Detachment Monitoring of Repair Mortar Applied to Historical Masonry Stone by Acoustic Emission Technique

Abstract

In the repair of historical masonry walls, the plaster de-bonding frequently happens because of the long-term mechanical incompatibility of new mortar. A new laboratory methodology is described for evaluate the mechanical adhesion of the repair mortar applied in the restoration work at the Sacro Monte di Varallo (UNESCO heritage site). The acoustic emission (AE) technique has allowed to predict the fracture mode and to evaluate the repair mortar applied to historical masonry stone. This non-destructive methodology was able to identify defects and damages in masonry structures. Through shear tests, the specific geometry of assembled specimen can verify the detachment process of repair mortar. The AE technique permits to estimate the amount of energy released in de-bonding surface between repair mortar and stone during damage process. The authors have elaborated a numerical simulation to follow the experimental data. The evolution of de-bonding process of a plaster in a stone brick – mortar system was assess by means of the Acoustic Emission technique, which can follow the numerical model. Therefore, the experimental procedure was able to characterize the mechanical behavior of detachment mortar, useful for selection of repair plaster applied to historical masonry stone.