Development of an axial constitutive model for alkali-activated slag recycled concrete–filled circular steel tube columns

Abstract

Alkali-activated slag recycled concrete (ASRC) effectively utilises slag and construction waste; nevertheless, its poor mechanical properties limit its popularization and application in construction engineering. Therefore, the ASRC–filled circular steel tube column structure (ASRC–FCSTC) is innovatively proposed, and its mechanical properties and constitutive model are studied. The influence of steel ratio and coarse aggregate type, the failure mode, bearing capacity, deformation capacity, and constitutive relationship of core concrete were investigated. The research results show that the failure of ASRC-FCSTC was caused by the shear failure of the core alkali-activated slag recycled concrete, resulting in the overall component failure. In addition, the steel ratio increasing can increase the bearing capacity of ASRC–FCSTC by 47.6-125.4%, and increase the ductility coefficient by 41.6-76.6%. Using recycled coarse aggregate can reduce the bearing capacity of ASRC–FCSTC by 3.3-22.2%. Moreover, the axial compression constitutive model of ASRC–FCSTC core concrete is established considering the effect of steel ratio. Last, the finite element model is established and verified, and the parameter extension analysis is carried out.