New Technology Sees Through Concrete To Detect Deterioration In Building

Posted: Apr 27 2017, 4:46am CDT | by , in News | Latest Science News

 
New Technology Sees Through Concrete to Detect Deterioration in Building
Credit: Per Loll, Denmark

Tne method can trace early stage corrosion before it causes any damage to foundation

Researchers from National Institute of Standards and Technology have developed a new technology that will help people detect early signs of deterioration in a building.

The new technology is based on the same principle as X-ray, CT scan or MRI, but in a more powerful form to trace damage in a wall or across the whole steel framework like bridges, roads and other aging physical infrastructure. The noninvasive technique reveals the scale of corrosion before it causes any significant damage to structure’s foundation. Researchers explain how their team’s system can see through walls and detect corrode.

When water and oxygen damage iron, they leave by-products, with the two most common being goethite and hematite.

“The brown rust that forms when you leave a hammer out in the rain is mostly goethite, and when a steel reinforcing bar (rebar) corrodes inside a concrete bridge deck, that is mostly hematite,” said NIST physical chemist Dave Plusquellic. “We have shown in our new study with goethite, and our previous work with hematite, that terahertz radiation – electromagnetic waves with frequencies 10 to 100 times higher than the microwaves used to cook food – can detect both corrosion products in the early stages of formation.”

People usually assess corrosion with the physical changes on a structure like cracks in exterior bricks or displaced molding. These warning signs show that more dramatic changes are already taking place in a foundation.

“Unfortunately, by the time such changes are detectable, the corrosive process is already well on its way toward causing cracks in the concrete.” Co-researcher Ed Garboczi said.

New technology uses terahertz waves to track changes in the physical state of the affected steel. Terahertz falls between microwave and infrared radiation. Most current methods rely on microwaves to get baseline measurements of a structure but they are not powerful enough to detect early-stage corrosion.

"Using terahertz sources with powers in the hundreds of milliwatts and state-of-the-art receivers with unprecedented signal-to-noise ratios, we should be able to penetrate 50 millimeters, the thickness of the concrete covering the first layer of rebar used in most steel-reinforced concrete structures." Plusquellic said.

Next researchers are attempting to find spectral fingerprint for akageneite – an iron corrosion product developed by seawater sources or road deicing salt.

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