基于碘离子传输特征的混凝土渗透性评价方法研究

发布时间：2018-03-04 14:15

本文选题：渗透系数　切入点：RIM　出处：《中南大学》2013年博士论文　论文类型：学位论文

【摘要】：渗透性能对于混凝土的寿命预测、耐久性设计与施工具有重要的意义,但对于内含氯离子混凝土试件,RCM的试验方法不再适用。为克服试验过程中试件内含氯离子对测试结果的影响,客观评价已受氯盐作用混凝土的耐久性能,本文采用碘离子代替氯离子作为试验的渗透离子,运用混凝土材料学、物理化学等基本原理,通过宏观试验和微观测试分析,重点研究了碘离子在混凝土中的迁移过程和结合机理,并与氯离子在混凝土中的传输过程进行对比分析,在此基础上提出基于碘离子传输特征的混凝土渗透性快速评价试验方法(Rapid Iodine Migration, RIM)。取得的主要研究成果如下： (1)系统分析了碘离子和氯离子作用对混凝土微观孔结构、表层渗水性能及水化浆体的影响,发现碘离子和氯离子对混凝土材料的作用有相似的效果,而且混凝土工程的服役环境及自身的材料组成都不含碘离子的特征,确定了碘离子代替氯离子作为试验渗透离子的有效性。 (2)提出了淀粉-碘酸钾显色法的试验方法,用于测试自由碘离子在混凝土中的渗透深度。 (3)研究了淀粉-碘酸钾显色法对测量碘离子渗透深度的有效性,以及水灰比和粉煤灰掺量对显色边界浓度的影响,对比分析了碘离子和氯离子显色边界浓度的相关性规律。 (4)引入浸泡溶蚀系数和离子渗透系数2个参数,建立了综合考虑离子结合能力、扩散系数的时间依赖性、服役环境和离子特性的混凝土离子扩散新方程,解决了不同离子在混凝土中扩散的问题,根据碘离子和氯离子实际扩散过程的试验结果验证了新方程的有效性。 (5)对比研究了自然浸泡下,碘离子和氯离子在混凝土中的沉积量和渗透深度的变化规律,渗透深度相同时,碘离子的累计沉积量大于氯离子,水灰比越大,沉积量的差值也越大,随着渗透深度的增加,碘离子和氯离子的累计沉积量逐步接近；发现渗透深度与水灰比的关系密切,可以使用含有水灰比的幂函数来反映渗透深度的变化规律。 (6)基于碘离子在混凝土中的传输特性和RCM的试验原理,建立了采用碘离子评价混凝土渗透性的快速试验方法(RIM)；引入显色深度修正系数,能将RIM试验结果转换为RCM结果；试验证明,RIM的试验方法可以测量内含氯离子混凝土试件的离子快速渗透系数。
[Abstract]:Permeability is of great significance for life prediction, durability design and construction of concrete. In order to overcome the influence of chloride ions on the test results, the durability of concrete with chloride salt has been evaluated objectively. In this paper, iodine ion instead of chloride ion is used as the osmotic ion of the experiment, and the basic principles of concrete material science, physical chemistry, etc., are analyzed through macroscopic test and microscopic test. The migration and binding mechanism of iodide ions in concrete were studied, and the transport process of iodine ions in concrete was compared with that of chloride ions. On this basis, a rapid Iodine migration (RIMA) method for the rapid Iodine migration of concrete is proposed, which is based on the characteristics of iodide ion transport. The main findings of the study are as follows:. 1) the effects of iodide ion and chloride ion on the microstructure of concrete, the permeability of surface layer and the hydration slurry are analyzed systematically. It is found that iodine ion and chloride ion have similar effect on the effect of concrete material. Moreover, the service environment and the material composition of concrete engineering do not contain iodide ion, so it is determined that iodine ion can replace chloride ion as experimental osmotic ion. In this paper, a new method for the determination of the penetration depth of free iodine ion in concrete is presented. (3) the validity of amylum-potassium iodate coloration method for measuring the depth of iodine ion permeation, and the influence of water / cement ratio and fly ash content on the color boundary concentration were studied. The correlation between iodine ion and chlorine ion color boundary concentration was compared and analyzed. By introducing two parameters, immersion dissolution coefficient and ion permeation coefficient, a new concrete ion diffusion equation considering ion binding ability, time dependence of diffusion coefficient, service environment and ion characteristics is established. The problem of diffusion of different ions in concrete is solved. The validity of the new equation is verified by the experimental results of the actual diffusion process of iodine ion and chloride ion. (5) the variation of deposition amount and permeation depth of iodine ion and chloride ion in concrete under natural immersion are studied. When the permeation depth is the same, the accumulated deposition amount of iodine ion is larger than that of chlorine ion, and the water / cement ratio is larger. With the increase of permeation depth, the accumulative deposition amount of iodine ion and chloride ion gradually approached, and it was found that the relationship between permeation depth and water-cement ratio was close. The power function with water cement ratio can be used to reflect the variation of permeation depth. Based on the transport characteristics of iodine ions in concrete and the experimental principle of RCM, a fast test method for evaluating the permeability of concrete by iodine ion is established, and the color depth correction coefficient is introduced to convert the results of RIM test to RCM results. It is proved that the RIM method can measure the ion fast permeability coefficient of concrete specimens containing chloride ion.
【学位授予单位】：中南大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU528

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