Mechanical properties of GFRP bars exposed to natural erosion environment: A case study

Unlike traditional steel bars, the long-term performance of GFRP (glass fiber reinforced plastic) bars in natural erosion environments remains unclear. This study simulated the water environment at the entrance of the Chai River, a tributary to Dianchi Lake in China, and investigated the mechanical properties of GFRP bars under varying corrosion concentrations. Microstructural analysis using SEM (scanning electronic microscopy) was also conducted to uncover the degradation mechanism. The results showed that after 180 days of immersion in natural water and exposure to environmental concentrations of 5 times, 10 times, and 20 times, the tensile strength of GFRP bars exhibited reductions of 2.8 %, 4.2 %, 7.2 %, and 9.5 %, respectively. However, the compressive strength decreased by 38.0 %, 48.6 %, 50.2 %, and 53.2 % under the same condition. As the number of corrosion cycles increased, the rate of strength decline decreased gradually. The combined action of hydroxyl ions generated through bicarbonate hydrolysis and water molecules in the solution led to the breakdown and swelling of the resin matrix, ultimately causing detachment at the fiber-resin interface. An analysis was conducted on the time-shifted regression equation of the accelerated conversion factor (ASF) under different concentrations, based on the correlation between natural erosion and acceleration testing. It was observed that a strong correlation exists between the strength retention rate and the natural erosion environment at 5 times the concentration. Finally, an improved time-shift method based on the Arrhenius theory was proposed to predict the tensile strength of GFRP bars in a natural erosion environment.