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Ultrasonic imaging of concrete elements: State of the art using 2D synthetic aperture

: Krause, M.; Mielentz, F.; Milmann, B.; Streicher, D.; Müller, W.

Wiggenhauser, H. ; Bundesanstalt für Materialforschung und -prüfung -BAM-, Berlin; Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V. -DGZfP-, Berlin:
Non-Destructive Testing in Civil Engineering 2003. CD-ROM : NDT-CE, Berlin, September 16-19, 2003
2003 (DGZfP-Berichtsbände 85-CD)
ISBN: 3-931381-49-8
International Symposium on Non-Destructive Testing in Civil Engineering (NDT-CE) <2003, Berlin>
Conference Paper
Fraunhofer IZFP ()
ultrasonic imaging; concrete

Since several years ultrasonic imaging techniques are used for testing concrete elements. Combined with a reconstruction calculation they lead to an acoustic imaging of scatterers and reflectors from the inside of the concrete element. For several testing problems it is an advantage to use a two dimensional synthetic aperture and to combine it with a three-dimensional reconstruction calculation (3D-SAFT, Synthetic Aperture Focussing Technique).
This enables the analysis of the tested volume by means of B-scans in two directions and C-scans (projections parallel to the surface), respectively. Using the 2D-scanning technique, especially the disturbing influence of the reinforcing rebars can be minimised.
In this contribution the state of the art of this method is demonstrated and analysed. Examples of the application are presented, concerning
Localisation of honeycombing and compaction faults
Characterisation of cracks (especially measuring the crack depth)
Investigation of tendon ducts
The results presented are obtained in the frame of a research initiative Non-destructive Evaluation of Concrete Structures Using Acoustic and Electromagnetic Echo-Methods supported by the German Science Council (FOR 384 of DFG, Deutsche Forschungsgemeinschaft). The methods are assessed and improved in cooperation with the partners participating in the project.