后张法孔道灌浆缺陷下钢绞线锈蚀研究

发布时间：2018-04-23 20:23

本文选题：灌浆缺陷 + 钢绞线锈蚀　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：后张预应力桥梁由于经济及结构优势,是预应力桥梁广泛使用的结构类型。实际工程中,后张预应力桥梁常出现孔道灌浆不密实情况,当处于沿海及冬季需除冰盐融雪地区时,其长期受到氯离子侵蚀作用,预应力筋易腐蚀,造成结构使用寿命缩短。基于上述背景,本文以后张预应力桥梁常见孔道灌浆缺陷(完全无灌浆、平行灌浆、垂直灌浆)为基础,研究了氯盐环境孔道灌浆缺陷下钢绞线锈蚀状况。完全无灌浆类型中钢绞线暴露在氯离子侵蚀溶液中,通过测试其极化电阻、极化曲线、质量损失等参数,研究氯离子浓度对钢绞线锈蚀影响。研究表明,氯离子浓度增加时,钢绞线锈蚀速度增加。平行及垂直灌浆类型中钢绞线部分暴露在氯离子侵蚀溶液中,部分处于水泥浆保护中,通过测试氯离子侵蚀溶液中钢绞线与水泥浆中钢绞线未通过导线连接时各自锈蚀电位、交流阻抗谱及连接后各自耦合电位、耦合交流阻抗谱、锈蚀形貌、质量损失及二者之间电偶电流,研究此两种孔道灌浆缺陷下钢绞线锈蚀机理与氯离子浓度、阴阳极面积比对锈蚀速度影响。研究表明,平行及垂直灌浆体系氯离子侵蚀溶液及水泥浆中钢绞线连接后,前者电势升高,后者电势降低,二者形成宏电池作用,前者作为宏电池阳极,后者作为宏电池阴极;形成宏电池后,阳极与阴极低频段容抗弧半径均减小,阳极锈蚀速度增加。平行灌浆体系中侵蚀溶液氯离子浓度及阴阳极面积比增加时,阳极锈蚀速度增加;氯离子浓度0.1%、平行及垂直灌浆体系阴阳极面积比60:1时,钢绞线锈蚀速度最快的灌浆类型是平行灌浆类型,其次是垂直灌浆类型,最后是完全无灌浆类型。采用混合电势理论及数值方法预测了孔道平行及垂直灌浆类型中宏电池阳极锈蚀速度,结果表明,混合电势理论的预测结果与实验值有较大偏差,数值方法预测结果与试验值相近。在此基础上,通过数值方法建立工程实际模型,研究了孔道空隙变化对钢绞线锈蚀速度影响,研究表明,预应力孔道出现平行空洞时,孔道空隙越小,阳极锈蚀速度越快;出现垂直空洞时,锈蚀速度最快的点是阴阳极交点。
[Abstract]:Post-tensioned prestressed bridges are widely used in prestressed bridges because of their economic and structural advantages. In practical engineering, post-tensioned prestressed bridges often occur the condition that the grouting of holes is not dense. When it is in the coastal and winter areas where deicing and salt melting snow, it is subjected to chloride ion erosion for a long time, and the prestress tendons are easy to corrode, thus shortening the service life of the structure. Based on the above background, this paper studies the corrosion of steel strands in chloride environment on the basis of common grouting defects (no grouting, parallel grouting, vertical grouting) of post-tensioning bridges. The steel strand without grouting type was exposed to chloride ion erosion solution. The influence of chloride ion concentration on the corrosion of steel strand was studied by measuring the parameters such as polarization resistance polarization curve and mass loss. The results show that the corrosion rate of steel strand increases with the increase of chloride ion concentration. The steel strands in parallel and vertical grouting types are partially exposed to chloride ion erosion solution and partly in cement slurry protection. The corrosion potential of the steel strand in the chloride ion erosion solution and the steel strand in the cement slurry is tested when the wire is not connected through the wire, Ac impedance spectrum and coupling potential, coupled AC impedance spectrum, corrosion morphology, mass loss and electric coupling current between them are studied. The corrosion mechanism and chloride concentration of steel strand under these two defects are studied. The effect of area ratio of anode and cathode on corrosion rate. The results show that the potential of the former increases and the potential of the latter decreases after the connection of the chloride ion erosion solution and the steel strand in the cement slurry in parallel and vertical grouting systems. The former acts as the anode of the macro cell and the latter as the cathode of the macro cell; the former is used as the anode of the macro cell and the latter is used as the cathode of the macro cell. After the formation of macro cell, the radius of capacitive arc resistance of anode and cathode in low frequency range decreased, and the corrosion rate of anode increased. In parallel grouting system, the corrosion rate of anode increases with the increase of chloride concentration and the area ratio of anode to anode in the erosion solution, and the anode corrosion rate increases when the concentration of chlorine ion is 0.1, and the area ratio of anode and anode in parallel and vertical grouting system is 60:1, The fastest grouting type of steel strand corrosion is parallel grouting type, followed by vertical grouting type, and no grouting type. The corrosion rate of the anode of macro cell in parallel and vertical grouting type is predicted by using mixed potential theory and numerical method. The results show that the prediction result of mixed potential theory is quite different from the experimental value. The predicted results by the numerical method are close to the experimental values. On this basis, the actual engineering model is established by numerical method, and the influence of pore void variation on the corrosion velocity of steel strand is studied. The results show that the smaller the pore gap is, the faster the anode corrosion rate is when the parallel cavity appears in the prestressing channel. When a vertical cavity appears, the fastest point of corrosion is the intersection of the cathode and the cathode.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.57

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