疲劳损伤混凝土梁内钢筋锈蚀试验与数值模拟研究

Experiment and simulation of the corrosion rate of steel bars in fatigue-damaged concrete beams

在海洋环境下,由氯盐侵蚀引起的钢筋锈蚀将导致钢筋混凝土结构耐久性服役性能快速劣化。为探讨钢筋混凝土梁疲劳损伤对纵向受拉钢筋锈蚀发展的影响,同时考虑环境氯离子在干湿循环作用下加速向混凝土内部侵蚀过程。在试验方法中,对各试件进行不同疲劳次数损伤加载,从而使梁底混凝土产生不同程度宏观裂缝和微观损伤发展。使用人工气候环境模拟箱进行氯盐加速侵蚀来诱导钢筋锈蚀。在理论和数值方法中,根据静电位场理论、腐蚀电化学动力学和广义法拉第定律,对钢筋表面电化学腐蚀过程和混凝土内部氧扩散过程进行耦合建模和求解,并将数值结果与试验结果进行对比和验证。研究结果表明:1)在短期干湿循环对氯离子的加速侵蚀过程中,氯离子扩散通量很小可以忽略不计,而毛细吸水传输通量占主导且非常迅速;2)各损伤试件内钢筋表面去钝化开始锈蚀,腐蚀电位一般低于-500 mV vs. CSE,腐蚀电流密度约为1.0~10.6μA/cm^(2);3)钢筋表面宏电池腐蚀过程中,阴极和阳极相接处腐蚀速率最大,钢筋表面锈坑最深位置为阴极-阳极界面处。试验和理论结果表明:在干湿交替海洋环境下,损伤开裂使混凝土内钢筋较早发生锈蚀,高疲劳损伤明显增加钢筋腐蚀速率,中低损伤对腐蚀速率影响较小。

In the marine environment, the corrosion of reinforcement caused by chloride will lead to a rapid deterioration of durability and service performance of reinforced concrete structures. The purpose of this study is to investigate the effect of fatigue damage to reinforced concrete beams on the corrosion development of longitudinal tensile reinforcement, considering the accelerated erosion of environmental chloride ions into concrete under drying-wetting cycle. In the experiment, firstly, each specimen was subjected to damage loading with different cycle times, producing different degrees of macro cracks and micro damage development of the bottom of the concrete, and then the artificial climate environment simulation system was used to accelerate the chloride ingression to induce the reinforcement corrosion. In the theoretical and numerical models, according to the electrostatic potential field theory, corrosion electrochemical kinetics and generalized Faraday’s law, the numerical model of electrochemical corrosion process on the surface of reinforcement coupled with oxygen diffusion process in concrete was established and solved, and the numerical results were compared and verified with the experimental results. The main results are as follows:(1) In the accelerated ingression process of chloride ions by short-term drying-wetting cycles, the chloride diffusion flux is very small and can be ignored,while the capillary absorption transport flux was dominant and very fast.(2) The reinforcement in each damaged specimen initiate corrosion after depassivation, with the corrosion potential generally lower than-500 mV vs.CSE and the corrosion current density nearly 1.0~10.6 μA/cm^(2).(3) In the macro-cell corrosion process on the reinforcement surface, the corrosion rate at the interface of cathode and anode is the greatest, leading to the deepest rust pit on the reinforcement surface. The experimental and theoretical results show that under the dryingwetting cycle marine environment, damage cracks will make the reinforcement in concrete rust earlier;besides,high fatigue damage will significantly increase the corrosion rate of reinforcement, and medium and low damage will have little effect on the corrosion rate.