Influence of external loading and loading type on corrosion behavior of RC beams with epoxy-coated reinforcements

Corrosion performance of RC beam specimens with epoxy-coated reinforcing bars under in-service environments and external loads is experimentally investigated, where 14 kN static and fatigue loads (2.8-14 kN) were applied as well as 500,000 and 1,000,000 fatigue loading cycles were considered to simulate loading conditions of RC elements under serviceability state. Test specimens were firstly subjected to the above-mentioned loads and then immersed in simulated seawater solutions. Monitoring of open-circuit potential and electrochemical impedance spectroscopy (EIS) was carried out. Results of actual coating thicknesses of the reinforcing bars in test specimens, crack monitoring after loading tests, first wet-cycle and dry-cycle open-circuit potentials and first wet-cycle EIS data of the reinforcing bars in test specimens are presented. Electrical equivalent circuits are used to model the EIS data. Influence of epoxy coating and coating thickness, external loads and loading type as well as fatigue loading cycles on corrosion behavior of reinforcing bars in test specimens is discussed. It is concluded that, under serviceability state of RC test specimens, one-time static load has little effect on corrosion behavior of uncoated and epoxy-coated reinforcing bars in specimens; while reduction of corrosion resistance of reinforcing bars is presented in test specimens subjected to fatigue load. When RC test specimens containing epoxy-coated reinforcing bars with 600 μm nominal coating thickness were subjected to fatigue load with longer loading cycles, larger reduction of corrosion resistance of epoxy-coated reinforcing bars is presented under the case of larger localized crack width and lower crack spacing in RC test specimen.