Methodological approach in the conservation of the Sardinian coastal towers

Coastal towers are an interesting and fascinating fragment of the historical heritage of Sardinia. Their historical and artistic value justifies the recovery of these emblematic artifacts. For the achievement of this objective we propose a methodological approach including: i) a macroscopic semi-quantitative evaluation of decay, ii) the application of diagnostic quantitative chemical-physical-mechanical methodologies, to assess the decay intensity, and define the criticalities for planning the restoration. The i) phase allows a fundamental pre-critical understanding of the building materials, the macroscopic alteration forms, the monument features, as well as the acquisition of information about potential causes and mechanisms of decay. During this phase, significant information for planning a targeted sampling of material to be analyzed, performing an appropriate selection of diagnostic techniques and/or for the monitoring, and defining the most urgent actions for recovery, must be acquired. Moreover, the architectural survey of monuments makes up the base for representing distribution of the constituent materials (rock types and mortars) and of the forms of decay. During the ii) phase, according to the information obtained by the macroscopic mapping of decay, sampling of building materials (natural stones, mortars, metals, wood) is planned. It is fundamental to georeference the sampling points and make an accurate photographic documentation. Laboratory analyses, to determine the soluble salts, crystalline phases, porosity as well as micro-textural features of the materials, are carried out by the application of suitable techniques. The chemical-physical-mechanical properties of the collected materials can be used to obtain the mappings of the decay forms, graphically represented on thematic atlas for each single monument. The final diagnosis, by the critical analysis of the visual and experimental results, is the cornerstone for planning the building recovery.