Microwave characterization of bricklaying materials for non-destructive evaluation of restoring treatment effectiveness

A novel technique for non-destructive test on bricklaying materials is proposed and described. Such method makes use of microwave devices for materials electromagnetic characterization: vector network analyzers are employed to measure samples microwave reflection, transmission and absorption properties in both free space and waveguide framework. The materials under testing include calcium carbonate- and silicate-based bricklaying stones where conventional artwork-restoring substances are applied on. The comparison between the microwave results obtained for the naked and the restored materials allows to evaluate the effectiveness of the strengthening treatment. In particular, the electromagnetic field skin depth retrieved from the measurements of the microwave scattering parameters may be correlated to the effective length of the capillary infiltration achieved by the restoring solutions, thus providing powerful informations about the restoring technique efficacy itself. The usefulness of the present research lies in identifying and developing an innovative non-destructive testing route for cultural heritage restoring, as well as suggesting new fields and modalities of microwave analysis applications.