混凝土硫酸盐侵蚀的二维非均匀模型及耐久性分析

发布时间：2018-06-21 21:48

本文选题：混凝土 + 耐久性　；参考：《广西大学》2017年硕士论文

【摘要】：硫酸盐侵蚀是引发混凝土结构耐久性损伤破坏的重要因素之一,侵蚀至混凝土结构内部的硫酸根离子可以与水化铝酸钙等水泥水化产物发生化学反应,生成钙钒石等膨胀性物质,当膨胀应变和应力超过了混凝土结构的极限抗拉强度,膨胀性裂缝随之产生,并随着侵蚀周期的延长而不断发展,最终导致混凝土结构的耐久性失效。本文主要从试验研究和数值模拟研究两方面共同探究了硫酸盐侵蚀混凝土的扩散-反应行为,并进行了相应的结构耐久性分析及服役寿命预测。主要研究内容包括:(1)提出了硫酸盐二维侵蚀的试验方法,并开展了相应的硫酸盐二维侵蚀的试验研究,试验中通过开展侵蚀后混凝土中硫酸盐的浓度测试和MTS力学测试分别获得了硫酸根离子侵入量及受硫酸盐侵蚀后的试块应力-应变等数据,并分析了胶凝材料的组份、养护时间以及粗骨料对硫酸盐侵蚀的影响规律。从硫酸根离子侵入量以及抗压强度值来看,研究表明:在12周的侵蚀周期内,HS型试块具有最佳的抗硫酸根离子侵入能力;而GU型水泥制成的试件在硫酸盐侵蚀环境中拥有最佳的力学性能;同时,粗骨料的存在会阻碍硫酸根离子的传输,导致硫酸根离子在骨料前方的聚集;(2)研究建立了混凝土硫酸盐侵蚀的二维均匀扩散-反应模型和二维非均匀扩散-反应模型,并推导了相应的有限差分格式。通过将模型计算结构与硫酸盐侵蚀试验数据进行对比,验证了模型的合理性与可行性。随后,基于所提出的混凝土硫酸盐侵蚀的二维均匀和非均匀模型,分别研究了侵蚀维度、扩散系数、初始铝酸钙含量、环境浓度、化学反应常数和粗骨料粒径、投放位置、形状、含量等对硫酸盐侵蚀混凝土结构的影响规律,研究表明:相较于一维侵蚀,二维侵蚀明显加剧了混凝土遭受硫酸盐侵蚀的程度;与均匀模型相比,非均匀模型中考虑了粗骨料对扩散-反应过程的影响,可以更合理地描述混凝土的硫酸盐侵蚀过程;在非均匀模型中,粗骨料的粒径和所处位置可以对硫酸盐侵蚀的扩散-反应行为产生显著影响;(3)提出了硫酸盐环境下混凝土结构耐久性分析方法,建立了硫酸盐环境下混凝土结构耐久性分析的极限状态方程及相应的服役寿命计算模型,并开展了不同硫酸盐环境条件和不同材料参数下混凝土结构的耐久性分析及服役寿命预测,研究表明,作为混凝土硫酸盐侵蚀的扩散控制和反应控制两个阶段的关键因素,硫酸根离子扩散系数和初始铝酸钙含量对硫酸盐侵蚀条件下混凝土结构的服役寿命有明显影响;在合理范围内增加混凝土中的粗骨料含量、提高混凝土结构的保护层厚度可以延长其在硫酸盐侵蚀条件下的服役寿命。
[Abstract]:Sulfate erosion is one of the most important factors that cause damage to the durability of concrete structures. The sulfate ions eroded into the concrete structure can react with the hydrated calcium aluminate and other cement hydration products to produce an expansive material such as calcium vanadite, and the expansion strain and stress exceed the ultimate tensile strength of the concrete structure. The expansive crack is produced and develops continuously with the prolongation of the erosion cycle, which eventually leads to the durability failure of the concrete structure. In this paper, the diffusion reaction behavior of the sulfate corroded concrete is investigated from two aspects of experimental research and numerical simulation, and the corresponding structural durability analysis and service life pre service are carried out. The main contents are as follows: (1) the experimental method of 2-D sulfate erosion was put forward, and the corresponding experimental study on 2-D sulfate erosion was carried out. In the experiment, the sulfate ion intrusion and the stress after the sulfate attack were obtained by carrying out the sulfate concentration test and MTS mechanical test in the concrete after erosion. The composition of the cementitious material, the curing time and the influence of the coarse aggregate on the sulfate erosion are analyzed. The study shows that the HS type specimen has the best anti sulfate ion invasion ability in the 12 week erosion cycle, and the specimens made of GU cement are in sulfur. Acid salt has the best mechanical properties in the environment. At the same time, the existence of coarse aggregate will impede the transmission of sulfate ion and lead to the accumulation of sulfate ion in front of the aggregate. (2) a two-dimensional homogeneous diffusion reaction model and a two-dimensional non-uniform diffusion reaction model are established, and the corresponding finite difference is derived. The reasonableness and feasibility of the model are verified by comparing the model calculation structure with the test data of sulfate attack. Then, based on the proposed two-dimensional and non-uniform model of concrete sulfate erosion, the erosion dimension, diffusion coefficient, initial calcium aluminate content, environmental concentration and chemical reaction constant are studied respectively. The effect of coarse aggregate particle size, placement, shape and content on the structure of sulfate corroded concrete has been studied. The study shows that compared with one dimension erosion, two dimensional erosion obviously aggravates the degree of sulfate erosion of concrete. Compared with the uniform model, the effect of coarse aggregate on the diffusion reaction process is considered in the non-uniform model. The sulphate erosion process of concrete is described reasonably. In the non-uniform model, the particle size and location of coarse aggregate can have a significant influence on the diffusion reaction behavior of sulfate erosion. (3) the durability analysis method of concrete structure under sulphate environment was put forward, and the durability analysis of concrete structures under sulphate environment was established. The limit state equation and the corresponding service life calculation model, and the durability analysis and service life prediction of concrete structures under different sulphate environment conditions and different material parameters are carried out. The study shows that the diffusion coefficient of sulfate radical is the key factor for the two stages of diffusion control and reaction control of concrete sulfate erosion. And the initial calcium aluminate content has an obvious influence on the service life of the concrete structure under the sulphate erosion condition. In a reasonable range, increasing the coarse aggregate content in concrete and improving the thickness of the concrete structure can prolong the service life of the concrete under the sulphate erosion condition.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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