Characterization of Calcium Carbonate Nanoparticles with Architectural Application for the Consolidation of Pietraforte

Abstract

Laboratory-synthesized CaCO₃ nanoparticles and their nanodispersion in 1,4-butanediol as a working medium have been first characterized and then tested on the surface of Pietraforte stone that forms the cladding of the bell tower of San Lorenzo. Both CaCO₃ nanoparticles and their nanodispersion in 1,4-butanediol were characterized in the church in Florence, Italy by X-ray diffraction, thermal analysis, Raman, and Fourier transform infrared spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray (EDX) spectroscopy, and transmission electron microscopy/EDX spectroscopy. The Pietraforte sample surface, before and after CaCO₃ nanodispersion treatments, was characterized by comparison of the porosity and specific surface area, capillary absorption, and surface hardness. An ultrastructural morphological investigation by SEM was also carried out, confirming and implementing the effective dynamics of the nanodispersion action. Lastly, differences in stone optical appearance before and after treatment were evaluated by colorimetric measurements. Considering the obtained results of the study, we conclude that CaCO₃ nanodispersion in 1,4-butanediol is an effective restorative agent that prevents water infiltration in the stone, reduces stone disruption, and promotes its consolidation without altering its appearance. Finally, the long-lasting stability of the CaCO₃ nanodispersion at ambient conditions makes it suitable for production and commercialization.

KEYWORDS:

• Alcoholic nanodispersion
• calcium carbonate nanoparticles
• enzymatic synthesis
• infrared spectroscopy
• Pietraforte
• Raman spectroscopy
• sandstone
• stone consolidation
• scanning electron microscopy
• transmission electron microscopy
• X-ray diffraction

Acknowledgments

The authors would like to express their sincere thanks to the director of restauratio site Arch. Fulvia Zeuli for access to the restoration area, set up at the Campanile di San Lorenzo (Florence, Italy). Furthermore, the authors wish to sincerely thank Arch. Hosea Scelza Superintendence of Archeology, Fine Arts and Landscape for the metropolitan city of Florence and the provinces of Pistoia and Prato, for access to the archaeological area of ​​the Monumental Complex of San Lorenzo, Florence. Furthermore, we thank the Opera Medicea Laurenziana and company Carlo Bugli srl (from Naples, Italy) and Prof. E. Bugli for technical support regarding consolidation processes on Pietraforte samples. The authors also wish to thank Dr. Michela Relucenti and Dr. Orlando Donfrancesco for their shared electron microscopy expertise in the morphological analysis of Pietraforte specimens. The contribution of Prof. Gianluca Sottili was the interpretation of the chemical-physical, and mechanical-engineering features of Pietraforte specimens. For this purpose, the authors wish to thank Prof. G. Sottili for her scientific contributions to this work. Furthermore, the contribution of Dr. Ida Pettiti was very valuable in the analysis of surface area and porosity of materials and in the revision of the manuscript. The scientific contribution of Dr. Valentina Mussi was important for the Raman characterization of the Pietraforte samples. Moreover, Dr. V. Mussi provided language help, writing assistance and article proofreading.

Additional information

Funding

The project was funded by the Ministry for Cultural Heritage for Tourism and by Opera Laurenziana.