sub-bases. They can occur due to overloading, wet subgrade, frost, or substandard design. These distresses usually occur from the bottom up, and the only remedies are overlays, removal and replacement (R&R) of the affected areas, or total removal and repaving. This includes R&R patching, overlays (with or without a fabric inner layer), or some form of removal and repaving (total removal, milling, pulverizing, and paving back).

Once a new pavement surface has been exposed to environmental factors, cracks, raveling, loose rocks, or a light gray appearance develops. If the cracks are not sealed with a crack sealant or by seal coating, water will enter into the aggregate base and eventually into the subgrade, causing future structural problems. If the structural integrity of the pavement has been weakened, major rehabilitation and maintenance will be required. If pavement defects are not repaired and the pavement maintained, reconstruction will become the only maintenance option available. The resulting large capital expenditures of major reconstruction are more costly than routine maintenance and are usually not included in the maintenance budget.

It is the responsibility of a community manager, property manager, or owner to ensure that proper maintenance applications are implemented to keep pavements in good to very good condition and maintain the overall appearance of the property as well as mitigating liabilities associated with poor and deteriorated surfaces. Poor pavement and highly distressed parking lots discourage prospective tenants (commercial and industrial properties) or residents (multihousing properties). Also, poorly or improperly maintained streets in a homeowners association can reduce the value of a property, not to mention the liability issues that are associated with potholes and other tripping and ankle-twisting exposures. Remember, first impressions are very important, and poorly maintained parking lots and streets may indicate a poorly managed property and can result in loss of prospective tenants or residents.

The U.S. Army Corps of Engineers and American Public Works Association (APWA) has developed a pavement management program for asphalt and concrete.

This program takes into consideration nineteen types of distresses that affect the design life of pavement, including airports, highways, and streets. Of theses nineteen distresses, the following apply to parking lots and homeowners association (HOA) streets:

Alligator cracking

Bleeding

Corrugation and shoving

Depressions

Fuel spills

Longitudinal and transverse cracking

Potholes

Raveling

Rutting

Thermal or block cracking

Alligator cracking, depressions, potholes and rutting are structural failures. Transverse cracking is a base failure. Longitudinal cracking is a form of structural failure found in wheel paths that have rutted or a cold joint in the laydown direction of the original construction. All other distresses are environmental. The following are the most common types of distresses found in asphalt streets and parking lots.

STRUCTURAL DISTRESSES

ALLIGATOR CRACKING-A series of interconnection cracks caused by fatigue failure of asphalt concrete surface under repeated traffic loading. Cracking begins at the bottom on the asphalt surface (base), where tensile stress and strain are highest under a wheel load. The cracks propagate to the surface, initially, as a series of parallel longitudinal cracks. After repeated traffic loading, the cracks connect, forming many-sided, sharpangled pieces that develop a pattern resembling chicken wire or the skin of an alligator. The pieces are less than two feet on the longest side. Alligator cracking occurs only in areas subjected to repeated traffic loading, such as wheel paths. Alligator cracking is considered a major structural distress and is often accompanied by rutting.

CORRUGATION AND SHOVING-A form of plastic movement typified by ripples (corrugation) or an abrupt wave (shoving) across the pavement surface. The distortion is perpendicular to the traffic direction. This usually occurs at points where traffic starts and stops (corrugation) or areas where HMA abuts a rigid object (shoving).

DEPRESSIONS-Localized pavement surface areas with slightly lower elevations than the surrounding pavement. Depressions are very noticeable after a rain, when they fill with water. Depressions are very common in parking lot construction and overlays.

POTHOLES-A type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a pothole. Sometimes called a kettle and known in parts of the western United States as chuckhole. Most potholes are formed due to fatigue of the pavement surface. As fatigue cracks develop, they typically interlock in a pattern known as "alligator cracking." The chunks of pavement between fatigue cracks are worked loose and may eventually be picked out of the surface by continued wheel loads, thus forming a pothole. The formation of potholes is exacerbated by cold temperatures, as water expands when it freezes and puts more stress on cracked pavement. Once a pothole forms, it grows through continued removal of broken chunks of pavement. If a pothole fills with water, the growth may be accelerated, as the water washes away loose particles of road surface as vehicles pass. In temperate climates, potholes tend to form most often during spring months when the subgrade is weak due to high moisture content. However, potholes are a frequent occurrence everywhere in the world, including in the tropics. Potholes can grow to several feet in width, though they usually only become a few inches deep, at most. If they become large enough, damage to tires and vehicle suspensions can occur.

