Characterization of calcium carbonate nanoparticles with architectural application for the consolidation of Pietraforte

Laboratory-synthesized CaCO3 nanoparticles and their nanodispersionin 1,4-butanediol as a working medium have been first characterizedand then tested on the surface of Pietraforte stone thatforms the cladding of the bell tower of San Lorenzo. Both CaCO3nanoparticles and their nanodispersion in 1,4-butanediol were characterizedin the church in Florence, Italy by X-ray diffraction, thermalanalysis, Raman, and Fourier transform infrared spectroscopy, scanningelectron microscopy (SEM)/energy-dispersive X-ray (EDX) spectroscopy,and transmission electron microscopy/EDX spectroscopy.The Pietraforte sample surface, before and after CaCO3 nanodispersiontreatments, was characterized by comparison of the porosityand specific surface area, capillary absorption, and surface hardness.An ultrastructural morphological investigation by SEM was also carriedout, confirming and implementing the effective dynamics of thenanodispersion action. Lastly, differences in stone optical appearancebefore and after treatment were evaluated by colorimetric measurements.Considering the obtained results of the study, we concludethat CaCO3 nanodispersion in 1,4-butanediol is an effective restorativeagent that prevents water infiltration in the stone, reduces stonedisruption, and promotes its consolidation without altering itsappearance. Finally, the long-lasting stability of the CaCO3 nanodispersionat ambient conditions makes it suitable for production andcommercialization.