新型核壳型纳米缓蚀剂的制备与优化及其对钢筋混凝土腐蚀的自修复作用与机理

Corrosion of the steel reinforcement can significantly influence the durability of reinforced concrete. A variety of techniques and methods have been developed for corrosion prevention and protection of reinforced concrete; however, there are some limitations and drawbacks, i.e. high cost and increased construction difficulties. In this project, the tailored core-shell nano organic corrosion inhibitors which are sensitive to pH and chloride concentration alterations and suitable for the application in reinforced concrete will be synthesized. The core-shell nano organic corrosion inhibitors can be dissolved in the mixing water and incorporated in fresh concrete with a good dispersion. Under the premise that the mechanical properties of concrete are not influenced, on one hand, the incorporated core-shell nano organic corrosion inhibitors can reduce the porosity and permeability of concrete, resulting in a delay of the reinforcing steel corrosion initiation; on the other hand, after corrosion initiation, the release of the organic corrosion inhibitors can increase both the chloride binding capacity of concrete and the corrosion resistance of the reinforcing steel and repair the steel surface. The investigations in this project include the inhibiting effect of the organic inhibitors, the trigger mechanisms related to the release of the organic corrosion inhibitors, the preparation and optimization of the core-shell nano organic corrosion inhibitors and their influence both on the material properties of concrete and the corrosion performance of the steel reinforcement. Therefore, the physical and chemical mechanisms related to the self-healing effect of the core-shell nano organic corrosion inhibitors on the corrosion damage in reinforced concrete will be revealed in order to provide the theoretical basis for a new high efficient corrosion protection or prevention method for reinforced concrete.

钢筋腐蚀严重影响钢筋混凝土的耐久性。前人虽然发展了多种钢筋混凝土腐蚀防治与保护的技术和方法，但既有局限性，又有成本和施工难度高等弊端。本项目拟制备因pH值或氯离子浓度变化而释放修复物质的适用于钢筋混凝土腐蚀自修复的核壳型有机纳米缓蚀剂。该种缓蚀剂能溶于混凝土拌合用水，因而在混凝土中具有很好的分散性，其在不影响混凝土力学性能的前提下，一方面能降低混凝土的孔隙率和渗透性，延缓钢筋腐蚀的诱发；另一方面，在钢筋腐蚀诱发后，释放的有机缓蚀剂可以有效地绑定氯离子，修复钢筋表面，提高钢筋的耐蚀性。课题将围绕有机缓蚀剂的缓蚀能力与提高、有机缓蚀剂释放的触发性、核壳型有机纳米缓蚀剂的制备和优化设计及其对混凝土性能和钢筋腐蚀行为的影响等方面展开研究，揭示核壳型有机纳米缓蚀剂的制备原理和对钢筋混凝土腐蚀产生自修复作用的物理化学机制，为研发钢筋混凝土腐蚀防护的高效新途径提供科学理论依据。

钢筋混凝土的腐蚀防护已被广泛研究，其中，钢筋混凝土腐蚀的自修复是本领域的研究前沿和重要问题。本课题将无机/有机修复组分包裹在核壳型有机纳米材料中，通过优化设计，制备了对环境因素变化敏感的新型核壳型有机纳米缓蚀剂；在此基础上，揭示了新型的核壳型有机纳米缓蚀剂对钢筋混凝土腐蚀的自修复过程。在以下几个方面取得了创新性成果：.（1）制备了阻锈效果良好的新型咪唑啉季铵盐缓蚀剂，揭示了其对钢筋混凝土耐腐蚀性改善的机理：（a）通过分子设计，采用潜溶剂法合成了阳离子型咪唑啉季铵盐缓蚀剂；（b）合成的缓蚀剂在模拟水泥孔溶液中能提高钢筋的耐腐蚀性，其原因是因为有机缓蚀剂以其N原子(或基团)的强供电子能力与Fe的d空轨道结合成键，牢固地吸附在钢筋表面形成“几何覆盖”而抑制腐蚀。.（2）基于双亲性嵌段共聚物，制备了核壳型有机纳米缓蚀剂，阐明了包裹在其中的修复物质的释放动力学过程：（a）采用原子转移自由基聚合法合成了聚乙二醇-b-苯乙烯（PEG-b-PS）嵌段共聚物；（b）采用溶液透析法，制备了分别包裹亚硝酸钠和苯并三氮唑的核壳型有机纳米缓蚀剂;（c）pH值对包裹在核壳型有机纳米缓蚀剂中亚硝酸钠的释放过程没有明显影响，但是包裹在核壳型有机纳米缓蚀剂中的苯并三氮唑的释放过程具有一定的pH值敏感性。.（3）揭示了核壳型有机纳米缓蚀剂对水泥基材料性能和钢筋耐腐蚀性影响的作用机制：（a）缓蚀剂可以有效吸附在水泥颗粒表面，改善水泥颗粒的分布和堆积密度，提高新拌浆体的工作性能以及硬化浆体的水化速度、微观结构和力学性能；（b）缓蚀剂可以促进水泥浆体中钙钒石的生长，提高其氯离子绑定能力，延迟钢筋腐蚀的诱发和累积；（c）包裹在核壳型有机纳米缓蚀剂中的修复物质的释放可以起到自修复的作用，提高钢筋的耐腐蚀性。