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Focus on Preservation at NCAT
Pavement Test Track Meeting

By Dr. Mary Robbins

Research findings from the half-mile stretch of experimental roadway dedicated to pavement preservation in Auburn, Ala., were revealed at the National Center for Asphalt Technology Test Track Conference. The 2 ½-day conference took place March 3-5 at the Auburn University and Dixon Conference Center.

Participants from local, state, and federal agencies – as well as the private sector – turned out in record numbers for a chance to tour the facilities and learn about advancements in asphalt pavement design, construction, technologies and maintenance. Held every three years, this was the fifth conference NCAT has hosted, and saw attendance grow to over 260 attendees, a 60 percent increase from the previous conference.

The conference, which serves as a bookend for each three-year Pavement Test Track cycle, is a platform from which NCAT researchers present findings from the cycle. The 2012 research cycle focused on minimizing life-cycle costs of asphalt pavements through the use of innovative materials, and extending pavement life through the use of pavement preservation treatments.

The first day of the conference featured work on sustainable pavements and innovative pavement materials being conducted at the NCAT Pavement Test Track. A tour of the 1.7-mile long track gave attendees an up-close look at the various pavement surfaces, as well as a glimpse inside the pavement structure and the possible modes of failure through open trenches in numerous test sections. A 90-minute tour also featured track instrumentation and testing equipment.

Focus on Preservation

Pavement preservation research at NCAT began in summer 2012, initiated, sponsored and underwritten by seven state DOTs, FP2 Inc. and its financial supporters. This research has the potential to scientifically quantify the life-extending benefits of pavement preservation for flexible pavements, and evaluates the benefits of a comprehensive list of pavement preservation treatments.

The focus of the second day of the conference was on pavement preservation research at NCAT. The day began with an introduction to the extensive work being conducted on Lee Road 159, and then group tours to the site provided participants with an opportunity to see firsthand the life-extending and condition-improving benefits of the wide range of treatments being investigated.

The second half of the day focused on benefits of the pavement preservation treatments on Lee Road 159 and the performance of the pavement preservation sections on the test track. Methods for achieving high construction quality were also presented.

Subgrade Moisture Reduction

A key finding from the pavement preservation study on Lee Road 159 was the reduction in subgrade moisture due to surface treatments.

Although this has been a long-held assumption in pavement preservation, there has been little data to back it up until now. Researchers also showed that as cracking progresses, additional moisture in the subgrade is observed.

As is shown in the accompanying plot, subgrade moisture (presented as a percent change from the more heavily cracked untreated control sections) tends to increase with an increase in cracking.

The sessions on pavement preservation were concluded with discussions on future work planned for the 2015 cycle, including expansion to a colder climate through a partnership with the Minnesota Department of Transportation (MnDOT), and inclusion of a higher volume route in Alabama (see NCAT, MnROAD Partnership New Era in Preservation Study, Winter 2014, pp 10-13).

The next Test Track Conference will examine research conducted in the upcoming sixth cycle and is scheduled for March 6-8, 2018.

Robbins is assistant research professor, National Center for Asphalt Technology

/Change in subgrade moisture relative to cracking/

Change in subgrade moisture relative to cracking.