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Proceedings Paper

Dielectric properties of concrete at S and X bands: a near-field investigation
Author(s): Karl J. Bois; Aaron D. Benally; Paul S. Nowak; Reza Zoughi
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Paper Abstract

When inspecting concrete structures with microwaves (radars, embedded microwave sensors, modulated scattering techniques, etc.) the dielectric properties of the concrete are considered as a ground truth data and must be known. During the past three years, extensive microwave near-field measurements of the reflection properties of concrete specimens with varying water-to-cement (w/c) ratios, sand-to-cement (s/c) ratios and coarse aggregate-to-cement (ca/c) ratios have been conducted. These experiments were conducted using open-ended rectangular waveguide probes radiating into a half-space of these concrete specimens. These measurements were conducted at S- (2.6 - 3.95 GHz) and X-bands (8.2 - 12.4 GHz). Moreover, an electromagnetic model, which took into account the presence of higher-order modes at the waveguide aperture, was also used to model this process. Finally, a root finding technique was applied to calculate the effective dielectric properties of the concrete specimens. This paper presents the results of these measurements and calculations as they related to determining the dielectric properties of concrete. Since concrete is a heterogeneous material, the results from many locations in a specimen are reported rendering effective dielectric properties showing the mean and standard deviation of the measurements and calculations at these frequency bands. The results of the dielectric constant can also be used to predict the reflection properties of concrete when using a standoff distance (i.e. non-contact measurements) or when using other types of microwave sensors.

Paper Details

Date Published: 15 October 1999
PDF: 7 pages
Proc. SPIE 3752, Subsurface Sensors and Applications, (15 October 1999); doi: 10.1117/12.365697
Show Author Affiliations
Karl J. Bois, Colorado State Univ. (United States)
Aaron D. Benally, Colorado State Univ. (United States)
Paul S. Nowak, Gonzaga Univ. (United States)
Reza Zoughi, Colorado State Univ. (United States)


Published in SPIE Proceedings Vol. 3752:
Subsurface Sensors and Applications
Cam Nguyen, Editor(s)

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