Damage analysis of brick-to-mortar interfaces

A novel 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 repair mortars tested here are suitable for production of dehumidifying plasters, to be used to stop the rising damp effects due to capillary action in historical masonry walls. Assessing the durability of repair products is a major concern, because of the potential de-bonding phenomena that could occur in time due to insufficient compatibility between original and repair materials, in terms of their mechanical characteristics. Therefore, the study of the long-term mechanical interaction between repair mortars and historical masonry substrate under fatigue loading turns out to be crucial for the design of durable repair works. The testing procedure here presented consists of a series of static and fatigue tests on brick-mortar specimens produced ad hoc, so as to investigate their long-term behaviour and express a judgement about the compatibility of different repair mortars in comparison with the mechanical characteristics of the historical masonry substrate. Special care is devoted to the study of fatigue phenomena at the interface between the materials, that could negatively affect the brick-mortar system. Experimental results are compared with the theoretical values obtained through the cohesive-crack model.