- NCAT Pavement Test Track
The NCAT Pavement Test Track is an oval-shaped track in Lee County, Alabama, 1.7 miles (2.7 km) long, used for testing experimental asphalt pavements. It is managed by the National Center for Asphalt Technology (NCAT), the largest asphalt research center in the western hemisphere and a cooperative venture between the National Asphalt Pavement Association's (NAPA) Research and Education Foundation and Auburn University.
Concerned with predicting and reducing pavement distresses, state Departments of Transportation (DOTs) supported construction of the track. The Alabama Department of Transportation funded the original construction of the facility, which was completed in the summer of 2000.
The original test pavements built for the first three-year research cycle were intended to answer the most important questions facing DOTs at the turn of the century. Questions included whether the new mix design methodology developed in the US (known as "Superpave") compares favorably to imported, higher cost European mixes with a reputation for rut resistance and high durability, whether the original Superpave methodology encouraged DOTs to design mixes with high coarse aggregate contents, whether mixes with a higher fine aggregate content (and potentially lower cost) perform just as well, and whether more expensive polymer modified asphalt binders improve performance enough to reduce life cycle cost.
In the summer of 2003, the facility was rebuilt for the second research cycle (2003–2006), combining different mill/inlay surface mixes and variable thickness structural sections. For the third research cycle (2006–2009), the structural sections were of more varied thickness. The current (2009) NCAT Pavement Test Track, in its fourth research cycle, consists of an even larger structural experiment and additional mill/inlay surface mixes. Research sponsorship was formally expanded to include industry partners in the private sector. Warm mix asphalt (WMA), high recycled content mixes, and alternative binder materials are major study areas in the 2009 research cycle. Research has also expanded into functional areas of pavement performance, such as noise and road spray reducing porous friction course (PFC) surfaces.
A fleet of five Class 8 tractors pulling heavy triple trailers runs on the track over 750,000 miles (1,210,000 km) a year. All non-steering axles of the trucks apply a load of 20,000 pounds (9.1 kN), the Federal legal bridge limit. The fleet, averaging a gross vehicle weight of 155,000 pounds (70,000 kg), runs five days per week, 16 hours each day. A two-year trucking cycle on the track, applying 10 million equivalent single axle loadings (ESALs), is equivalent to 20 years of normal pavement damage. A three-year research cycle at the Pavement Test Track approximately costs the same as one hour of paving in the United States. The annual savings from improvements in pavement design, however, are estimated at up to US$1,000,000,000. In comparison, a federally funded project in the 1990s known as "WesTrack" cost approximately twice as much to induce half the pavement damage. State DOTs are willing to invest in accelerated performance testing on a closed track because they would have to wait 10 to 15 years on their own field projects to obtain less reliable information.
Almost five million miles (eight million kilometers) have been driven on the NCAT Pavement Test Track since trucking operations began back in the fall of 2000. Each month, the fleet consumes approximately 15,000 US gallons (57,000 L) of diesel fuel. While testing experimental pavements for longevity, the continuously monitored and highly controlled trucking operation, to reduce operating costs, serves as a platform for running certain types of vehicle tests. The Program for Advanced Vehicle Evaluation (PAVE) is a complementary research program that is used by the trucking industry to study the impact of new technology on fuel economy and vehicle emissions.
Results from the first research cycle were presented at the National Transportation Symposium in the fall of 2002. It was found that fine graded mixes could perform just as well as coarse graded mixes. It was also found that polymer modified binders cut rating rates in half, which meant that polymer modified asphalt mixes could be designed with higher asphalt contents to optimize durability. Performance results from the track were correlated with test results from the laboratory, providing mix designers with some assurance of quality in their future work. Critics of the project pointed out that rutting overall was very low; however, statistically significant relationships provided research sponsors with enough confidence to implement findings.
The research generated by the 2000 project also produced useful tools for mix design and performance prediction. Rut depths were measured weekly on the surface of all 46 experimental pavements. As pavement temperatures changed with the seasons, the relationship between rate of rutting, temperature and age was identified. It was found that truck axle passes could be grouped into temperature bands, with progressively greater weight factors applied to axle passes at higher temperatures. A model was developed to predict rutting performance as a function of temperature banded ESALs, laboratory performance and age. This methodology was later used successfully to compare rutting performance from the Pavement Test Track to rutting performance under a Heavy Vehicle Simulator (HVS).
The impact of the 2000 research cycle was recognized by the engineering community. In 2003, the project was inducted into the Alabama Engineering Hall of Fame. Slabs of pavement were removed from the track and presented to the Smithsonian Institution's National Museum of American History for inclusion in the America on the Move exhibition that opened in November 2003.
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- ^ Willis, Richard; et al. (December 2009). "Phase III NCAT Test Track Findings" (PDF). National Center for Asphalt Technology. Archived from the original on April 5, 2010. http://www.webcitation.org/5olgDoxAc. Retrieved April 4, 2010.
- ^ National Center for Asphalt Technology (November 12, 2008). "Pooled Fund Announcement: Accelerated Performance Testing on the 2009 NCAT Pavement Test Track" (PDF). Transportation Pooled Fund Program. Archived from the original on April 5, 2010. http://www.webcitation.org/5olgxTrTt. Retrieved April 4, 2010.
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- ^ "Making the Grade at Auburn: University's Test Track Provides Product Testing Opportunities". Fleet Maintenance and Technology (American Trucking Associations): 30. Winter/Spring 2009. http://www.truckinginfo.com/clean-green/news-detail.asp?news_id=68884&news_category_id=62.
- ^ Brown, E.R.; et al. (November 2002). "NCAT Test Track Construction, Design, and Performance" (PDF). National Center for Asphalt Technology. Archived from the original on April 5, 2010. http://www.webcitation.org/5olqs7RVg. Retrieved April 4, 2010.
- ^ Brown, E. Ray (January 2003). "Scoring at Home". Roads and Bridges (Scranton Gillette) 41 (1): 28. http://www.roadsbridges.com/Scoring-at-Home-article3590.
- ^ Powell, Raymond (August 15, 2006). "Predicting Field Performance on the NCAT Pavement Test Track". Auburn Theses and Dissertations. Auburn University. hdl:10415/342. Archived from the original on April 5, 2010. http://www.webcitation.org/5olstA6Jf. Retrieved April 4, 2010.
- ^ Powell, R. Buzz (February 2008). "Comparing Rutting Performance under a Heavy Vehicle Simulator to Rutting Performance at the NCAT Pavement Test Track" (PDF). Third International Conference on Accelerated Pavement Testing. Archived from the original on April 5, 2010. http://www.webcitation.org/5olvHutth. Retrieved April 4, 2010.
- ^ State of Alabama Engineering Hall of Fame. "Hall of Fame Members". Archived from the original on April 5, 2010. http://www.webcitation.org/5oltaSQfs. Retrieved April 4, 2010.
- ^ Hot Mix Asphalt Technology (National Asphalt Pavement Association): 34. July/August 2002.
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