Move over, Superman! New method sees through concrete to detect early stage corrosion

When you undergo a fall or  undergo some  other traumatic blow, the first thing the doctor will do is take an X-ray, CT scan or MRI to determine if anything has been damaged internally. Researchers at the National Institute of Standards and Technology (NIST) are using the same principle, but in a more powerful form, to detect corrosion, the primary danger threatening the strength of the steel framework within the nation's bridges, highways and other aging physical infrastructure.
A non-invasive  "spectral fingerprint" technique that reveals the corrosion of concrete-encased steel before it can cause any significant degradation of the structure it supports. current  imaging methods for uncovering corrosion use microwaves to record changes in the physical state of the affected steel, such as changes in the thickness of a rebar within the concrete of a bridge or other structure. that's a real problem since the average age of the 400,000 steel-reinforced concrete bridges is 50 years and there is no baseline data available for many of  them .The NIST terahertz wave detection method works because goethite and hematite are antiferromagnetic.

With current advances in terahertz sources and detectors, the new NIST non -destructive evaluation technique has the potential to rapidly detect tiny amounts of iron-bearing oxides from early-stage corrosion of steel surrounded by concrete, polymer composites (such as pipe insulation in a factory), paints and other protective materials.

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