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  • November 12, 2002
    Finding the cause of those pesky potholes
    By Kelli Whitlock

    About four out of five Americans are eligible to drive on the more than one million miles of highways and roads that link the continental United States. Roads in every city, county, and state share some of the same highway hazards that wreak havoc on drivers and motor vehicles alike. But before engineers can find the solutions to these roadblocks on the path to driving nirvana, they must first understand the causes. And, after two hundred years of building roads, scientists finally have the technology to do just that.

    "For many years we assumed we knew what caused some of these problems, but we had no way of knowing for sure, because the technology did not exist to prove or disprove our hypotheses," says Shad Sargand, Russ Professor of civil engineering at Ohio University. "Now, we have high-tech sensors that will help us single out what contributes to these road failures. From there, the next step is to figure out how to solve the problems."

    Road Research video These high-tech sensors can record 250,000 data points a second, recording information about stress and load from traffic and the effects of varying climates. More than a thousand of them are embedded in a three-mile stretch of pavement on U.S. Highway 23 in Delaware County, Ohio, as part of a national road project that could one day help engineers build better, more durable roads. Started in 1987, the Strategic Highway Research Program (SHRP) is a $150 million research effort taking place in all fifty states and six Canadian provinces. The test site in Ohio is a collaborative effort between six Ohio universities, the Ohio Department of Transportation (ODOT), and the Federal Highway Administration (FHWA).

    Sargand and the Center for Geotechnical and Environmental Research in the Russ College of Engineering and Technology at Ohio University are leading the $13 million effort, one of the only projects of its kind in the United States. Other universities involved are Case Western Reserve University in Cleveland, the University of Cincinnati, Ohio State University in Columbus, the University of Toledo, and the University of Akron.

    Located about twenty-five miles north of Columbus, the test road site was opened to traffic in August 1996, two years after construction of the test area began. Faculty and students from participating universities set eleven types of sensors on the road site before the pavement was placed. The sensors monitor changes in the road that contribute to wear and tear on the pavement, such as varying temperatures; moisture from rain, ice, and snow; and stress from heavy traffic. Cables link the sensors to computers, which store and analyze the information.

    A small road sign denoting the site as a test road is the only indication travelers have that they are helping researchers in their quest to build a better road. With every passing vehicle, researchers are able to collect more data on pressure, load, and strain on the pavement caused by traffic. And they won't wait until the project is over to implement changes in road construction based on their findings. Four sections of the test area on U.S. Highway 23 will be rebuilt later this year and two additional sections will be replaced in 1998. Researchers then will study the redesigned sections to see how they fare.

    "Many of our roads are very old. When they were built, engineers didn't anticipate the heavy traffic on the roads today or the amount of stress it would place on the pavement," Sargand says. "We want to build roads that take all of this into account and last longer, but we want to do it in an economically feasible way. Instead of building an entire road without knowing how it will perform, we will build a few sections of a road, test them, see how they work, and improve on the design."

    Hitting the road

    Researchers employ this philosophy in all pavement research operations under way at Ohio University. The projects are interrelated and share a similar goal of improving roads in Ohio and the nation, says Gayle Mitchell, chair and Russ Professor of civil engineering and director of the Center for Geotechnical and Environmental Research. Faculty and students currently are studying road performance at six sites in Ohio, including the test road in Delaware County. In October, the university received nearly $1 million from state and federal transportation agencies to continue monitoring these sites for the next five years.

    One project, started last fall, calls for the integration of blast furnace slag - a waste material resulting from the burning of iron ore - with conventional pavement materials along a highway near Athens, Ohio. The substance has been used in the construction of bridges for several years, but this is the first time engineers have used it in road construction in Ohio.

    "We suspect it will improve road performance, and that's something we'll be studying closely," Mitchell says. "It's a unique application for this material, and gives us an opportunity to recycle a substance that normally is a waste material."

    Working with new materials is a major research focus of faculty and students in the center. Scientists will have a new place to carry on their work this spring - one that will allow them to experiment with new pavement materials and construction techniques on a smaller scale before applying the technology to actual roadways. The Accelerated Pavement Load Facility at Ohio University's regional campus in Lancaster, Ohio, will be the largest indoor test facility for the study of roads designed for commercial travel in the United States. The 4,100-square-foot building, a project sponsored by the Ohio Board of Regents Investment Fund, will allow researchers to do a variety of tests to measure road performance and durability. Environmental controls within the facility will enable scientists to mimic different weather conditions - ranging temperatures from 10 degrees to 130 degrees Fahrenheit, and creating moisture conditions that imitate rain, snow, or ice. Special loading mechanisms will make it possible to apply up to 30,000 pounds of force on the pavement and monitor the impact on durability under different climate conditions. But more importantly, the indoor facility will allow researchers to collect in a matter of months information that can take years to gather from an actual road.

    "We can simulate environmental and load conditions that reflect actual conditions on the roads," Mitchell says. "It's a unique research opportunity for our faculty and our students and ties in nicely with our research projects, including the site in Delaware County."

    Driving by degrees

    The learning component is an important part of all research projects in the Center for Geotechnical and Environmental Research, Mitchell says. Students from Ohio University and other universities take part in every experiment and record the majority of the data. The experience prepares them for a professional career by giving them actual work experience while they are still in school, says Jeff Von Handorf, a graduate student in civil engineering at Ohio University.

    Von Handorf works with other students to monitor sensor readings on the test road site on U.S. Highway 23. During the warmer months, students spend about sixty hours a week collecting data and performing road tests. During winter, they analyze the data. It's a year-round job for them, which Von Handorf says has made the experience even more valuable. "It's nice to see how what we learn in the classroom actually relates to working in the field," he says.

    The information Von Handorf and his colleagues are collecting eventually will be available to engineers and other researchers around Ohio through a computer database designed by Ohio University civil engineering faculty. Sargand envisions a program that would be available through a university mainframe and could be accessed through the Internet. Users could download data found at the Web site. The database ultimately could be merged with a similar national database being explored by federal highway authorities. Information collected from all of the road projects would be available, Sargand says, including study results from the indoor facility in Lancaster. That information could be especially useful to other states, since researchers plan to simulate climate conditions that could be found across the country.

    "We have already had inquiries from engineers and researchers about our studies here, so there is a clear interest in the data," Sargand says. "This will help improve the quality of roads not just in Ohio, but around the country."

    Kelli Whitlock is the director of Research Communications.


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