Assessing aesthetic and structural deterioration in historic buildings – a contribution

Abstract

An important part of our cultural heritage assets is built of natural stone since it has always been a material of excellence due to its inherent characteristics. Despite the physical and mechanical properties that give relatively long durability as a construction material, some characteristics are less durable, namely color or eventual surface finishes. The alteration of its aesthetic features may be followed by the alteration of the physical and mechanical properties of the stone. In this way, it is crucial to characterize the material and perform regular diagnoses in the buildings classified as local cultural heritage to provide the necessary tools for future intervention campaigns of conservation and restoration. Considering its chemical composition, each stone has a specific behavior when placed in a particular environment. Factors like humidity or temperature are strongly influenced by the weather, which will also influence the nature of microbial colonization. Keeping this in mind, the work here presented aims to demonstrate a non-invasive and non-destructive analytical methodology applied in the identification of deterioration phenomena in natural stone buildings, either by geochemical or biogenic pathways, using X-rays based techniques and through the identification of colonizing populations. This methodology was successfully performed in the marble on the main cloister of the Convent of “São João da Penitência”. The Convent is located in Estremoz (Portugal), is dated from the 16th century, and presents applications of local marble. Several pathologies were identified, ranging from aesthetic damage, where the color is strongly compromised, to detachment of relatively large fragments. Impurities in the calcite matrix and the action of microbial and pollution agents were considered as the main factors that are contributing for the deterioration of the natural stone applied in this historic building.