Inspection and evaluation of cement-based materials such as concrete is of great interest to the construction industry. In particular, real-time and on-site evaluation of water-to-cement ratio (w/c) is an important practical issue, since the compressive strength of a concrete structure is significantly influenced by its w/c. Currently, there is no single real-time, on-site, relatively in-expensive, easy-to-implement, and operator friendly technique for evaluating this parameter. Microwave nondestructive testing and evaluation techniques have shown great promise when used for inspection and evaluation of the properties of cement-based materials. In this paper, the optimal design of a monopole antenna probe used to evaluate w/c of fresh cement-based materials in real-time and in-situ is presented. This probe, operating at 3 GHz, is used along with a reflectometer whose dc output voltage is shown to be linearly correlated to w/c of fresh cement paste and fresh concrete specimens. This paper presents the optimal probe design procedure, the experimental verification of the results, and the results of using the custom-made reflectometer for quick and robust w/c measurement of fresh cement paste and concrete.


Electrical and Computer Engineering


Portland Cement Association

Keywords and Phrases

Microwave Testing; Monopole Antennas; Near Field Microwave Nondestructive Evaluation; Water-to-Cement Ratio; Design; Dielectric Properties; Electric Potential; Electromagnetic Waves; Optimization; Portland Cement; Reflectometers; Water; Microwave Antennas; Cement Paste; Concrete; Fresh Water-to-Cement Ratio (w/c)

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2001 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Oct 2001