Impact performance of fibre reinforced geopolymer concrete beams with steel-FRP composite bars

Global warming has driven the rapid development of sustainable and durable materials in infrastructure construction in recent years. Demand is increasing as more economies around the world are booming. Geopolymer concrete (GPC), basalt macro fibres (BMFs), and steel-fibre reinforced polymer composite bars (SFCBs) are such materials that enable enhanced structural performance and longevity of structures whilst reducing carbon emissions. SFCB is a kind of new rebar comprising steel rebar as a core and fibre-reinforced polymer (FRP) as an outer layer, i.e., SGCB, SBCB, and SCCB (denoting SFCBs with glass FRP, basalt FRP, and carbon FRP layer, respectively). This study proposes new BMF-reinforced GPC structures reinforced with SFCBs (named BMF-GPC-SFCB structures). Laboratory tests were conducted to investigate the flexural behaviour of BMF-GPC-SFCB beams against impact load with three designed impact velocities (0.23 m/s, 1.56 m/s, and 3.79 m/s), on which the effects of reinforcement type, BMF content, SFCB type, and SFCB ratio were considered in this study. The test results show that the GPC-SBCB beam had smaller residual mid-span deflections than the GPC-Steel beam, and the failure mode changed from flexure in the GPC-Steel beam to flexure-shear in the GPC-SFCB beam due to the higher tensile strength of SBCBs. Increasing the tensile strength and modulus of SFCBs as well as the reinforcement ratio enhanced the impact performance of the GPC beams. This study provides valuable insight into the application of SFCBs for reinforcing GPC beams and test data for the calibration of numerical models. • First study on impact performance of GPC beams with hybrid SFCB bars. • Damage mechanism of beams under pendulum impact is revealed. • Effects of rebar type, BMF content and SFCB ratio on performance are uncovered. • Impact resistance of beams with green and durable materials is demonstrated.