Ductile, durable, and reliable alternative to FRP bars for reinforcing seawater sea-sand recycled concrete beams: steel/FRP composite bars

•Effects of aggregate types and kinds of SFCBs on the flexural behavior of seawater sea-sand concrete beams were clarified.•The feasibility of using SFCBs to replace conventional FRP bars in terms of reinforcing seawater sea-sand concrete beams is evaluated and discussed.•A theoretical model that can predict the load-deflection response of SFCBs reinforced seawater sea-sand concrete beams is developed. The combination of seawater, sea-sand and recycled concrete aggregate (RCA) to make the so-called seawater sea-sand recycled concrete (SSRC) is a promising alternative to mitigate the shortage of raw construction materials, e.g. river sand, freshwater and crushed stone. Although equipped with anti-corrosion and high strength, the reduced ductility due to the linear elastic nature of conventional fiber-reinforced polymer (FRP) bars hinders their application scope in civil engineering. Inherited the advantages of FRP bars, steel fiber-reinforced polymer composite bars (SFCBs) are also characterized by good ductility and stable post-yield stiffness, which can potentially be ideal reinforcement for concrete structures made with un-desalted corrosive raw materials. This paper presents experimental and theoretical investigations on the flexural performance of SFCB reinforced SSRC beams. Test results indicate that the displacement ductility factor of almost all the SFCB reinforced SSRC beams are in a range from 3.7 to 4.9. The ratios of peak load-to-yielding load of SFCB reinforced SSRC beams varied from 1.5 to 3.1, indicating a remarkable post-yield behavior. Compared with the counterparts with natural aggregates, SSRC beams show slightly reduced flexural strength and comparable ductility. Theoretical models were proposed to predict the load-deflection responses of SFCB reinforced SSRC beams, which paves the way for the design of such members.