动电纳米粒子和氯离子双向迁移协同提升钢筋混凝土耐蚀机理研究

To maintain service quality and extend the service life of concrete structure and material in harsh environments, the performance recovery and improvement is very important. For the issue of some vertical and complicated shape concrete structural elements which can’t be treated by conventional Ti-RuO2 mesh in traditional electrochemical extraction of chlorides (EEC) methodology, in this project, we will propose one convenient, high efficiency, and novel conductive cement paste as anode. The extraction chloride mechanism and its influence on the interfacial bonding properties of reinforced concrete will be revealed. Based on above study, one novel methodology for the extraction of chlorides and evaluation criterion will be established. Next, the charged mechanism of nano-particles and their interactions will be explored. One stable and reliable alumina-coated silica colloidal will be designed, and its particle with nano-size in diameter has positive charge. We will reveal the whole process of the positively charged nano-particles: importing to the conductive cement-based materials, reaction in the concrete and production in the interface of reinforced concrete, and quantitatively descript the performance change in the interface of reinforced concrete after remediation. Finally, mathematical model of chloride ions and positively charged nano-particles in electro-migration process will be established. By monitoring the microstructure evolution of the concrete before-, during-, after- electrochemical treatment, a quantitative relationship will be established between the concrete transportation performance and electrochemical treatment, and the mechanisms of cooperative enhancement of the corrosion resistance in the reinforced concrete through bidirectional electro-migration of electrokinetic nanoparticles and chloride ions will be revealed. Based on the proposed research, a novel remediation methodology to deteriorated concrete will be established，which offers one new way to remediate the deteriorated concrete structure.

混凝土结构性能的恢复与提升是保证并延长严酷环境下混凝土结构服役寿命的重要途径。本项目针对传统的除氯方法在修复垂直和异型构件时应用金属钛网阳极加电解液的组合不能形成闭合回路的问题，构建一种便利、高效、新型的导电水泥基材料来做阳极，揭示除盐效率机理和对钢筋和混凝土界面粘结性能的影响规律，提出新型除氯系统和评价体系；然后探明纳米胶粒带正电机理和相互作用规律，设计出稳定可靠且胶粒半径小的带正电纳米胶体，揭示其在导电水泥基材料、混凝土及其钢筋-混凝土界面中导入-反应-生成产物的全过程，定量描述修复后钢筋和混凝土界面性能变化；建立电场作用下氯离子与带正电纳米胶粒电迁移过程的数学模型，以电化学处理前、中、后混凝土微观结构演变为纽带，确定混凝土传输性能与电化学处理之间的定量关系，揭示动电纳米粒子和氯离子双向迁移协同提升钢筋混凝土耐蚀机理，提出性能恢复与提升新方法，为劣化混凝土结构性能修复提供一条崭新途径。

影响钢筋混凝土服役寿命的两个重要界面：一是混凝土与外界环境的界面；二是混凝土与内部钢筋的界面。这两个界面是混凝土耐久性的薄弱环节，因此是影响其耐久性的最重要因素之一。改善钢筋混凝土界面的传统方法一般是表面涂层和使用阻锈剂，但这两种方法一般用于新建混凝土，对于劣化混凝土，需要一种更有效的方法来同时提升这两个界面的性能。. 本项目采用动电纳米的理念，即在外加电场作用下将带电的SiO2、Al2O3胶体或者阻锈剂迁移到材料内部甚至钢筋表面，实现钢筋混凝土耐久性能的大幅提升。首先合成了SiO2基带正电纳米胶体及阳离子阻锈剂并通过电迁移方法导入水泥基材料中分析其对基体以及界面微结构的影响，通过分子动力学的方法筛选出性能优异的阳离子阻锈剂并探索其迁移能力以及对钢筋的阻锈能力。此外，还研究了动电纳米最重要组分纳米氧化铝（NA）作为一种活性铝源对水泥基材料抗侵蚀的影响，并使用分子动力学理论解释水泥基体系C-(A)-S-H凝胶氯离子吸附机理。最后，采用电化学除氯和电迁移纳米胶体/阻锈剂的双向迁移方法从多角度提升结构的基体及界面性能。结果表明，电迁移纳米胶体或阳离子阻锈剂可以改善水泥基材料微结构和保护钢筋表面，而外加电场还可以去除混凝土中的锈蚀源-氯离子，两者都可以减少锈蚀的发生；铝相的掺加有助于提升基体离子吸附能力，硅铝替换增加了硅链的电负性，提升基体对钠离子的吸附能力，进而促进氯离子的吸附。. 本项目通过电迁移的方法使用纳米胶体或者阻锈剂可以有效强化钢筋混凝土中的两个界面，提高体系吸附氯离子的能力并减少体系中的氯离子，为降低氯离子腐蚀，进而改善劣化混凝土的性能提供了科学依据，对复杂海工环境下研究提升钢筋混凝土的耐久性具有重要意义。