Integrated ultrasonic, laser scanning and petrographical characterisation of carbonate building materials on an architectural structure of a historic building

Several non-destructive (ND) techniques are presented as a tool for the evaluation of the conservation state of carbonate building materials of the “Palazzo di Città”, a historic building in the centre of Cagliari, a town in Italy. In this study, considering both the nature of the building materials and the constructive types of the investigated architectural structure, ultrasonic investigations were carried at 54 kHz. The ultrasonic measurements were performed both in the laboratory and in situ using the portable ultrasonic non-destructive digital indicating tester (PUNDIT Lab plus©) by Proceq (Schwerzenbach, Switzerland). The ultrasonic measurements were integrated by a petrographical and petrophysical study of the investigated stone materials in order to correlate their petrographical-petrophysical features with the elastic ones. A further implementation was carried out comparing elasto-mechanical and petrographical-petrophysical features of the investigated carbonate materials with surface geometric anomalies computed by means of the architectonic terrestrial laser scanner (TLS) application. In particular, we used a Leica HDS-6200 TLS to study the complex shape of some artifacts from the “Palazzo di Città” monumental compound. A multi station approach was adopted in order to acquire more than 180 million points by performing 30 high resolution structured scans. After TLS data elaboration with JRC 3D Reconstructor® software, the 3D model of the buildings together with morphological anomalies of some artifacts were computed in order to highlight the zones where the deformation was more evident.