Evaluation of the long-term performance and durability of basalt fiber reinforced polymer bars in concrete structures

Abstract

To simulate the internal corrosion process of basalt fiber reinforced polymer (BFRP) bars in an alkaline environment of concrete, a diffusion based model was employed and modified in this study according to Fickian diffusion and diffusion coefficients at 25 ℃, 40 ℃, and 55 ℃ obtained from existing studies. Thus, the long-term corrosion medium concentration diagram, degraded depth, and strength retention of BFRP bars in the concrete environment at any ambient temperature can be predicted. Durability tests of BFRP bars in an alkaline solution at 60 ℃ were conducted to verify that the diffusion based model’s predictions were accurate. Moreover, long-term bonding tests between BFRP bars and concrete were conducted. The results indicate that the predicted results of the degraded depth and strength degradation of BFRP bars corresponded well to the experimental data. Morphology analysis by scanning electron microscopy (SEM) indicates that the alkaline solution intrusion caused the resin matrix to deteriorate, the fibers and the resin to debond, and the reaction between OH- and SiO2 in the fibers to occur, which in turn caused the tensile and bonding strengths of FRP bars to degrade. Moreover, after 63 days of corrosion at 55 ℃, the degraded depth exceeded 7 times that of 25 ℃ and 2 times that of 40 ℃, which implies that the ambient temperature had an obvious influence on the deterioration of BFRPs. The degradation rate was extremely slow at room temperature and rapidly accelerated with the rise in temperature.