Romanesque and Territory The construction materials of Sardinian Medieval ch urches: new approaches to the valorisation, conservation and restoration

This paper is intended to illustrate a multidiscip linary research project devoted to the study of the constructive materials of Sardinian Romanesque chur ches during the Giudicati period (11th -13th centuries). The project focuses on the relationship between a s election of monuments and their territory, both fro m a historical-architectural perspective and from a mor e modern perspective addressing future restoration works. The methodologies of the traditional art-historical research (study of bibliographic, epigraphic and a rchival sources, formal reading of the monuments) are flank ed by new technologies: digital surveys executed wi th a 3D laser-scanner, analyses of the materials (stones , mortars, bricks) with different instrumental meth ods: X- ray fluorescence (XRF) and inductively coupled mass spectrometry (ICP-MS) for chemical composition, X- ray diffractometer (XRD) to determine the alteratio n phases (e.g., soluble salts), optical microscopy and electronic (SEM) to study textures, mineral assembl ages and microstructures, termogravimetric/differen tial scanning, calorimetric analysis (TG/DTA) for the co mposition of the binder mortars. This multidiscipli nary approach allows the achieving of important results in an archaeometric context: 1) from a historical p oint of view, with the possible identification of ancient t raffics, trade routes, sources of raw materials, co nstruction phases, wall textures; 2) from a conservative point of view, by studying chemical and physical weather ing processes of stone materials compatible for replace ment in case of future restoration works. Sardinian Romanesque architectural heritage is particularly r emarkable: about 200 churches of different types an d sizes, with the almost exclusive use of cut stones. Bichromy or polychromy, deriving from the use of d ifferent building materials, characterizes many of these mon uments, becoming also a vehicle for political and c ultural meanings. The paper will present some case studies aimed to illustrate the progress of the project and the results achieved