Eccentric compression performance and CFRP strengthening mechanism of reinforced concrete columns subjected to chloride corrosion

Chloride-induced reinforcement corrosion can substantially reduce the load-carrying capacity of reinforced concrete (RC) columns, particularly under eccentric compression. Although carbon fiber-reinforced polymer (CFRP) jacketing is a widely adopted retrofitting technique, its effectiveness on corroded RC columns under eccentric compression remains poorly understood. This study investigated the coupled effects of chloride corrosion duration (0, 120, 240, and 360 d), load eccentricity (0, 25, and 50 mm), and CFRP layer count (1–3 layers) on the eccentric compressive performance of corroded circular RC columns through laboratory tests on 21 large-scale specimens. The tests revealed a pronounced coupling amplification effect: after 360 d of corrosion, the peak load decreased by 11.8% under concentric loading but by 34.2% at an eccentricity of 50 mm. The spiral reinforcement corroded approximately 1.8 times more severely than the longitudinal bars, weakening the confinement of the core concrete. For the specimens corroded for 360 d, applying three CFRP layers increased the peak load by 33.2% and enhanced the energy dissipation by approximately 86.6%, although a clear confinement-saturation trend was observed. CFRP-induced load recovery did not necessarily produce a corresponding increase in section moment because lateral deformation was also reduced.