【作者】 郭育霞；

【导师】 贡金鑫；

【作者基本信息】 大连理工大学 ， 结构工程， 2010， 博士

【摘要】 氯盐侵蚀引起钢筋腐蚀,从而导致钢筋混凝土的劣化是一个世界性难题。为了延长被氯盐侵蚀的混凝土结构的使用寿命,国内外学者在阴极防护的基础上提出一种无损修复方法——电化学除氯盐(ECE)技术。该技术是在混凝土表面安装一个临时阳极,在临时阳极与混凝土内的钢筋(阴极)之间通以直流电,将氯离子驱离钢筋,排出混凝土外。本文通过试验,对电化学除氯效果及其可能产生的副作用,进行了研究,包括以下几方面的内容：1.研究了初始氯含量、电流密度及电量对除氯效率的影响。结果表明：电化学除氯可以有效除去混凝土内有害的自由氯离子。初始氯离子含量越低,除氯效率越高。但是相同条件下,初始氯离子含量越高,除去的氯离子绝对量越高。除氯效率主要受电量的影响,电流密度的影响不大。电量越大除氯效率越高,但电量超过1500A·h／m2时,随着电量的增加,除氯效率的提高幅度减小。采用半电池电位法测定了除氯前后钢筋的电位,发现除氯后钢筋电位向正向偏移,说明钢筋腐蚀可能性降低。X射线衍射物相分析表明,除氯后钢筋周围混凝土中Ca(OH)2含量增加,有利于钢筋钝化恢复.2.对电化学处理后的混凝土试件进行了抗压强度和抗渗性能试验,结果表明,电化学除氯对混凝土的抗压强度无明显影响,除氯后混凝土抗渗性能有所提高。3.采用梁式试件,对经过不同电流密度和电量处理的钢筋混凝土粘结性能进行了试验研究。结果表明：电化学除氯处理会导致钢筋与混凝土之间粘结退化。所采用的电流密度和电量越大,除氯后钢筋—混凝土界面粘结退化越严重。初始氯化物含量对粘结性的影响很小。给出了粘结强度与电流密度和电量的关系。4.对冻融钢筋混凝土电化学除氯后的氯离子含量进行了测定,发现混凝土的冻融次数对除氯效果影响很小。电流密度和电量对冻融混凝土和未冻融混凝土除氯效果的影响是一致的。5.对冻融钢筋混凝土电化学除氯后的粘结性能进行了试验研究,结果表明：冻融与电化学除氯共同作用引起钢筋与混凝土之间粘结强度退化,退化程度不是二者作用效果的简单叠加。电化学处理时采用的电流密度和电量越大,混凝土经历的冻融循环次数越多,钢筋与混凝土之间的粘结退化越严重。电化学除氯本身对未冻融混凝土与钢筋间粘结性能的影响大于对冻融混凝土与钢筋间粘结性能的影响。6.电化学除氯过程中,由于钢筋与混凝土之间的粘结强度受到了一定的损伤,可能会导致试件抗震性能的退化。对7根经过不同程度电化学处理的钢筋混凝土柱进行了低周反复试验,研究了电化学除氯对其抗震性能的影响。试验表明：除氯会导致柱的抗震性能退化,但退化程度要小于相同除氯参数下梁式试件粘结强度的退化程度。随着除氯电流和电量的增大,试件的承载力略有降低,峰值荷载后刚度退化速率增加,延性系数和耗能能力降低。提出了计算电化学除氯后钢筋混凝土柱骨架曲线的方法。更多还原

【Abstract】 Corrosion of steel bar in concrete due to chloride ions attacking is one of the major reason leading to the degradation of reinforced concrete structures (RC) throughout the world. In order to extend the service life of existing RC structures contaminated by chloride ions, a non-destructive repair technique electrochemical chloride extraction (ECE) of reinforced concrete was developed, which involving mounting a temporary anode on the surface of the concrete and applying a direct current between this anode and the embedded steel bar to drive chloride ions away from steel bar and out of the concrete. Based on experiment of ECE, the efficiency of electrochemical chloride extraction and the side-effect may occurred in the process of electrochemical chloride extraction were studied. The details as follows:1. The effect of initial content of chloride, current density and electric quantity on efficiency of ECE was studied by determining the content of chloride ion in concrete. It is indicated that free chloride ion could be extracted from concrete by electrochemical chloride extraction.The less the initial content of chloride ion is, the higher the efficiency of electrochemical chloride extraction is. But for the same conditions of current density and electric quantity, the absolute amount of chloride ion extracted from concrete increased with the increasing of initial content of chloride ion. Current density adopted in ECE treatment has a little effect on the efficiency of ECE. Electric quantity adopted in ECE has an important effect on the efficiency, the more the electric quantity is, the higher the efficiency of electrochemical chloride extraction is. However, the increment of the efficiency is not clear when the electric quantity exceed 1500A·h/m2. The potential of steel bar was measured before and after ECE. It was found that the potential increased to more positive after ECE, which means the corrosion probability of steel bar decreased. And XRD results shows the content of Ca (OH)2 increased after ECE which contributes to the repassivation of steel bar.2. Compressive strength and permeability of specimens experienced ECE with different current density were measured. It is concluded that electrochemical chloride extraction has a little effect on the macro-compress strength of concrete, and improves the impermeability of concrete.3. The bond behaviour between steel bar and concrete after ECE treatment was studies using beam specimens. It is indicated that the bond behaviour between steel bar and concrete was deteriorated after electrochemical chloride extraction, the more the current and the electric quantity of ECE are, the more the loss of bond strength is. The effect of initial content of chloride ion on the bond strength can be neglected.4. By determining the content of chloride ion in freeze-thawed concrete after ECE treatment, it is shown that for the freeze-thawed reinforced concrete contaminated by chloride, the number of freeze-thaw cycle has a little effect on the efficiency of electrochemical chloride extraction, and the effect of current density and electric quantity on the efficiency is similar with that of unfreeze-thawed reinforced concrete.5. The bond behaviour between steel bar and freeze-thawed concrete after ECE treatment was studies using beam specimens. It can be concluded that the combined action of freeze-thaw cycles and electrochemical chloride extraction treatment results in the degradation of bond between steel bar and concrete, and the degree of bond degradation is not a simple superposition of the two action effect. With the increase of current density, electric quantity of electrochemical chloride extraction and the increase of freeze-thaw cycles, the bond strength obviously decreases. The effect of electrochemical chloride extraction on the bond strength of unfreeze-thawed specimens is greater than that of freeze-thawed specimens.6. Based on the test results of 7 ECE treated reinforced concrete columns under low reversed cyclic loading, the effects of ECE on seismic behavior of reinforced concrete column is analyzed. Owing to the degradation of bond between steel bar and concrete induced in the process of electrochemical chloride extraction treatment, the seismic behavior of reinforced concrete circular column contaminated by chloride was deteriorated, but the degree of deterioration is lower than that of bond strength of beam specimens which experienced electrochemical chloride extraction treatment with the same current density and electric quantity. With the increasing of current density and electric quantity, the bearing capacity, ductility and energy dissipation capacity of column decreased and the deterioration rate of stiffness increased.更多还原