Assistant Professor, Politecnico di Torino, Italy

Eng. Alessandro Grazzini is an Assistant Professor in Structural Mechanics at the Department of Structural Building Geotechnics Engineering of the Politecnico di Torino (Italy). He graduated in Building Engineering in 2001 and he received the PhD degree in Structural Engineering in 2005 at the same institution. His research interests include structural monitoring of historic buildings, non-destructive tests materials, mechanical compatibility between strengthening materials and masonry structures through laboratory fatigue tests, damage analysis on historic masonry structures and related strengthening techniques. He collaborated for 12 years for the restoration works of the Royal Palace of Venaria (the biggest restoration site in Europe). He was involved in several international programs focused on structural mechanics and damage assessment for Cultural Heritage. From 2005 to 2015, He was assistant lecturer in Static and Stability of Masonry Buildings at the Politecnico di Torino. From 2017, He is assistant lecturer in Fundamental of Structural Mechanics at the same institution.

Speech Title: Delamination of plasters applied to historical masonry walls: analysis by acoustic emission technique and numerical model

Aims: Masonry walls of historical buildings are subject to rising damp effects due to capillary or rain infiltrations, which in the time produce decay and delamination of historical plasters. In the restoration of masonry buildings, the plaster detachment frequently occurs because of mechanical incompatibility in repair mortar. An innovative laboratory procedure is described for test mechanical adhesion of new repair mortars.

Methods: Compression static tests were carried out on composite specimens stone block-repair mortar, which specific geometry can test the de-bonding process of mortar in adherence with a stone masonry structure. The acoustic emission (AE) technique was employed. This non-destructive methodology allowed estimating the amount of energy released from fracture propagation in adherence surface between mortar and stone.

Results: A numerical simulation was elaborated based on the cohesive crack model, able to follow the experimental data. The evolution of detachment process of mortar in a coupled stone brick–mortar system was analyzed by triangulation of AE signals, which can improve the numerical model and predict the type of failure in the adhesion surface of repair plaster.

Conclusions: The experimental procedure was useful for pre-qualification of repair plaster applied to masonry stone, selecting the product that is best in keeping with the mechanical characteristics of the original masonry walls. Through the cohesive crack model, it was possible to interpret theoretically the de-bonding phenomena occurring at the interface between stone block and mortar. Therefore, the mechanical behavior of the interface is characterized. The parameters obtained can be used for the analysis of a problem with different boundary conditions.