Microscopic characterisation of old mortars from the Santa Maria Church in Évora

Abstract

Evora Cathedral (one of the most emblematic monuments of Evora—Portugal) has suffered several conservation and restoration interventions through the ages, without, however, any type of previous knowledge about mortars and materials used. This work was carried out in order to identify the mortar's composition in different locations, which were attributed to different construction or conservation periods. The characterisation methodology involved a multidisciplinary set of chemical, physical, microstructural and mechanical techniques, and gave special attention to the use of microstructural characterisation techniques, particularly petrographical analysis and scanning electron microscopy for the identification of the mortar's constituents as well as in the evaluation of the state of conservation. The test results showed that two types of aerial binders were used, dolomitic and calcitic limes, the former being predominant. The aggregates used have a siliceous nature and are similar in composition to the granodiorites of the region around Evora. The mortars differ in the aggregate contents and, in some cases, crushed bricks were used as an additive.