Rationalist architecture in rural villages: petro-morphological characterization of natural asbestos fibers in decorative plasters used for artificial stones

At the beginning of the twentieth century, artificial stones became commonly used as structural building materials, masonry materials, and architectural decorative elements. The main purpose of this work was to characterize the building materials used in a historical building in Codigoro, a small town near Ferrara, northeastern Italy. This building was constructed according to the Italian rationalist rules for monumental architecture and is an example of the rationalist architecture found in rural villages, which uses innovative materials and decorations including artificial stone. The samples analyzed in this work were imitation natural stone, such as "fake travertine" and 'fake Ceppo di Gre" , composed of reinforced concrete slabs coated with white mortar. Asbestos minerals have been observed in the fillers in these materials. Petrographic, mineralogical, and chemical characterization of samples of artificial stones and concrete was performed with optical transmitted light microscopy, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction analyses. The results revealed chemical and biological degradation in almost all the artificial stones examined and enabled identification of the presence of calcite, iron oxychloride complexes, and asbestos lizardites used as fillers in two of the analyzed samples. This study aimed to describe a general investigation methodology used to examine the artificial stone facades of the Ex Casa del Fascio of Codigoro, whose architecture is particularly representative of the rationalist architecture in rural villages. The results highlight the relevance of compatible and suitable conservation measures that should be monitored during all restoration interventions to minimize post-degradation fracturing and transformation into elements harmful to human health and the environment.