Comparative durability of GFRP composite reinforcing bars in concrete and in simulated concrete environments

Many studies suggest that the durability of glass-fiber-reinforced-polymer (GFRP) bars in a simulated concrete pore solution is very different than the same bars in an actual concrete environment. This study conducted a comparative evaluation of the durability of GFRP bars in concrete and in simulated concrete environments by investigating their interlaminar shear strength. It focused on evaluating the physical, mechanical, and micro-structural properties of GFRP bars subjected to high moisture, saline, and alkaline environments. Bare GFRP bars and cement-embedded GFRP bars were immersed in solutions at different temperatures (23 degrees C, 60 degrees C, and 80 degrees C) and for different exposure times (28, 56, and 112 days). The results show that the percentage water uptake and the apparent diffusivity of the GFRP bars were strongly dependent on the type and temperature of the immersion solution. The interlaminar shear strength of the GFRP bars directly immersed in a solution degraded more significantly than those embedded in concrete and immersed. Moreover, the alkaline solution was more aggressive to the GFRP bars than tap water or saline solution, affecting bar fiber, matrix interface, and chemical structure. As a result of this study, master curves and time-shift factors were developed to correlate the retention of interlaminar shear strength from the accelerated aging test to the service life of GFRP bars in an actual concrete environment.