<scp>Axial</scp> compression performance of slurry‐wrapping recycled aggregate concrete‐filled steel tube short columns under freeze–thaw cycles

Abstract The inherent limitations of recycled aggregates restrict the application of recycled concrete in cold regions. In this paper, both steel tube confinement and slurry‐wrapping treatment were employed to improve the frost resistance of recycled concrete. The influence of different aggregate types and number of freeze–thaw cycles on the freeze–thaw effect was investigated experimentally. The results show that with the increase of freeze–thaw cycles, the axial strength of concrete‐filled steel tube (CFST) short columns decreases regardless of aggregate type. The frost resistance of slurry‐wrapping recycled aggregate concrete‐filled steel tube short columns is superior to that of recycled aggregate concrete‐filled steel tube (RACFST) short columns due to slurry‐wrapping treatment; however, they are still not as good as natural aggregate concrete‐filled steel tube short columns. The initial stiffness diminishes as the number of freeze–thaw cycles increases. As the number of freeze–thaw cycles increases, the effect of aggregate type on the ductility of CFST short columns decreases. Based on the test results, a modified formula applicable to the strength of recycled concrete is proposed and combined with Eurocode EC4 to predict the ultimate compressive strength of RACFST short columns under freeze–thaw cycles.