Durability of carbon fiber-reinforced polymer (CFRP) rebar exposed to long-term alkaline environment

초록

The durability of carbon fiber-reinforced polymer rebar was evaluated to assess its applicability in concrete subjected to an alkaline environment. The durability assessment was conducted via analysis of the rebar's mechanical properties, specifically its tensile and shear strength, following ASTM standards. The key variables are the duration of Carbon fiber rebar's exposure to an alkaline environment and the specimen diameter. The study used a total of 100 specimens separated into 40 specimens for tensile strength testing and 60 specimens for shear strength testing. Following the mechanical tests, scanning electron microscopy analysis was performed to investigate the microstructural changes induced by the specimens' exposure to alkaline. The results indicate that, with prolonged exposure to an alkaline environment, the tensile strength of the smaller diameter (10 mm) specimens increased by up to 19 %, whereas the larger diameter (13 mm) specimens exhibited a maximum increase of 12 percent. In contrast, the shear strength of the Carbon fiber rebar specimens remained unaffected by alkaline exposure, as no significant difference was observed between specimens exposed to the alkaline environment and those that were not. The shear strength of CFRP rebar is primarily governed by the interfacial bonding with the epoxy resin, and the alkaline-resistant epoxy resin used in this study underwent additional curing rather than degradation at 60 degrees C, resulting in no reduction in shear strength. To interpret the observed strength development more accurately, this study focused on applying the post-cure model, which provided a consistent explanation of the experimental results and demonstrated its effectiveness for predicting the long-term durability of CFRP rebar in alkaline exposure environments. The results confirm that carbon fiber rebar can sustain stable mechanical performance over an extended period without significant strength degradation.

키워드