Monitoring and Evaluation of Pietra Serena Decay Adopting NDT Techniques: Application on Building Stones in Situ

Diagnostic investigations are fundamental procedures for the conservation and safeguarding of buildings belonging to the historical-artistic Heritage. In last five years, some corbels placed below balconies and eaves fell in Florentine area. Among the many episodes that have occurred it is important remember the visitor died in Santa Croce Basilica in October 2017, for dropping the ceiling off a stone corbel. To avoid damaging the Cultural Heritage and to protect people safety the Department of Earth Science - University of Florence has developed a new diagnostic approach, adopting fast, inexpensive and reliable techniques [1]. The diagnostic project includes the ultrasonic and Schmidt hammer tests, nondestructive techniques (NDTs) used to investigate the state of conservation of the stone used as an architectural component in the façades. This approach focuses on measurements carried out on Florentine Pietra Serena sandstone corbels of balconies belonging to historical buildings in Florence (Italy) and it is supported by laboratory studies as minero-petrographic analysis. Pietra Serena is a Florentine sandstone used in historical buildings in the Renaissance period and also in XIX century mainly for the balcony’s construction. The aim of this paper is the extension of a study protocol already started on previous artefacts, to investigate the corbels of new Florentine case studies: Pucci- Sansedoni Palace, Rimbotti Palace, Salone delle Feste Palace, Badia Fiesolana monastery and an historical building. The ultrasonic and rebound measurements collected, were inserted in reference database, to fast perceive the Pietra Serena decay, for distinguishing the weak points and unsteady elements, allowing the best intervention to make the stone elements safe and to ensure people safety.