Prediction of Long-Term Performance and Durability of BFRP Bars under the Combined Effect of Sustained Load and Corrosive Solutions

TLDR

The long‑term performance of basalt‑fiber reinforced polymer (BFRP) bars under severe environmental conditions is poorly understood compared to CFRP and GFRP bars. This study evaluates the residual tensile properties of unstressed and stressed BFRP bars exposed to alkaline, salt, acid, and de‑ionized water at 25–55 °C. Residual tensile strength in alkaline solution was used with Arrhenius theory to predict long‑term performance, while SEM microstructural analysis revealed the degradation mechanism. Durability was most affected by alkaline exposure; sustained stress below 20 % of ultimate strength had little effect, but higher stress accelerated degradation, and a 50 % strength loss in alkaline solution is predicted after ~16.1 years at 5.7 °C mean annual temperature for a 6‑mm bar.

Abstract

Unlike carbon-fiber-reinforced polymer (CFRP) bars and the maturely developed glass FRP (GFRP) bars, the long-term performance of the newly developed basalt-fiber reinforced polymer (BFRP) bars under severe environmental conditions remains unclear. This paper evaluates the residual tensile properties of unstressed and stressed BFRP bars exposed to four types of simulated harsh environments: alkaline solution, salt solution, acid solution, and de-ionized water at 25, 40, and 55°C. Microstructural analysis using scanning electronic microscopy (SEM) was also conducted to reveal the inherent degradation mechanism of BFRP bars in alkaline environment. The residual tensile strength of unstressed BFRP bars exposed to alkaline solution was used for long-term performance prediction based on Arrhenius theory. The results showed that the effect on the durability of BFRP bars exposed to acid, salt, and deionized water was less than that for bars exposed to alkaline solution. The effects of sustained stress on the degradation of BFRP bars were not obvious when the stress level was less than 20% of the ultimate strength, but if the stress exceeded this level, the degradation processes were accelerated. The predicted exposure time required for a reduction in strength of 50% at a mean annual temperature of 5.7°C in alkaline solution, which represents an area with a northern latitude of 50°, was estimated at approximately 16.1 years for the 6-mm BFRP bar.