Coupled corrosion and fatigue in reinforced concrete beams: Experimental interpretation of mechanical and electrochemical synergy

Abstract

This study investigates the synergistic effects of coupled corrosion–fatigue loading of reinforced concrete beams subjected to simultaneous cyclic loading and electrochemical degradation. A novel two-beam experimental setup was developed to enable direct comparison between coupled and sequential loading conditions. Reinforcement corrosion was accelerated using an impressed current density of 700 $\mu$A/cm${}^2$, and real-time corrosion kinetics were monitored using the Linear Polarization Resistance technique. Lightly reinforced beams were employed to minimize electrochemical complexity and isolate the interaction between localized corrosion and flexural fatigue. Results show that coupled loading reduced fatigue life by 22%–31%, compared to 3%–9% in sequentially loaded beams, relative to plain fatigue specimens. Mid-span deflections at failure in coupled beams were twice as large as in sequential or plain fatigue specimens. Flexural stiffness in coupled specimens exhibited a continuous monotonic decline, whereas sequential beams showed partial recovery. The corrosion current density in coupled specimens increased progressively, in contrast to stabilization after 100,000 cycles in sequential specimen. Microscopy confirmed that fatigue cracks consistently initiated from corrosion pits localized within 1–2 cm of the flexural crack tip in coupled specimens, compared to a broader 7–8 cm distribution in sequential beams. These findings underscore the critical role of pit localization in structural degradation. While mass-loss based assessments have been widely used, this study demonstrates that such global measures do not capture localized damage mechanisms. The insights gained highlight the importance of real-time electrochemical monitoring for service-life prediction of reinforced concrete structures in aggressive environments.