Microwave Compressive Strength Estimation of Cement Paste Using Monopole Probes
In-situ evaluation of the compressive strength of existing concrete structures using a direct approach is the objective of this investigation. The principle factor affecting the compressive strength of a concrete structure is its water/cement (w/c) ratio. The reflection properties of four cement paste samples with w/c ratios of 0.35, 0.40, 0.50, and 0.55 were measured using several monopole probes at microwave frequencies of 5, 9, and 12 GHz. The effect of several parameters, such as the operating frequency, the probe length (h), and the properties of the cement paste (w/c ratio) on the measurement sensitivity, were studied theoretically as well. For a given monopole probe (fixed diameter),h and the operating frequency can be optimized such that any slight change in the w/c ratio causes a large change in the reflection coefficient. Lower microwave frequencies are shown to be more sensitive in detecting variation in the reflection coefficient of these samples as a function of the w/c ratio. After the reflection coefficient measurements for these samples were conducted, they were tested to measure their compressive strength. Subsequently, a correlation between the compressive strength and the reflection coefficient of these samples was shown. The effect of an air gap around the monopole was investigated as well.
W. Shalaby and R. Zoughi, "Microwave Compressive Strength Estimation of Cement Paste Using Monopole Probes," Research in Nondestructive Evaluation, Springer-Verlag, Jun 1995.
The definitive version is available at http://dx.doi.org/10.1007/BF02538825
Electrical and Computer Engineering
Keywords and Phrases
Compressive Strength; Concrete Structures; In-Situ Evaluation; Electromagnetic Formulation-Probe Development and Antennas; Infrastructure Testing and Cement-Based Material Evaluation; Material Characterization
Article - Journal
© 1995 Springer-Verlag, All rights reserved.