矿物掺合料对混凝土氯离子结合能力的影响

发布时间：2018-07-23 18:36

【摘要】：混凝土的氯离子结合性能对钢筋混凝土建筑的寿命预测及其耐久性能都具有重要意义。以结合的形式存在的氯离子对钢筋混凝土中的钢筋锈蚀不产生危害。它延缓了氯离子的扩散速率,延长了钢筋混凝土结构的寿命。本论文基于混凝土结合氯离子的不同方式及其原理,研究了矿物掺合料种类、掺量及其掺入方式、侵蚀环境中氯离子浓度和侵蚀液p H值对混凝土砂浆的氯离子结合性能的影响。主要研究内容和研究结果如下:分析比较了化学滴定法、电位滴定法、离子选择电极法在混凝土氯离子浓度测量时的优劣,并选用离子选择电极法作为本实验测量氯离子浓度的方法。针对选用的离子选择电极的响应p H值范围较小,采用常用方法时,酸溶性氯离子浓度的测量无法满足响应p H值的问题,对测量方法做了部分改进。经过试验测量及检验校核,该改进方案能很好地满足实验要求。研究了不同掺量下,单掺粉煤灰、矿渣、以及双掺粉煤灰和矿渣对混凝土的氯离子结合性能的影响。研究发现,粉煤灰和矿渣均能极大提高混凝土的氯离子结合能力,且掺量相同的情况下,前者提升作用优于后者;二者提高的主要机理分别为物理吸附作用和化学结合作用。研究了侵蚀环境中的氯离子浓度对混凝土的氯离子结合性能的影响。研究发现,氯离子浓度的升高,能促进AFm相转化为Friedel盐的进程,也能增大CSH凝胶等水化产物物理吸附氯离子的量。但由于结合剂总量一定,可结合的氯离子的总量一定,随着氯离子浓度的升高,虽然混凝土结合的氯离子的量有所增加,但其氯离子结合能力会下降。研究了侵蚀液的p H值对混凝土的氯离子结合能力的影响。研究发现,侵蚀液p H值的增大,不但会阻碍AFm相转化为Friedel盐的进程,也会降低CSH凝胶等水化产物对氯离子的物理吸附能力。但对于掺矿物掺合料的实验组来说,当侵蚀液p H值超过一定的值时,p H值的增大能促进矿物掺合料的二次水化反应,进而提高混凝土的氯离子结合能力。
[Abstract]:The chloride binding properties of concrete are of great significance to the life prediction and durability of reinforced concrete buildings. The presence of chloride ions in the form of combination does not harm the corrosion of steel bars in reinforced concrete. It delays the diffusion rate of chloride ions and prolongs the life of reinforced concrete structures. Based on the different ways and principles of chloride ion binding in concrete, the types, amounts and ways of mineral admixtures are studied in this paper. Effects of chloride concentration and pH value of erosive fluid on chloride binding properties of concrete mortar. The main contents and results are as follows: the advantages and disadvantages of chemical titration, potentiometric titration and ion selective electrode in the measurement of chloride concentration in concrete are analyzed and compared. The ion selective electrode method was used to measure the concentration of chloride ion in this experiment. In view of the small range of response pH value of the ion selective electrode, the measurement of acid soluble chloride ion concentration can not meet the problem of response pH value when the commonly used method is used, so the measurement method has been partially improved. After experimental measurement and verification, the improved scheme can well meet the requirements of the experiment. The effects of fly ash, slag, fly ash and slag on the chloride binding properties of concrete were studied. It is found that both fly ash and slag can greatly improve the chloride binding capacity of concrete, and the lifting effect of the former is better than that of the latter when the content is the same, and the main mechanisms of their improvement are physical adsorption and chemical binding respectively. The effect of chloride concentration in erosive environment on chloride binding properties of concrete was studied. It was found that the increase of chloride concentration could promote the conversion of AFm phase to Friedel salt and increase the amount of chloride ions physically adsorbed by hydration products such as CSH gel. However, because the total amount of binder is constant and the total amount of binding chloride is constant, with the increase of chloride ion concentration, the amount of chloride ion bound in concrete increases, but the chloride binding capacity of concrete decreases. The effect of pH value of erosive fluid on chloride binding capacity of concrete was studied. It is found that the increase of pH value not only hinders the process of AFm phase conversion to Friedel salt, but also reduces the physical adsorption ability of hydrated products such as CSH gel to chlorine ions. But for the experimental group with mineral admixture, when the pH value of erosive fluid exceeds a certain value, the increase of pH value can promote the secondary hydration reaction of mineral admixture, and then improve the chloride binding ability of concrete.
【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】：TU528

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