Effect of sustained loads on the durability of GFRP bars with and without UHP-ECC cover

Fiber-reinforced polymer (FRP) bar reinforced ultra high-performance engineered cementitious composite (UHP-ECC) structures (referred to as FRP-UHP-ECC structures) have been demonstrated to have excellent mechanical properties, while their durability in the alkaline environment has never been explored, particularly when being subjected to tensile loadings. To this end, this article aims to investigate the effects of sustained loads on the durability performance of Glass FRP (GFRP) bars embedded in UHP-ECCs while immersed in an alkaline solution. The test results revealed that the effect of elevated temperatures was exacerbated when specimens were subjected to even a low sustained load (20 % of ultimate strength). Furthermore, UHP-ECC covers considerably postponed the degradation of GFRP bars. Nevertheless, the protective effects of UHP-ECC covers were nearly entirely compromised when the specimens were subjected to sustained loads. The findings of this study provide useful knowledge for a comprehensive evaluation of the durability of GFRP bars under UHP-ECC environments. •The effect of elevated temperatures on GFRP bar degradation was exacerbated under sustained loads.•This study revealed that even lower-level sustained loads (i.e., 20 %) led to evidently more pronounced degradation of UHPECC-embedded GFRP bars compared to those without sustained loads.•UHPECC covers effectively postponed the degradation of GFRP bars, but their protective effects were nearly completely compromised under sustained loads.•SEM and X-CT analysis revealed that the degradation of GFRP bars may be associated with the development of porosity or connected porosity after exposure.