基于界面空间结构性能的再生混凝土复合盐侵蚀损伤演化研究

Under the policy guidance of provincial governments in the northwest region of China, recycled concrete has been increasingly used in new engineering structures. However, the complex multi-interface-transition-zone (multi-ITZ) structure of recycled concrete leads to the rapid diffusion of aggressive ions in the environment and thus seriously threatens structure durability and safety. At present, the damage evolution of recycled concrete subjected to composite salt has not been explored. This project aims to elucidate the damage evolution and mechanism of composite salt corrosion of recycled concrete in northwest China. By combining indoor-accelerated simulation experiment, numerical simulation, and mathematical statistical analysis, the durability of recycled concrete subjected to composite salt is systematically studied on the basis of the durability damage characteristics of structural foundation and the underlying members in this project. The evaluation criteria of “spatial structure & mechanical property parameter” of recycled concrete ITZs is proposed, and the spatial structure & mechanical property parameter, which reflects the microstructure and microscopic mechanical properties of ITZs is obtained. Based on the evaluation criteria and parameter, the damage evolution model of recycled concrete exposed to composite salt is established. Meanwhile, the aggressive ions diffusion path and process in the ITZs and mortar of recycled concrete, and the influence of ions diffusion on the spatial structure & mechanical properties are analyzed. And then, combined the microstructure characterization of the damage layer, the damage evolution mechanism of recycled concrete is revealed. The results of this project can provide reliable theoretical basis and technical support for the recycling utilization of wasted concrete, scientific and reasonable application of recycled concrete and for the design and evaluation of recycled concrete structure durability on the northwest region of China.

在西北地区的政策引领下，再生混凝土已被应用于新建结构之中。再生混凝土复杂的多界面结构导致环境中的侵蚀离子向其内部快速扩散，严重威胁结构的耐久性与安全性。目前，针对再生混凝土复合盐侵蚀的损伤演化研究尚未涉及。本项目以揭示西北地区再生混凝土复合盐侵蚀损伤演化过程及机理为目标，采用室内加速模拟实验、数值仿真模拟及数理统计分析相结合的方法，考虑结构基础及底层构件的侵蚀特点，系统开展再生混凝土复合盐侵蚀耐久性研究。提出再生混凝土界面“空间结构性能参数”评价标准，得出综合反映界面微观结构和微观力学性能的空间结构性能参数，建立再生混凝土复合盐侵蚀损伤演化模型；分析离子在再生混凝土界面及砂浆中的扩散途径及过程，研究离子扩散对界面空间结构性能的影响，揭示再生混凝土损伤演化机理。本项目的研究成果可为西北地区废弃混凝土可循环利用、再生混凝土科学合理应用及再生混凝土结构耐久性设计与评估提供理论依据和技术支撑。

我国西北地区再生混凝土结构长期遭受高浓度侵蚀性盐类的腐蚀，耐久性问题异常严重。长期以来，再生混凝土盐侵蚀耐久性研究的重点在中、低浓度单离子或双离子侵蚀方面且形成了相应的成果，而西北地区高浓度复合盐侵蚀下再生混凝土耐久性损伤特征与机理尚不明晰，极大限制了西北地区再生混凝土在工程中的应用。本项目基于西北地区气候环境与土壤高盐特点，采用室内耐久性加速模拟实验与长期浸泡实验相结合、数理统计分析与理论分析相结合的方法，利用先进的材料细、微观性能表征手段，考虑再生混凝土结构构件不同部位耐久性破坏特征，采用干湿交替、部分浸泡与长期浸泡方式，重点研究了多元胶凝材料体系再生混凝土高浓度复合盐侵蚀耐久性损伤规律及响应机制；围绕复合盐侵蚀损伤再生混凝土界面过渡区结构性能时变规律及侵蚀离子在混凝土中的分布规律，分析损伤再生混凝土界面过渡区结构性能衰变-宏观力学性能影响，研究高浓度复合盐侵蚀下再生混凝土结构不同部位的耐久性能退化规律，建立了损伤再生混凝土侵蚀离子扩散模型；综合考虑损伤再生混凝土复合盐侵蚀产物经时变化-离子扩散规律、界面过渡区结构性能时变-离子扩散规律、界面过渡区结构性能时变-宏观力学性能退化间关系，探明了高浓度复合盐侵蚀再生混凝土耐久性损伤演化机理，为西北地区建筑固废循环利用、再生混凝土科学合理应用及再生混凝土结构耐久性设计与评估提供理论依据和技术支撑。