Effect of Post High Temperature Exposure on the Behaviour of Composite Column with Ferrochrome Slag as a Fine Aggregate

Ferrochrome slag (FCS), a type of industrial solid waste, has promising properties that make it a viable alternative aggregate for concrete production. This can be a partial solution to reduce the pressure on natural aggregates. However, the usage of this solid waste in concrete or composite structures is not documented well. As a result, the purpose of this study is to evaluate experimentally the effect of employing FCS concrete in the concrete-filled steel tube (CFST) on strength and its fire-resistant capabilities. The influence of heating temperatures ranging from 200 to 800 °C and the level of FCS fine aggregate substitution on load–displacement behaviour, ultimate load, and failure mechanism was examined. The CFST stub columns were filled with three different concrete mixtures: one with 100% natural fine aggregate and the other two with 50% and 100% FCS fine aggregate. The findings demonstrate that the ultimate load and stiffness of the CFST stub columns increased as the amount of FCS fine aggregate in the concrete increased. Similar results were found for residual strength and stiffness after high-temperature exposure. The fine natural aggregate can be fully replaced by the FCS fine aggregate without compromising any strength properties of concrete, as well as CFST columns at room and high temperatures. The Eurocode 4 and ACI codes show a conservative estimation of ultimate strengths for the CFST stub columns at room and elevated temperatures compared to the experimental results for all three concrete mixes. However, Eurocode 4 provides a closer estimation for the ultimate load for all concrete mixes than the ACI recommendation.