RUTTING-Surface depression in the wheel path. Pavement uplift (shearing) may occur along the sides of the rut. Ruts are particularly evident after a rain, when they fill with water. There are two basic types of rutting: pavement rutting and subgrade rutting. Pavement rutting occurs when the pavement surface exhibits wheel path depressions as a result of compaction/mix design problems.

SHOVING-A longitudinal displacement of a localized area of the pavement surface. It is generally caused by braking or accelerating vehicles, and it is usually located on hills or curves, at intersections, and where pavement abuts a rigid object (curb, concrete swale, valley gutter, concrete pad, etc.). Shoving is also present with fabric overlays where traffic has moved the pavement on the fabric inner layer. It also may have associated vertical displacement.

SWELL-A long, gradual wave of more than ten feet long, characterized by an upward bulge in the pavement's surface. Swelling can be accompanied by surface cracking. This distress is usually caused by frost action in the subgrade or by swelling soil.

STRUCTURAL OR ENVIRONMENTAL DISTRESSES

LONGITUDINAL AND TRANSVERSE CRACKING-Longitudinal cracks are parallel to the pavement's centerline or laydown direction. Usually a type of fatigue cracking. Cracking is in the direction of flow of traffic, usually at the edge of wheel paths. Transverse cracks are perpendicular to the pavement's centerline, longitudinal joint. Usually a type of thermal cracking.

ENVIRONMENTAL DISTRESSES

BLEEDING-A film of asphalt binder on the pavement surface. It usually creates a shiny, glass-like reflecting surface, bubbles that appear like blisters, or a buildup of asphalt binder on the surface that can become quite sticky. Bleeding occurs when asphalt binder fills the aggregate voids during hot weather and then expands onto the pavement surface. Since bleeding is not reversible during cold weather, asphalt binder will accumulate on the pavement surface over time. This can be caused by one or a combination of the following: excessive asphalt binder in the HMA (either due to mix design or manufacturing), excessive application of asphalt binder during bituminous surface treatment application, or low HMA air void content (i.e., not enough room for the asphalt binder to expand into during hot weather).

BLOCK (THERMAL) CRACKING-Cracking in the shape of blocks, which are interconnected cracks that divide the pavement into approximately rectangular pieces. The blocks may range in size from approximately one foot by one foot to ten feet by ten feet. Block cracking usually indicates that the asphalt has hardened significantly. Block cracking normally occurs over a large proportion of pavement area, but sometimes will occur only in nontraffic areas. Block cracking is also referred to as "thermal cracking," since it is a result of environmental exposures and aging, which makes it hard and oxidized.

BUMPS AND SAGS-Bumps are small, localized, upward displacements of the pavement surface. They are different from shoves, as they are caused by unstable pavement. Bumps can be caused by several factors, including buckling or bulging of underlying Portland cement concrete slabs. This is where asphalt pavement has been overlaid over concrete pavement. Frost heaves can cause bumps from expansion under the paved surface. Spalling of crack edges is caused by oxidation, especially under chip seals. Roots growing under pavement can cause large bumps and infiltration and buildup of material in a crack in combination with traffic loading (often referred to as tenting). Sags are small, abrupt and localized depression or elevated areas that are a result of settlement or displacement in the pavement surface. Also, pavement shoving and displacement caused by subgrade (native ground) swelling or displacement due to tree roots. Sags cause large and/or long dips in the pavement.

EDGE CRACKING-Edge cracking is generally on the edges of unconfined asphalt pavement. Unconfined (no curbs or other forms of edge barriers) pavement will yield during the compaction process or will develop as the pavement ages, oxidizes, and becomes brittle. Edge cracking is generally in the shape of the letter "C" along the edge of the street, road, or parking lot.

JOINT REFLECTION CRACKING-Cracks in a flexible overlay of a rigid pavement. The cracks occur directly over the underlying rigid pavement joints. Joint reflection cracking does not include reflection cracks, which occur away from an underlying joint or from any other type of base (e.g., stabilized cement or lime).

LANE/SHOULDER DROPOFF-The difference in elevation between the pavement edge and the shoulder. This distress is caused by shoulder erosion, by shoulder settlement, or by building up the roadway or edge of a parking lot without adjusting the shoulder level.

PATCHING AND UTILITY CUT PATCHING-An area of pavement that has been replaced with new material to repair the existing pavement. There are two types of patches: remove and replace, and skin (or surface). A patch is considered a defect, no matter how well it performs.

POLISHED AGGREGATE-Areas of hot mixed asphalt pavement where the portion of aggregate extending above the asphalt binder is very small or there are no rough or angular aggregate particles. This occurs after repeated traffic applications. Generally, as a pavement ages, the protruding rough, angular particles become polished and can reduce skid resistance. This can occur quicker if the aggregate is susceptible to abrasion or subject to excessive studded tire wear.

