Post-fire structural behavior of reinforced concrete columns incorporating two types of waste glass: Experimental and numerical investigation on residual load-bearing capacity

This study investigates the axial compressive behavior and residual load-bearing capacity of concrete columns incorporating waste glass sand (GS) and waste glass powder (GP) after exposure to fire. Reinforced concrete short columns were prepared with GS as a partial replacement of fine aggregate at ratios of 0%, 20%, 60%, and 100%, while GP consistently replaced 20% of cement by mass. ISO 834 standard fire tests and post-fire axial compression tests were conducted. The surface appearance after high-temperature exposure and the axial compression failure modes were observed. The cross-sectional temperature distribution, load–displacement curves, and lateral deformation patterns were analyzed. Results show that thermal cracks appeared on the specimen surfaces, and melted and re-solidified glass beads were visible when the GS replacement ratio was high. The incorporation of GS reduced the thermal conductivity of concrete, steepened the temperature gradient across the section, and lowered the measured point temperatures as the replacement ratio increased. In the axial compression tests, all specimens failed by concrete crushing. The residual load-bearing capacity decreased with increasing GS replacement ratio and fire duration, while larger cross-sectional dimensions and thicker concrete cover helped preserve the capacity. Based on parametric analysis, a calculation method for the post-fire residual load-bearing capacity of waste glass concrete columns was developed. The calculated results agree well with finite element simulations and are conservative, providing a reference for fire resistance design and post-fire assessment of such structural members.