Characterization of mortars of Giotto's Bell Tower for radiocarbon dating

A complete characterization of mortars of Giotto's Bell Tower (Florence) was performed in order to identify samples or portions of them suitable for dating by radiocarbon. In principle, considering at least the case of an aerial mortar, the material which can be dated is the carbon contained in the binder, since that carbon is derived from the calcite that forms in the moment of mortar hardening by interaction with atmospheric CO2. Six core samples were obtained from foundation and from different levels of the Bell Tower, each of them related to a different construction phase. A multianalytical approach was performed using X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), optical and electronic microscope to characterize binder and aggregates. Physical and mechanical parameters were also evaluated. Four samples, either from lumps or binder itself, were identified as possible candidates to be dated by radiocarbon. Obtained data have been encouraging.