Innovative application on mortars of the radiocarbon dating technique with ultra sensitive Accelerator Mass Spectrometry (AMS) developed at CIRCE Lab.



Mortar, the adhesive used to connect the several parts of a building, belongs to a class of materials essentially made of a blend of different materials (i.e binder, aggregates, water..). Existing scientific literature concerning the possibility of dating mortar samples using the radiocarbon technique shows different results leading, however, to conclusions still to make clear.

The scarce accuracy of the dating method often depends on the presence of carbon aggregates, increasing the age estimation because of the high rate of limestone.

Almost all existing methods of treatment of samples are based on chemical or physical separation of binder, keeping track of the Carbon 14 timestamp of the atmosphere absorbed during the hardening process, of other materials and in particular of carbon aggregates.

At CIRCE Lab, through a series of isotope characterizations (i.e. Carbon 13 and Carbon 14) of different mortar matrix, the complete process of production and hardening of mortars have been simulated and isotope “prints” of absorbed CO2 have been compared with the C sign extracted from the mortar produced through a protocol of physical separation representing an adaptation of Nawrocka procedure (2005).

The tweaked procedure has been validated evaluating the accuracy, allowing to produce mortar datings not affected by bias”.

The innovative methodology allows to increase the efficiency of the suppression of the contamination of depleted C, due to the presence of carbon materials introducing an ageing effect of the radiocarbon signal of binder (which should be similar to that of the atmosphere at the moment of the hardening of the mortar).