Mechanical and chemical-physical characterization of sandstone from the Phoenician-Punic necropolis of Tharros (Sardinia, Italy) with the aim of its conservation and strengthening

The archaeological site of Tharros, located in the province of Oristano in Sardinia, annually hosts about 106,000 visitors. The site consists of an archaeological area already accessible by tourists and a Punic necropolis object of excavations for several decades, which has brought to light archaeological artifact of great cultural value. To fully exploit the archaeological site of Tharros, the necropolis should be at the disposal of the tourist interest. For this reason, the idea of a conservation project arose, aimed at making this area of the site accessible. The study derives from the need to improve the knowledge about the characteristics of the sandstone in which the necropolis is carved, as such sandstone suffers from structural problems and natural weathering. In DICAM Laboratories, in Bologna, mechanical characterization tests were performed to identify the compressive and tensile strength of the stone. Preliminary fracture mechanics tests were also carried out. Regarding the chemical-physical characterization, capillarity absorption test, X-ray diffraction (XRD), Ion Chromatography, Mercury Intrusion Porosimetry (MIP) and Calcimetry test were performed. Finally, a study on the effectiveness of ethyl silicate consolidant (TEOS) on Tharros sandstone was carried out, in terms of mechanical properties and colour variation.