Martha Tavares

Microstructural Characterization of Consolidant Products for Historical Renders: An Innovative Nanostructured Lime Dispersion and a More Traditional Ethyl Silicate Limewater Solution

The conservation and durability of historical renders must be carried out through compatible techniques and materials. An important operation is the restitution of historical renders cohesion, turned friable by the loss of binder, usually due to physical and/or chemical actions. Surface consolidation is based on the use of materials with aggregating properties. This operation is reached usually through the application of organic or mineral consolidants, but inorganic consolidants are becoming preferred due to better compatibility and durability. In this article two mineral compatible consolidation products were studied: a commercial suspension of calcium hydroxide nanoparticles in propanol and a limewater dispersion of ethyl silicate. Microscopy (optical and scanning electron microscopy) and X-ray microanalyses of the consolidation products and of the consolidated mortar specimens were carried out. To assess the mechanical properties and products efficacy, analyses of the compression, flexural strength, and superficial hardness were performed. Microscopy results show that limewater dispersion of ethyl silicate forms platelike silica gels, which can interfere in product penetration. Otherwise, nanolime particles permit homogeneous distribution and optimum penetration on the treated substrate, improving cementing action and the agglomeration process.

Characterization of Renders and Plasters from a 16th Century Portuguese Military Structure: Chronology and Durability

In coastal areas of Portugal, many historical buildings and fortresses still exist that were constructed in masonry with aerial lime mortars. These mortars are often found to be in good condition, showing appropriate cohesion and adhesion to the background, although usually they show surface degradation as a result of the aggressive marine environment. The aim of this paper is to present and characterize the mortars used for the renders and plasters of one of these fortresses, that of Nossa Senhora da Luz which was constructed and modified over several centuries. The study of the mortars permitted to identify a construction period chronology improving the knowledge of the changes in formulation of the aerial lime mortars thus allowing to select compatible repair solutions.

Diagnosis, Characterisation and Restoration of the Internal Renders of Santíssimo Sacramento Church in Lisbon

The Santissimo Sacramento Convent in the Alcântara quarter of Lisbon is one of the most important ecclesiastical structures of the Filipino Period (1580–1640), showing an innovative architectural layout. An intervention aiming at the repair and restoration of the interior plasters of the Santissimo Sacramento Church was performed in 2009 and 2010. To support the restoration plan, a physical, mechanical and chemical-mineralogical characterisation of the internal plasters of the church was carried out. In this paper the main results are presented, such as various types of plasters, mortars, stuccos and pigments; and also the nature of the main anomalies were identified and characterized. The results obtained contributed to the identification of the main decorative programs characterized by the use of different materials and techniques. The mortars are in very good condition, being composed of aerial calcitic lime with quartzitic and basaltic aggregates. The stuccos are comprised by gypsum and non-hydraulic lime, while the decorative layers features lime with some precious pigments, such as ultramarine (lapislazzuli) and gold-foil gildings. The plaster conservation and restoration works were performed with compatible repair materials selected according to the physical-chemical characterisation and on the evaluation of the conservation state.