基于氯离子时变扩散钢筋混凝土锈胀裂缝时变可靠度研究

基于氯离子Fick扩散定理和法拉第定律,通过研发的四电极传感器体系获得含氯离子混凝土模拟液中腐蚀电流密度规律以及混凝土中氯离子时变扩散系数,建立氯离子时变扩散钢筋腐蚀速率模型;在此基础上基于弹性断裂力学和坑蚀模型,建立坑蚀锈胀裂缝时变可靠度模型,采用Monte Carlo方法求得钢筋混凝土锈胀裂缝时变可靠度.研究表明,基于研发的MnO2参比电极四电极传感器体系平均腐蚀电流密度随氯离子浓度增加而线性增加,随时间增加趋于恒定.采用考虑氯离子时变扩散钢筋腐蚀电流在服役期间钢筋腐蚀电流密度减小.坑蚀锈胀裂缝开始时间在第10~15年;随保护层厚度和钢筋直径增加以及表面氯离子浓度减小,钢筋混凝土坑蚀裂缝宽度减小.研究结果对氯离子诱发的钢筋混凝土坑蚀腐蚀裂可靠度预测具有重要的参考价值.

Time-dependent Corrosion Crack Reliability Analysis Considering on Time-dependent Chloride Diffusion

Based on the Fick's Law and Faraday's Law, the chloride-induced corrosion velocity in synthetic concrete pore solution and the time-dependent chloride diffusion coefficient in concrete were experimented by using the four-electrode sensor system. Then the chloride-induced time-dependent corrosion velocity was raised, and the pitting corrosion crack reliability model was presented considering the elastic-fracture mechanics and pitting corrosion model. The experimental results show that the mean corrosion velocity linearly increases with chloride concentration and has the largest value with the increasing of time. The corrosion velocity with time-dependent chloride diffusion coefficient is smaller than the one with time-independent coefficient. The Monte Carlo analysis of pitting corrosion crack shows that the crack is initiated on the 10th to 15th year, and the crack width is decreasingly affected by the increase of the cover and the steel diameter and the surface chloride concentration's decreasing. The study results are referred to predict the chloride-induced corrosion crack and to evaluate the durability of reinforced concrete with pitting corrosion.