长期浸泡下混凝土硫酸盐传输—劣化机理研究

发布时间：2018-02-14 00:54

本文关键词： 混凝土硫酸盐硫酸根离子分布扩散模型强度模型　出处：《深圳大学》2015年硕士论文　论文类型：学位论文

【摘要】：混凝土结构依附的自然环境均可能含有一定量的硫酸盐,它们通过多种途径传输到混凝土内部造成混凝土自身性能劣化的同时,也降低了与钢筋共同工作的能力和对钢筋的保护作用,因此展开对于混凝土抗硫酸盐侵蚀机理和理论模型的的试验研究,有利于为混凝土使用寿命(再)设计奠定重要的理论基础和依据。为此,本文展开了长期浸泡环境下混凝土硫酸盐侵蚀试验研究并取得了如下主要研究结果:(1)文章研究了C25混凝土受10%硫酸钠溶液一维腐蚀下的强度随侵蚀龄期劣化规律,表明受腐蚀混凝土强度前期的提高主要是因为自身水化作用的贡献,而侵蚀膨胀产物对混凝土强度提高的贡献最大仅为4%,而后期对混凝土造成的破坏是非常显著的。(2)通过分层切片、离子滴定等化学手段得到了1%、5%、10%硫酸盐浓度下C25混凝土和10%硫酸盐浓度下C50、C70混凝土由表到里的SO42-分布情况,分析了不同硫酸钠溶液浓度和混凝土强度对混凝土内SO42-传输的影响,表明不同工况下SO42-在混凝土内的传输劣化机理基本一致,只是演变进程存在差异。(3)利用微观测试技术ESEM(环境电镜扫描)和EDS(能谱元素分析仪)对受腐蚀混凝土微观结构形貌和侵蚀产物进行定性分析,揭示了硫酸盐对混凝土微结构产生的损伤机理和演变规律。并通过宏微观相结合进行深入分析,表明混凝土宏观力学性能的劣化和硫酸根离子在混凝土内部传输过程的演化都是微观结构的变化在宏观和传输方面的反映。(4)以扩散理论为基础,试验结果为指导,推导建立了不同工况下硫酸盐在混凝土内部的传输模型,包括浓度分布模型和侵蚀深度预测模型,并通过试验数据证明了模型的正确性和适用性。文章最后提出了受腐蚀混凝土平均强度预测模型,并通过自有数据和其他文献数据对其进行了验证;同时基于腐蚀厚度对受腐蚀混凝土截面分析,计算得到了腐蚀层混凝土的平均强度,并建立了与腐蚀层厚度相关的腐蚀层混凝土平均强度预测模型,另外在已有学者研究基础上数学推导了腐蚀层混凝土强度分布模型。
[Abstract]:The natural environment on which concrete structures are attached may contain a certain amount of sulphate, which can be transported to the concrete interior through many ways, which results in the deterioration of concrete's own performance at the same time. It also reduces the ability to work with the steel bar and the protective effect of the steel bar, so the experimental study on the mechanism and theoretical model of the sulfate resistance of concrete has been carried out. It is beneficial to lay an important theoretical foundation and basis for the design of concrete service life. In this paper, the experimental study on sulfate erosion of concrete under long-term immersion environment is carried out and the main results are as follows: 1. The strength of C25 concrete subjected to one-dimensional corrosion of 10% sodium sulfate solution is studied in this paper. The results show that the improvement of the strength of corroded concrete in the early stage is mainly due to the contribution of self-hydration. The maximum contribution of the corrosion expansion product to the strength of concrete is only 4, while the damage caused to the concrete in the later stage is very significant. The distribution of SO42- in C25 concrete at 10% sulphate concentration and in C50C70 concrete at 10% sulfate concentration was obtained by ion titration and other chemical methods. The effects of different sodium sulfate solution concentration and concrete strength on so _ 42- transport in concrete were analyzed. It shows that the transport degradation mechanism of so _ 4 _ 2-- in concrete is basically the same under different working conditions. However, the evolution process is different.) the microstructure and corrosion products of corroded concrete are qualitatively analyzed by means of ESEM (Environmental Electron microscope scanning) and EDS (Energy Spectrum element Analyzer). The damage mechanism and evolution law of sulfate to concrete microstructure are revealed. It is shown that both the deterioration of macroscopic mechanical properties of concrete and the evolution of sulfate ion transport process in concrete are the reflection of the change of microstructure in macroscopic and transport aspects, which is based on the diffusion theory and guided by the experimental results. The transport models of sulfate in concrete under different working conditions are derived, including concentration distribution model and erosion depth prediction model. The model is proved to be correct and applicable by experimental data. Finally, a model for predicting the average strength of corroded concrete is proposed, which is verified by its own data and other literature data. At the same time, the average strength of the corroded concrete is calculated based on the analysis of the section of the corroded concrete based on the corrosion thickness, and the prediction model of the average strength of the corroded concrete is established, which is related to the thickness of the corrosion layer. In addition, the strength distribution model of corroded concrete is derived on the basis of previous research.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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