多场耦合作用下氯离子侵蚀混凝土的数值模拟研究

Reinforced concrete structures in the littoral long-timely suffer the erosion of chloride ions, which leads to the corrosion of reinforcement embedded in concrete and further arouses significantly carrying capacity reduction of structure, and the results of these do damage to the durability of structure. With the potential safety hazard of concrete structures in the complicated chloride environment as the background, a numerical simulation on prediction and prevention of chloride ions erosion in concrete structure under multifactor coupling will be done in this project. The emphases of this project are focused on the three aspects of the subject. Firstly, a coupled thermo-hygro-mechanical mathematical model to quantitatively predict the transportation and distribution of chloride ions in concretes exposed to chloride environment will be proposed. Secondly, a coupled elastoplastic-damage constitutive model taking into account chloride-induced elastoplastic-damage effects for the simulation of coupled chemo-thermo-hygro- mechanical behavior in concretes under chloride environment will be developed. Finally, various methods for protecting concrete structures against excessive degradation in chloride conditions will be numerically analyzed by means of the proposed model. According to efficiency of these methods, the optimal protection strategy for concrete structures in different chloride conditions is discussed, which will provide important reference for the anticorrosion design of concrete structures in practical engineering application.

沿海地区的钢筋混凝土结构，长期受到氯离子的侵蚀，从而致使混凝土中的钢筋产生锈蚀，结构的承载能力明显下降，导致结构较早损坏，给钢筋混凝土结构的耐久性带来极大危害。本项目在以复杂氯盐环境下的混凝土构件和结构氯离子侵蚀破坏这一重大安全隐患问题为背景，开展混凝土结构耐久性与使用寿命的预测及提高的数值模拟研究。发展混凝土中热-湿-气-力学全耦合的氯离子传输模型，全面有效地预测和评估渗有氯盐混凝土中的氯离子传输和分布规律；建立氯离子侵蚀下的混凝土弹塑性－损伤耦合本构模型及其相应的求解方法，数值模拟渗有氯盐的混凝土中化学-热-湿-力学耦合作用下的材料非线性力学行为；利用建立的数值模型和方法探讨各种氯离子侵蚀预防措施的有效性及改进方法，寻找预防氯盐腐蚀的最优解决方案。本项目的研究成果将可广泛用于混凝土构件和结构的减防腐蚀灾害设计中，服务于工程实际，具有重要的理论意义和广阔的应用前景。

富含氯化物环境中，钢筋混凝土结构长期受到氯离子的侵蚀，从而致使混凝土中的钢筋产生锈蚀，结构的承载能力明显下降，导致结构较早损坏，给钢筋混凝土结构的耐久性带来极大危害，如何预测氯离子侵蚀过程以及提高结构抗侵蚀能力是混凝土结构工程师所必须面临的最严峻挑战。为此，本项目建立了考虑温湿影响的多相耦合氯离子侵蚀模型，模型中考虑到了作为非饱和多孔材料的混凝土中热量、水分、气体与氯离子耦合运输过程，以及伴随发生的相变现象，发展了氯离子侵蚀下的混凝土弹塑性－损伤耦合本构模型及其相应的求解方法，利用建立的数值模型和方法进行了各种因素对氯离子侵蚀过程的影响分析探讨。通过基于本项目模型数值分析与试验结果发现：氯离子的传输过程要同时受到对流和扩散两种传输机理控制，短期内（混凝土饱和之前）对流作用的影响效果要大于扩散作用，而从长期角度则氯离子的传输将主要以扩散过程为主；材料内的盐分会随温度和湿度变化而发生相变现象，并且这种现象主要集中于靠近外表面区域附近；温度的升高不仅提高了材料内湿分的迁移速度，更会加速氯离子在混凝土中的传输过程，使混凝土受盐分侵蚀破坏程度更剧烈。上述研究结果将可有效用于实际混凝土结构耐久性评估与设计中，具有重要的理论意义和广阔的应用前景。