X-ray computed micro-tomography to study the porous structure and degradation processes of a building stone from Sabucina (Sicily)

Understanding the behaviour of building stones when they are subjected to weathering processes represents an important research field related to the conservation and restoration of Cultural Heritage. Salt growth is a significant cause of damage for natural stones. In addition to the properties of the salt and the climatic conditions, the effects of salt weathering are strongly related to the structural and textural features of materials. Therefore, detailed knowledge of the internal structure of building stones is fundamental in order to estimate durability and prevent degradation processes. In this work we show the potential of X-ray micro-tomography in understanding the mechanism by which salts can damage building materials. In detail, we focus on weathering effects due to sodium sulphate on a calcarenite from Sabucina (Sicily) widely used as local building and replacement stone. Overall, the obtained results allow for visualisation and quantification of the changes in the porous structure caused by salt crystallization, supporting the comprehension on how the pore network is modified in coarsegrained stone materials. In particular, salt weathering induces fractures in Sabucina stone, leading to an increase of the total porosity. The resulting pores are characterized by a higher maximum opening and equivalent diameter compared to the pores of a freshly quarried stone.