Story and Photos By Steven Stiefel
Tucked away in a wooded area off of Lee County Road 151 in Opelika sits a 1.7-mile oval track where researchers evaluate innovative asphalt technologies. The experiments conducted at this “accelerated pavement testing facility” allow the rapid deployment of materials and design methods that advance safer, more durable and sustainable asphalt pavements.
Experiments at the National Center for Asphalt Technology (NCAT) Test Track are sponsored over a three-year research cycle. The current cycle is scheduled to end in early 2024, when five tractor trailer rigs will complete 11 million miles of circling the track sometime in early January.
The truck drivers simultaneously complete hundreds of laps each day in order to intentionally deteriorate the pavement.
The heavily-loaded trucks, each carrying about 18,000 pounds of loaded metal, simulate the damage that happens from more than a decade of interstate-type traffic on actual highways, but in a drastically shortened time frame of just two years.
Using the controlled test environment gives researchers safe ways of evaluating the impact of using various materials, construction practices and design methods. Twenty-six highway agencies and private sector partners funded experiments in the 46 main test sections, each nominally 200 feet in length.
NCAT operates the Test Track because it provides unique opportunities to determine the field performance of breakthrough materials and concepts without the risk of failure on public roads. This gives highway agencies clear proof of what new ideas are ready to implement or what needs further development.
Studying the results of all this wear-and-tear gives the sponsors greater confidence to make specification decisions. Since the facility’s construction in 2000, the data collected has saved state highway departments an estimated $160 million in taxpayer dollars. Meanwhile, the public has been rewarded with longer-lasting roads that are also safer to drive on.
Test Track Manager Jason Nelson said some of the sections are divided into subsections depending on the objective of the experiment. Twenty-six sections are located on the straight segments and the remaining 20 sections are equally divided between the two curves.
At the end of the current research cycle next year, the damaged pavement will be carefully analyzed, then the sections will be scraped away with new asphalt pavements specifically prepared to test aspects such as resistance to cracking and how roadways react to the use of recycled materials. Beneath the surface of these sections, NCAT installs strain gauges, pressure plates and temperature probes to monitor pavement structural response to traffic loading and temperature changes.
Nelson said that the Opelika track tests the impact of hot summer days, while an ongoing partnership with the Minnesota Road Research Facility (MnROAD) provides a means of comparing how extreme cold temperatures affect the surface mixtures.
NCAT, led by Director Randy West, was established in 1986 as a partnership between Auburn University and the National Asphalt Pavement Association (NAPA) Research and Education Foundation to provide practical research and development to meet the needs of maintaining America’s highway infrastructure. The researchers aim to provide innovative, relevant and implementable research, technology development and education that advances safe, durable and sustainable asphalt pavements.
The organization stresses credibility in its research, offering honest assessments of how various materials end up performing under the stresses of debilitation. The practical research and development often lead to groundbreaking discoveries. Mixtures used can vary greatly based on the availability of materials from different parts of the nation. Those materials are typically shipped to the NCAT Laboratory in Auburn for forensic examination of asphalt samples.
“When the right treatment is applied to the right road at the right time, roads can be kept in good condition instead of performing costly rehabilitation and reconstruction alternatives later in the pavement’s life when the structure has deteriorated,” said Associate Research Professor Adriana Vargas, an expert on preservation efforts.
Another huge part of NCAT’s mission is educating and training those working in the asphalt industry, offering workshops where the researchers share the latest findings so road engineers can become certified and employ the latest strategies. Graduate students from Auburn’s civil engineering program get hands-on experience studying these treatments.
NCAT and affiliated programs under the Auburn’s Transportation Research Institute secure millions in funding each year for research, education and outreach efforts — levels of funding for transportation greater than any other single research topic on the Auburn campus.
The Opelika Test Track is a huge part of what makes this groundbreaking research possible.
On May 7 through 9, NCAT will host its annual Test Track Conference, a two-and-a-half day showcase of what is learned from the accelerated pavement testing. Hundreds of engineers from across the world will gather at the Hotel at Auburn University and Dixon Conference Center to learn the latest advancements. The event will include a bus tour of the Opelika track. To learn more about the Test Track Conference, visit the website at www.eng.auburn.edu/research/centers/ncat/testtrack/conference.html.