RAVELING-The progressive disintegration of a hot mixed asphalt layer from the surface downward, as a result of the dislodgement of aggregate particles, which is the loss of bond between aggregate particles and the asphalt binder. This occurs as a result of a dust coating on the aggregate particles that forces the asphalt binder to bond with the dust rather than the aggregate, aggregate segregation, inadequate compaction during construction (poor compaction, cold asphalt pavement, cold weather paving), or exposure to water (from sprinklers or puddles), creating a stripping process.

RAILROAD CROSSING-Railroad crossing defects are depressions or bumps around or between tracks.

SLIPPAGE CRACKING-Crescent or half-moon shaped cracks generally having two ends pointed in the direction of traffic. This can also be referred to as edge cracking.

Other distresses not specifically listed by the Corps of Engineers include cold joint and seal coat checking distresses.

COLD JOINT-Very common in parking lots, inverted crowns (constructed drainways in the center of streets), and low traffic streets. A cold joint is a longitudinal joint that occurs in an asphalt pavement when fresh hot mix asphalt is laid adjacent to an existing pavement. The cold joint is the boundary between the two HMA mats. Most often, differences in the temperature and mat plasticity cause an improper bonding of the fresh HMA with the older asphalt, subsequently causing the longitudinal joint to possess a significantly lower density than the rest of the pavement. Over time, a longitudinal crack usually occurs between the asphalt mats, permitting the intrusion of water, increasing roughness, and potentially limiting the life of the pavement. This type of distress is very common in inverted crowns. Asphalt pavement laid next to a concrete structure (valley gutter or swale, dumpster pad, cast-in-place curb, or combination curb and gutter) will create a cold joint after the asphalt has oxidized and shrunk.

CHECKING IN SEAL COAT-Very common when too much sealer is applied to an existing pavement. This can be the result of too much sealer accumulated over a period of years or too much applied at the time of application. Seal coat, whether asphalt or coal tar emulsion, is not an aesthetic coating. Too much buildup or application will cause the material to shrink and develop a checkered pattern (much the same as a dried lake bed). The edges will eventually curl and allow water to infiltrate between the sealer and the bottom layer, creating a delaminating problem. Once this occurs, no other maintenance application can be applied over or on top of a delaminating seal coat because the sealer will continue to separate, taking any other applications off with it.

The Corps of Engineers has developed a condition rating system for pavement known as the pavement condition index (PCI). With PCI, a pavement is given a rating from 0 to 100, with 100 representing a new pavement in ideal condition. Getting to know and utilizing PCI is advantageous in managing a paved street, parking lot, or other pavement.

When a pavement is evaluated for the first time, it must be assumed that the previous condition was a newly constructed pavement, therefore, having a past PCI of 100. Depending on the type and severity (high, medium, or low) of the distresses, values are deducted from 100 to yield a current PCI. The difference of the previous PCI (100 initially) and the current PCI, divided by the age of the pavement, yields a deterioration rate for the period in time. It is important to remember that the PCI graph is a curve and that the deterioration rate will rise or fall depending on the where the PCI is located on the chart. With the current PCI and the deterioration rate, a property manager or owner can prioritize pavement sections, calculate future pavement conditions, and predict condition benefits after maintenance has been performed. All pavements deteriorate at a calculated rate per year similar to Figure 1.1, based on the types and severity of distresses and traffic exposures. As indicated in the deterioration graph, the cost of maintenance increases substantially as time passes. Figure 1.2 depicts a maintenance policy that can reduce the overall cost of pavement maintenance and prolong the life of the pavement.

The condition of the pavement as shown in Figure 1.2 ranges from good to very good after twenty years versus very poor to failed, as shown in Figure 1.1 for the same period of time. This helps illustrate how a wellplanned pavement management program, when adhered to, will reduce the cost of pavement maintenance over the life of the pavement and provide the excellent aesthetics required to show that a property is well maintained.

A simple pavement evaluation is included at the end of this chapter. The only thing that can be calculated is a condition index, not a deterioration rate. If you wish a comprehensive evaluation, with a resulting budgetary planning model and maintenance policy, you can use a computer program, or pavement consultants can provide these services. The software package available for in-house evaluations is MicroPaver, distributed by the American Public Works Association. If the pavement has a large amount of structural failure or a very low PCI coupled with a high deterioration rate, you need the services of a pavement design consulting engineer or a pavement consultant trained and versed in the Paver program.

(Continues...)

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