Engineers complete two years of testing at asphalt track

Engineers expect to complete the first phase of testing this month at a 1.7-mile asphalt track where four fully loaded tractor-trailers have been taking turns driving for two years.

The oval test track, operated by the National Center for Asphalt Technology at Auburn University in Alabama, consists of 26 test sections on its tangents and 20 test sections on the curves. Sponsors for each section determined the mix attributes for their pavement segments, and NCAT researchers documented the condition of each section weekly throughout the project.

The track will be subjected to the research target of 10 million equivalent single axle loads, or ESALs, sometime in December. Each tractor used in the experiment pulled three trailers weighing approximately 152,000 pounds – 20,000 pounds for each of seven loaded axles and 12,000 pounds for the front steer axle.

Researchers monitored the sections weekly to evaluate rutting, cracking and other surface-related problems. They tested the pavement monthly to evaluate friction, roughness and densification. During construction, engineers placed instruments in the pavement to determine the moisture content of the subgrade material and the temperature at four elevations in the structure.

Here are some pavement performance observations researchers outlined in a November report.