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Non-destructive characterisation of mortar layers for concrete repair using radar and ultrasonics
For the investigation of layer thickness of different repair mortar systems sprayed and filled on the surface of reinforced concrete structures, two complementary NDT methods have been selected: radar and ultrasonics. Both methods are impulse-echo techniques being applicable to constructions which are accessible from one side only. For testing and selecting the optimum methodology for on-site measurements, a pilot study was initiated based on the design, construction and investigation of test specimen. From the investigation of all surfaces of these test specimens it can be deduced that the single transducer equipment (single probe technique) can be applied in most cases for the determination of the thickness of the mortar layer with the best accuracy (due to the smallest wavelength of the ultrasonic waves of about 4mm in concrete). Only in few cases, results have been unreliable. With the ultrasonic array system which works at much lower frequencies, clear reflections appear only in few cases. And due to the high wavelength, also the accuracy was less than with the single transducer. With radar, in most cases only the mortar/concrete thickness above the reinforcement can be determined, which is also useful, since in most cases this thickness is equal to the thickness of mortar for repair. This assumption was approved by most of the cores taken from the test specimen and from the dam as well. Since radar requires no coupling agent and thus enables fast measurements along large areas, this technology was selected for on-site measurements. From all measured traces and by calibration with several cores, the thickness of the repair mortar could be determined and as a result it varied between 3 and 10 cm. The accuracy of the thickness determined at one position is about +/-1.5 cm. Thus, this mortar layer was too thin in most of the investigated areas of the carrying walls.
Non-destructive characterisation of mortar layers for concrete repair using radar and ultrasonics
For the investigation of layer thickness of different repair mortar systems sprayed and filled on the surface of reinforced concrete structures, two complementary NDT methods have been selected: radar and ultrasonics. Both methods are impulse-echo techniques being applicable to constructions which are accessible from one side only. For testing and selecting the optimum methodology for on-site measurements, a pilot study was initiated based on the design, construction and investigation of test specimen. From the investigation of all surfaces of these test specimens it can be deduced that the single transducer equipment (single probe technique) can be applied in most cases for the determination of the thickness of the mortar layer with the best accuracy (due to the smallest wavelength of the ultrasonic waves of about 4mm in concrete). Only in few cases, results have been unreliable. With the ultrasonic array system which works at much lower frequencies, clear reflections appear only in few cases. And due to the high wavelength, also the accuracy was less than with the single transducer. With radar, in most cases only the mortar/concrete thickness above the reinforcement can be determined, which is also useful, since in most cases this thickness is equal to the thickness of mortar for repair. This assumption was approved by most of the cores taken from the test specimen and from the dam as well. Since radar requires no coupling agent and thus enables fast measurements along large areas, this technology was selected for on-site measurements. From all measured traces and by calibration with several cores, the thickness of the repair mortar could be determined and as a result it varied between 3 and 10 cm. The accuracy of the thickness determined at one position is about +/-1.5 cm. Thus, this mortar layer was too thin in most of the investigated areas of the carrying walls.
Non-destructive characterisation of mortar layers for concrete repair using radar and ultrasonics
Zerstörungsfreie Charakterisierung von Mörtelschichten für die Betonreparatur mittels Radar und Ultraschall
Maierhofer, C. (author) / Wöstmann, J. (author) / Krause, M. (author) / Milmann, B. (author) / Behrendt, B. (author) / Müller, H.S. (author)
2003
9 Seiten, 7 Bilder, 9 Quellen
(Nicht paginiert)
Conference paper
Storage medium
English
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