钢筋混凝土构件通电锈蚀试验适用性研究

发布时间：2018-06-15 00:43

本文选题：钢筋混凝土 + 耐久性　；参考：《三峡大学》2014年硕士论文

【摘要】：钢筋锈蚀是导致混凝土结构耐久性丧失的首要原因，目前，对钢筋锈蚀的研究都采用方法简单、周期短、成本低的通电加速锈蚀法，但众多学者对此法的控制因素及锈蚀效果说法不一。因此，有必要对通电加速锈蚀法进行系统地研究，并提出锈蚀效果与自然锈蚀最为相似的控制指标。在混凝土保护层开裂前后两个阶段，通过控制三个变量即不同的钢筋类型、不同的电流密度、不同的通电方式对通电加速锈蚀试验方法进行了研究，同时用同种材质的裸筋对比分析了法拉第电解定律对钢筋锈蚀率预估的准确性。试验过程中，发明了一种防水效果较好的混凝土表面防水应变片，并专门设计了一种多功能混凝土试件劈拉装置使得试验顺利进行。研究结果表明，在相同的通电条件下，混凝土中钢筋通电锈蚀后实测锈蚀率均低于理论锈蚀率，而裸筋通电加速锈蚀后，实测值均高于理论值，但实测锈蚀率与用法拉第电解定律计算所得理论锈蚀率具有很好的相关性，不同工况下的实测锈蚀率可由理论锈蚀率乘以相应系数得出。在相同氯盐浓度和电流密度下，光圆裸筋在通电加速锈蚀后锈蚀效率比变形裸筋更高，造成二者锈蚀效率不同的本质原因主要是两种钢筋的表面形状不同。在相同氯盐浓度和钢筋类型下，低电流密度时裸筋的锈蚀效率比高电流密度更高；在相同的钢筋类型和电流密度下，氯盐浓度的不同对裸筋锈蚀效率的影响并不明显。钢筋混凝土试件通电锈蚀保护层开裂前和开裂时两个锈蚀阶段，在其他条件都相同的情况下，全浸泡通电方式加速锈蚀时钢筋的锈蚀效率最高，半浸泡次之，电迁移锈蚀效率最低；在相同氯盐浓度和电流密度下，光圆钢筋的锈蚀效率比变形钢筋更高，与裸筋通电锈蚀结论相同。针对试验过程中产生的锈蚀钢筋及其产物分别进行了锈蚀形态和锈蚀成分的分析，分析结果表明：混凝土中钢筋的锈蚀部位与负极放置位置及电流走向相关，因此，在通电过程中，可人为控制钢筋的锈蚀效果。钢筋混凝土试件通电加速锈蚀保护层开裂前锈蚀产物含有更多的Fe3O4，而保护层开裂时各工况的锈蚀产物含有更多的Fe2O3和FeO(OH)；全浸泡通电方式下锈蚀产物多为Fe2O3，半浸泡通电方式下锈蚀产物多为Fe3O4，电迁移通电后锈蚀产物成分主要为Fe(OH)2、FeO(OH)；三种不同通电方式下得到的锈蚀产物的形貌特征也存在差异；通电锈蚀产物密实度低于自然锈蚀产物，且自然锈蚀产物主要为Fe和O的化合物，而通电锈蚀产物主要为铁锈和水泥凝胶体的混合体。根据相关公式推导，得到锈蚀产物体积膨胀率的计算公式，由此公式可知其体积膨胀率仅与各锈蚀成分的密度、膨胀率以及质量百分比有关，不同工况下钢筋锈蚀产物的体积膨胀率较为接近，约为2.05~2.63之间。
[Abstract]:The corrosion of steel bar is the primary cause of the loss of durability of concrete structure. At present, the corrosion of steel bar is studied by means of simple method, short period and low cost. However, many scholars have different opinions on the controlling factors and corrosion effect of this method. Therefore, it is necessary to systematically study the method of electric accelerated corrosion, and put forward the control index which is the most similar to natural corrosion. In the two stages before and after the cracking of the concrete cover, by controlling three variables, namely, different types of steel bars, different current density and different ways of electrification, the test method of electric accelerated corrosion is studied. At the same time, the accuracy of Faraday's law of electrolysis to estimate the corrosion rate of steel bar is analyzed by comparison of bare bars of the same material. In the course of the test, a kind of waterproofing strain gauge with better waterproof effect was invented, and a multi-function concrete specimen splitting and drawing device was specially designed to make the test proceed smoothly. The results show that under the same electric condition, the measured corrosion rate of reinforced bars in concrete is lower than the theoretical corrosion rate, and the measured corrosion rate is higher than the theoretical value after the electric corrosion of bare bars is accelerated. However, there is a good correlation between the measured corrosion rate and the theoretical corrosion rate calculated by Faraday electrolysis law. The measured corrosion rate under different working conditions can be obtained by multiplying the theoretical corrosion rate by the corresponding coefficient. Under the same chloride concentration and current density, the corrosion efficiency of the bare bars is higher than that of the deformed bars. The main reason for the difference in corrosion efficiency between the two bars is that the surface shapes of the two kinds of bars are different. Under the same chloride concentration and reinforcement type, the corrosion efficiency of bare bars at low current density is higher than that of high current density, but the effect of chloride concentration on the corrosion efficiency of bare bars is not obvious under the same reinforcement type and current density. Under the same other conditions, the corrosion efficiency of the steel bar is the highest when the electric corrosion protective layer of the reinforced concrete specimen is accelerated by the full immersion and electrified mode, and the second is the semi-immersion, when the corrosion stage is before and during the corrosion of the electric corrosion protective layer of the reinforced concrete specimen, and when the other conditions are the same, the corrosion efficiency of the steel bar is the highest. Under the same chloride concentration and current density, the corrosion efficiency of light circular steel bar is higher than that of deformed steel bar, which is the same as that of bare steel bar. The corrosion morphology and corrosion composition of the corroded steel bar and its products produced during the test are analyzed respectively. The results show that the corrosion position of the steel bar in concrete is related to the position of the negative pole and the direction of the current, so the corrosion position of the steel bar in the concrete is related to the position of the negative pole and the direction of the current. In the process of electrification, the corrosion effect of steel bars can be artificially controlled. There are more Fe _ 3O _ 4 and Fe _ 2O _ 3 in the corrosion products under different conditions before the corrosion of the protective layer is accelerated by electrification of the reinforced concrete specimen. The corrosion product contains more Fe _ 3O _ 4 and more Fe _ 2O _ 3 and Fe _ 2O _ 3 during the cracking of the protective layer. The corrosion products are mostly Fe _ 2O _ 3 under full immersion mode and Fe _ 3O _ 4 under semi-immersion electrification mode, and the main corrosion products after electromigration are Fe _ 2O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2), and the morphologies of the corrosion products obtained under three different modes of electrification are also different. The compactness of the corrosion product is lower than that of the natural corrosion product, and the natural corrosion product is mainly Fe and O compounds, while the electric corrosion product is mainly a mixture of rust and cement gel. According to the related formula, the calculation formula of volume expansion rate of corrosion product is obtained. The volume expansion rate is only related to the density, expansion rate and mass percentage of each corroded component. The volume expansion ratio of the corrosion products of steel bars under different working conditions is close to that of 2.05 ~ 2.63.
【学位授予单位】：三峡大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU375

【引证文献】