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NCAT Reports 2012 Cycle Results,

2015 Preservation Activities



By Dr. Buzz Powell, P.E.

The NCAT Pavement Test Track Conference – hosted by the National Center for Asphalt Technology at Auburn University Mar. 3-5 – marked the end of the 2012 research cycle and the beginning of the 2015 research cycle.

Pavement preservation research at NCAT began in the summer of 2012, initiated, sponsored and underwritten by seven state DOTs, FP2 Inc. and its 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.

There, tours and technical presentations highlighted successful test sections on the NCAT Pavement Test Track, as well as on Lee Road 159. Hundreds of industry professionals participated in this event and left
Auburn University with an appreciation for the value of track research in mix and materials, structural pavement design and performance, and pavement preservation.

The benefits of closely monitored, high-quality construction and weekly performance testing were apparent in the technical sessions presented on the second day of the conference. On this day the focus of the technical content and tours was almost exclusively on Lee Road 159.

Although data presented at the track conference — including the life-extending and condition-improving benefit of pavement preservation – only included performance measurements through October of 2014, weekly data collection has continued on Lee Road 159 and is expected to be extended until the end of the new 2015 research cycle in 2018.

Additionally, as part of the 2015 research cycle, new pavement preservation treatments and treatment combinations will be placed on the westbound outside lane of U.S. 280, a higher ADT roadway in close proximity to the NCAT Pavement Test Track. Sections on U.S. 280 will be designed longer (1/10-mile) than the 100-ft.-long sections on Lee Road 159, although the same approach will be applied in order to identify the relationship between pretreatment condition and life extending/condition improving benefits.

By installing the same treatments that were placed on Lee Road 159, a low ADT roadway, and on the NCAT Pavement Test Track (which experiences damage at a greatly accelerated rate), sections on U.S. 280 are expected to define this relationship in the mid-damage range.

Although the final experiment design will be determined by state DOTs in partnership with FP2, it is expected that both cold and hot recycling sections will be included in the work on U.S. 280. In an effort to expand on the success of the 100 percent RAP cold central plant recycle base mix with a Thinlay [thin-lift asphalt] surface on Lee Road 159, cold recycling sections will be installed using both in-place and central plant processes that utilize both foamed and emulsified asphalt binder. High aged binder replacement thin overlay mixes likely will serve as the wearing surfaces in these sections.

The start of the 2015 research cycle also kicks off the newly formed partnership between NCAT and MnROAD. This partnership will expand the scope of the pavement preservation and asphalt mix performance testing to include both cold weather and concrete pavements.

Many of the same treatments that are installed on U.S. 280 will also be installed on I-94 at MnROAD, north of Minneapolis. This parallel study is aimed at producing findings that can be directly implemented by state DOTs in the northern region who have concerns that findings from the NCAT Pavement Test Track and Lee Road 159 may not be directly applicable to their climate. Northern states can join the Track pooled fund with confidence that their research dollars will be used to install and monitor pavements at MnROAD.

Performance will be monitored on these new sections at both facilities until 2018. Thereafter, it is expected that data collection and research on pavement preservation sections needed to completely define the relationship between pretreatment condition and life extending benefit will be spun off into a new pooled fund that will likely be managed by MnROAD.

The cost of this second phase of research will be greatly reduced because the startup costs (e.g., construction, instrumentation, etc.) will have been funded in the first (2015 cycle) phase. State DOTs interested in participating in research in asphalt mix performance testing and pavement preservation with a nationwide implementation impact should contact either MnROAD operations engineer Ben Worel, P.E. (Ben.Worel@dot.state.mn.us), or me (buzz@auburn.edu).

Powell is assistant director and Test Track manager, National Center for Asphalt Technology, Auburn, Ala.