混凝土裂缝对氯离子传输及水分影响深度的研究

发布时间：2018-04-14 03:01

本文选题：开裂混凝土 + 混凝土耐久性　；参考：《浙江大学》2013年硕士论文

【摘要】：氯离子传输过程对混凝土结构耐久性和服役寿命预测都具有非常重要的意义,因为它直接决定了钢筋的脱钝时间。然而,就目前的研究现状,一些关键并且必要的因素往往被忽略,为此本文的主要目的在于完善目前的氯离子传输机理。本文主要研究如下几个内容： (一)建立了干湿交替环境下氯离子在开裂混凝土中的传输模型。存在于混凝土中的裂缝会加速氯离子侵入进程,进一步影响混凝土结构耐久性。为了弄清干湿循环条件下,氯离子在开裂混凝土中的侵蚀机理,本文建立新的模型来描述这个过程,同时由相关试验进行验证。本文认为氯离子在完好多孔介质中的输送机理同样适用于开裂混凝土。对其中的水分对流部分,分别考虑了裂缝的宽度、表面粗糙度、表面迂曲度和毛细孔等参数,根据流体力学Poiseuille方程建立了在其传输模型。由此进一步提出了氯离子在各项异性介质中的传输控制方程,并对其中主要参数进行了敏感性分析。最后,考虑裂缝影响之后,对现有菲克第二定律进行了修正。 (二)建立了多重环境和荷载作用下的氯离子传输模型框架。氯离子在混凝土内的传输过程中受到外界环境温湿度变化的影响,也由于混凝土材料自身蠕变特性而不断变化,即氯离子传输过程呈现非线性和时变性。无论是外界环境还是材料自身的收缩徐变,对混凝土的传输特性而言,从本质上改变了混凝土自身孔结构或产生了内部微裂缝,进一步表现为对氯离子传输的增大或减小。本文主要创新点在于将外界环境的变化与结构自身的响应通过截面纤维模型关联起来,进而根据输出的应力或应变值来进一步建立与氯离子扩散系数的关系,最终在试验的基础上得出荷载对氯离子扩散系数影响的计算公式。 (三)进行了氯离子侵蚀过程的模糊概率分析和寿命预测体系的建立。氯离子传输规律涉及诸多的不确定性,包括客观不确定性(随机性)和主观不确定性(模糊性)。本文在随机场理论和模糊理论的基础上,建立了基于随机场理论和模糊集合理论的氯离子传输模型,并且考虑裂缝对混凝土结构寿命预测评价体系的影响,通过蒙特卡洛技术进行该过程的模拟分析。 (四)进行了裂缝对氯离子扩散系数和水分对流层深度试验和理论分析。真实混凝土结构往往存在裂缝,因此应用菲克第二定律进行简单预测时,有必要考虑裂缝对其的影响而进行修正。本文通过试验研究,讨论氯离子扩散系数和水分影响深度这两个重要参数的影响。首先分析开裂区附近氯离子含量,氯离子在裂缝处的浓度分布采用电子探针技术(EMPA)分别提取准确的浓度,根据通量守恒原理,考虑裂缝宽度和混凝土配合比,进行了相关的理论分析,提出了氯离子在裂缝区的扩散系数公式；另一方面,在对水分影响深度的试验分析中,通过一系列带有不同裂缝宽度的试件,在人工模拟环境箱进行试验,测试试件中温湿度的变化,试验条件包括周期性的温湿度变化,雨淋和雾气环境,以及雨淋后的干燥过程。
[Abstract]:Chloride transport process is very important for the durability of concrete structure and service life prediction, because it directly determines the blunt stripping time of steel. However, the current research status, some important and necessary factors are often ignored, in this paper the main purpose is to improve the current mechanism of chloride ion transport. This paper mainly studies the following contents:
(a) is established under the environment of chlorine ion transport model in cracked concrete wet dry. Cracks exist in the concrete in the accelerated chloride penetration process, further influence the durability of concrete structure. In order to find out the cycle of dry and wet conditions, the erosion mechanism of chloride ion in concrete cracking, this paper established a new model to describe the at the same time, by the relevant test. This paper argues that the transport mechanism of chloride ion in porous medium is also applicable to concrete cracking. The water convection part, considering the crack width, surface roughness, surface tortuosity and pore parameters according to the fluid mechanics equations are established in the transmission Poiseuille the model is proposed. The transport of chloride ions in the anisotropic medium control equation, and the main parameters of the sensitivity analysis is carried out. The test. After considering the effect of cracks, the existing Fick's second law was amended.
(two) establish a chloride transport model and the framework of multiple environmental loads. Affected by the temperature and humidity changes in the external environment of the transmission process of chloride ion in concrete in concrete material itself due to creep and changing, namely the chloride transport process is nonlinear and time-varying. Both the shrinkage and creep outside the environment is the material itself, the transmission characteristics of concrete, essentially changed the concrete pore structure or the internal micro cracks, further for the transport of chloride ions increases or decreases. The main innovation of this paper is to change the external environment and the structure of its response through cross section fiber model associated with them, and according to the output of the stress or strain to further establish the relationship with chloride ion diffusion coefficient, finally based on the experimental results of load on chloride ion diffusion A formula for calculating the influence of a coefficient.
(three) the establishment of the system of fuzzy probability analysis and life prediction of chloride ion erosion process. The chloride ion transport law involves many uncertainties, including objective uncertainty (randomness) and subjective uncertainty (fuzziness). Based on the random field theory and fuzzy theory on the basis of a random field fuzzy set theory and the chloride ion transmission model based on the theory and considering the influence of evaluation system of concrete structure crack life prediction, simulation and analysis of the process by Monte Carlo technique.
(four) the cracks on the chloride ion diffusion coefficient and water depth of the experimental and theoretical analysis. The real concrete structure cracks often exist, so the application of Fick's second law simple prediction, it is necessary to consider the influence of cracks on its correction. This paper discusses the influence of chloride diffusion coefficient and the water two important parameters in depth. The first cracking analysis of chloride ion content near the electron probe technique in the cracks of chloride ion concentration distribution (EMPA) were extracted from the accurate concentration, according to the flux conservation principle, mixture ratio and crack width of concrete considering, analyzed the related theory, put forward the formula of chloride diffusion coefficient ion in the crack area; on the other hand, the effect of water depth in the experimental analysis, through a series of specimens with different crack width, in artificial ring The test is carried out in the box, and the changes of temperature and humidity in the test piece are tested. The test conditions include periodic temperature and humidity change, rain and mist environment, and the drying process after rain.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU375

【共引文献】