Effect of Supplementary Cementitious Materials on Post-fire Performance of Concrete Columns

This study evaluates the material behavior of heated concrete with varying supplementary cementitious material (SCM) contents and quantifies its effect on the post-fire performance of reinforced concrete (RC) columns. The novelty of this research lies in examining the influence of SCM content on the residual behavior of heated concrete and its application to RC columns exposed to fire. Concrete specimens were prepared with different mix ratios of fly ash and slag ranging from 0% to 30% of the total binder weight. Residual stress–strain responses were obtained by testing the specimens after exposure to elevated temperatures. These material properties were then incorporated into finite element (FE) models of full-scale RC columns. Thermo-mechanical coupled analyses and structural analyses were sequentially performed to predict the post-fire performance of the columns. The results indicate that the load-bearing capacity of fire-damaged columns cannot be explained solely by the material behaviors of concrete. Notably, the column containing concrete with 10% fly ash and 10% slag demonstrated greater residual load capacity than other models, despite having strength and elasticity not always higher compared to other concrete mixtures. Nonetheless, the residual strength ratio of the columns correlates with that of concrete in general. A comparison between structural and material behaviors indicates that the residual strength ratios of the columns align with those of concrete heated to 400–500 ℃.