An innovative multidisciplinary methodology to evaluate the conservation state of cultural sites as a whole: “Casa di Diana" (Ostia Antica, Italy)

Archaeological sites, perceived as open museums, are particularly complicated to study because of the extensive number of environmental stressors affecting their conservation state. Diagnostic methodologies can easily omit some of them, causing irreparable and inestimable damages to these sites. In this sense, multidisciplinary studies seem to constitute the most suitable approach to understand the decaying processes that occur. Up until now, these types of studies have been applied within local programmes, leading to loss of strategic output, risk of duplication and reduction in the international competitiveness of the research. Therefore, in this Joint Doctoral Thesis, a new protocol for the preservation and accessibility of the archaeological sites, based on the synergic combination of physical, geological and analytical chemistry methodologies, is presented, in order to understand the sites as a whole. The project was born in 2012 within a multidisciplinary study on Ostia Antica Mithraea, as the result of my master degree. Successively, thanks to an international cooperation (Italy-Spain) and institutional effort (National and International Research centers and Departments) it was possible to combine different disciplines developing a new analytical approach. The final aim of this approach was assess the conservation state of the building under study, pointing out the areas most at risk, resolving important issues emerged during the investigation, and identifying the origin of the decay, suggesting also possible repair tools. The diagnostic protocol consists in a dynamic model, developed as a pyramid that includes three steps or levels that can be summarised into anamnesis (the state of art, the macroscopic observation on both environment and materials), analysis (the development of a protocol that includes the investigation actions that lead to the identification of damage’s sources) and a conservation step (the real state of conservation of the site under study). This last action also considers some suggestions for a future and global conservation and lays the “ad-hoc designing” to create a whole conservation plan. The final goal is the conservation, safeguard and “usability” of open museums or cultural sites in general, thanks to the protocol flexibility, organised in steps procedures. The base of the pyramid is built on an initial hypothesis based on the “content and container” axiom, the relationship between the environment and the materials. In order to validate the proposed diagnostic protocol, the model has been implemented in a complex building, the “Casa di Diana” Mithraeum, a Roman masonry dated 130 CE, found in Ostia Antica (Italy), the port of the old city of Rome, obtaining a well-developed pyramid. The rising damp represents the key between all the actions successively developed, both geophysical and chemical surveys, and is the result of a synergic interaction. Thanks to the well-planned multi-analytical procedure, the results obtained point out towards the rising damp and acids gases as the main environmental stressors. It was possible to associate the rising damp to the presence of freshwater at shallow depth, which causes the preliminary hydration phase on bricks, and the attack of the wall-building materials by the atmospheric acid gases through dry deposition mechanism. Furthermore, the results obtained by non-destructive spectroscopic analyses have led to the hypothesis that the observed yellow bricks could date back to a different historic period, for instance Byzantine, which corresponds to the last period of utilization of this house, while the red bricks derive from the Roman period. In addition to the new protocol, each methodology is characterised by several novelty keys, obtaining in this sense, 12 research articles published/reviewed on important international journals. Some processes of this multidisciplinary study involve an important economic effort, but the present method allows making an objective decision, through a solid analytical protocol, which has an important value in the management of Cultural Heritage.