Microwave Nondestructive Determination of Sand-to-cement Ratio in Mortar


Microwave nondestructive testing methods have shown great promise for the inspection of cement-based materials. Previously it has been shown that the magnitude of reflection coefficient from cement paste specimens can be correlated to their water-to-cement (w/c) ratios and more importantly to their compressive strengths. For mortar specimens, the sand-to-cement (s/c) ratio plays an important role in its physical, mechanical, and microwave reflection properties. To determine the w/c ratio and other properties of mortar specimens, one also needs to know its s/c ratio. To illustrate the ability of microwave reflection measurements for this purpose, two sets of four mortar specimens are produced with w/c ratios of 0.50 and 0.60 and with s/c ratios of 1.0, 1.5, 2.0, and 2.5. The microwave reflection coefficients of these specimens are measured using an open-ended rectangular waveguide sensor, in the G- (3.95-5.85 GHz), J- (5.85-8.2 GHz), and X-band (8.2-12.4 GHz) frequency ranges. It is shown that a simple relationship between the standard deviation of the magnitude of the reflection coefficient of mortar and its s/c ratio exists, and a more sensitive relationship exists for higher frequencies (waveguide bands). This approach may be extended to nondestructively determine the aggregate volume content and size distribution in concrete specimens.


Electrical and Computer Engineering


Electric Power Research Institution
National Science Foundation (U.S.)

Keywords and Phrases

Cement-Based Materials; Microwave Nondestructive Testing Methods; Mortar Specimens

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Document Type

Article - Journal

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