On the technical properties of the Carovigno stone from Apulia (Italy): physical characterization and decay effects by means of experimental ageing tests

Apulia (southern Italy) is typified by widespread outcrops of rocks exploited in the last centuries in historical architectures and religious constructions, as building and decorative stone. Today, as in the past, these stones represent an important source for region economy and prestige, due to their uses for modern works, restoration of local medieval churches and also exporting abroad. Among these, a noteworthy and still poorly known material is the Carovigno stone. In this paper, firstly an overall view on the, mineralogical and petrophysical features of the stone was reached through a multianalytical approach based on several investigation procedures and techniques, including ultrasonic test, X-ray diffractometry, scanning electron microscopy, optical microscopy, mercury intrusion porosimetry. In order to simulate decay phenomena, the Carovigno stone samples were processed to three different ageing tests: cycles of thermal treatments at different high temperatures, cycles of heating–cooling and cycles of exposure to decahydrate sodium sulphate and sodium chloride saline solutions. During and after each ageing processes, mineralogical transformations and petrophysical changes were evaluated. Results suggested that the Carovigno stone is a fine-grained calcarenite, pure or nearly pure, characterized by high porosity and, consequently, very notable thermal stress resistance. Conversely, the type and amount of porosity causes stone predisposition to salt crystallization decay.