The technological properties of natural stone from Itria Valley for the protection of Cultural Heritage

A major challenge in the approach to the sustainable management of landscapes and cities is the identification, conservation and protection of Cultural Heritage. In a geographic area like Itria Valley, which is recognised by UNESCO as a site of great relevance in territorial identity because of the dense presence of trulli, masserie and dry-built walls, natural stone protection is even more demanding, because of a lack of characterisation of this material employed for building and ornamental purposes, both in terms of geological and technological properties. Standardised methods of investigation, both destructive and non-destructive, on stone samples coming from different sources and sites can help in the process of classification. The variability and unpredictability of natural stone is an important drawback in the study of these materials on-site. Many factors – both external and intrinsic – can affect the reliability of non-destructive testing. Furthermore, these investigations can only assess the properties of the medium indirectly. On the other hand, laboratory tests – although conducted in a controlled environment – necessitate a robust and representative population of samples to overcome the variability of natural stone. This can represent an obstacle in the case of material coming from cultural heritage sites, since the availability of samples can be very limited, making the advantages of laboratory testing irrelevant. The main goal of this work is to further characterise Itria Valley natural stone, by means of robust correlations between physical-mechanical properties, including water absorption, open porosity, petrographic analysis, accelerated ageing and flexural strength. All these tests are compared with ultrasonic pulse velocity (UPV) measures, which represent a quick and reliable way of on-site investigation, to simplify direct on-site characterisation in the case of natural stone coming from Itria Valley cultural buildings, such as churches and trulli, and have an immediate understanding of strategies for choice, use and restoration of the material.