Neutronographic investigation of water transfer in porous limestones

In this work, a comparative neutron radiography (NR) investigation was carried out on two different limestones, i.e., Pietra di Lecce and Pietra d'Aspra, widely employed as building materials during the Italian baroque epoch (XVI-XVII century). The effect of the application of two different mm-thick layer of consolidating products, namely nanosilica (Nano Estel® ) and nanolime (CaLoSiL® ), was evaluated with the aim to qualitatively determine the best protective effectiveness against artificial external stimuli. In this framework, NR represents a wellestablished approach capable to highlight, in a completely non-destructive way, the water suction process by spontaneous imbibition occurring inside porous building materials. Water dynamics represents a powerful marker both for the evaluation of the extent of the weathering process and for the quantification of the consolidating action of a specific product. In our case, the water flow through the porous network of investigated limestones indicated two types of porosity, as revealed by the different "smoothness" of the corresponding water content vs. sample height profiles. The effect of the application of commercially available consolidants was distinguished by monitoring the wetting front positions as a function of time. The obtained results give insight into the different coating/limestone interaction mechanisms, whose understanding appears particularly useful for the selection of a proper intervention plan to be applied.