NCAT                     

Brief Description:

The Pavement Test Track is a full-scale accelerated performance test (APT) facility managed by the National Center for Asphalt Technology (NCAT) at Auburn University.  The project is funded and directed by a multi-state research co-op in which sponsors ship in their own local hot-mix asphalt materials and methods for placement on the Track.  Forty-five different 200 ft sections have been built around the 1.7-mile oval to facilitate field performance comparisons in an identical climate where traffic conditions are precisely monitored.  The primary objective of the project is to identify pavements with superior field performance and lower life cycle costs through the application of a design lifetime of truck traffic (10 million ESALs over 1.6M miles) in 2 years.

The Track was originally constructed in the summer of 2000, with many sections replaced in the summer of 2003 after the first cycle of truck traffic had been completed.  All 2000 sections survived with minimal rutting, but many were replaced to facilitate new research in the 2003 experiment.  Eight sections were rebuilt in 2003 from the subgrade up to facilitate a mechanistic structural response experiment and 14 sections were milled from ¾” to 4” to facilitate new mix performance studies.  The 2006 experiment is currently being planned to again encompass options for traffic continuation, surface mix performance, and structural response test sections.  It is anticipated that the 2006 structural experiment will be a comprehensive validation of mechanistic pavement design.

After pavement test sections have been rebuilt in the first year of each research cycle, a design lifetime of truck traffic is applied to the surface of experimental mixes in years 2 and 3 of each research cycle in order to accelerate damage.  NCAT operates a fleet of 5 rigs (heavy triples with 1 legal single) 5 days a week over 2 shifts in order to accomplish this goal.  The necessity of the 1.6 million mile trucking operation also provides an opportunity to conduct research for the trucking industry.  Examples of studies utilized to offset the cost of fleet operations include tire wear rate studies (which require an aggressive rotation scheme), axle durability testing, fuel economy determination studies using synthetics lubricants and fuels, etc.

Trucking operations are suspended on Sunday and Monday to allow for drivers’ down time, preventive and corrective maintenance on trucks, and field performance testing.  As traffic accumulates over the course of the 2-year trucking operation, weekly testing is conducted to document how the experimental pavements are changing with traffic and time.  Cracking, rutting, roughness, texture, high-speed pavement response and density are monitored weekly.  Deflection and surface friction are measured monthly.  Each test section is outfitted with multi-depth temperature probes (at 0”, 2”, 4” and 10”) and moisture sensors (3” below top of subgrade) that are used to thoroughly document relevant environmental conditions for each research pavement.  Structural sections are also equipped with response instrumentation such as strain gauges, pressure cells, etc. that are used to calibrate mechanistic design methodologies.

Another objective of the research is to utilize laboratory testing to successfully predict differences in performance that are observed in the field.  Samples prepared before, during and after construction are included in the study.  The testing plan includes compaction testing (e.g., gyratory shear), simulative testing (e.g., Asphalt Pavement Analyzer) and fundamental testing (e.g., confined cyclic creep).  Methods have been developed to successfully predict field performance from data generated in the laboratory.

Sponsoring state DOTs have modified their methods and materials as a result of participation in Track research.  Progressive mixes have been implemented that provide both structural (e.g., SMA) and functional (e.g., OGFC) benefits.  Questionable materials have been evaluated under actual heavy truck traffic without exposing the motoring public to unacceptable safety hazards (e.g., new products, polishing aggregates, etc.), and design methodologies have been evaluated to determine their return on investment (e.g., bumping binder grade, changing gradation, increasing asphalt content, changing modifier type, etc.).  Structural sections have been used to validate response estimation techniques and calibrate predictive models (e.g., fatigue cracking, rutting performance, etc.).

Links to Facility's:      Website         Publications page
 

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Last Updated:
December 28, 2005