Reinforced concrete (RC) structures suffer from different types of loads during service life, and the corrosion characteristics of steel bars embedded in concrete under load are different from those under non-load. In this paper, when the interface between steel bars and concrete (IBSC) cracked and the concrete cover surface (CCS) cracked, the effects of load on the critical corrosion depth of steel bars were analysed based on the thick-walled cylinder model, and a prediction model for the corrosion-induced longitudinal cracking (CLC) time (i.e., initiation cracking time) of the CCS of RC structures under load was proposed. Finally, the influence of load on the CLC time of CCS was discussed on the basis of the proposed prediction model. The results showed that the load had a significant effect on the critical corrosion depth of steel bars when the IBSC cracked induced by corrosion, while the influence of load on the critical corrosion depth of steel bars when the CCS cracked induced by corrosion was not obvious. When the CCS cracks induced by corrosion under load, the influence of the rust-filling layer on the critical corrosion depth of steel bars was larger than that of the load. With the increase in load, the CLC time of CCS decreased. The calculated values of the proposed prediction model were in reasonable agreement with the experimental values, which can provide a reference for durability evaluation and service life prediction of RC structures and lay the foundation for the investigation of the corrosion depth of steel bars in concrete under load.

To investigate the flexural behavioral characteristics of recycled concrete beams under the combined action of steel corrosion and static pre-loading, twelve recycled concrete beam specimens, encompassing a combination of three recycled coarse aggregate (RCA) replacement ratios (0, 50%, 100%) and four static pre-load levels expressed as ratio of the ultimate moment capacity (0, 0.2, 0.4, 0.6), were designed for accelerated corrosion test and four-point bending test. The effects of static pre-load level and RCA replacement ratio on flexural capacity and deformation behavior of corroded beams were studied. The relationship between the corrosion depth of longitudinal tension steel bars and the width of corrosion-induced longitudinal cracks was analysed, and theoretical degradation models for the ultimate moment capacity and the yield moment capacity of corroded beams were established. The test results indicated that under a given RCA replacement ratio of the beams, the maximum width of corrosion-induced longitudinal cracks exhibited a linear relationship with the corresponding corrosion depth of longitudinal tension reinforcement. For the beam specimens with 50% RCA replacement ratio, when the applied static pre-load level increased from 0 to 0.6, the ultimate load and ultimate deflection respectively reduced by 10.4% and 21.2%, whereas for the beam specimens with 100% RCA replacement ratio, the corresponding reduction of ultimate load and ultimate deflection were respectively 8.9% and 35.5%. From the proposed theoretical degradation models, analytical values of ultimate moment capacity and yield moment capacity of corroded recycled concrete beams were in good agreement with the experimental values. This study provides useful reference for practical analysis of recycled concrete beams, which promotes the sustainability of concrete construction.

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