Noninvasive patch resonator-based measurements in cultural heritage materials

In this work, a noninvasive microwave-based system for monitoring water content in stone materials used in Cultural Heritage structures is presented. By placing a planar resonator in front of the considered stone sample, trough reflection scattering parameter measurements, it is possible to associate the resonant frequency of the resonator to the moisture content of the stone sample. In this way, an experimental relationship between resonant frequency and moisture content can be obtained. Experimental tests arecarried out on two types of materials, namely gentile and carparostones: whichare typically found in Cultural Heritage structures in Southern Italy and they are particularly affected by deterioration and decay phenomena. Measurements were performed for five levels of water content of the stone samples, and the empirical relationship between each consideredlevel of water content and the corresponding measured quantity were derived. The obtained results demonstratethat this solution appears robust.