TY - JOUR A1 - Lai Wai-Lok, Wallace A1 - Kind, Thomas A1 - Wiggenhauser, Herbert T1 - Frequency-dependent dispersion of high-frequency ground penetrating radar wave in concrete N2 - This paper studies the dielectric dispersion of high frequency radar wave in concrete in early-aged and hardened concrete specimens. Frequency-dependent spectra of phase velocity ν(ω) were measured to deduce the spectra of real part of dielectric permittivity ε'(ω). The dispersion was measured by three high nominal ground penetrating radar frequencies (1.5, 1.6 and 2.6 GHz), experimenting on two steel bars with concrete cover 50 and 100 mm. It was found that ν(ω) and ε'(ω) dispersed at lower frequency, but became stable at high frequency regions, which agrees with the classical GPR plateau. The same frequency components at different nominal antenna frequencies show a close range of ν(ω) and ε'(ω) in concrete of different ages. The results in this paper warrant further investigation of using GPR wave to study material properties. KW - Frequency-dependent dielectric dispersion KW - Ground penetrating radar (GPR) KW - Phase velocity KW - Real part of dielectric permittivity KW - Concrete PY - 2011 U6 - https://doi.org/10.1016/j.ndteint.2010.12.004 SN - 0963-8695 VL - 44 IS - 3 SP - 267 EP - 273 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-26289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Gardner, S. A1 - Kind, Thomas A1 - Kaiser, R. A1 - Grunwald, Marcel A1 - Yang, G. A1 - Redmer, Bernhard A1 - Waske, Anja A1 - Mielentz, Frank A1 - Effner, Ute A1 - Köpp, Christian A1 - Clarkson, A. A1 - Thompson, F. A1 - Ryan, M. A1 - Mahon, D. T1 - Muon Tomography of the Interior of a Reinforced Concrete Block: First Experimental Proof of Concept N2 - Quality assurance and condition assessment of concrete structures is an important topic world-wide due to the aging infrastructure and increasing traffic demands. Common topics include, but are not limited to, localisation of rebar or tendon ducts, geometrical irregularities, cracks, voids, honeycombing or other flaws. Non-destructive techniques such as ultrasound or radar have found regular, successful practical application but sometimes suffer from limited resolution and accuracy, imaging artefacts or restrictions in detecting certain features. Until the 1980s X-ray transmission was used in case of special demands and showed a much better resolution than other NDT techniques. However, due to safety concerns and cost issues, this method is almost never used anymore. Muon tomography has received much attention recently. Novel detectors for cosmic muons and tomographic imaging algorithms have opened up new fields of application, such as the investigation of freight containers. Muon imaging also has the potential to fill some of the gaps currently existing in concrete NDT. As a first step towards practical use and as a proof of concept we used an existing system to image the interior of a reference reinforced 600 kg concrete block. Even with a yet not optimized setup for this kind of investigation, the muon imaging results are at least of similar quality compared to ultrasonic and radar imaging, potentially even better. The data acquisition takes more time and signals contain more noise, but the images allowed to detect the same important features that are visible in conventional high energy X-ray tomography. In our experiment, we have shown that muon imaging has potential for concrete inspection. The next steps include the development of mobile detectors and optimising acquisition and imaging parameters. KW - Concrete KW - Muon KW - Radar KW - Ultrasound KW - X-ray PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-529974 VL - 40 IS - 3 SP - 1 EP - 14 PB - Springer Nature AN - OPUS4-52997 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -