Characterization of mortar from Casa Barbot (Portugal), a case study from the beginning of the 20th century

Abstract

The popularity of natural cement (Roman cement) in buildings from the late 19th and the beginning of the 20th century and the high diversity of characteristics of natural cement demand research of mortar and binders used in the buildings of this period in Portugal. Understanding the type of binder used in the historic buildings will help the project/intervention team to make the best decisions in terms of the development of compatible mortars for historical conservation purposes. Casa Barbot is one of the Art Nouveau examples of the beginning of the 20th century in Portugal. The garden of this building is characterized by peculiar elements in terms of materials and architecture. Full characterization of the mortars employed in the construction of this building as well as identification of the used binder is the main objective of this study. The study comprises a wide range of laboratory characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), petrography, open porosity, density, water absorption by capillarity, and compressive strength. The results show the diversity of compositional characteristics in the mortars used in the decorative elements in the period garden of Casa Barbot. All mortars are composed of Portland cement with a mix of additives such as blast furnace slag, limestone filler, air lime, and the occasional presence of charcoal. The results raise doubt about the use of natural cement as stated in the historical documents. This study will broaden the scientific knowledge of the materials of that period in Portugal to provide a comprehensive plan for the preservation of historical buildings.