SEM-XRD investigation of deterioration morphologies and consolidation prior to restoration: the case of Porta Nuova in Ravenna (Italy).

Porta Nuova in Ravenna (Northern Italy), built in the XVi century, has been the object of an interdisciplinary study, comprising an architectural survey of the Gate, mapping ashlars stones and drawing thematic maps. The following ornamental stones have been identified: Pietra d’Istria, Rosso Ammonitico Veronese, Marmor Proconnesium, Marmor Troadense, Pietra di Prun and Trachite dei Colli Euganei. Among these, Marmor Proconnesium and Marmor Troadense could be ancient materials recovered from monuments of Roman age. In order to carry out conservative restoration, it is of primary importance to know not only the nature and provenance of ornamental stones and building materials for possible replacement and/or integration, but also to define accurately their deterioration morphologies. The in situ analysis, implemented by mineralogical-petrographic analysis, SEM-EDS and XRD investigations, allowed drawing a map of the main types of deterioration morphologies, i.e. differential deterioration, black crusts, oxalate films, rust spots, fracture systems, biological patina and presence of vegetation (Norma UNI 11182 - 2006). Moreover, the enhanced deterioration of the architectonic structure of the Gate has required specific investigation by microseismicity, endoscopic tests and georadar analyses. These results allowed to make a preliminary intervention with consolidation of fractured and detached stone elements, and to secure the building elements prior to the restoration intervention.