Microwave nondestructive detection of chloride in cement based materials

Abstract

Preliminary results pertaining to the near-field microwave nondestructive detection and evaluation of chloride in cement paste and mortar specimens are presented. The technique used for this purpose utilizes an open-ended rectangular waveguide at the aperture of which the reflection properties of the specimens are measured. It is shown that the magnitude of reflection coefficient is a useful parameter for detecting chloride in these specimens. Furthermore, the difference in the amount of chloride present in these various specimens, at the time of mixing, can also be determined. Reflection property measurements were conducted in S-band (2.6 GHz-3.95 GHz) and X-band (8.2–12.4 GHz) for two sets of four mortar specimens with 0.50 and 0.60 water-to-cement ratio and varying salt (NaCl) contents added to the mixing water used in producing these specimens. It is shown that the reflection properties of these materials vary considerably as a function of their chloride content. Also, by monitoring the daily variatio...