Romanesque and territory. The construction materials of Sardinian medieval churches: new approaches to the valorization, conservation and restoration

Alberto VIRDIS¹ / Rossana MARTORELLI¹ / Lorenzo TANZINI¹ / Fabio PINNA¹ / Stefano COLUMBU² / Marco MARCHI² / Fabio SITZIA²/ Marcella PALOMBA³
(¹University of Cagliari, Department of History, Cultural Heritage and Territory / ²University of Cagliari, Department of Chemical and Geological Sciences / 3CNR – National Research Council, Italy: IGAG , Institute of Applied Geology and Geoengineering – Operative Support Unit, Cagliari, Italy)

Keywords:Art-historical approach, Construction stone, Petro-archaeometric approach, Provenance, Alteration

Abstract:
This paper is intended to illustrate a multidisciplinary research project devoted to the study of the constructive materials of the Romanesque churches in Sardinia during the “Giudicati” period (11th -13th centuries). The project focuses on the relationship between a selection of monuments and their territory, both from a historical-architectural perspective and from a more modern perspective addressing future restoration works. The methodologies of the traditional art-historical research (study of bibliographic, epigraphic and archival sources, formal reading of artifacts) are flanked by new technologies: digital surveys executed with a 3D laser-scanner, analyses of the materials (stones, mortars, bricks) with different instrumental methods: X-ray fluorescence (XRF) and inductively coupled mass spectrometry (ICP-MS) for chemical composition, X-ray diffractometer (XRD) to determine the alteration phases (e.g., soluble salts), optical microscopy and electronic (SEM) to study textures, mineral assemblages and microstructures, termogravimetric/differential scanning, calorimetric analysis (TG/DTA) for the composition of the binder mortars.
This multidisciplinary approach allows the achieving of important results in an archaeometric context: 1) from a historical point of view, with the possible identification of ancient traffics, trade routes, sources of raw materials, construction phases, wall textures; 2) from a conservative point of view, by studying chemical and physical weathering processes of stone materials compatible for replacement in case of future restoration works.
Sardinian Romanesque architectural heritage is particularly remarkable: about 200 churches of different types and sizes, with the almost exclusive use of cut stones. Bi- or poly-chromy, deriving from the use of different building materials, characterizes many of these monuments, becoming also a vehicle for political and cultural meanings. The paper will present some case studies aimed to illustrate the progress of the project and the results achieved.