Creep behavior of composite steel tubular columns filled with weathered steel slag aggregate concrete

Weathered steel slag coarse aggregate concrete-filled steel tube (WSACFST) columns have the potential to enhance the application of steel slag. Although the static and dynamic characteristics of WSACFST columns have attracted increasing scholarly attention, limited studies are available on their time-dependent behavior, especially on their creep behavior. The creep behavior of WSACFST columns is anticipated to vary greatly from that of natural aggregate concrete-filled steel tube (NACFST) columns, because of the notable disparity in stiffness between the weathered steel slag coarse aggregate (WSCA) and the natural aggregate (NA). In that perspective, creep experiments for 210 days were performed on twelve WSACFST columns to explore the impact of WSCA on the creep. A model for forecasting the creep responses of WSACFST columns was theoretically developed by employing a two-phase composite material theory. The investigation shows that: (1) the WSCA decreases the final creep of WSACFST by 12 %–42 % but does not influence the creep development rate; (2) the developed model can forecast the creep deformation of WSACFST columns, with a maximum deviation value of 10.1 %.