混凝土中氯离子扩散系数的概率预测模型研究

发布时间：2018-06-25 18:30

本文选题：混凝土 + 耐久性　；参考：《广西大学》2017年硕士论文

【摘要】：在海洋氯化物环境下,混凝土结构的耐久性劣化问题主要是由于外部腐蚀性氯离子侵入混凝土内部诱导钢筋发生锈蚀造成的。由于氯离子扩散系数是决定氯离子在混凝土中传输快慢的重要参数之一,所以直接影响混凝土结构的服役寿命。氯离子扩散系数不仅受材料参数和环境条件的影响,具有显著的随机性,而且随着混凝土龄期的增加而逐渐降低,呈现显著的时变特性。因此,有必要综合考虑环境条件、材料参数和时变特性的影响,建立混凝土中氯离子扩散系数的概率预测模型,进而开展混凝土结构的概率服役寿命预测。鉴于此,本文分别基于室内加速试验数据和自然暴露试验数据,建立了室内加速试验和自然暴露条件下混凝土中氯离子扩散系数的概率预测模型,在此基础上提出了海洋氯化物环境下混凝土结构的概率服役寿命预测方法。主要研究内容包括:(1)基于所收集的295组利用室内加速试验(RCM法)测试的氯离子扩散系数的试验数据,定量分析了水胶比、粉煤灰掺量、矿粉掺量等因素对氯离子扩散系数的影响规律,并利用逐步回归分析法遴选显著变量,建立了混凝土中氯离子扩散系数的确定性预测模型,进而综合考虑主观不确定性和客观不确定性的影响,结合贝叶斯理论和马尔科夫链蒙特卡洛法,建立了室内加速试验条件下混凝土中氯离子扩散系数的概率预测模型。(2)基于所收集的913组利用自然暴露试验数据拟合确定的氯离子扩散系数数据,综合考虑材料参数和环境条件的影响,建立了海洋潮汐区、浪溅区、大气区和水下区环境条件下混凝土中氯离子扩散系数与暴露时间、配合比参数(水胶比、矿物掺合料d{量)之间的确定性关系模型,进而综合考虑主观不确定性和客观不确定性的影响,结合贝叶斯理论和马尔科夫链蒙特卡洛法,建立了海洋氯化物环境下混凝土中氯离子扩散系数的概率预测模型,并建立了室内加速试验条件与自然暴露条件下混凝土中氯离子扩散系数之间的转换关系。(3)基于氯离子扩散系数的概率预测模型,结合混凝土中钢筋锈蚀(诱导期)的服役寿命预测模型,提出了海洋氯化物环境下混凝土结构的概率服役寿命预测方法,并定量分析了环境条件(如潮汐区、浪溅区、大气区和水下区)、材料参数(如水胶比和矿物掺合料)、混凝土保护层厚度等重要因素对海洋氯化物环境下混凝土结构概率服役寿命的影响规律。
[Abstract]:In marine chloride environment, the deterioration of durability of concrete structures is mainly caused by the corrosion of steel bars induced by external corrosive chloride ions intruding into the concrete. The chloride diffusion coefficient is one of the important parameters to determine the speed of chloride ion transport in concrete, so it directly affects the service life of concrete structure. The chloride diffusion coefficient is not only affected by material parameters and environmental conditions, but also decreases with the increase of concrete age. Therefore, it is necessary to establish a probabilistic prediction model of chloride diffusion coefficient in concrete considering the influence of environmental conditions, material parameters and time-varying characteristics, and then to predict the probabilistic service life of concrete structures. In view of this, based on indoor accelerated test data and natural exposure test data, the probabilistic prediction model of chloride diffusion coefficient in concrete under indoor accelerated test and natural exposure condition is established in this paper. On this basis, the probabilistic service life prediction method of concrete structures under marine chloride environment is proposed. The main contents are as follows: (1) based on the data collected from 295 groups of chlorine ion diffusion coefficient measured by indoor accelerated test (RCM), the water binder ratio and fly ash content are quantitatively analyzed. The influence of mineral powder content on chloride diffusion coefficient is studied. The deterministic prediction model of chloride ion diffusion coefficient in concrete is established by using stepwise regression analysis to select significant variables. Furthermore, considering the influence of subjective uncertainty and objective uncertainty, combined with Bayesian theory and Markov chain Monte Carlo method, A probabilistic prediction model of chloride diffusion coefficient in concrete under accelerated indoor test was established. (2) based on 913 groups of data obtained from natural exposure test, the chloride diffusion coefficient was fitted. Considering the influence of material parameters and environmental conditions, the chloride diffusion coefficient, exposure time and mixing ratio parameters (water / binder ratio) of concrete in marine tidal zone, splash zone, large air zone and underwater area were established. The deterministic relation model between mineral admixtures d {quantity], then considering the influence of subjective uncertainty and objective uncertainty, combined with Bayesian theory and Markov chain Monte Carlo method. The probabilistic prediction model of chloride diffusion coefficient in concrete under marine chloride environment is established. The conversion relationship between the indoor accelerated test conditions and the chloride diffusion coefficient in the concrete under natural exposure is established. (3) the probability prediction model based on the chloride ion diffusion coefficient is presented. The probabilistic service life prediction method of concrete structures in marine chloride environment is proposed, and the quantitative analysis of environmental conditions (such as tidal zone, wave splash zone) is also given, combining with the prediction model of service life of steel bar corrosion (induced period) in concrete, and the probabilistic service life prediction method of concrete structure under marine chloride environment is presented. The influence of material parameters (such as water-binder ratio and mineral admixture) and the thickness of concrete cover on the probabilistic service life of concrete structure in marine chloride environment.
【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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