Axial compressive performance of FRP-strengthened reinforced concrete columns in corrosive environment

An experimental investigation was conducted on the axial compressive performance of reinforced concrete (RC) columns strengthened with Fiber Reinforced Polymer (FRP) sheets. A total of eight RC columns were cast and retrofitted to examine the influence of key parameters, including FRP type, number of FRP sheet layers, and accelerated corrosion exposure on the strengthening effectiveness. The structural performance under axial compression was evaluated through a comprehensive analysis of failure modes and load-displacement curves obtained during testing. The results showed that Carbon Fiber Reinforced Polymer (CFRP) demonstrates a superior load-carrying capacity enhancement compared with Glass Fiber Reinforced Polymer (GFRP) in column strengthening. Columns retrofitted with three layers of CFRP exhibited a 58.9% higher load-bearing capacity than those with one layer, whereas the specimens strengthened with three GFRP layers showed only a 26.7% increase compared with those with single layer. Under the post-corrosion condition (180 days), three-layer CFRP and GFRP retrofitted columns retained 93.1% and 91.9% of their original capacities, respectively; outperforming single-layer counterparts (90.1% and 87.7% retentions for the use of CFRP and GFRP, respectively). This confirms that additional FRP layers can improve corrosion resistances. Digital Image Correlation (DIC) analysis revealed that at ultimate loads, strain distributions consistently exhibited distinct diagonal patterns across all specimens, indicating shear dominated failure mechanisms. This failure mode remained consistent in both uncorroded and corroded columns, demonstrating that corrosion exposure did not alter the failure mechanism. Finally, a comparison of ACI 440.2R-17, FIB Bulletin 14, and GB 50367–2013 for predicting compressive strengths of FRP-strengthened RC columns under corrosion shows notable differences. Overall, FIB Bulletin 14 performs better but all design codes have limitations in capturing corrosion effects accurately.