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Microwave Could Detect Concrete Flaws

Monday, September 28, 2015

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A new study could help engineers use microwave technology to test for concrete cracking and rebar defects.

While the research, under the direction of Missouri S&T University professor Kristen Donnell, is years away from completion, early signs show that active microwave thermography (AMT) could be used as nondestructive testing (NDT) to show flaws in those materials that could compromise safety or effectiveness, according to a university statement.

“It’s another tool in the NDT toolbox,” said Donnell, who is an assistant professor of electrical engineering, in the statement.

Testing Method

The test works by sending microwave energy to heat a defined section of material, which is examined using infrared thermography imaging. Donnell uses a 1 GHz to 20 GHz high-frequency horn antenna to heat the objects and then views them with an infrared sensor, the university said. That information then is sent to a computer that helps analyze the results.

©iStock.com / baalihar

Kristen Donnell, an assistant professor of electrical engineering at Missouri S&T University, is using an active microwave thermograph (AMT) to test concrete for weaknesses.

The university said that because the heat bursts last only for a few seconds, Donnell’s tests reduce the risk of heat damage that can occur using flash heat lamps. AMT also can focus the heat at a predetermined depth instead of heating the whole object.

It’s not an X-ray, the professor said, “But it does allow us to look inside the interior of a structure to show defects or problems.”

Donnell said she can set the system to focus on the middle of a 4-inch section of concrete, for example. When the computer produces the images, those images can show if the rebar is corroded or broken or if the concrete has cracks or other defects that could weaken it.

Future Uses

The professor also uses AMT to look at materials wrapped in carbon fiber, according to the statement. The test can check the carbon fiber’s adhesion for areas that aren’t bonded properly. Donnell also can use the test to look at rehabilitated aluminum for weak spots.

AMT testing also could be used on bridges or aircraft, Donnell said. It even could be used to detect cancer someday.

But the engineer cautioned that industry use is still a hope for the future.

©iStock.com / ImageegamI

Aside from the possibilities that the AMT testing could be used to detect flaws in concrete and rebar, Donnell said her method could be used to detect cancer someday.

“It’s probably a good 10 years away from use as an industry method for testing,” she said.

Donnell is a research team member at the Applied Microwave Nondestructive Testing Laboratory and a senior member of the Institute of Electrical and Electronics Engineers (IEEE), according to the university statement. She is also an at-large administrative committee member of the IEEE Instrumentation and Measurement Society, and she is the distinguished lecturer program chair.

Before starting her PhD program at Missouri S&T (which she completed in 2010), Donnell worked in systems and electrical engineering for Raytheon.


Tagged categories: Bridges; Concrete; Concrete defects; Engineers; Rebar; Research and development

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