Durability of GFRP bars in the simulated marine environment and concrete environment under sustained compressive stress

Abstract

The accelerated aging test results of the study on the compressive performance of glass fiber reinforced polymer (GFRP) bars under sustained compressive stress in the marine environment simulated by a salt solution and the concrete environment simulated by an alkaline solution were presented in this paper. The test parameters were sustained stress levels (0%, 20%, 40% of the ultimate compressive strength), exposure temperature (40 °C, 60 °C, 80 °C) and exposure time (16 d, 60 d, 90 d). The test results indicated that high temperature led to postcure of the resin matrix which was beneficial to the compressive performance of the GFRP bars. The conditioned GFRP bars failed due to the longitudinal splitting of the resin matrix or the fracture of the fibers and the debonding of the fiber/matrix interface. After immersing in the salt solution at 80 °C for 90 d, the strength retentions of the specimens with stress levels of 0%, 20% and 40% were 67%, 62% and 55% respectively. After immersing in the alkaline solution at 80 °C for 90 d, the strength retentions of the specimens with stress levels of 0%, 20% and 40% were 44%, 36% and 24% respectively. The compressive strength retention of the conditioned GFPR bars decreased with the increase of the sustained stress level, exposure temperature or exposure time. Increasing the exposure temperature or the sustained stress level could increase the degradation rate of the compressive strength of the GFRP bars. The compressive strength retention of the GFRP bars conditioned in the alkaline solution was lower than that in the salt solution. And the higher the temperature, the more obvious the detrimental effect of the stress level on the compressive strength of the GFRP bars was. Based on the test results, a degradation model for the compressive strength of the GFRP bars under sustained compressive stress in the simulated marine and the simulated concrete environments was proposed.