Performance of FRP-masonry joints under on-site conditions: influence of water and salts.

Nowadays, masonry is still commonly found in building structures, but low bearing capacity and poor seismic resistance make it necessary to strengthen masonry buildings. Externally bonded fiber-reinforced polymer (FRP) composites have emerged as a valid technique since the past decades. The aim of this study is to investigate the bond behavior of SRP-masonry joints considering the effects of water and salt. An experimental campaign was designed: SRP composite was applied to masonry blocks, which were previously subjected to an accelerated weathering protocol. Other SRP-masonry joints were suffered to moist condition, as well certain specimens were prepared as references. i) Direct shear tests were conducted to determine the bond behavior, while digital image correlation (DIC) is employed to obtain detailed displacement and strain information. ii) Pull-off tests were carried out to further investigate the local bond. iii) To give deeper understanding on what the part substrate properties played in debonding, supplementary tests were performed, including three-point bending flexural tests and Brazilian splitting tests. iv) In addition, ion chromatography provided the salts amount and distribution of salt-laden specimens, contributing to interpret the results from shear tests. Furthermore, the theoretical bond strength prediction method suggested by the Italian Guidelines CNR DT 200/R1/2013 was calibrated by collected previous and current studies specifically for SRP composite, and then compared with the experimental results from this study, providing more consolidated knowledge on the bond strength between SRP and masonry blocks, and on the other hand validating the results gained in the shear tests conducted in this study.