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Caractérisation électromagnétique des métariaux traités de génie civil dans la bande de fréquence 50 MHz - 13 GHz

Abstract : The aim of this work is the identification and the development of techniques allowing the measurement of the complex permittivity of concrete in the frequency range of the geophysical radar or GPR (Ground Penetration Radar). Two typical techniques were developed: a coaxial/cylindrical waveguide cell (50 MHz - 1,6 GHz) and two ended rectangular waveguide probes (spectral bands: [ 4 - 7 GHz ] and [ 7 - 13 GHz ]).

These methods presented the advantages that they are broadband and less destructive. In addition, the numerical simulations carried out with a 3D electromagnetic software showed that these techniques presented a great penetration depth, as well as a good sensitivity of measurement. Then, they make it possible to satisfy the Representative Elementary Volume criterion (REV - minimal size of material to have representative measurements).

The theoretical study of the probes/cellule required the analysis of the direct and inverse problems. The study of the direct problem allowed the calculation of the reflection coefficient according to the dielectric properties of the material under test. The calculation of the permittivity from the measured reflection coefficient defines the inverse problem. After the design of the measurement devices, the developed softwares have been validated by testing different materials with known permittivity.

The measurements carried out on different mixtures showed that the type of the aggregates influence considerably the variation of the permittivity, the maximum size of the aggregates influences the permittivity in the centimetric wave range, and this latter varies linearly according to the compacity.
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Submitted on : Friday, November 24, 2006 - 7:22:27 PM
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Mourad Adous. Caractérisation électromagnétique des métariaux traités de génie civil dans la bande de fréquence 50 MHz - 13 GHz. Sciences de l'ingénieur [physics]. Université de Nantes, 2006. Français. ⟨tel-00110739⟩

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