Permittivity Determination of Fresh Cement-Based Materials by an Open-Ended Waveguide Probe Using Amplitude-Only Measurements

An open-ended waveguide probe has been adapted for complex permittivity determination and hence mechanical property inspection of cement-based materials. The probe uses amplitude-only reflection measurements at different frequencies for this goal, which is suitable for industrial based applications when cost and ease of use are important considerations. We have derived expressions by taking into account of the wave-material interaction. The reference plane for measurements is set inside the waveguide to measure solely the reflected signal of the dominant mode. It is shown that the measurement results are in good agreement with the theory.