Evaluation of preservation state of monumental buildings by ND acoustic and mineralogical studies

In recent years non-destructive (ND) techniques, based on the analysis of sonic or ultrasonic pulse transmission, have become increasingly important both in the acquisition of objective information on the conservation state of building materials and in the investigation of the effectiveness of repair actions to damaged or deteriorated masonry structures. Altered and weakened zones inside the structures as well as cracks and flaws beneath the surface of the material are characterized by lower acoustic velocity values with respect than values in unaltered and intact materials. It is a known fact that the characteristics of the acoustic signals are strictly related to the mechanical status of the material. In the present study, to contribute to the knowledge on the mechanical characteristics of the investigated materials, ultrasonic velocity measurements by the direct transmission technique (transmitter and receiver on two opposite faces) were carried out on unaltered samples of different materials prevalently used as building stones on most monumental structures of the historical city center of Cagliari (Italy).