Effect of Loading Rate and Chemical Corrosion on Mechanical Properties of Large-Diameter Basalt-Glass Fiber-Reinforced Polymer Bars

In the past few decades, the mechanical and durability properties of glass fiber reinforced polymer (GFRP) bars with relatively small diameters (< 20 mm) have been extensively studied. However, the performance of larger size GFRP bar is still not well understood, due to its remarkable anisotropy and size effect. In this study, the end anchorage device for large diameter FRP bar was firstly developed, based on which the direct tensile mechanical properties of 25 mm diameter GFRP bars were tested with different loading rates, and their damage modes and mechanism were analyzed. In addition, with regard to the relative low resistance of GFRP to the alkaline attacks, a new type of FRP bar was manufactured by replacing the glass fibers on the periphery of GFRP bar with basalt fibers. Based on this, the 25 mm diameter basalt-glass fiber reinforced polymer (B-GFRP) bars with different thicknesses of basalt FRP protecting layers (0, 1, 3 and 5 mm) were immersed in H2SO4 solution (pH=1), distilled water (pH=7) and NaOH solution (pH=14) at 20°C for 30, 70 and 120 days, respectively. The mass, ultimate tensile strength, elastic modulus and elongation ratio of different samples were tested both before and after the immersion treatment. The results show that, with the increase of loading rate, the tensile strength and elongation ratio of GFRP bar increase considerably, while the elastic modulus remains roughly constant. The addition of BFRP protecting layer is also proved to be an effective way to enhance the resistance of GFRP bars to the chemical attacks.