复合因素作用下混凝土中钢筋锈蚀研究

发布时间：2018-06-28 02:19

本文选题：电化学方法 + 加速锈蚀　；参考：《青岛理工大学》2013年硕士论文

【摘要】：钢筋混凝土是当今世界使用最广泛的工程材料。海水、盐雾及除冰盐中氯离子渗透到混凝土内部导致钢筋锈蚀是威胁混凝土耐久性的最主要原因。考虑海水中存在氯离子、硫酸根离子等多重腐蚀离子，混凝土结构在服役过程中承受一定的荷载作用。本文采用浸泡腐蚀、恒电位加速腐蚀以及电化学特性研究等试验方法，系统研究钢筋、钢筋混凝土在多重腐蚀离子、荷载-腐蚀耦合作用下的腐蚀损伤行为。研究主要结论如下：（1）采用不同浓度氯盐溶液、硫酸盐溶液，氯盐和硫酸盐复合溶液，不同PH值下的氯盐溶液作为模拟溶液，研究钢筋在上述腐蚀溶液中的电化学行为。结果表明：随着氯离子浓度增加，极化电阻随之降低，腐蚀电流密度随之增加，钢筋锈蚀临界氯离子浓度为0.05mol/L；溶液pH值越小，钢筋锈蚀临界氯离子浓度相应降低；溶液中硫酸根离子的存在，减缓了钢筋的锈蚀，且减缓作用随硫酸根离子浓度增加而增强。（2）通过对3组（4种粉煤灰掺量、5种矿粉掺量、10种腐蚀溶液）钢筋混凝土试件进行电化学加速锈蚀试验，研究钢筋混凝土锈裂损伤形态及其规律。结果表明：钢筋腐蚀电流强度随时间增加而下降，混凝土裂缝宽度随通电时长增加而呈二次函数关系增加，裂缝宽度随电流强度下降而线性增加。混凝土初裂时间和达到0.2mm裂缝宽度时间随粉煤灰和矿粉掺量增加而增加；当粉煤灰、矿粉掺量为15%时，混凝土中钢筋锈蚀率最小；内掺腐蚀溶液对混凝土的初裂缝的影响主要体现在复合溶液的促进和减缓双重作用。（3）采用四点弯曲加载方法，对两种配合比混凝土施加不同等级荷载后，浸泡于氯盐、氯盐和硫酸盐复合溶液7个月，研究混凝土中氯离子传输规律。结果表明：弯曲荷载作用下混凝土中氯离子浓度随深度增加而减少，达到一定深度处趋于稳定。复合溶液中硫酸根离子与水化铝酸钙反应生成钙矾石，，填充了混凝土的孔隙，延缓了混凝土中氯离子传输。随荷载等级增加，受拉区混凝土中氯离子传输速度相应增加。（4）采用四点弯曲和电化学加速锈蚀试验方法，研究未掺矿物掺合料、双掺矿物掺合料钢筋混凝土中钢筋锈蚀及其氯离子迁移规律。试验表明：加载30%时，混凝土受力区的的初始电流值为受拉区＞受压区＞未加载区，且电流强度随着时间增加而减小。受拉区的氯离子含量、锈蚀率大于其他受力区。混凝土中钢筋的初始电流值、受拉区锈蚀率随着荷载等级增加而增加，加载50%时，前期受力区裂缝开裂较慢，后期随着钢筋锈蚀开裂速度迅速。未掺矿物掺合料混凝土中钢筋的初始电流值大于双掺矿物掺合料混凝土中钢筋的初始电流值，但双掺矿物掺合料混凝土中钢筋的锈蚀率高，锈蚀严重。
[Abstract]:Reinforced concrete is the most widely used engineering material in the world. The corrosion of steel bar caused by chloride in seawater, salt spray and deicing salt is the main reason that threatens the durability of concrete. Considering the presence of chloride ions and sulfate ions in seawater, concrete structures are subjected to certain loads. In this paper, immersion corrosion, potentiostatic accelerated corrosion and electrochemical characteristics are used to systematically study the corrosion damage behavior of steel bar and reinforced concrete under the action of multiple corrosion ions and load-corrosion coupling. The main conclusions are as follows: (1) different concentrations of chloride solution, sulfate solution, chloride and sulfate complex solution, different PH value of chloride solution as simulation solution, The electrochemical behavior of steel bars in the above corrosion solution was studied. The results show that with the increase of chloride concentration, the polarization resistance decreases and the corrosion current density increases. The critical chloride ion concentration of steel bar corrosion is 0.05 mol / L, and the lower the pH value of the solution is, the lower the corrosion critical chloride ion concentration is. The presence of sulfate ions in the solution slows the corrosion of steel bars. The mitigation effect was enhanced with the increase of sulfate ion concentration. (2) the electrochemical accelerated corrosion test was carried out on three groups of reinforced concrete specimens (4 kinds of fly ash and 5 kinds of mineral powder and 10 kinds of corrosion solution). The rust-cracking damage pattern and its regularity of reinforced concrete are studied. The results show that the corrosion current strength of steel bar decreases with the increase of time, the crack width of concrete increases in a quadratic function with the increase of the current duration, and the crack width increases linearly with the decrease of the current intensity. The initial crack time of concrete and the time to reach 0.2mm crack width increase with the increase of fly ash and mineral powder content, when the content of fly ash and mineral powder is 15, the corrosion rate of steel bar in concrete is the least. The effect of corrosion solution on the initial crack of concrete is mainly reflected in the dual effect of the compound solution. (3) after applying the different grade load to the two kinds of concrete, the method of four-point bending loading is adopted. The chloride ion transport in concrete was studied by immersing in chloride salt, chloride salt and sulfate compound solution for 7 months. The results show that the concentration of chloride in concrete decreases with the increase of depth and tends to be stable at a certain depth under bending load. Ettringite was formed by the reaction of sulfate ion with calcium aluminate hydrate in composite solution, which filled the pores of concrete and delayed the chloride ion transport in concrete. With the increase of load grade, the rate of chloride ion transport in the concrete in tension zone increases accordingly. (4) by means of four-point bending and electrochemical accelerated corrosion test, the mineral admixture is studied. Corrosion of steel bars and chloride ion migration in reinforced concrete with double mineral admixtures. The experimental results show that the initial current value of the concrete under loading is the tensile zone > the compression zone > the unloaded zone, and the current intensity decreases with the increase of time. The chloride content and corrosion rate in the tensile zone are higher than those in the other stress regions. The initial current value of steel bar in concrete, the corrosion rate of tensile zone increases with the increase of load grade. When the load is 50%, the crack cracking in the early stress zone is slower, and the corrosion crack rate in the later stage is rapid with the reinforcement corrosion rate. The initial current value of steel bar in concrete without mineral admixture is higher than that in concrete with double mineral admixture, but the corrosion rate of steel bar in concrete with mineral admixture is high and corrosion is serious.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528.571

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