Tensile behavior and durability prediction of GFRP-steel composite bars under chloride environments

Abstract

A fiber-reinforced polymer (FRP)-steel composite bars (FSCBs), with an inner steel core and outer FRP jacket, is a novel type of reinforcement designed to inherit good durability and ductility suitable for seawater sea sand concrete structures. The long-term tensile behavior of FSCBs in chloride environments is important. The long-term tensile behavior of glass-type FSCBs with different fiber layer thicknesses under chloride environment attack was investigated in this study. FSCBs with an inner steel bar of fixed diameter (8 mm) and an outer FRP jacket of three thicknesses (2, 4, and 6 mm) were used for research. Seawater-immersion accelerated-aging experiments at three different aging temperatures (23, 40, and 60 °C) and aging times (1, 6 and 12 months) were conducted. The failure modes, equivalent elastic modulus, pseudo strain hardening moduSTlus, and tensile strength retention of the FSCBs under the above mentioned aging temperatures and times were analyzed. The experimental results determined that the chloride environment had no significant effect on the equivalent elastic modulus of the FSCBs. However, the pseudo-strain hardening modulus of the FSCBs decreased with increasing aging time. Moreover, the tensile strength retention of the FSCBs decreased with increasing temperature under the same aging time and FSCBs diameter. A prediction model for the tensile strength retention of FSCBs with different FRP layer thicknesses at different aging temperatures and times was proposed and validated. The results provided a better understanding of the durability of FSCBs in marine hydrothermal environments to establish the criteria and standards of design.