Soft calcarenites constituting as materials in the architectural baroque architectural heritage in of Southern Italy: factors influencing the decay response

This paper deals with preservation issues involving the curch of S. Maria Maddalena in the town of Uggiano la Chiesa (Lecce, Southern Italy). An example of the baroque heritage of the Salento peninsula, it was built with the soft calcarenite locally known as pietra leccese. Decay, mainly consisting of exfoliations and scaling, has been observed in many points on the façade, specific to some isolated ashlars randomly distributed. The initial hypothesis to explain such decay was that it arose from some previous restoration work, but no information about this has been obtained from the available documentation. Traces of products applied to the stone were found by FT-IR analyses, while contact angle measurements yielded a weak response. The study also addressed the role of the intrinsic characteristics of the different varieties of Lecce Stone employed in the building. A mineralogical-petrographic study was carried out, paying special attention to the structural characteristics of the stones and to the nature and composition of the insoluble residue inside them; in addition, porosimetric measures and water absorption tests were performed. Further analyses were carried out on micro-cores taken from the surface of weathered ashlars and subjected to X-ray diffractometry, FT-IR spectrophotometry, porosimetric measurements and observations by optical and SEM microscope in order to identify the type of product applied and to investigate the causes and mechanisms that led to the observed decay.