Architetture e murature
In: Storia della tecnica edilizia e restauro dei monumenti: 12, 2022
The morphology of the land greatly influenced the fortified systems studied. Such morphology is denser and more homogeneously distributed in the island’s west, particularly towards the north, due to different geographical systems and the rugged territory. The close link with the natural context also emerges from comparing on-site materials and those used to construct the architectural structures. These represent a sort of territorial footprint, as they generally use local materials, revealing Sardinia’s lithological heterogeneity. A systematic investigation showed that many architectural structures are totally abandoned. Only a small number are in a sufficiently good state of preservation to meaningfully facilitate the study of the masonry structures. The study and comparison of the main characteristics of the various fortified buildings analysed revealed the recurrence of formal, structural, morphological, dimensional, technological and material characteristics. These characteristics make it possible to adopt a typological classification, sometimes closely linked to precise construction phases. The structures in question are city walls and castles, divided into four subcategories: fortified palaces, dwelling-forts, keeps and fortresses. Classifications of the masonry samples were based on various qualitative-morphological and quantitative/measurement-related parameters of the natural and artificial stone elements and the vertical joints and mortar beds. Three macro-categories classified the samples – coursed rubble masonry (A), blocks (B) and ashlars (C). They were also differentiated in terms of texture (in rows, sub-horizontal, coursed), courses (jointed, in bands, in horizontal axes), morphology and stoneworking techniques (bosses, blocks, ashlars). The typological classification of the mortar took into account the following parameters: the mineralogical and morphoscopic characteristics of the aggregate and binder; the detection of additives (mainly cocciopesto, crushed terra cotta or brick); the binding-to- aggregate ratio; the distribution of the aggregate and the possible detection of clumps. Concerning the relationship between masonry techniques and chronologies, the most frequent class among the three macro types is type A, coursed rubble masonry used continuously over the centuries. Type B, block masonry, was predominant in castles built between the 12th and 13th centuries. Type C, ashlar masonry, was used continuously between the 12th and 14th centuries.