预应力混凝土中氯离子扩散试验研究及概率分析

发布时间：2018-03-02 17:14

本文选题：预应力混凝土　切入点：氯离子　出处：《长沙理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：预应力混凝土结构具有性能好、跨度大的特点,在我国土木、水利与交通工程等领域得到了广泛应用。然而大量工程实践表明预应力混凝土结构在长期使用过程中会由于许多预料不到的原由从而致使结构功能退化,导致服务年限不能达到目标年限。这其中主要原因就是由于钢筋锈蚀,而对钢筋锈蚀影响最大就是氯离子侵蚀。文章研究了压应力状态下混凝土的氯离子侵蚀问题,进行了人工气候环境下氯离子侵入混凝土的试验。试验考虑了水灰比与应力水平两种因素,设计了三种不同的水灰比与应力状态。本文所做的工作及研究内容如下:(1)设计人工气候环境下无应力与压应力状态下混凝土进行氯盐喷雾试验,记录并分析试验数据。(2)基于Fick第二定律,综合考虑了预应力、温度、混凝土氯离子结合能力、氯离子扩散系数的时间依赖性和结构缺陷等多方面因素的影响,建立了多因素作用下预应力混凝土的氯离子扩散模型。(3)通过对试验数据分析发现不同水灰比的混凝土在人工气候环境下,低水灰比的混凝土会比高水灰比的在抵抗氯离子侵入这一方面要提高一定比例。混凝土在承受压应力时会对在其内的氯离子扩散有较为大影响,同一水灰比的混凝土在不同的应力状态下,氯离子在其中的扩散随压应力的逐渐增大而扩散速率降低。(4)通过本次试验的数据对本文研究的氯离子扩散模型进行了验证,验证结果表明此扩散模型有较好的适用性,为氯盐环境下的预应力混凝土结构耐久性研究提供了理论依据。(5)分析了初锈模型的影响因素,研究发现基本参数的服从的概率密度函数各不相同。对初锈时间模型进行了敏感性分析,研究发现初锈模型对这些参数的敏感性程度也各不相同,其中对保护层厚度敏感性最强,其次是临界浓度,而对扩散系数敏感性次之,其对表面浓度与应力水平最低。
[Abstract]:Prestressed concrete structure has the characteristics of good performance and large span. The field of water conservancy and traffic engineering has been widely used. However, a large number of engineering practices have shown that the function of prestressed concrete structures will degenerate due to many unexpected original reasons during their long-term use. The main reason is that the corrosion of steel bar is the main reason, and the corrosion of chloride ion is the most important influence on the corrosion of steel bar. In this paper, the problem of chloride ion erosion in concrete under compressive stress is studied. The experiment of chloride ion intrusion into concrete in artificial climate was carried out. Two factors, water-cement ratio and stress level, were taken into account in the experiment. Three different water-cement ratio and stress states are designed. The work and research contents in this paper are as follows: (1) the chlorine spray test of concrete under the condition of no stress and compressive stress in artificial climate is designed. Based on the second law of Fick, the influences of prestress, temperature, chloride binding capacity of concrete, time dependence of chloride diffusion coefficient and structural defects are comprehensively considered. The chloride diffusion model of prestressed concrete under multi-factor action is established. By analyzing the experimental data, it is found that the concrete with different water-cement ratio is in artificial climate. The concrete with low water-cement ratio will increase its resistance to chloride ion intrusion by a certain proportion than the concrete with high water-cement ratio. When the concrete is subjected to compressive stress, it will have a greater influence on the chloride ion diffusion in the concrete. Under different stress states of concrete with the same water-cement ratio, the diffusion rate of chloride ions decreases with the increasing of compressive stress. The results show that the diffusion model has good applicability and provides a theoretical basis for the durability study of prestressed concrete structures under chloride environment. It is found that the probability density function of the basic parameters is different. The sensitivity of the initial rust time model is analyzed, and the sensitivity of the initial rust model to these parameters is also different. The thickness of the protective layer is the most sensitive, followed by the critical concentration, the second is the diffusion coefficient, and the lowest is the surface concentration and stress level.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU378

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