FIRE PERFORMANCE OF CORRODED REINFORCED CONCRETE COLUMNS

Abstract

Reinforced concrete (RC) structures are ageing, with corrosion being one of the most dominant deterioration mechanisms among others such as sulfate attack, acid attack, freeze-thaw action etc. Additionally, fire poses a significant threat to infrastructure during the service life of these structures. Current guidelines for determining the fire resistance of RC columns typically do not account for deterioration caused by corrosion, focusing solely on pristine components. Fire resistance is defined as the duration, in terms of minutes or hours, during which a particular element exposed to fire will not lose its strength, stability, and insulation. Recognizing that corroded RC columns behave differently from their non-corroded counterparts, it is imperative to rigorously investigate the impact of corrosion on their performance under fire conditions. A comprehensive study was carried out in four parts to address the crucial problem of corrosion affecting the fire resistance of RC columns. In the first part, the focus was on quantifying the impact of corrosion on the fire performance of RC columns. For this, nine full-scale columns were cast, comprising three with normal strength concrete (NSC) and six with high strength concrete (HSC), each measuring 300 x 300 x 3150 mm. An accelerated corrosion technique was employed to induce various extents of corrosion in six of these columns. Both corroded and non-corroded specimens were subsequently subjected to fire testing in a furnace to evaluate the impact of corrosion on fire resistance. The findings revealed that the corroded columns experienced severe and early spalling of the cover concrete. This early spalling led to the corroded reinforcements being exposed to fire at a much earlier stage, causing a rapid degradation in the strength and stiffness of the columns under fire conditions. The results indicated a significant detrimental impact of corrosion on fire resistance, with a 40-44% loss in fire resistance compared to their non-corroded counterparts. The study underscored the critical importance of investigating the effects of corrosion on the fire performance of RC columns, demonstrating that corrosion significantly compromises the fire resistance and necessitates revised guidelines to account for this factor.