Comparative Investigation on Tensile Performance of FRP Bars after Exposure to Water, Seawater, and Alkaline Solutions

This paper presents experimental investigations to compare the effect of three environmental solutions on the degradation of tensile performance of fiber reinforced polymer (FRP) bars. Three kinds of FRP bars, basalt FRP (BFRP), carbon FRP (CFRP), and E-glass FRP (GFRP), were tested in tension after conditioning in tap water, artificial seawater, and alkaline solutions at room temperature for different exposure periods of 0, 45, 90, 135, and 180 days. The test results showed that the changes of the surface appearance of GFRP bars were more obvious that those of BFRP and CFRP bars after 180 days of exposure to three environmental solutions. The tensile failure mode and load-displacement curves of all tested FRP bars exhibited similar characters regardless of the immersion solution, the exposure period, or type of FRP bars. By comparing the residual mechanical properties of three kinds of FRP bars tested in this study, it has been found that the chemical attack of harsh environments simulated by immersion in seawater solution and alkaline solution resulted in a significant damage to BFRP bars. The effect of the seawater solution on the strength loss of CFRP bars was more obvious than those of the other two solutions. While the alkaline solution caused the greatest strength damage on GFRP bars. These findings were in accordance with the properties of material susceptibility to aggressive solutions and the moisture absorption of the matrix. No significant degradation of the elastic modulus of the three kinds of FRP bars had been found after exposure to aggressive solutions because their glass transition temperatures were kept unchanged in the experiment. Finally, based on the Arrhenius theory, the time-dependent tensile strength retention of all tested FRP bars exposed to the three aggressive solutions were fitted with experimental data obtained in this study. They were also compared with various test results collected from previous studies. The comparison results indicated that our experimental data were in good agreement with the predictions and most of the existing results.