Steel slag aggregate concrete filled-in FRP tubes: Volume expansion effect and axial compressive behaviour

Abstract

Using steel slag as concrete aggregate is an effective, eco-friendly method of steel slag disposal. However, the volume expansion of steel slag aggregates (SSAs) creates premature cracks and reduces the mechanical property and durability of concrete, limiting steel slag aggregate concrete (SSAC) applications. A concrete filled-in fiber-reinforced polymer (FRP) tube (CFFT) is a structural member that exploits the high tensile strength of FRP and the lateral expansion of concrete under compression. FRP tubes can be used for the external confinement of concrete to increase its strength and ductility. In this paper, a steel slag aggregate concrete filled-in FRP tube (SSACFFT) is proposed for steel slag disposal. The physical and mechanical properties of an SSACFFT were investigated experimentally. The volume changes in the SSAC and SSACFFT during high-temperature curing were measured using 3D laser scanning. The results showed that the SSAs in concrete expand and cause cracking/spalling during hydration, which is effectively restrained by the FRP tube. The strength, failure modes and stress–strain relationships of the SSACFFT were investigated via axial compression tests. Finally, the SSACFFT was proposed as a prefabricated structural component called FRP-tube-confined concrete core encased prestressed rebar (FCCC-PR) to capitalize on the volume expansion characteristic of SSAC.