氯离子非均匀电迁移下钢筋混凝土耐久性劣化的时空分布特征研究

With the service life increasing, the durability deterioration of reinforced concrete located at corrosive environments became as an important issue. Electrochemical chloride extraction (ECE) is a main technique for repairing the durability of reinforced concrete. However, the research on long-term durability evaluation of reinforced concrete after electrochemical chloride extracting is insufficient. In this project, the function of non-uniform chloride distribution and non-uniform chloride diffusion coefficient in concrete after ECE is established by numerical simulation and fractal theory respectively. The precise chloride diffusion model based on Fick’s second law of diffusion is obtained by introducing parameters of non-uniform chloride distribution and chloride diffusion coefficient. It is suitable for ECE treated concrete durability evolution. The accelerated corrosion test by artificial corrosive environment simulation and corrosion-induced concrete cracking monitoring experiment based on distributed optical fiber sensor (BOTDA) are carried out to learn the effectiveness of established model. The results of this project can be utilized to evaluate the temporal and spatial characteristics of durability deterioration for ECE treated reinforced concrete. Specially, the results can be used for determining the time of second ECE treatment, and also can act as a tool to describe the damage of concrete without a timely second ECE treatment.

随着钢筋混凝土结构服役年限的增长，氯盐环境中钢筋混凝土结构的耐久性劣化问题越来越突出。基于电化学原理的电迁除氯技术是钢筋混凝土耐久性修复重要方法，然而，电化学修复后钢筋混凝土结构的长期耐久性评估还有待研究。本项目针对电化学修复后钢筋混凝土结构微、细观的变化，通过数值模拟和分形理论构建电化学修复后的氯离子非均匀重分布和氯离子非均匀扩散系数。修正Fick第二扩散定律，建立基于内蕴电迁信息的精确氯离子扩散模型，使其适用于电化学修复后钢筋混凝土的耐久评估。采用人工气候模拟试验进行电化学修复后钢筋混凝土耐久性加速劣化试验，并由分布式光纤传感技术（BOTDA）跟踪监测劣化过程的钢筋混凝土锈胀开裂信息，用以验证模型的有效性。研究成果可用于评估电化学修复后钢筋混凝土耐久性劣化的时空特征分布，为实际工程的"再次电化学修复"时间点选择及"再次修复不及时“钢筋混凝土的病害分析提供支持。

电化学修复后混凝土结构微、细观均会产生变化，进而影响电化学修复后的氯离子非均匀重分布和氯离子非均匀扩散系数，本项目的研究目的是开展Fick第二扩散定律修正，使其适用于电化学修复后钢筋混凝土的耐久评估。基于此，本项目进行了如下内容的研究：进行了钢筋混凝土内预埋电极进行混凝土内部电场测试试验；以Nernst-Plank方程、电流平衡方程及电中性方程为理论基础，进行了基于Comsol的数值模拟；开发了基于光纤传感的钢筋混凝土锈胀开裂监测方法并开展了试验；进行了非均匀电迁作用下钢筋混凝土劣化特征特征试验研究；开展了非均匀电迁后混凝土试件的孔隙结构变化特征试验研究；研究了钢筋混凝土电化学修复后非均匀劣化的防治方法。经过基础研究和应用研究，本项目取得了如下研究成果：开发了电极阵列传感器，探明了混凝土电化学作用下混凝土内部电场分布特征；提出了采用Comsol软件对电化学修复过程中混凝土内部非均匀电场进行仿真模拟的方法；开展了电化学修复后钢筋混凝土耐久性劣化试验，获取了非均匀电迁后劣化时空分布特征；提出了适用于电化学修复后的Fick第二定律：研发了适用于防治电化学修复非均匀劣化特征的双向电迁技术，从根本上保护钢筋，可有效避免非均匀电迁残余氯离子对钢筋锈蚀状况的影响，并开展了工程应用研究。