In-situ evaluation of composites-to-masonry bond in a natural aggressive environment

Composite materials, such as Fibre-Reinforced Polymers (FRP) and, more recently, Textile- Reinforced Mortars (TRM), are nowadays widely used in civil engineering applications as well as on historic masonry. Nevertheless some conditions may cause damaging on these last applications, such as moisture, thermal effects, creep, fatigue, ultraviolet radiation (especially for organic matrices) and fire. An experimental research, made in collaboration with Politecnico di Milano and University of Padua, has been performed with the aim of evaluating the influence of aggressive environmental conditions (moisture, temperature and soluble salts presence) on the bond between composites and masonry substrate. Pull-off tests has been carried out on site on full-scale masonry models representative of historic masonry, naturally exposed to environment (thermal excursion, R.H. and UV cycles); furthermore they were artificially subjected to salt crystallization cycles. Two types of FRPs (carbon and glass) and a TRM (carbon net) applied with two inorganic matrices (pozzolanic lime based mortar and cement polymer modified mortar) were tested on two different masonry substrates, made by soft-mud bricks and sandstone units with lime mortar. The comparison of the results showed both theeffect of the environmental induced damage and of the intrinsic properties of the reinforcement system.