干湿交替环境下混凝土硫酸盐侵蚀机理与耐久性评估

Under drying-wetting alternate environment, the degradation mechanism of concrete subjected to the sulfate attack is complex, and the corresponding concrete structures are badly damaged. However, the existing researches have not investigated the deterioration mechanism, damage mode and durability evolution of concrete under sulfate attack. Based on the theories of chemical thermodynamics and kinetics, this study will investigate the effect of erosion media, deterioration condition and damage model on the sulfate attack mechanism of concrete. Both qualitative and quantitative analysis methods for representing the deterioration process of concrete subjected to sulfate attack are proposed, and the sulfate attack mechanism of concrete is also deduced. Under the coupled effect of sulfate attack and the environmental loads generated by drying-wetting alternate environment, the degradation process and damage model are proposed. By comparing the evaluation indexes, the evaluation criteria and the quantitative approach of the sulfate attack are put forward. Numerical simulations and tests are carried out to investigate the whole processes of the micro cracks’ production and aggregation and the macro cracks’ formation and extension in concrete are also explored. In addition, the durability evolution of concrete under drying-wetting alternate environment is deduced, which provides the technical support for the durability assessment and life prediction of concrete structures.

干湿交替环境下混凝土硫酸盐侵蚀机理复杂且破坏严重，既有研究尚未合理地阐释混凝土硫酸盐侵蚀机理、损伤模式和耐久性演变历程。本项目拟基于化学热力学和动力学理论，分析侵蚀介质特性、侵蚀条件和侵蚀模式等对混凝土硫酸盐侵蚀影响，开展混凝土硫酸盐侵蚀的定性和定量分析，剖析混凝土硫酸盐侵蚀机理。探讨干湿交替环境变化引发的环境载荷和硫酸盐耦合作用下混凝土硫酸盐侵蚀过程，构筑干湿交替环境下混凝土硫酸盐侵蚀模型；优选适宜的混凝土硫酸盐侵蚀损伤评价指标，提出混凝土硫酸盐侵蚀损伤评判准则和量化方法。融合数值仿真和试验，分析混凝土硫酸盐侵蚀微裂纹生长-聚合、宏观裂纹形成-扩展-破坏全过程，推导干湿交替环境下混凝土硫酸盐侵蚀耐久性演化过程，为相应的混凝土结构耐久性评估和寿命预测提供技术支撑。

干湿交替环境下的混凝土硫酸盐侵蚀耐久性劣化是当前土木工程领域研究的焦点，现有研究尚未全面揭示混凝土硫酸盐侵蚀机理和耐久性演变规律。本项目采用化学热力学和动力学理论，研究了硫酸盐种类、侵蚀模式、侵蚀时间、组成材料等对混凝土硫酸盐侵蚀性能影响。采用理论和实验结合方式，开展了典型混凝土硫酸盐产物的定性分析，深入剖析了混凝土硫酸盐侵蚀因素、机理和产物之间的内在关联。同时，研究了不同侵蚀模式（全浸泡、半浸泡、干湿交替）下的混凝土硫酸盐侵蚀前后的静态和动态性能、侵蚀产物和劣化过程，建立了干湿交替环境下混凝土硫酸盐侵蚀模型。分析了体相和表相性能参数表征混凝土硫酸盐侵蚀可行性，优选出了混凝土表层动弹模量、泊松比、阻尼比等作为混凝土硫酸盐侵蚀损伤的评价指标。基于Fick第二定律，研究了混凝土表层硫酸盐浓度分布及其侵蚀深度变化，开展了混凝土硫酸盐侵蚀耐久性评估和使用寿命预测。研究成果为干湿交替条件下的混凝土结构耐久性评估和寿命预测提供重要技术支撑。