Probabilistic damage evolution in masonry strengthened with FRCM subjected to aggressive environment

This paper concerns the applications of advanced Fibre Reinforced Cementitious Matrix (FRCM) systems on existing masonry structures. At the state of the art, it shows that the FRCM-to-masonry bond is affected significantly by substrate properties and environmental conditions. For this purpose, an experimental campaign was realised recreating different experimental scenarios, and the results thereby achieved were critically and comparatively discussed. In particular, specimens constituted of two types of fired-clay bricks (either with a single brick or a running bond masonry) were reinforced with a carbon fibre grid, externally glued by means of a cementitious or a lime-based matrix, and then exposed to salt crystallisation induced by capillarity over several months. Visual observation combined with laser profilometer measurements revealed a progressive deterioration of the surface with material loss and signs of bulging between the composite - masonry interface. Pull-off tests on deteriorated samples confirmed the progressive weakening of the bond in terms of nominal strength. To interpret the amount of data, a novel probabilistic model was proposed, apt to predict possible damaging effects on the surface of reinforced masonry elements.