For plain concrete materials, the degradation of concrete by seawater is mainly reflected in the corrosion of sulfate ions. In this study, the variation in the flexural strength of concrete specimens with different water-cement ratios under different sulfate concentrations for 470 days is explored, and the effect of sulfate environment on the decay of flexural strength of concrete with corrosion time is experimentally examined. The results show that the evolution of flexural strength can be divided into three stages: strength attenuation stage, strength recovering stage and strength re-attenuation stage. According to the experimental results, the mechanism of strength attenuation, rebound and re-attenuation is established. Combining the chemical reaction rate equations of continued hydration, delayed growth of ettringite and growth of hydroxy-AFm, a new model for the flexural strength degradation of concrete under sulfate corrosion is proposed. Further, the influence of water-cement ratio and corrosive sulfate solution concentration on the flexural strength of concrete is analyzed. Since the ability of concrete to resist sulfate corrosion can be different for different corrosion systems, a unified method is proposed for evaluating the sulfate corrosion resistance of concrete.

对于素混凝土材料，海水对混凝土的降解主要体现在硫酸根离子的腐蚀上。本研究探讨了不同水灰比的混凝土试件在不同硫酸盐浓度下470 d的抗弯强度变化，并通过试验研究了硫酸盐环境对混凝土抗弯强度随腐蚀时间衰减的影响。结果表明，抗弯强度的演变可分为三个阶段：强度衰减阶段、强度恢复阶段和强度再衰减阶段。根据实验结果，建立了强度衰减、回弹和再衰减的机理。结合继续水化、钙矾石延迟生长和羟基-AFm生长的化学反应速率方程，提出了硫酸盐腐蚀下混凝土抗弯强度退化的新模型。进一步分析了水灰比和腐蚀性硫酸盐溶液浓度对混凝土抗弯强度的影响。由于混凝土抗硫酸盐腐蚀的能力因不同的腐蚀体系而不同，因此提出了一种统一的方法来评价混凝土的抗硫酸盐腐蚀能力。