Mineralogical and chemical study of the salt alteration of masonry blocks in the baths of Antoninus ruins at Carthage, Tunisia

Salt-induced deterioration poses a significant threat to the structural integrity and aesthetic appeal of the Baths of Antoninus ruins at Carthage, Tunisia. A comprehensive mineralogical and chemical study reveals that calcarenite masonry is heavily contaminated by halite (NaCl), gypsum (CaSO₄·2H₂O), and traces of nitrates, originating from sea spray, atmospheric pollutants, and saline groundwater. These contaminants contribute to the formation of honeycombs and black crusts, accelerating physical and chemical decay under Tunisia's seasonally variable Mediterranean climate. The study employed advanced techniques including X-ray diffraction (XRD), ion chromatography, inductively coupled plasma emission spectroscopy (ICP-OES), digital and scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS), helium porosimetry, and optical microscopy to characterize the deterioration mechanisms. These findings underscore the urgent need for targeted conservation strategies to mitigate salt-related damage in this UNESCO World Heritage Site.

Mannai, A., Guellouz, L., Mejri, E., Achour, M., Hommel, J., Helmig, R., & Bouhlila, R. (2025). Mineralogical and chemical study of the salt alteration of masonry blocks in the baths of Antoninus ruins at Carthage, Tunisia. STAR: Science & Technology of Archaeological Research, 11(1). https://doi.org/10.1080/20548923.2025.2553367