中文摘要：

通过试验模拟干湿循环作用下混凝土受不同质量分数硫酸钠的侵蚀特点,从不同侵蚀时间后混凝土的表观特征、质量经时变化规律、混凝土中硫酸根离子分布、侵蚀深度、混凝土轴心抗压强度、劈裂抗拉强度经时退化规律、变形经时变化规律等方面全面衡量混凝土的硫酸盐侵蚀损伤特征;讨论硫酸盐溶液质量分数、侵蚀龄期对混凝土损伤累积规律的影响;根据SEM图像分析受蚀混凝土的微观结构特征,揭示了干湿循环和硫酸盐侵蚀共同作用下,不同侵蚀时期后混凝土损伤的演变机理.试验结果表明,在干湿循环作用下硫酸钠对混凝土的侵蚀损伤是侵蚀产物与硫酸盐结晶膨胀共同作用的结果;在侵蚀初期由于晶体的填充密实作用,使得受蚀混凝土的质量、强度与延性增大;随着侵蚀时间的延长,混凝土不仅受到钙矾石、石膏等侵蚀产物的膨胀损伤作用,而且叠加了干湿循环过程中Na2SO4.10H2O的结晶膨胀作用,使得混凝土损伤反复进行并不断累积,加速了混凝土的受蚀劣化速度,质量、强度逐渐降低,脆性变大;由于拉应力的叠加效应,混凝土劈裂抗拉强度对硫酸盐侵蚀损伤更敏感.

英文摘要：

Some experiments were conducted to simulate the deterioration of concrete under sodium sulfate and wet-dry cycle environment in order to reveal the damage mechanism of sulfate attack. The damage development was evaluated by apparent characteristics of attacked concrete, weight changes over erosion time, profile of sulfate ions in concrete, erosion depth, degradation of compressive and splitting tensile strengths with erosion time, and deformation over attacked time. The parameters; effects such as the mass fraction of sulfate solution and the attacked time on the damage accumulation were analyzed. According to the SEM images, the damage mechanism was achieved by analyzing the microstructures of deteriorated concretes at different erosion periods. Experimental results show that the damage of concrete under sodium sulfate and wet-dry cycle environment is caused by the expansion of chemical reaction products and crystal- lization of sodium sulfate. The weight, strengths and ductility of concrete increase with the increase of erosion time due to the filling effect of crystals at the beginning periods. However, with the increase of erosion time, the combined expansions of ettringite, gypsum and crystal of sodium sulfate decahydrate （Na2SO4 · 10H2O） accelerate the evolution of damage, which results in a reduction of concrete strength and increases of weight loss and brittleness. Compared with the compressive strength, the tensile strength is more sensitive to the sulfate attacked damage due to the superimposed effect of tensile stress.