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Pavement Management

How the Pavement Condition Index (PCI) Determines Your Street Improvements

Streets are designed and installed to last at least 30 years; however, streets will not last that long without periodic maintenance. How does the City determine what maintenance treatments are needed for each street? Let's start by looking at how asphalt deteriorates.

Asphalt Deterioration

New asphalt roads look great; their Pavement Condition Index (PCI) rating is very high. The asphalt is hot and flexible. However, once the asphalt is laid, several factors start working against it to make it more brittle. Most people think those factors are traffic, more traffic, snow and ice. In reality, the main enemy to your new street is oxidation. Oxidation occurs with exposure to temperature change, sunlight, heat and moisture. As the asphalt absorbs oxygen, it becomes more brittle and less flexible. The PCI rating decreases. As the pavement becomes less flexible, traffic can cause cracking and the sand (fines) and gravel (aggregates) in the asphalt can begin to erode away. The PCI rating drops some more! Cracking lets the moisture into the road's base - which can cause greater problems. The PCI rating can get dangerously low! What can we do?

Pavement Management and Treatment

The City utilizes a pavement management process that begins with assessing the condition and determining the PCI rating of each street. Ratings range from 0 to 100 (a perfect street has a 100 rating) and is established by considering several technical conditions. Each PCI rating indicates a specific type of "treatment" for each road.

There are three general categories of treatment: 1) seals, 2) overlays, and 3) reconstructions (the complete rebuilding of the pavement roadway). The City uses a Pavement Management System software to prioritize street needs and to determine the most efficient and effective use of funds.

How do we decide what kind of treatment is used on a road? We analyze a number of factors, including street type, street use (i.e., number of lanes, total traffic volumes and heavy truck volumes), PCI rating and cost. The result of this analysis is a five-year list of roadways and treatment schedules that maximizes citywide pavement life using available and anticipated funding. Addressing the pavement needs with appropriate, less costly treatments can extend the lifespan of a roadway and postpone treatments that add cost.

Below are photographs depicting examples of five (5) different PCI scores.

Click on each to enlarge.

Street with a PCI rating of 21.

Street with a PCI rating of 40.

Street with a PCI rating of 68.

Street with a PCI rating of 75.

Street with a PCI rating of 95.

PCI = 21

PCI = 40

PCI = 68

PCI = 75

PCI = 95

 

 

PCI Range

Current % of Streets with this Rating

Rehabilitation Action

Cost of Treatment per Lane Mile

85 to 100

24

Routine maintenance such as crack sealing, and fog seals

$14,000

70 to 85

49

Localized repairs and light weight treatments such as slurry seals, micro seals and chip seals

$28,000

55 to 70

17

Localized repairs followed by a thin to moderate overlay or cape seal

$63,000

45 to 55

6

Localized repairs followed by a moderate to progressively thicker overlays

$91,000

35 to 45

2

Progressively thicker overlays or surface replacement

$119,000

0 to 35

1

Full re-construction including base layers

$315,000

 

The current average PCI rating for all City streets is 75. Maintaining this rating would require annual funding of $2 million per year. The City focuses on the most cost-effective strategies to maintain the best pavement condition Citywide, based on the funds available.

As the number of lane-miles of City streets increases and the street inventory ages, additional funding will be needed to maintain the average PCI rating. If funding is deferred, the cost of restoring the average PCI for our streets grows even larger, in proportion to the length of time that maintenance is postponed.

Pavement Maintenance Techniques

Here are some of the most commonly used pavement maintenance techniques:

Street crews crack sealing a roadway.

Crack Seal

Cracking will continue throughout the usable life of the roadway surface. To limit deterioration, cracks are filled with a rubberized sealant (crack seal) to prevent water penetration. Water between the asphalt and base can cause premature pavement failures, deterioration and potholes. Crack sealing is very cost effective in extending the life of pavement.

Fog Seal

Fog seal is a thin spray of emulsified asphalt (asphalt that is heated and treated to remain in a liquid state) that is used to rejuvenate pavement that is starting to oxidize. A small amount of binder is added to the top of the asphalt to help prevent further loss of aggregates (the gravel in asphalt). It is used with new pavements that are starting to lose fines (sand components of the asphalt), exposing larger aggregates and creating a rough surface.

Street crews fog sealing a roadway.

Street crews slurry sealing a roadway.

Slurry & Micro Seals

Seals are a mixture of emulsified asphalt and aggregates applied in a thin layer to replace the loss of aggregate, protect the original surface and provide a new wearing surface. This treatment is most effective when applied to low volume streets with little cracking (usually pavements less than ten years old).  Micro seals add a synthetic polymer to the mixture which allows the emulsion to set more quickly and withstand heavier traffic.  These are typically used on streets that carry more traffic.

A street that has been micro sealed.

A street overlay.

Street Overlay

When a street is showing signs of structural failure, potholes or "alligator" cracking (multiple cracks that make a pavement look like the scales of an alligator), it may be milled down to the good pavement base. Milling a street down refers to grinding away the top layer.  A new layer of asphalt is applied to extend the life cycle of the original pavement.

Rubberized Asphalt

Rubberized asphalt reduces noise on arterial streets, although this is less noticeable on streets with lower speed limits.

 

Learn More

If you would like to learn more about pavement, please explore the following links:

Federal Highway Pavement Administration

American Concrete Pavement Association (ACPA)

The National Center for Pavement Preservation

Foundation for Pavement Preservation

Pavement Management - A Manual for Communities

Pavement Management - Past, Present and Future

 

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Last Updated: 2/8/2010


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City of Goodyear • 190 N. Litchfield Road • Goodyear AZ 85338 • Phone 623-932-3910 • Toll-Free 1-800-872-1749
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