Stucco Marble in the Portuguese Architecture: Multi-analytical Characterisation

Abstract

The presence of stucco marble in the Portuguese architecture is not surveyed and studies addressing the materials used to produce it are almost inexistent.

In this paper, the results of the multi-analytical characterisation using XRD, SEM-EDS, Py-GC/MS and the determination of capillary water absorption and dynamic modulus of elasticity of 15 samples belonging to seven case studies are presented and discussed. XRD showed that gypsum is the main constituent, but anhydrite is also present in most samples. These results were consistent with the observations by SEM-EDS, attesting temperatures of calcination above 350ºC. The use of a multiphase gypsum plaster as a binder was probably intentional. The treatment of the surfaces, which is used to obtain an aesthetical appearance similar to the natural stone, has also a major influence in the main properties of the final materials. The search for organic compounds showed the presence of animal glues in the inner core and beeswax and oils at the surface.

The dynamic moduli of elasticity are extremely high in the samples incorporating anhydrite and the capillary water absorption is almost inexistent.

The results obtained intend to contribute to promote sustainable interventions on this type of materials, namely the future development of compatible restoration products.