Influence of Salt Crystallization on Composites-to-Masonry Bond Evaluated on Site by Pull-Off Tests

A research, made in collaboration with Politecnico di Milano and University of Padua, has started with the aim of evaluating the influence of aggressive environmental conditions (moisture, temperature and soluble salts presence) on the bond between FRP/TRM and masonry substrates. Experimental tests were carried out on site on full-scale masonry models, built in open air in a polluted area in the hinterland of Milan, naturally subjected to thermal, R.H. and UV cycles; furthermore, they were artificially subjected to capillary rise of a solution of water and Sodium Sulphate so as to create salt crystallization cycles. On two different masonry substrates, representing a simple historic masonry structure, made either by soft-mud bricks or sandstone units with lime mortar, various FRP and TRM strips were vertically applied in order to evaluate the bond at three heights. TRM were applied with two different premixed inorganic matrices (pozzolanic lime based mortar and cement polymer modified mortar) and FRP with an organic matrix (epoxy resin). The fibres used were unidirectional carbon and glass fabrics for FRP, and a bidirectional carbon net for TRM. The bond was evaluated by means of pull-off tests and the first results, herein presented, show the influence of moisture presence and of salt crystallization cycles on the different used matrices.