A multidisciplinary approach for monitoring the conservation state of the sandstones of the Palazzo Ducale in Camerino (MC)

While negative impacts of climate-related and other hazards on urban areas are widely discussed in the scientific literature, their impact on historic buildings is still understudied (Bigio et al., 2014). In this regard, the 2016-2017 seismic sequence in Central Italy, which represents the second major disastrous event in the last decade on the Apennines, caused heavy damage of tens of municipalities, thousands of buildings and mostly important, life losses. These events highlighted the need to involve innovative non-invasive techniques to preserve the existing architectural heritage, carrying out studies on both the structural and decorative elements of historic buildings (e.g., columns, capitals and other stone elements such as architraves or facade adornment). This is the case of the Palazzo Ducale, one of the main historic buildings in the town of Camerino (Central Italy) protected by the Superintendent for cultural heritage of Marche Region (peripheral body of the current MiBAC Ministero per i Beni e le Attività Culturali), where a multidisciplinary study on the sandstone columns was carried out for its restoration. In this regard, the use of Equotip hardness tester was proposed to implement a new approach for non-destructive evaluation of both the superficial and the internal hardness of the sandstone columns, useful to understand the rule that weathering plays on the mechanical rock properties (Mammoliti et al., 2021). In addition, a sedimentological study coupled with mineralogical-petrographic analyses (thin sections and XRD) were used to assess the extraction site of the sandstone columns, investigating an outcrop at the Botanical Garden of the city, just beneath the building of Palazzo Ducale. This aspect was essential to find a suitable site to extract rock samples for the Uniaxial Compressive test. In this way, the impossibility of using invasive techniques that could damage historical structures was overcome and a comparison of the mechanical properties was possible. Eventually, a conservative treatment on the surface was proposed and Equotip has been also tested to verify the effective improvement of rock hardness after the intervention.