Diagnosis and conservation by using portable equipment: the case of St. Maria Cathedral in Randazzo (Sicily)

Abstract

The diagnosis of historical building materials is quite relevant for a complete knowledge of construction rules as well as during focused restoration actions. In particular, the identification of natural building stones employed in the manufacture of historical monuments is the first step to understand causes of weathering processes, to choose the most appropriate conservation and/or protection treatments and to select the materials to employ in replacements during the restoration works. In some cases, the high architectural value of the investigated elements prevents any sampling, needing the application of portable instruments for the non-destructive in situ analysis of building stone materials. However, the routinely application of portable methodologies to diagnosis and conservation actions imply the standardization of testing procedures and creation of appropriate reference database to carry out reliable comparisons between building and (probable) quarry materials. For the aforementioned, in this contribute we present an experimental study performed by using a portable X-ray device, namely the Bruker Tracer IV instrument on reference basalt natural stones sampled in some of the Sicilian quarries and used in the local historical architecture to standardize and subsequently for in situ analysis of building materials. Thus, non-destructive measurements have been carried out on the basalt columns of the St. Mary Cathedral in Randazzo (Sicily) - a relevant historical building founded in the 12th century, but completely renovated during the Renaissance period (Cultrone et a., 2001; Sanfilippo, 2008) - in order to test the method for stone classification and identification of quarries. This approach has allowed to identify raw materials employed in the manufacture of the columns of the Cathedral, supporting the creation of a database of Etna lavas quarried over the time for building manufacture and the standardization of the instrument for future in situ applications