ABSTRACT
Castel Nuovo is a medieval castle, landmark of the city of Naples, Italy. Multiscale X-ray micro-CT imaging of samples of yellow tuff called Tufo Giallo Napoletano (TGN) collected from the façade of Castel Nuovo has been carried out in order to study the stone decay and the black crusts on the surface of that rock material. The 3D image analysis algorithm of “successive opening” allowed to determine the size distribution and the connectivity of the outer connected pores of the TGN as well as the crust thickness distribution and its development inside the pores under the surface. Black crusts exhibited an average thickness of 39.3 microns with propagation below the surface of the stones of about 1.2 millimeters. Transmitted light microscopy on thin sections of the crusted layers allowed to identify as gypsum the main composition of the black crusts. Overall, the applied analysis approach revealed to be useful for better addressing the restoration treatments of porous construction materials of cultural heritage.
