RF moisture measurement of concrete with a resonator sensor

Non-destructive methods are becoming more and more crucial in the evaluation of concrete in construction engineering and also for needs analysis of renovation in old targets. When detecting of the possible water leaks inside concrete the non-destructive methods provide undisputedly the best means when houses are evaluated. In this paper a feasibility study of moisture measurement of concrete with the RF resonator sensor method is carried out. The resonator method is based on the resonant frequency shift when the permittivity of the material under test (MUT) increases with growing water content. A concrete sample is measured when it is completely dry and when it has been saturated in tap water and at 21 saturation levels until a completely dry state. The results indicate that the used resonator is sensitive enough for the moisture measurement of the concrete in question. The effect of the moisture content of the sample on the resonant frequency shift is studied by measurements. The dependency between the resonant frequency shift and the moisture content is determined.