【作者】 蒋敏强；

【导师】 陈建康；

【作者基本信息】 扬州大学 ， 水利水电工程， 2005， 硕士

【摘要】 本文以淮河入海水道滨海枢纽工程混凝土抗侵蚀性研究为工程背景,对海水侵蚀条件下混凝土材料的微结构演化及宏观力学性能进行了研究。将连续损伤力学理论和细观力学理论结合,给出了考虑孔洞内压和基体损伤演化的混凝土材料的宏观本构关系,并且根据得到的本构关系提出了海水侵蚀下混凝土材料有效弹性模量的一个演化模型。 首先,采用微观实验方法对砂浆中的钙矾石的生长规律进行了研究,通过定量X衍射分析测定了钙矾石含量随侵蚀时间的演化规律。制备了纯钙矾石晶体,应用环境扫描电子显微镜(ESEM)的冷台状态原位观测了晶体的形成、生长规律,并且定期观察了不同浓度硫酸盐侵蚀条件下砂浆内部微观结构随侵蚀时间的演化规律。实验研究的成果为第四章的细观理论分析提供了依据和验证。 其次,采用普通硅酸盐水泥,分别配制了水灰比在0.4-0.8范围内的水泥砂浆试件,采用宏观的加速、对比腐蚀实验,研究了水泥砂浆材料在硫酸盐侵蚀条件下,其动弹性模量、抗压强度、线膨胀量和抗折强度随侵蚀时间的演化规律,并且通过微观实验(环境扫描电镜观测(ESEM)、X射线衍射分析(XRD)以及能谱分析(X-EDS))分析了宏观力学性能演化的机理。分析表明:硫酸盐侵蚀混凝土材料,从而引起材料宏观力学性能演化这一过程本质上包含两个问题:一是化学问题即硫酸盐渗透导致钙矾石形成,引起混凝土材料凝聚性降低,导致强度降低;二是力学问题即钙矾石形成后,其自身的结构特性、力学性能以及生长对混凝土材料的相互作用导致混凝土材料中微损伤发展,引起材料宏观力学性能的演化,并最终使材料耐久性降低形成破坏。 最后,应用损伤力学和细观力学相关理论,研究了海水侵蚀环境下混凝土材料的宏观本构关系,并且基于本构关系提出了海水侵蚀下混凝土材料的有效模量演化模型。首先将钙矾石的影响等效为孔洞内压和基体内的微损伤,把混凝土材料看成两相模型——含内压的圆球形孔洞和含微损伤的固体基体;其次,在考虑孔洞内压的基础上,研究了海水侵蚀下混凝土材料的宏观本构关系,在该本构关系的研究中,考虑了损伤演化的影响;更多还原

【Abstract】 This paper is from the research on corrosion resistance of concrete in Binhai hydra-junction, Huaihe River Project. The evolution of micro-structure and macro-mechanical performance of concrete in marine water erosion were studied. A macroscopic constitutive relation of concrete with considering the internal pressure of void and the evolution of micro-damage in seawater erosion was proposed with the theories of continuum damage mechanics and micro-damage mechanics. Based on the macroscopic constitutive relation, a evolution model of concrete’s module in seawater erosion was proposed.Firstly, the growth law of ettringite in mortar was studied by using of micro-experiments, and the quantity evolution of ettringite vs. erosion time was measured with the method of quantitative XRD (X-Radial Diffraction). The formation and growth law of ettringite crystal are observed in situation by Environment Scan Electron Microscope (ESEM) with the method of "Cold-Platform", and the evolution of micro-structure in mortar vs. erosion time in sulfate erosion with different concentration is observed regularly. The micro-experiments of the charter may be used to supply some reference basis for the micro-analysis of the fourth charter.Secondly, according to the accelerated and contrast corrosion test of common Portland cement sample, water cement ratio from 0.4 to 0.8, the evolution of the dynamic modulus, compressive strength, expansion and anti-fold intensity vs. erosion time were studied. The evolution mechanism of macro-mechanical performance is analyzed by ESEM, XRD, X-Energy Dispersive Spectrometer(X-EDS). The analytical results show that the evolution process of concrete’s macro-mechanical performance due to sulfate erosion includes two aspects: one is a chemical problem viz. the reduce of concrete material’s coherence results from the ettringite formation, which results in the decrease of strength; the other is a mechanical problem viz. with the formation of ettringite, the evolution of concrete’s mechanical properties depend on the structural and mechanical properties of ettringite and theinteraction between ettringite and the materials, which results in the durability reduction and damage of concrete materials.Finally, the ettringite formation is considered as the internal pressure of void and the micro-damage of matrix, and the concrete materials is regardedas a two-phase composite------the void with internal pressure and the matrixwith micro-damage. A macroscopic constitutive relation of concrete with considering the internal pressure and the evolution of micro-damage was derived with the theories of continuum damage and micro-damage mechanics. Based on the constitutive relation, an evolution model of concrete’s modulus in seawater erosion was proposed. Numerical results under the uniaxial loading indicate that the modulus of composite increases in seawater erosion to a peak in the initial stages, and then keeps on a constant, finally decreases rapidly. Curve-fitting results show that the model can simulate the experimental curves with some proper parameters. The influence of the void pressure on overall constitutive relation are also discussed under the uniaxial loading by the numerical method. Numerical result shows that the void pressure not only has some effect on effective modulus, but also can lead to an initial stress (or initial strain). With the increasing of void pressure, the modulus gradually decreases but the initial stress (or initial strain) is on the increase.Compared with other researchers, there are three main characteristics in this paper. The first is that the experimental method includes macro and micro aspects. The second is that the theoretical analysis includes qualitative describe and quantitative analysis. The third is that the evolution model of modulus is proposed based on continuum damage mechanics and micro damage mechanics. The present work as a basic research may be used to supply some guidelines and references for improving the attack resistance of concrete materials.更多还原