Mechanical properties of steel tubes filled with coal gangue concrete in a corrosive environment

To achieve the in-situ utilization of coal gangue, coal gangue concrete filled steel tube (CGCFST) was applied in coal mine roadways as support structure. However, the reliability of the structure was negatively impacted by corrosive environment in coal mines. This study tested the axial compression performance of twenty-four circular CGCFST stubs with corrosion damage, considering the influence of coal gangue replacement rate and steel corrosion rate. The test results showed that the failure mode of the specimens was shear failure. The ultimate load, ductility, and stiffness of the CGCFST stub decreased with the increase of the corrosion rate and replacement rate, with corrosion rate having a more significant impact on the mechanical properties of the specimens. For the C30 CGCFST stub with a replacement rate of 100 %, when the corrosion rate is 30 %, the ultimate load, ductility, and stiffness of the CGCFST stub were reduced by 19.9 %, 48.8 %, and 27.3 %, respectively. Compared to high-strength concrete specimens, in addition to ductility, the effects of replacement rate and corrosion rate on the ultimate load and stiffness of low strength concrete were more significant. Finite element analysis was conducted to assess the impact of the steel ratio, material strength, and corrosion rate on the ultimate load of the CGCFST stub. The results indicated that concrete strength exerted the most significant influence on the ultimate load of the stub, suggesting that improving the strength of concrete is an effective strategy to ensure its safety. A design method for the ultimate load of CGCFST stubs in a corrosive environment was proposed. The CO₂ emission of CGCFST stubs was evaluated, suggesting to use concrete with high strength and natural aggregates completely replaced by coal gangue in practical engineering.