Characterisation of a new protocol for mortar dating: 14C evidences

Presented at the 38th International Symposium on Archaeometry – May 10th-14th 2010, Tampa, FloridaInternational audienceMortars represent a class of material basically constituted by a mixture of different phases (i.e. binder, aggregates, water) and widespread used for constructive uses and artworks. Current scientific literature regarding the possibility of mortar radiocarbon dating reports different and still contradictory results. Most of the observed inaccuracy of the dating method often derives from the presence of carbonaceous residuals of limestone origins drastically increasing the mortar age estimation contributing with significant aliquots of dead carbon. Most of the existing methodologies aim to isolate binder from other materials, preserving a trace of the 14C signature of the atmosphere absorbed during mortar setting. In this work a series of measurements (i.e. %C and 14C) of different matrices involved in the mortar production process simulated in a simplified version in the laboratory environment will be shown. More in detail the isotopic signature of the CO2 present in the laboratory air during mortar setting is compared with the signal extracted from the synthesised mortar by means of a separation protocol of the binder. Our analyses are performed with the aim to evaluate this procedure of dead C suppression efficiency for accurate mortar radiocarbon dating