Bending performance of concrete beams reinforced with hybrid GFRP/steel rebars under combined effects of composite salt wet-dry cycling and sustained loading

To investigate the long-term flexural behavior of reinforced concrete beams exposed to corrosive service environments, this study experimentally examines the combined effects of composite salt attack and sustained loading. A total of 39 beams were tested, including 13 steel-reinforced beams, 13 GFRP-reinforced beams, and 13 steel-GFRP hybrid reinforced beams. Accelerated corrosion was induced through wet-dry cycles in a composite salt solution, and four-point bending tests were conducted on specimens in three conditions: uncorroded, salt-attacked, sustained loading with salt-attacked conditions. The results indicate that increasing the number of wet-dry cycles leads to varying degrees of degradation in ultimate load-carrying capacity and deformation capacity for all beams, accompanied by a significant increase in crack width. Sustained loading markedly accelerates performance deterioration. Under the combined effect of composite salt attack and sustained loading, GFRP-reinforced beams exhibit the most severe reduction in ultimate load-carrying capacity. The degradation rate of RC beams ranges from 18.7% to 35.2%, whereas that of hybrid reinforced beams is limited to 11.6%-27.6%. Meanwhile, the ductility index of RC beams decreases by 43.4%-56.7%, compared with a smaller reduction of 25.7%-41.1% for hybrid reinforced beams. These results demonstrate that steel-GFRP hybrid reinforcement effectively mitigates the adverse effects of composite salt attack and sustained loading, providing superior load-carrying capacity retention and ductility. The findings offer valuable experimental evidence for the application of hybrid reinforced concrete beams in aggressive corrosive environments.