水泥石碳化性能的影响因素及其机理研究

发布时间：2018-02-24 05:22

本文关键词： 水泥石碳化碳酸钙水灰比相对湿度　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：钢筋锈蚀是混凝土破坏的主要原因之一，我国每年因钢筋锈蚀引起的混凝土结构损伤破坏的损失达1000亿。混凝土碳化、氯离子引起钢筋去钝化和酸性介质是引起钢筋锈蚀的三个主要原因。由于CO2在大气环境中无所不在，所以碳化无所不在，而且，近年来大气中CO2的浓度有所攀升，进一步加剧了混凝土碳化，因此对混凝土碳化的研究迫在眉睫。水泥石是混凝土中唯一直接发生碳化的组分，因此，集中力量研究水泥石的碳化是解决碳化问题的关键。本论文采用化学分析法，用自制碳化装置逐层测定了水泥石中碳酸钙的含量，研究了水灰比、碳化相对湿度、CO2浓度、养护方式、减水剂以及碳化时间等因素对水泥石碳化的影响并研究了其碳化机理，得出的主要结论如下： 1）随着水灰比增大，水泥石碳化程度增加，部分碳化区的宽度也在逐渐增大。水灰比0.45是水泥石抗碳化性能的转折点：当水灰比高于或等于0.45时，随着水灰比增大，水泥石碳化程度加剧显著，部分碳化区增加；当水灰比小于0.45时，，部分碳化区很短，水泥石碳化程度低。 2）碳化湿度对于水泥石碳化性影响显著，环境湿度接近59%是影响水泥石碳化性能的临界湿度：当湿度高于或等于59%时，部分碳化区较窄，此时碳化速度是由CO2扩散速度来控制的；而当湿度低于59%时，随着湿度降低水泥石碳化程度显著增加，且部分碳化区增加，此时碳化是由化学反应的速度来控制的。 3）CO2浓度越高，水泥石碳化越严重，从实验过程中还发现CO2浓度对水泥石碳化性能的影响似乎与碳化湿度有一定关系，当碳化湿度较高时，水泥石碳化程度差别不是很大；当碳化湿度较低，CO2浓度较高时，水泥石碳化程度有显著增加，但是仍需更多试验来验证； 4）养护方式不同水泥石碳化性能不同。在饱和Ca(OH)2溶液中养护时，有部分Ca(OH)2进入水泥石结构，有利于水泥石中碱储备增加，所以与水养相比采用饱和Ca(OH)2溶液养护能提高水泥石抗碳化性。 5）当水灰比较低时，掺减水剂对水泥石碳化性能影响短期并不明显。水灰比较高时，掺加减水剂能够改善水泥石的抗碳化性能。减水剂掺量的改变对水泥石碳化性能并没有多大影响。 6）随着碳化时间的增加，碳化程度在逐渐增加。当水灰比较低时碳化深度随着时间增加而增大的比较缓慢，而水灰比在0.35及更高时，其开始碳化速度较快，后来逐渐减缓。碳化时间和碳化深度有一定的函数关系。 7）化学分析法比酚酞滴定法更能表征真正的碳化程度。
[Abstract]:The corrosion of steel bar is one of the main causes of concrete failure. The damage and damage of concrete structure caused by corrosion of steel bar in China every year is 100 billion. Chloride ion induced deactivation of steel bar and acidic medium are the three main causes of steel bar corrosion. Because CO2 is ubiquitous in atmospheric environment, carbonation is ubiquitous, and the concentration of CO2 in the atmosphere has increased in recent years. The study of concrete carbonization is urgent. Cement stone is the only direct carbonation component in concrete. Therefore, the key to solve the carbonation problem is to concentrate on the carbonization of cement stone. In this paper, the content of calcium carbonate in cement stone was determined layer by layer by means of chemical analysis and self-made carbonization device. The water-cement ratio, the concentration of carbonation relative humidity and CO _ 2, and the curing mode were studied. The effects of water reducer and carbonation time on the carbonation of cement stone are studied. The main conclusions are as follows:. 1) with the increase of water-cement ratio, the carbonization degree of cement stone increases, and the width of partial carbonization zone increases gradually. The water-cement ratio 0.45 is the turning point of cement stone carbonation resistance: when the water-cement ratio is higher than or equal to 0.45, with the increase of water-cement ratio, When the water-cement ratio is less than 0.45, the carbonization area is very short and the carbonization degree of cement stone is low. 2) the influence of carbonation humidity on the carbonation of cement stone is significant. The environmental humidity of 59% is the critical humidity that affects the carbonation performance of cement stone. When the humidity is higher than or equal to 59, the partial carbonization zone is narrow. The carbonation rate is controlled by the diffusion velocity of CO2, but when the humidity is lower than 59, the carbonization degree of cement stone increases significantly with the decrease of humidity, and the carbonization zone increases. In this case, the carbonation rate is controlled by the rate of chemical reaction. (3) the higher the CO _ 2 concentration, the more serious the carbonation of cement stone. It is also found that the influence of CO2 concentration on the carbonation performance of cement stone seems to be related to the carbonation humidity. When the carbonation humidity is higher, the carbonation degree of cement stone is not very different. When the carbonation humidity is lower and the CO _ 2 concentration is higher, the carbonation degree of cement stone increases significantly, but more tests are needed to verify it. 4) when curing in saturated Ca(OH)2 solution, part of Ca(OH)2 enters the structure of cement stone, which is beneficial to increase the alkali reserve in cement stone. Therefore, the carbonation resistance of cement stone can be improved by saturated Ca(OH)2 solution curing. 5) when the cement ash is low, the influence of water reducing agent on the carbonation property of cement stone is not obvious in the short term. The addition of water reducing agent can improve the carbonation resistance of cement stone, but the change of the content of water reducing agent has little effect on the carbonation property of cement stone. 6) with the increase of carbonization time, the carbonization degree increases gradually, and the carbonation depth increases slowly with the increase of time when the water cement ratio is low, and the carbonization rate is faster when the water-cement ratio is 0.35 or higher. The carbonation time has a certain function relation with the carbonization depth. 7) Chemical analysis is more effective than phenolphthalein titration to characterize the true degree of carbonation.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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