06-30-04

Iowa State University researchers hit the pavement for an academic road show

AMES, Iowa -- Iowa State University scientists are poised to reach concrete solutions to highway materials and construction problems, thanks to the recent donation of a trailer that will serve as a mobile concrete laboratory.

The $130,000, 44-foot by 8.5-foot trailer, donated to the university by concrete industry sponsors, will be used by researchers affiliated with the Center for Portland Cement Concrete Pavement Technology, which is located in the ISU Research Park. The scientists will tow the mobile lab to road construction sites throughout the United States to test samples of "plastic," or wet, concrete during the most critical phase of a pavement's life - the first hour - and then also after the concrete has hardened.

Testing concrete materials at the actual job site will help detect compatibility problems before a pavement is built. Because the "recipe" for creating concrete has evolved over the years, often adding recycled materials such as fly ash and slag to improve quality, more needs to be learned about the complexities of the mixtures. To help ensure that the new concrete recipes will perform as expected, mobile lab scientists will evaluate about 25 concrete tests. Researchers also hope to develop practical tests that field technicians can perform, all with the goal of longer-lasting highways.

In order to evaluate these tests, the mobile lab has been outfitted with about $100,000 in equipment, including a highly sensitive instrument called an air void analyzer (AVA). The AVA measures the volume and size distribution of tiny air bubbles whose presence and proper position are critical for concrete roads subject to freeze-thaw cycles.

However, any vibration, such as wind buffeting the trailer, will dramatically skew the AVA's results. Consequently, the trailer, which was built by Iowa manufacturer Featherlite, was designed with a two-foot-square trapdoor in the floor to accommodate the AVA. When the lab is parked, the base of the AVA will rest on the ground through the hole, protected by the trailer but not touching it.

An open house and ribbon cutting for the mobile lab will be 2 to 4 p.m. Tuesday, July 6, in the ISU Research Park parking lot, 2901 South Loop Drive, Ames.

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