氯盐侵蚀下考虑开裂-渗透行为动态相互作用的钢筋非均匀锈蚀过程研究

Recently, the issue of chloride-induced steel corrosion for RC structures has attracted more and more attentions. However, with the progression of the research, some faults on the fundamental assumptions and mechanism have also been found. For example, the corrosion product in natural environment is more prone to be non-uniformly distributed rather than to be uniformly distributed, the effect of cracks on chloride permeability in concrete is still unclear, and the interaction between the crack propagation and the ingress of aggressive agents in concrete is often ignored. In this project, the penetration characteristics of chloride along cracks will be first investigated through a bending test on concrete beams and a chloride penetration test on concrete blocks with artificial cracks. The chloride distribution along the crack depth and the chloride profile near crack area will be investigated. Based on this, a reasonable chloride diffusion boundary model for cracked concrete will be proposed. Then, a numerical program will be built, which includes a FEM model for the mechanical analysis on cracking propagation, a diffusion analysis for the transport of temperature, humidity, chloride and oxygen in concrete, and an electrochemical analysis for the non-uniform corrosion process incorporating the coupled macro- and micro-cell corrosion mechanism. Moreover, through external event controlling method, the mechanical analysis and the diffusion analysis will be interactively performed and the diffusion boundary conditions will be modified each time as the cracking status changes. Therefore, the real-time interaction between the cracking propagation and the ingress of aggressive agents can be considered by the process.

近年来，氯盐侵蚀下的钢筋混凝土结构锈蚀问题受到了广泛的关注。然而，随着研究和认识上的不断深入，一些前提假设和机理上的问题也逐渐显现，如自然环境下的钢筋腐蚀形态更倾向于非均匀腐蚀而不是均匀腐蚀，裂缝对氯离子渗透性的影响尚不清楚，裂缝扩展与侵蚀质渗透之间的动态相互作用常被忽略等。本项目拟首先通过混凝土弯折试验和氯离子渗透试验，研究不同裂缝参数条件下氯离子沿裂缝的分布形态以及近裂缝区域的渗透特性，建立考虑裂缝影响的氯离子扩散分析合理边界模型；在此基础上，通过数值编程和外部程序控制，将考虑非均匀腐蚀形态的力学分析、考虑裂缝存在的扩散分析以及考虑宏电池与微电池腐蚀耦合的电化学分析合成一个完整的数值过程，并将力学分析与扩散分析交互进行，进而实现考虑裂缝扩展与侵蚀质渗透动态相互作用的腐蚀全过程分析。

氯盐侵蚀是引起钢筋锈蚀混凝土结构耐久性劣化的主要原因。氯盐侵蚀下的钢筋混凝土结构锈蚀问题受到了广泛的关注。然而，随着研究和认识上的不断深入，一些前提假设和机理上的问题也逐渐显现，如自然环境下的钢筋腐蚀形态更倾向于非均匀腐蚀而不是均匀腐蚀，裂缝对氯离子渗透性的影响尚不清楚，裂缝扩展与侵蚀质渗透之间的动态相互作用常被忽略等。本项目通过开展混凝土弯折试验，确定结构性荷载裂缝特征；通过开展氯离子在开裂混凝土中的自然渗透和非稳态迁移试验，揭示裂缝对氯离子渗透性的影响，提出考虑裂缝宽度和裂缝深度的氯离子合理扩散系数，建立包含裂缝的氯离子扩散分析合理边界模型；完成钢筋均匀和非均匀锈蚀下的混凝土保护层开裂过程有限元分析，建立均匀和非均匀锈蚀下的混凝土保护层开裂模式；并结合氯离子的渗透过程、钢筋腐蚀的电化学原理，建立考虑裂缝扩展与侵蚀质渗透动态相互作用的非均匀腐蚀数值分析方法与过程，评估腐蚀物的非均匀分布形态、结构应力场与破坏形态、腐蚀速率演化以及结构预测寿命等。