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Localization of steel-reinforcements in concrete - Determination of their diameter and cover-thickness maeasurement by magnetic stray flux.

Lokalisierung von Armierungen in Stahlbeton. Bestimmung des Armierungsdurchmessers und Messung der Überdeckungsdichte mit magnetischem Streufluß
 
: Dobmann, G.; Goebbels, K.

Review of Progress in Quantitative Nondestructive Evaluation. 7A
New York: Plenum Publishing, 1988 (Review of Progress in Quantitative Nondestructive Evaluation 7A)
S.533-539
Annual Review of Progress in Quantitative Nondestructive Evaluation <14, 1987, Williamsburg/Va.>
Englisch
Konferenzbeitrag
Fraunhofer IZFP ()
Armierung; Betonüberdeckungsdicke; Hall-Sonde; Korrosion; Prüfgerät; Prüfung(magnetisch); Sonden-Array; Stahlbeton; Streuflußprüfung(magnetisch)

Abstract
An insufficient cover-thickness of concrete is the main reason for corrosion of steel-reinforcements in civil engineering. The volume enlargement of the corroded steel produces at the concrete matrix, initiating cracks, crack growing and finally cover destruction. Codes therefore demand a certain cover-thickness y sub c as function of the steel reinforcement diameter d and the environmental corrosion conditions. A new method is presented to measure the relevant parameters y sub c, d non-destructively, based on classical Maxwell-theory: a magnetic field produced by an DC-electromagnetic yoke magnetizes the reinforcement resulting in a stray field. This is measured by an array of Hall-probes situated between the pole shoes. The evaluation leads to the position and diameter of the reinforcement as well as to the cover thickness. A prototype equipment was built using a 32 elementary realized in SMD-technique. An electric motor scans the array with increments of 0.1 mm over a distance of 5 mm resulting in stray-field data with high local resolution. The results show that the method meets the practical requirements. (IZFP)

: http://publica.fraunhofer.de/dokumente/PX-22223.html