硫酸盐侵蚀混凝土细观动态本构关系研究

发布时间：2018-04-08 18:54

本文选题：硫酸盐侵蚀　切入点：多边形骨料　出处：《哈尔滨工业大学》2014年硕士论文

【摘要】：硫酸盐广泛存在于大气、土壤以及水体之中，在长期作用下可导致混凝土力学性能劣化乃至膨胀破坏，硫酸盐腐蚀已成为对混凝土结构耐久性影响最大的环境腐蚀之一。在细观层次上，混凝土由砂浆、粗骨料以及过渡界面组成的三相复合材料。建立基于粗骨料真实分布特征的细观数值模型，掌握硫酸根离子在混凝土中的扩散规律及砂浆受硫酸盐侵蚀的劣化规律，，是深入了解硫酸盐侵蚀混凝土材料动态力学性能劣化规律及其损伤演化规律的关键。利用改进的硫酸钡重量法对不同腐蚀周期砂浆和混凝土试块进行了硫酸根离子浓度的检测与分析，对硫酸根离子在砂浆中的扩散规律进行了研究；对不同侵蚀周期的砂浆试块进行了动态抗压试验和抗折试验，研究了硫酸钠侵蚀对砂浆强度应变率效应的影响；测试了混凝土在不同加载速率下的劈裂抗拉强度。研究结果表明：随着腐蚀周期的增长，硫酸根离子的扩散速度逐渐减慢；硫酸钠侵蚀砂浆的抗压强度随着应变率的增长而增长，并且在不同的侵蚀周期表现出不同程度的率效应。使用MATLAB图像处理技术，在尽量保持骨料真实面积和形貌的前提下，对混凝土截面骨料边界进行了多边形拟合。首先得到了骨料顶点坐标值,进一步采用多边形拟合数据的方式对骨料的几何特征信息进行了统计分析。统计结果表明：多边形骨料边数、形状不规则度和尺寸不规则度服从高斯分布，骨料面积以及等效半径服从对数正态分布。并在此基础上建立了混凝土二维细观数值模型。基于ABAQUS有限元平台，分别使用蒙特卡洛方法和骨料多边形分析结果，建立了随机圆形骨料模型和多边形骨料模型，并分析了二者的数值模拟结果。结果表明：多边形骨料模型比圆形骨料结果更接近于实验结果，更能反映混凝土内部的实际损伤情况。另外，使用细观数值模型对混凝土抗压实验和混凝土劈裂实验进行了数值仿真，分析结果表明：细观数值模型可较好的反映混凝土抗压强度和劈裂抗拉强度的率效应；随着应变率的增加，混凝土内部损伤面积逐渐扩大。建立了硫酸根离子浓度与砂浆强度的关系，对硫酸盐侵蚀混凝土力学性能劣化规律进行了预测。
[Abstract]:Sulfate widely exists in atmosphere, soil and water, which can lead to deterioration of concrete mechanical properties and even dilatation damage under long-term action. Sulfate corrosion has become one of the most important environmental corrosion factors affecting the durability of concrete structures.At the meso level, the concrete is composed of mortar, coarse aggregate and transition interface.A mesoscopic numerical model based on the true distribution characteristics of coarse aggregate was established to master the diffusion law of sulfate ion in concrete and the degradation law of mortar subjected to sulfate erosion.It is the key to understand the degradation law of dynamic mechanical properties and damage evolution law of sulphate corroded concrete materials.The concentration of sulfate ion in mortar and concrete samples with different corrosion cycles was measured and analyzed by the improved barium sulfate gravimetric method, and the diffusion law of sulfate ion in mortar was studied.Dynamic compressive and flexural tests were carried out on mortar samples with different erosion cycles, the effect of sodium sulfate erosion on the strength strain rate effect of mortar was studied, and the splitting tensile strength of concrete under different loading rates was tested.The results show that the diffusion rate of sulfate ion decreases with the increase of corrosion cycle, and the compressive strength of sodium sulfate erosion mortar increases with the increase of strain rate.And the rate effect is different in different erosion periods.Using MATLAB image processing technology, the concrete cross-section aggregate boundary is fitted with polygon under the premise of keeping the real area and morphology of aggregate as far as possible.Firstly, the coordinate value of aggregate vertex is obtained, and the geometric characteristic information of aggregate is statistically analyzed by means of polygonal fitting data.The statistical results show that the number of polygonal aggregate edges, shape irregularity and size irregularity are distributed from Gao Si, and the aggregate area and equivalent radius from logarithmic normal distribution.On this basis, a two-dimensional meso-numerical model of concrete is established.Based on the ABAQUS finite element platform, the random circular aggregate model and the polygonal aggregate model are established by using Monte Carlo method and polygonal aggregate analysis results, respectively, and the numerical simulation results of the two models are analyzed.The results show that the polygonal aggregate model is closer to the experimental results than the circular aggregate model and can reflect the actual damage of concrete more effectively.In addition, the mesoscopic numerical model is used to simulate the concrete compression test and the concrete splitting experiment. The results show that the meso-numerical model can better reflect the rate effect of concrete compressive strength and splitting tensile strength.With the increase of strain rate, the damage area of concrete expands gradually.The relationship between sulfate ion concentration and mortar strength was established and the deterioration law of mechanical properties of sulphate corroded concrete was predicted.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU375

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