Bond strength's degradation of GFRP-concrete elements under aggressive exposure conditions

An experimental study was performed to determine the environmental durability of adhesive bond between Glass Fibre Reinforced Polymer pultruded profile and concrete. The specimens were subjected to two artificial ageing regimes before being tested to failure. Some specimens were exposed to 50 freeze-thaw cycles and other were immersed in water at 45 °C for varying time periods. Furthermore, some specimens were exposed to natural outdoor conditions to up to one year. The water effect on the adhesion of the joints was found to be significant, especially at longer immersion times; the shear strength of push out specimens reduced by 71% after ten months of immersion and the failure mode was shifted from cohesive within concrete to adhesive at the adhesive/concrete interface. The results also show that the ultimate shear strength deteriorated measurably during freeze-thaw cycling, about 56% of reduction was obtained after just 50 cycles, while after one year of outdoor exposure, the shear strength dropped by 27.7% compared to those without ageing. The study suggests that the ageing tests can provide information about the effects of environmental agents in the durability of bonded structures but cannot estimate the real amount of deterioration in real service life of such structures.