The Compression of Time and Asphalt
THE PAVEMENT RESEARCH FACILITY, NEAR Baton Rouge, Louisiana, is a torture chamber for roads. On the six acre site, strips of asphalt are hammered, vibrated, and pounded, while being precisely monitored and, at the end of it all, dissected.
The star attraction at the Pavement Research Facility is the Accelerated Loading Facility (ALF), a device used to simulate and accelerate vehicle loads on a sample stretch of roadway. The 100 foot long machine runs a weighted wheel assembly across the asphalt in one direction, for a duration of ten seconds, then returns the wheel to the starting position, and runs it across the surface again. The loaded wheel looks like one rear dual-wheel of a typical truck, and has regular truck tires, which have to be replaced often during long tests. By running ALF 24 hours a day, it is possible to compress the effects of 20 years of road use into one month.
In the nine parallel lanes that can be spanned by the moveable ALF machine, normal road types are constructed and worn out, and experimental aggregate mixtures and layers are tested. Levels of rutting and cracking are observed, and a "post-mortem" is conducted on failed surfaces, to better understand the dynamics of destruction.
Test pavements are built with full-scale construction equipment and closely model normal highway construction. Strain gauges and other instruments are placed within each test section to monitor pavement response to loading. The information is then transmitted to a computer-controlled data acquisition system which allows instant access to pavement response data on moisture, temperature, and strain.
Based on an Australian design, ALF is unusual. Only two other machines of this type exist in the United States, both are located at the Federal Highway Administration's Turner Fairbank Research Facility in McLean, Virginia.
Other facilities at the six acre Pavement Research Facility include laboratories for concrete, soil, and geosynthetics, and the Falling Weight Deflectometer, a "nondestructive" device that measures the durability of a road surface by dropping a heavy weight on it, as well as the Dynaflect device, which vibrates a 1,000 pound weight on the road surface for long intervals.
The Pavement Research Facility is located 5 miles south of Baton Rouge, just across the Mississippi River on Rt. 1, and is operated by the Louisiana Transportation Research Center. Visitors are welcome, though call ahead at (504) 767-9112.
