High-Temperature Measurements of Moisture Content in Refractory Concrete with Microwave Resonators

Refractory concrete materials require a time and energy intensive drying and dehydration process at temperatures up to approximately 600°C before safe use in industrial applications is possible. To monitor the dehydration process of hydrate phases, a measurement setup based on a high-temperature resistant microwave resonator is presented. The resonator is constructed with conventional, commercially widely available materials and measurements are conducted with inexpensive measurement hardware while allowing for real-time data acquisition during the heating cycle. The resonance frequency f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> and the 3 dB-bandwidth are extracted from measurement data and related to the dehydration process. The measurement results correspond to the loss of evaporated water from the refractory castable material. Ultimately, the temperature stability and reliability of the measurement setup are confirmed.