NDTnet 1998 Aug, Vol.3 No.8

Abstract

Nuclear magnetic resonance (NMR) possesses remarkable potential for material characterization due to its high sensitivity to molecular structure and dynamics. 1h NMR standard equipment the sensor encloses the specimen, consequently the maximum sample size is restricted and measurements on large specimen require a sampling. Recently, exceptional NMR devices have been developed, which are one-sided accessible to the specimen, and therefore offer the possibility to measure NMR signals directly in oil wells (1), or on car tires (2). One of the most striking technical realizations of one-sided access NMR (OSA-NMR) was designed by Southwest Research Institute (San Antonio, TX) (3). With it, a depth profile of the NMR signal can be detected inside the component with a resolvable depth increment of 1 mm.

In Hydrogen-NMR (¹H-NMR), the amplitude of the signal, strongly correlates with the moisture content of a solid material. Therefore, with OSA-NMR the moisture depth profile can be measured in an individual component of masonry, wood, polymers a.s.o. In concrete structures, ingressing moisture is responsible for most deterioration mechanism. The ¹HNMR relaxation times - specific lifetime characteristics of the signal - are highly sensitive to the physical state of moisture. Using this additional information, also quality affecting properties of concrete, as hydration degree and pore-size distribution can be determined (4).

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, it was decided to develop a fully automatic, portable, low-cost OSA-NMR system for in-field concrete inspection. In our presentation, results of several studies will be outlined, which shows the whole range of OSA-NMR application possibilities for concrete characterization and the design characteristics and the accomplishment of our measuring system will be described.

1. R. L. Kleinberg, The Industrial Physicist 2, No. 2, p. 18, 1996.
2. G. Eidmann, R. Savelsberg, P. Blumler, and B. Blumich, J. Magn. Res., A 122, p. 104,1996.
3. R. F. Paetzold, G. A. Matzkanin, and A. De Los Santos, Soil Sci. Soc. Am. J: 49, p. 537,1985.
4 B. Molter, and G. Dobmann, Int. Symp. NDT-CE, Sept. 26-28, Berlin, Proc. Vol 1, p.,181, 1995.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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