Analytical techniques for the characterisation of historical building materials. Case study "Casa di Diana" mithraeum (archeological site in Ostia Antica, Italy)

Nowadays, a broad range of analytical techniques are available and applied in the preservation of cultural heritage. However, to characterise the historical materials and to obtain quantitative and qualitative information of their composition and structure, it is necessary to choose the appropriate analytical instruments. In fact, for each study, analytical aim and nature of the analysed materials, it is necessary to combine the scientific and technological knowledge of the devise used in order to define an adequate plan of action. In the field of cultural heritage conservation, destructive techniques should be avoided, wherever possible, to preserve the integrity of the historical buildings. Therefore, the development of non-invasive, non-destructive and in-situ analysis is extremely important. Taking all of this into account, this chapter contains the main advantages of the more useful selected analytical techniques to characterise ancient building materials, taking into consideration a particular case study: a roman masonry, dated 130 a. C., found in the Ostia Antica archaeological site. Specifically we will deal with bricks and mortars, the wall building materials of the “Casa di Diana” Mithraeum. The combined use of techniques such as polarized microscope, X-ray diffraction (XRD), Raman spectroscopy and, X-ray fluorescence (XRF) allow us to extract information in terms of phase identification, quantification of crystalline compounds and complex poly-phasic mixtures (solid solutions), identification of deterioration products and determine their nature. In this way, it is possible to analyse the complete life-cycle of the manufacturing processes, starting from the raw materials, through to the man-made production and constructive techniques evolution. Moreover, the obtained results enable us to study the forms of degradation, as well as to choose and apply a suitable procedure for the preservation and safeguard of the materials taken into consideration.