Estudo de incompatibilidade entre rebocos cimentícios e paredes de adobe

: a Casa Gandaresa como caso de estudo

Abstract

Adobe architecture, widely used in Portugal until the mid-20th century, represents a heritage of high cultural value but shows significant vulnerabilities when subjected to interventions with industrial materials. Among these, cement renders stand out due to their recurrent application in rehabilitation processes, despite their physico-chemical and hygrothermal incompatibility with adobe substrates. This dissertation aimed to analyze the compatibility of cement renders applied to adobe masonry through the case study of the Casa Gandaresa de Santo António in Vagos and complementary laboratory tests. Mineralogical and chemical analyses were carried out using X-ray diffraction (XRD) and acid dissolution tests, along with physical tests of apparent density (Archimedes method), capillary absorption, and colorimetric analysis, in order to characterize the interaction between cement-based coatings and the adobe substrate, with particular attention to the phenomena of transport and crystallization of soluble salts. The results revealed the presence of phases typical of cement hydration (portlandite and hydrotalcite), as well as soluble salts such as gypsum, thenardite, and butlerite, associated with active degradation processes. Physical tests showed that salt crystallization and the formation of cement hydration products led to partial blockage of the pore network. This obstruction reduced water vapor permeability, promoted moisture retention inside the walls, and created favorable conditions for salt accumulation and progressive degradation of the adobe. In summary, it is concluded that the use of cement renders in adobe masonry accelerates the deterioration of the building system, reinforcing the need to employ compatible replacement materials, such as lime-based mortars with natural additives, in order to ensure the conservation and sustainability of this heritage.

Date of Award	7 Jan 2026
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Eduarda Vieira (Supervisor) & Alice Tavares (Co-Supervisor)