Experimental and numerical analysis of delamination repair plaster appled to historical masonry building

Often masonry walls of historical buildings are subject to rising damp effects due to capillary or rain infiltrations. In the time, their cyclic action produces decay and delamination of historical plasters. An experimental laboratory procedure for the pre-qualification of repair mortars is described. Long-term plaster delamination frequently occurs because of the mechanical incompatibility of new repair mortars. The tested mortars are suitable for new dehumidified plasters applied to historical masonry walls. Compression static tests were carried out on composite specimens stSone block-repair mortar, which specific geometry can test the de-bonding process of mortar in adherence with historical masonry structure. A numerical simulation based on the cohesive crack model was used to follow the experimental data, in order to describe the evolutionary phenomenon of de-bonding as a function of a small number of parameters. This method supplies useful indication for selecting the product that is best in keeping with the mechanical characteristics of the historical material, thereby avoiding errors associated with materials that are not mechanically compatible. Currently, the methodology is being used at Sacro Monte di Varallo Special Natural Reserve (UNESCO heritage site) in Piedmont (Italy).