寒区氯盐环境下在役混凝土构件受力性态衰变机理研究

Salt frozen damage is a main factor that destroys the durability of concrete structures in cold and chloride environment. The researches on the salt frozen damage mechanism of concrete have been focused mostly on the material level, but fewer on the member level. But the resistance of the member doesn't depend on material properties completely. To assess the durability of concrete structures in cold regions reasonably, it's essential to develop the freeze-thaw research on member and structure level. The existing research on structures' anti-freeze durability are mostly based on water-freeze, that is to say, the comprehensive effect of load and environment factors are not considered fully. Besides, the previous tests are limited by test machines, usually for small specimens, so the size effect is inevitable. By the artificial climate room, the salt-frost test will be carried out for the member bearing the load throughout . Based on that, the project will study the coupling influence rule of load and salt-frost action on transfer process of chloride ion, steel corrosion, bond property between steel bar and concrete, section integrity and the stratification change of concrete mechanical properties. The mechanism of resistance decay under the action of force and salt-frost coupling will be proclaimed by simulation and theoretical analysis, and the computing method will be established to lay the foundation for the lifetime prediction of the existing reinforced concrete structures in cold and chloride environment.

盐冻破坏是寒区氯盐环境下影响混凝土结构耐久性的主要因素，学者们在材料层次对混凝土冻融破坏特性进行了广泛研究，但在构件层次的研究却很少，而构件的抗力并非材料力学性能的简单表征。为了能对寒区混凝土结构耐久性做出合理评判，展开构件、结构层次上的冻融研究十分必要。然而，现有构件抗冻耐久性的研究多基于水冻融作用，较少考虑荷载及多环境因素共同作用的影响，且受冻融机功能制约，试件尺寸普遍较小，尺寸效应难以避免。为此，本项目拟利用人工气候环境室，通过对全过程负载构件的盐冻融试验，探究荷载与盐冻耦合作用对混凝土中氯离子传输、钢筋锈蚀、钢筋混凝土粘结作用、构件截面完整性以及混凝土力学性能分层变化特征的影响规律，基于仿真和理论分析揭示力与盐冻环境多因素协同作用下混凝土构件抗力性能衰变机理，并建立相应的计算分析方法，为寒区氯盐环境下在役钢筋混凝土结构的寿命预测奠定基础。

沿寒区氯盐环境下混凝土结构生命周期，围绕荷载、冻融和锈蚀共同作用对钢筋混凝土构件耐久性影响这一主题，深入地探究了盐冻环境下持载构件保护层内氯离子的输运机制、钢筋与混凝土粘结性能演化机制、在役钢筋混凝土梁适用性劣化机制及钢筋混凝土构件通电加速锈蚀与自然锈蚀的相似性。基于试验、仿真及理论分析，构建了盐冻环境下在役混凝土结构中钢筋脱钝时间预测模型和结构混凝土强度的评估方法；确定了混凝土中钢筋锈蚀产物力学参数的取值范围；提出了影响通电加速锈蚀混凝土构件锈蚀形态的主控因素，指明了达到自然锈蚀形态的实现途径；建立了盐冻环境下钢筋与混凝土粘结滑移本构方程；研发了冻融、负载锈蚀梁持续劣化的加载设备，揭示了盐冻环境下在役钢筋混凝土梁抗力性能衰变的特性及规律。所得成果可为寒区氯盐环境下混凝土结构耐久寿命评估提供有价值的参考。