Experimental Analysis of the Post-Fire Structural Performance of Corroded Geopolymer Concrete Columns

This study investigates the combined effects of corrosion and fire on the structural performance of reinforced geopolymer concrete (GPC) columns. Four full-scale specimens were exposed to accelerated corrosion and ISO 834-standard fire conditions for 60–90 min. Key structural parameters—including axial load capacity, stiffness, ductility, toughness, and energy absorption—were evaluated to assess post-fire performance. Results show that both corrosion and fire independently reduce strength and stiffness, but their combined impact leads to severe degradation. The most heavily damaged specimens exhibited up to 79% loss in ultimate load, 64% loss in stiffness and over 90% reduction in energy absorption capacity. While some increases in ductility were observed under combined exposure, they were accompanied by substantial losses in load-bearing capacity. These severe reductions suggest that standard fire resistance assessments, when applied without considering prior corrosion, may significantly overestimate post-fire capacity, underscoring the need for corrosion deterioration models in structural fire design.