Experimental characterization of composite-to-brick masonry shear bond

The paper presents a Round Robin Test (RRT) devoted to the characterization of the shear bond performance of fibre-reinforced strengthening systems bonded with epoxy resin to brick masonry. The research was carried out by six laboratories involved in the RILEM TC 250-CSM (Composites for the Sustainable strengthening of Masonry) as a continuation and an extension of a previous RRT1 performed within the RILEM TC 223-MSC (Masonry Strengthening with Composites). In this second investigation (RRT2), the same FRP (basalt, carbon and glass textiles) and SRP (comprising steel textiles) composites were tested, but shear bond tests were carried out on both brick units and masonry prisms. The role of the bed joints of mortar was investigated in terms of shear bond strength, load-displacement response curve, axial strains profile along the bonded area and effective transfer length, for each of the four considered strengthening systems. Single lap and double lap testing setups were used and the comparison of experimental outcomes provided a validation of both results and test methods. Finally, test outcomes led to the determination of the mean and the characteristic values of the experimental-based calibration coefficient provided by design codes for the evaluation of the composite-to-substrate bond strength.