DELAMINATION OF THE DEHUMIDIFIED REPAIR MORTARS: A NEW EXPERIMENTAL AND NUMERICAL ANALISYS

An innovative laboratory procedure, developed at the Non Destructive Testing Laboratory of the Politecnico di Torino, as a preliminary design stage for the pre-qualification of repair mortars applied to historical masonry buildings is described. The tested repair mortars are suitable for the new dehumidified plaster in order to stop the rising damp effects by capillary action on historical masonry walls. Long-term plaster delamination occurs frequently as a consequence of not compatible mechanical characteristics of mortar. Preventing this phenomenon is the main way to increase the durability of repair work. The use of materials similar to that historical in terms of mechanical, chemical and thermo-hygrometric performances is better. The procedure consists in the application of static loads to mixed stone block-mortar specimens having peculiar characteristics in terms of geometry and adhesion at the interface, with continuous monitoring of the longitudinal and transverse displacements. A numerical simulation based on the cohesive crack model was used to follow the experimental data, so as to describe the evolutionary phenomenon of de-bonding as a function of a small number of parameters. The methodology is in progress of carrying out at the Special Natural Reserve of the Sacro Monte di Varallo (UNESCO heritage site) in Piedmont (Italy)