Study on degradation of mechanical properties of BFRP bars wrapped with seawater sea sand concrete under chloride dry wet cycle

Based on the tensile test, the effects of different thickness of seawater sea sand concrete, chloride concentration, temperature and dry wet cycle times on the ultimate tensile strength, elastic modulus and ultimate tensile strain of BFRP bars wrapped with seawater sea sand concrete under chloride dry wet cycle were studied. The results show that the BFRP bars wrapped by seawater sea sand concrete will be gradually corroded and degraded under the dry wet cycle of chlorine salt; The ultimate tensile strength of BFRP bars decreases gradually with the increase of erosion age, and the environmental factors that have a great impact on it are temperature and the thickness of seawater sea sand concrete protective layer. The higher the temperature is, the thicker the protective layer is, the more obvious the strength degradation is; Chloride concentration has certain influence on strength, elastic modulus and ultimate tensile strain, but the influence degree is small; The elastic modulus and ultimate tensile strain have no obvious degradation law, but they all show a downward trend with the age of erosion; The deterioration mechanism of reinforcement is analyzed according to the SEM results. Finally, based on the Arrhenius model and the improved FHWA model, the degradation degree of mechanical properties of seawater sea sand concrete wrapped BFRP bars under chlorine salt dry wet cycle is predicted, and the strength retention rate after 50 years of chlorine salt dry wet cycle in five different coastal areas is predicted to be more than 70 %.