Flexural Performance of Steel Bar Reinforced Sea Sand Concrete Beams Exposed to Tidal Environment

The advancement of marine engineering has brought close attention to the durability of concrete structures. In order to investigate the time-varying performance of reinforced concrete beams in a marine environment and to better apply sea sand directly in marine engineering, this paper describes tests and analysis on the flexural performance of reinforced sea sand concrete beams after being exposed to a tidal environment. Eight beams were tested using four-point static loading equipment. The variation parameters included the type of mixing water, longitudinal reinforcement rate, sea sand replacement rate and duration of service. The force damage process and damage pattern were observed. The load–maximum width crack curve and load–deflection curve were obtained. The effects of each variation parameter on the mechanical properties such as ultimate bearing capacity, initial rigidity, energy dissipation coefficient and ductility coefficient were analyzed. The test results show that compared with the specimens exposed to the tidal environment for 90 days, the peak load of the specimens decreased by 5.6%, the initial rigidity decreased by 60.9% and the ductility coefficient decreased by 41% after 270 days of exposure, while the peak deflection and energy dissipation indexes first increased and then decreased. The seawater mixing can enhance the peak load and cracking load of the specimens, but the initial rigidity, peak deflection, energy dissipation coefficient and ductility coefficient of the specimens are reduced to some extent. The initial rigidity of the specimens tended to increase with the increase in the sea sand replacement, but the peak load decreased. Under the same reinforcement rate, reducing the diameter of the reinforcement is beneficial to improve the initial rigidity of the specimen, while using the reinforcement with higher elongation can effectively enhance the peak deflection of the specimen. Based on the Chinese code, the calculation method of flexural bearing capacity with modified concrete strength is proposed, and the calculation results are in good agreement with the test results.