Long-term flexural behavior of concrete beams with hybrid FRP and steel reinforcements in simulated marine environment

In this study, the long-term flexural behavior of beams reinforced by basalt fiber-reinforced polymer (BFRP) and steel in a simulated marine environment was investigated. Nine beams were designed based on the principle of equal-rigidity, and they were reinforced with steel rebars, BFRP bars and grids. Four-point flexural experiments were carried out after accelerated corrosion treatment for 0, 3 and 6 months respectively. The experimental results indicated that the flexural capacity, stiffness after yielding and crack control of the beams with hybrid reinforcements were effectively improved compared to the reinforced concrete (RC) beams. Compared with the beams without soak, the flexural behavior of the RC beams decreased after 6 months, on the contrary, the beams reinforced with steel and BFRP bars did not show any degradation. For steel bars-BFRP bars and grids hybrid reinforced beams, the additional grids led to a more outstanding flexural behavior before steel yielding compared to the RC beam, however, a sustained decline in flexural behavior was observed after steel yielding owing to the thinner cover and higher sustained loads in the simulated ocean environment. The secondary stiffness and ductility of the hybrid reinforced concrete beams changed slightly after conditioning. Further, the hybrid reinforced concrete beams exhibited narrower crack width compared to RC beams during the entire experimental period.