Pavement Professor Breaks New Ground in Quality Control.

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Author: Hampton, Tudor

EQUIPMENT

For years, construction engineers have used ground-penetrating radar to locate unseen materials. But one scientist is trying to use the same technology to scan the molecular makeup of those materials.

The new radar method has the attention of some pavement engineers who are on the hunt for more accurate, non-destructive test methods. The technique has the potential to save owners "a lot of money," according to Michael Lithman, vice president of Ellis & Associates Inc.

The Jacksonville, Fla.-based engineering firm has hired Electronic Pavement and Infrastructure Charting Inc. (EPIC), Tomball, Texas, to handle scans for recent quality-control projects and was pleased with the results. "You can get rid of most of the cores on the job," Lithman says.

Florida Dept. of Transportation is experimenting with EPIC's radar system in order to check the compaction of asphalt pavement during construction, says Tim Ruelke, an FDOT district engineer. He is cautiously interested, saying, "We're not ready to go out into the rest of the state." But he says FDOT is "very intrigued."

So are others. The National Center for Asphalt Technology in Auburn, Ala., began testing the new scanning service in late October, with a full report expected in six to nine months.

Formerly a unit of Uretek USA Inc., a pavement rehabili-tation contractor, EPIC spun off as a separate company last year. Its proprietary radar scan is the "next generation" of material testing, says Randall W. Brown, a retired Air Force engineer and president of EPIC.

The inventor, Robert L. Lytton, is a civil engineering professor at Texas A&M University. He wrote the original logic that became the backbone of the new process. Unlike traditional radar, which detects the location of materials, EPIC uses an antenna array linked to a custom software program that parses a material's properties. It works for asphalt, concrete, aggregate and soils, the company claims.

"It never occurred to anyone to try to determine the composition of the layers," says Lytton, who in 1995 helped Texas A&M receive a patent for the technique. EPIC owns an exclusive license to use the technology. Lytton is a founding owner.

The 68-year-old inventor conceived the idea in 1991. Lytton says he had been researching the mechanical properties of materials "for some time [but] never thought of applying the same discipline to the analysis of radar signals." To do that, "I had to get outside the field of radar and go into micromechanics," he explains. The research took Lytton into the study of light waves and the speed at which light travels through materials. By focusing radar signals into pavements, he not only could detect their thickness, but also the electromagnetic signatures of the materials inside. A special software program then could sort out the data and show a pavement technician the results in minutes. "I didn't run down the hallway yelling 'Eureka,' but I felt like it," he says.

EPIC performs such scans with radar antennas mounted on the rear of a large truck. It takes a reading up to 12 ft wide and 18 in. deep by simply driving down the road. It costs up to $9,000 for the first day and $4,000 for each additional day. Taking random core samples can cost about $50 per core but that method has other "hidden" costs, engineers say. These include shutting down lanes and not knowing where to drill in the first place. The new method still requires some initial cores for calibration.

Ultimately, Lytton believes the radar technique could open the door for longer-life pavements that are engineered and constructed with tighter quality controls. That would save taxpayers "wads of money," he says.

GRAPH: Hot Spots. Patented radar technique reveals pavement composition, including relative compaction.

PHOTO (COLOR): LYTTON

PHOTO (COLOR): Discreet. The EPIC truck may look like a family camper, but it is stuffed with an array of ground-penetrating radar equipment.

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By Tudor Hampton