Enhancement of Detecting Reinforcement Cover by Microwave Thermography with Reflection Approach and radar method

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The present study proposes the combinaison of radar method and microwave thermography method with reflection approach in order to enhance the detection of concrete cover. A methodology based experimental campaigns with microwave thermography allowed to determine the cover thickness of reinforcement bars (12 mm in diameter and regularly placed at 100 mm) in mortar wall (700 mm x 700 mm x 65 mm). The reflection approach with different angles of microwave antenna, and the Snell- Descartes law (which gives the relation between the incident waves, refracted waves, and the dielectric constant of the detected material), also led to deduce the approximate dielectric constant of the mortar. A GPR system was used to monitor the dielectric constant of the mortar during the infrared thermography tests. The combinaison of both electromagnetic methods clarified how the diffraction and interference affected the thermograms, led to validate a new outcome of detecting reinforcement cover by infrared thermography with reflection approach. It also opens perspectives to other studies on the state of the reinforcement cover which is sensitive to its dielectric constant.