Monday, September 10, 2012

Pavement Preservation Concepts: Pay Me Now, or Pay Me MUCH More Later

Roads deteriorate over time, due to climate (water, freeze and thaw, sunshine, heat, etc.) and traffic. From the moment the road is constructed, it begins to age.

"Most pavements will deteriorate through the phases listed in the [PASER (Pavement Surface Evaluation and Rating)] rating scale. The time it takes to go from excellent condition (10) to complete failure (1) depends largely on the quality of the original construction and the amount of heavy traffic loading. Once significant deterioration begins, it is common to see pavement decline rapidly. This is usually due to a combination of loading and the effects of additional moisture. As a pavement ages and additional cracking develops, more moisture can enter the pavement and accelerate the rate of deterioration." PASER Manual - Asphalt Roads, page 14.

Water is deemed the roads' worst enemy. Most of pavement preservation is designed to prevent the damage that water causes. Once a pavement cracks, whether it be concrete or asphalt, water in the cracks freezes and thaws with enormous force, causing further damage to the pavement. Water in the cracks washes out particles of pavement as traffic hits the cracks and the cracks become potholes. Water infiltrating the surface into the subsurface or "base" begins to undermine the surface causing the surface to sag. Water infiltrating from the sides through improper drainage causes similar damage. So, when we are talking about pavement preservation, and particularly so in the early stages of the pavements' life, we are talking about preventing these water damages.

However, asphalt naturally aging is also something we need to be concerned about. Asphalt is composed of asphaltenes and maltenes. The maltenes are the volatile components that escape into the atmosphere over time, drying out the asphalt which causes the asphalt to shrink and ultimately develop cracks. Thus, some of the more recent pavement preservation methods involve replacing some of the maltenes to “rejuvenate” the asphalt. These relatively low cost treatments are usually applied very early in the asphalt’s life, to prevent the cracks from even starting. (So now you know one of the reasons road agencies are doing work on roads that look in perfect condition, while other roads in worse shape are left alone.) (For an excellent introduction to asphalt aging and the use of rejuvenators, see Bob Boyer’s presentation.)

The PASER pavement condition ratings are generally related to the maintenance or repair that is needed

Rating 9 & 10 No maintenance required
Rating 8 Little or no maintenance
Rating 7 Routine maintenance, crack sealing and minor patching
Rating 5 & 6 Preservative treatments (sealcoating)
Rating 3 & 4 Structural improvement and leveling (overlay or recycling)
Rating 1 & 2 Reconstruction

However, the potential treatments vary widely and must be matched to the age of the pavements, the specific defects in the pavements, the climatic conditions, and the traffic, as well as the budget.

Typical defects in an asphalt pavement include:

  • Surface defects: Raveling, flushing, polishing.
  • Surface deformation: Rutting, distortion—rippling and shoving, settling, frost heave.
  • Cracks: Transverse, reflection, slippage, longitudinal, block, and alligator cracks.
  • Patches and potholes
    PASER Manual - Asphalt Roads, pages 3-13 for excellent descriptions and photos of these distresses for asphalt.

Source:Asphalt Pavement Rejuvenation, presentation by Robert E. Boyer, PhD, PE, Consultant Engineer-Asphalt Pavements, Lynn Haven, Florida, at the August, 2012 National Pavement Preservation Conference.

See descriptions of several asphalt pavement preservation methods demonstrated at the August, 2012 National Pavement Preservation Conference.

Monday, September 3, 2012

Asset Management and Pavement Preservation are “Best Practices” for Michigan’s Roads and Bridges

Getting value for our taxpayers’ money is critical in spending our limited dollars for road and bridge maintenance. Applying the principles of asset management and pavement preservation are ways Michigan road agencies are attempting to get the biggest bang for our bucks.

“The term ‘asset management’ means a strategic and systematic process of operating, maintaining, and improving physical assets, with a focus on both engineering and economic analysis based upon quality information, to identify a structured sequence of maintenance, preservation, repair, rehabilitation, and replacement actions that will achieve and sustain a desired state of good repair over the lifecycle of the assets at minimum practicable cost.’’ H. R. 4348 (2012) MAP-21 Sec. 1103(2) (The new law passed this summer authorizing the Federal highway program for fiscal years 2013 and 2014 named “Moving Ahead for Progress in the 21st Century Act”, but more commonly called MAP-21.)

“Pavement preservation” methods are the techniques used to implement "asset management", i.e., a structured sequence of cost-effective capital preventive maintenance, preservation, repair, rehabilitation, and replacement actions that will achieve and sustain a desired state of good repair over the lifecycle of the assets at minimum practicable cost.

“The goal of infrastructure preservation is to cost-effectively and efficiently improve asset performance, as measured by attributes such as ride quality, safety, and service life.

Infrastructure preservation programs represent a departure from traditional approaches to maintenance, in which deficiencies are addressed as they occur. Preservation seeks to reduce the rate of deterioration.

The preventive approach is generally less costly and time-consuming than the traditional, more reactive approach. However, a strategy of prevention may be more difficult to justify because the public’s expectation is that the worst roads demand immediate attention. Furthermore, the public often interprets activities related to pavement preservation as “fixing something that isn’t broken.” . . . .

[T]ools such as life-cycle cost analysis . . . have the potential to demonstrate that implementation of a preservation strategy may cost less over the life of an asset than more “traditional” approaches that wait until the deficiencies are evident.”

In selecting an optimal pattern of preservation practices, one considers the normal life cycle of a specific stretch of pavement and performs the appropriate “fix” at the appropriate time to lengthen the useful life of the pavement at the lowest life cycle cost. Doing the preventive maintenance early in the pavement’s life extends the life of the pavement at a much lower cost per lane mile life than postponing any treatments until the pavement needs more drastic and more expensive treatments.

Most people understand this concept, which is why we change the oil in our cars rather than wait for the engine to fail. “Pay me now, or pay me MUCH more later,” as the oil change ad says.


So how do you incorporate a sound Capital Preventive Maintenance (“CPM”) element into an overall asset management program? In asset management we are MANAGING GROUPS OF PAVEMENTS not simply individual road segments. This is a critical distinction.

When considering an entire network of roads, whether it be a statewide network such as the state trunkline system MDOT is responsible for administering, or the roads that a county road commission is responsible for, an additional analysis is required.

This additional level of analysis is more complicated than will be discussed here (but discussed in exceptional clarity in Larry Galehouse’s presentation). Suffice it to say here that responding to political pressure and fixing the worst roads (“worst first”) will not purchase the optimal increases in lane mile lives. That is, not only do we need to select the right fix at the right time, but also on the right roads to fully implement pavement preservation into the asset management program. To preserve or increase the value of the transportation system asset the road agency is responsible for, the right combination of roads need to be worked on utilizing the limited resources utilizing the appropriate fix for the condition of the road.

With today's limited resources, pavement preservation must take top priority in the spending of our transportation dollars. Taxpayers are demanding value for money spent on all government services, including roads and bridges.

P.S. (Some of these cost effective pavement preservation methods implemented in Michigan were highlighted at the August 16 “Best Practices Conference on Road and Bridge Maintenance” held in Lansing. The presentations from the conference can be viewed at .