Salt Crystallization and Heritage Materials: Improving Durability by Understanding Porosity and Mineral Composition

The current research examines the role of salt crystallization, a major factor in atmospheric pollution in coastal regions, on the degradation of biocalcarenite stones used in monuments in the Rabat-Sal & eacute; area of Morocco. Focusing on Bouknadel and Bouskoura stones samples, the study conducted seven cycles of imbibition and desiccation with Na2SO4 and NaCl solutions (70 g/L and 100 g/L) to simulate marine aerosol effects. Additionally, capillary absorption was measured, and mass changes were documented after immersion in distilled water. X-ray diffraction and scanning electron microscopy were utilized to evaluate the chemical, mineralogical, and textural properties of the stones. The findings revealed that Bouknadel stone, despite its higher porosity (38 +/- 9%), exhibited greater resistance to salt damage than Bouskoura stone (25 +/- 5% porosity). This variation in response is attributed to differences in mineral composition, notably the presence of quartz in Bouknadel stone and sulfur in Bouskoura stone. Bouskoura stones faced significant deterioration, especially with Na2SO4, linked to the crystallization of thenardite. In contrast, Bouknadel stones maintained structural integrity despite halite crystal formation. These results underscore the importance of mineralogical composition and porosity in assessing stone susceptibility to salt degradation, offering critical insights for the conservation of cultural heritage in coastal ecosystems.