氯离子侵蚀下表面纳米化耐蚀钢筋在混凝土中的腐蚀行为和机理研究

Rebar corrosion is the key factor leading to the deterioration of reinforced concrete structure (RCS), therefore improving corrosion resistance of rebar is very important to extend the life of RCS. Surface Nanocrystallization (SNC) will endow steel excellent mechanical properties, and its benefit to the steel's corrosion resistance can also be expected. In view of the urgent need of corrosion-resistant reabr used in high-durable marine RCS,the SNC modified corrosion-resistant rebar will be fabricated via high-speed rotation wire-brushing (HRWD) in this study.The core mechanism of this SNC modification method is that using the special microstructure of NC surface to improve the passivity and corrosion resistance of rebar in concrete. To completely understand the corrosion behavior of the SNC rebar in the concrete subject to chloride contamination, several testing methods will be used comprehensively to investigate its corrosion characteristics and corrosion resistance in the simulated concrete pore solutions and concrete specimen, respectively. Meanwhile, the time-varying regularity of corrosion rate of the SNC rebar will also be disclosed. To understand the anti-corrosion mechanism of the SNC rebar, the microstructure and performance of passive film will be used as a link and breach to build the inner relationship between the microstructure of NC surface and the corrosion resistance of the SNC rebar. And finally, the mechanism of the SNC modification to the improvement of passive film stability and corrosion resistance of rebar will also be disclosed. This study will benefit the research and development of corrosion-resistant rebar with low cost and long life. Based on this study, more than 2 patents will be applied, and more than 4 SCI/EI indexed scientific papers will be published.

钢筋锈蚀是导致混凝土结构劣化的主要原因，提高钢筋耐蚀性对延长混凝土结构服役寿命至关重要。表面纳米化改性可赋予钢材优异的力学性能，并有望明显提高其耐蚀性。鉴于高耐久性海工混凝土结构用耐蚀钢筋开发的迫切需求，本项目拟借助高速旋转丝变形技术进行钢筋表面纳米化耐蚀改性，藉此调控钢筋表层显微组织以获得特殊微结构的改性层，显著提高混凝土中钢筋的钝化性能和抗氯离子侵蚀能力。为全面掌握氯离子侵蚀下表面纳米化钢筋在混凝土中的腐蚀行为，拟综合采用多种技术手段对比研究其在模拟混凝土孔溶液和混凝土试件中的腐蚀行为和耐蚀性，探明其腐蚀速率的时变规律；并以表面纳米化钢筋钝化膜的结构-性能为纽带和突破口，构建纳米化改性层的显微组织与钢筋腐蚀特征和耐蚀性的内在关系，揭示表面纳米化改性对钢筋耐蚀性和钝化膜稳定性的作用机制，为低成本长寿命耐蚀钢筋的研发打下坚实的理论基础。拟申请专利≥2 项、发表SCI/EI论文≥4篇。

本项目以氯盐侵蚀下钢筋混凝土结构耐久性提升为目标，从钢筋表面组织改性和钢筋基体合金元素调控两方面入手，实现了钢筋自身耐蚀性有效提高。研究过程中，以HRB400碳素钢筋为主要研究对象，采用高速旋转丝变形法对碳素螺纹钢筋进行表面纳米化（SNC）改性，以Cr为主要耐蚀合金元素调控钢筋基体组织和耐蚀合金元素，系统研究SNC钢筋和微合金化耐蚀钢筋的显微组织；其次，以腐蚀电化学、腐蚀失重和腐蚀形貌观察为主要研究手段，系统研究了表面纳米化钢筋和微合金化耐蚀钢筋在中性氯化钠溶液、多碱度混凝土模拟孔溶液和砂浆试块中的钝化行为和氯离子侵蚀下的腐蚀行为，获得了钢筋在侵蚀介质中的关键耐蚀性指标；最后，借助多种材料微结构分析测试手段，重点研究钢筋全寿命周期各阶段耐蚀性微结构“钝化膜、基体组织和锈层”等的成分、结构和性能演变，探明了表面纳米改性和微量合金元素对钢筋耐蚀性微结构性能的提升机理。研究结果表明，得益于钢筋表面纳米晶层的电化学特性和氧化皮的去除，使得SNC改性钢筋在氯盐侵蚀条件下的混凝土环境中表现出明显优于普通热轧螺纹钢筋的钝化性能和氯离子侵蚀能力。微合金化耐蚀钢筋，在氯离子侵蚀条件下长期服役，可以形成Cr元素富集的的致密内锈层，抑制侵蚀介质扩散而有效提升钢筋耐蚀性和服役寿命。结合项目研究，以第一作者和通讯作者发表SCI论文4篇，中文核心期刊论文3篇，合作发表SCI论文2篇；授权发明专利1项，申请公开发明专利1项。培养博士研究生2名，硕士研究生3名，参加国际会议1次。