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One-Sided Access NMR for Concrete Inspection

 
: Wolter, B.; Dobmann, G.; Herzer, H.-R.; Laub, U.; Bloem, P.

Comite Europeen sur les Essais Non Destructifs -ECNDT-, Paris:
7th European Conference on Nondestructive Testing 1998. Vol. 1
Broendby, Denmark, 1998
ISBN: 87-986898-0-00
S.975-982
European Conference on Nondestructive Testing (ECNDT) <7, 1998, Copenhagen>
Englisch
Konferenzbeitrag
Fraunhofer IZFP ()
concrete inspection; moisture; nuclear magnetic resonance; one-sided access NMR (OSA NMR); wood

Abstract
In nuclear magnetic resonance (NMR) standard equipment the sensor encloses the specimen, consequently the maximum size is restricted and measurements on large specimen require a sampling. Recently, exceptional NMR devices have been developed, which can be applied to the specimen similar to an ultrasound sensor. With this one-sided access (OSA) NMR, a depth profile of the signal can be non-destrucitvely detected inside the component with a resolvable depth increment of typically 1 mm. In Hydrogen-NMR (H-NMR), the measuring parameter spin-density strongly correlates with the moisture content of a solid material. Therefore, with OSA-NMR the moisture depth porfile can be measured in an individual component of concrete, masonry, wood, polymers, a.s.o. In concrete structures, penetrating moisture is responsible for most deterioration mechanism. The H-NMR spin-mobility is highly sensitive to the physical state of moisture. Using this additional information, also quality affecting properties o f concrete, as hydration degree and pore-size distribution can be determined. To apply OSA-NMR as an useful inspection technique on concrete building sites, also operational restraints of conventional equipment, as apparatus size, weight, cost and handling have to be removed. For that reason, ist was decided to develop a fully automatic, portable OSA-NMR system for in-field concrete inspection.

: http://publica.fraunhofer.de/dokumente/PX-27232.html