Over the last few decades, the composite structural system in high-rise buildings is widely used and concrete-filled steel tubular (CFST) column is part of this system as well as there is great effort to use alternative materials to produce concrete in order to enhance the mechanical properties, reduce environmental impact and saving cost and resources. Meanwhile, composite columns exposure to fire can lead to a serious structural deterioration and possible failure of columns. Therefore, this thesis presents a study on the behavior and mechanical properties of CFST stub columns with three different concrete mixes using conventional fine aggregate, 50% and 100% ferrochrome slag (FCS) as a fine aggregate replacement at ambient and elevated temperatures (200°C, 400°C, 600°C and 800°C). The literature review highlights that there is no research conducted to investigate the behavior of CFST columns made with FCS as a fine aggregate at ambient and elevated temperatures. The results show that the ultimate strength of CFST stub columns enhances at ambient and almost all elevated temperatures, the compressive stiffness and ductility of CFST stub columns are higher compared with the conventional CFST stub columns at ambient temperature. The EC4 and ACI codes show a conservative prediction of the value of ultimate strength for the CFST stub columns at ambient temperature compared to the experimental results for the three concrete mixes and this is supportive by other researches. Furthermore, the ultimate strength and compressive stiffness of CFST stub columns that contains 50% to 100% of FCS in the concrete mix is better than a conventional CFST stub column at ambient temperature. Meanwhile, the residual ultimate strength and compressive stiffness are higher compared with the conventional CFST stub columns at almost all elevated temperatures. Therefore, FCS is a good replacement to conventional fine aggregate in the concrete mix of CFST stub columns.