氯盐侵蚀混凝土过程的精细化数值模拟与试验研究

发布时间：2019-04-29 08:56

【摘要】：氯盐侵蚀混凝土结构是混凝土耐久性研究的一个重点和难点。由于近些年自密实混凝土在公路和桥梁中的应用越来越广泛,其耐久性能的研究并不充足,因此自密实混凝土耐久性的研究显得更为迫切和重要。随着混凝土材料向高性能方向的发展,以节约能源和节省原材料、采用活性矿物掺合料与高效减水剂来配制高性能、高耐久性的混凝土已成为全世界的建筑课题,粉煤灰、矿粉和硅粉等活性矿物常被作为掺合料而成为混凝土的组成成分。由于氯盐侵蚀混凝土的机理尚不完善,国内外关于氯盐侵蚀混凝土的耐久性的研究大多以试验为主,关于氯离子侵蚀自密实混凝土的耐久性能的研究更少,对于掺和了矿物掺合料的自密实混凝土的研究更是寥寥无几。在调研已有的研究成果的基础上,本文主要对以下内容进行了研究:首先,进行了氯盐溶液浸泡侵蚀自密实混凝土的试验和氯盐盐雾侵蚀自密实混凝土的试验,试验过程中把水胶比、掺合料种类、掺合量和氯盐组成成分作为控制变量。试验选用三种不同的矿物掺合料(粉煤灰、矿粉和硅粉)进行研究,试验中掺和了矿物掺合料的自密实混凝土试件共有九种不同的配比。每种配比的自密实混凝土试件选用一种掺合料,对于选用了同一种掺合料的自密实混凝土试件选用两种不同的掺合量,保证不同配比的自密实混凝土试件的掺合料类型和掺合量是不同的,同时,试验过程中选用不掺矿物掺合料的自密实混凝土试件作为对照组。试验过程中每隔30天从试验装置中取出自密实混凝土试件,测定混凝土试件内部不同深度处的自由氯离子浓度和总氯离子浓度以及立方体抗压强度,进而对氯盐侵蚀自密实混凝土的耐久性能进行研究。其次使用RCM法对自密实混凝土的氯离子扩散系数进行试验研究,试验选用NaCl溶液对自密实混凝土试件进行氯盐溶液浸泡试验。从自密实混凝土圆柱体试件浸泡到氯盐溶液中开始,每隔30天测量一次自密实混凝土试件的氯离子扩散系数,通过Matlab对不同浸泡龄期的自密实混凝土的氯离子扩散系数进行拟合分析,得到了九种不同配比的自密实混凝土的氯离子扩散系数随时间变化的曲线,根据拟合结果对不同龄期的自密实混凝土的氯离子扩散系数进行预测。最后,在Fick第二定律的基础上,在偏微分方程组中引入反应项,建立了更为合理的考虑氯离子扩散反应和吸附-释放动态平衡反应耦合作用的偏微分方程组。利用三级配骨料理论和孔隙概率密度函数,使用Matlab软件编写了混凝土骨料投放的程序,同时基于Abaqus商业软件的二次开发,通过编写Matlab程序在一定程度上实现了氯盐侵蚀自密实混凝土的多尺度精细化数值化模型的建立和计算。通过模型计算结果和试验实测数据的对比,验证了本研究中新建偏微分方程组、的合理性和准确性。
[Abstract]:Chloride erosion of concrete structure is a key and difficult point in the study of concrete durability. Since the application of self-compacting concrete in highway and bridge is more and more extensive in recent years, the research on durability of self-compacting concrete is not enough, so the research on durability of self-compacting concrete is more urgent and important. With the development of concrete materials in the direction of high performance, in order to save energy and raw materials, using active mineral admixture and superplasticizer to prepare high performance, high durability concrete has become the construction subject of the world, fly ash, Active minerals, such as mineral powder and silica powder, are often used as admixtures and become the components of concrete. Because the mechanism of chloride erosion concrete is not perfect, the durability of chloride erosion concrete is mostly studied by experiment at home and abroad, and the research on durability of chloride-ion erosion self-compacting concrete is less than that of chloride-ion erosion self-compacting concrete. The study of self-compacting concrete mixed with mineral admixture is rare. Based on the existing research results, the main contents of this paper are as follows: firstly, the test of chloride solution immersion erosion self-compacting concrete and the test of chloride salt spray erosion self-compacting concrete are carried out. During the experiment, the ratio of water to binder, the type of admixture, the amount of admixture and the composition of chlorine salt were used as the controlling variables. Three kinds of mineral admixtures (fly ash, mineral powder and silica powder) were used in the experiment. There were nine different ratios of self-compacting concrete specimens mixed with mineral admixtures. One admixture is selected for each self-compacting concrete specimen, and two different admixtures are selected for the self-compacting concrete specimen with the same admixture. The type and amount of admixture of self-compacting concrete specimens with different proportions are different. Meanwhile, the self-compacting concrete specimens without mineral admixture are selected as the control group during the test. During the test, self-compacting concrete specimens were taken out every 30 days, and the free chloride concentration, total chloride concentration and cube compressive strength were measured at different depths within the concrete specimen. Furthermore, the durability of self-compacting concrete corroded by chloride salt was studied. Secondly, the chloride diffusion coefficient of self-compacting concrete was studied by RCM method. The NaCl solution was used to soak the self-compacting concrete specimen in chloride solution. The chloride diffusion coefficient of self-compacting concrete specimen is measured every 30 days, starting from immersion of self-compacting concrete cylinder specimen into chloride solution. According to the fitting analysis of chloride diffusion coefficient of self-compacting concrete with different immersion age by Matlab, the curve of chloride diffusion coefficient of nine kinds of self-compacting concrete with different proportion with time has been obtained, which shows that the diffusion coefficient of chloride ion in self-compacting concrete varies with time. According to the fitting results, the chloride diffusion coefficient of self-compacting concrete of different ages is predicted. Finally, on the basis of Fick's second law, the reaction term is introduced into the partial differential equations, and a more reasonable partial differential equation system considering the coupling action of chloride diffusion reaction and adsorption-release dynamic equilibrium reaction is established. Based on the three-grade aggregate theory and the pore probability density function, the program of concrete aggregate delivery is compiled by using Matlab software. At the same time, the secondary development of commercial software based on Abaqus is carried out. The multi-scale refined numerical model of self-compacting concrete corroded by chlorine salt is established and calculated by programming Matlab program to a certain extent. The rationality and accuracy of the new partial differential equations in this study are verified by the comparison between the calculated results of the model and the measured data.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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