Effect of coarse aggregates on FRP strain distribution in an FRP-to-concrete bonded joint

Advanced fibre-reinforced polymer (FRP) composites have been widely used for strengtheningconcrete structures. The bond behaviour between FRP and concrete plays the crucial role in thistechnique. Commonly the test of this bond behaviour is conducted using a single or double shear pulloff test of an FRP-to-concrete bonded joint, or similar bending tests. Such test setups are usuallymodelled as a two dimensional (2D) plane stress or plane strain structure. However, the test setup is inreality a three-dimensional (3D) structure due to many factors. One of the main factors is that theconcrete behaviour is three dimensional because of the presence of coarse aggregates. Because ofthe random distribution of coarse aggregates in concrete, it may be expected that the non-uniformity ofstrain distribution is also random. Compared to concrete, mortar is a much more uniform material. Inthe research work presented in this paper, an experimental study is employed to investigate the straindistribution in the FRP in a bond test, where the FRP was bonded to either concrete or mortar. Theresults confirm that the presence of coarse aggregates in the concrete leads to much more variation inthe FRP strain distribution.