盐冻环境下混凝土构件耐久性及寿命预测研究

发布时间：2018-01-05 12:09

本文关键词：盐冻环境下混凝土构件耐久性及寿命预测研究　出处：《西安建筑科技大学》2014年博士论文　论文类型：学位论文

【摘要】：钢筋混凝土结构耐久性失效，会导致巨大的经济损失，影响社会经济发展。盐冻损伤对混凝土材料产生的不可逆累积损伤，会加快环境中腐蚀介质的渗透与扩散，加速混凝土中钢筋锈蚀与混凝土保护层锈胀开裂，影响混凝土结构的正常使用。研究盐冻环境下混凝土耐久性，对新建混凝土结构工程耐久性设计和在役混凝土结构工程的耐久性评定及维护具有重要的理论意义和工程价值。本文以除冰盐环境与寒冷地区海洋环境中的钢筋混凝土结构为研究对象，研究盐冻损伤对混凝土耐久性的影响，预测盐冻环境混凝土结构耐久性使用寿命，主要研究内容如下：（1）通过以3.5%NaCl溶液为冻融介质的粉煤灰混凝土快速盐冻试验，研究了盐冻循环作用对混凝土损伤的影响规律，分析了钢筋对混凝土盐冻损伤变化的影响。研究了受盐冻粉煤灰混凝土的静弹性模量变化规律，建立了混凝土静弹性模量与盐冻损伤度的关系模型，为盐冻环境钢筋混凝土构件耐久性研究及承载性能评价奠定了基础。（2）开展了受盐冻钢筋混凝土构件氯离子扩散规律的试验研究，，基于冻融作用对粉煤灰混凝土表层结构的影响，研究了盐冻损伤对混凝土中自由氯离子扩散过程的影响规律，建立了氯离子扩散系数与盐冻损伤度的关系模型。基于Fick第二定律，考虑盐冻损伤对混凝土中氯离子扩散的影响，建立了盐冻环境混凝土中氯离子扩散模型，并对建立的氯离子扩散模型进行了工程验证。通过分析钢筋对混凝土中氯离子扩散的阻滞效应，提出了盐冻环境混凝土中钢筋表面氯离子浓度计算方法。（3）通过分析盐冻环境混凝土中钢筋锈蚀过程控制，考虑盐冻损伤对混凝土中氯离子扩散及钢筋锈蚀的影响，建立了盐冻环境混凝土保护层锈胀开裂前钢筋锈蚀速率预测模型，分析了各因素对混凝土保护层锈胀开裂前钢筋锈蚀速率的影响规律，并对该预测模型进行了工程验证。（4）基于盐冻环境混凝土保护层锈胀开裂加速试验研究，分析了混凝土盐冻损伤程度、混凝土保护层厚度与钢筋直径比值等因素对混凝土锈胀开裂形态、开裂时的钢筋锈蚀率的影响。建立了盐冻环境混凝土保护层锈胀开裂时钢筋锈蚀率模型，为盐冻环境下混凝土结构耐久性寿命预测提供了理论依据。（5）开展了盐冻环境锈蚀钢筋混凝土结构耐久性寿命预测研究。通过分析混凝土冻融循环寿命与冻融循环疲劳作用的关系，得出混凝土冻融损伤寿命的概率分布特征，提出了实际冻融环境混凝土耐久性寿命预测方法。通过分析混凝土中钢筋初始锈蚀条件、保护层锈胀开裂条件，基于可靠性理论提出了盐冻环境中混凝土结构钢筋初始锈蚀寿命预测方法与混凝土保护层锈胀开裂寿命预测方法，为混凝土结构耐久性设计提供了参考。
[Abstract]:Durability failure of reinforced concrete structures will lead to huge economic losses and impact on social and economic development. Salt freezing damage to concrete materials caused by irreversible cumulative damage. It will accelerate the permeation and diffusion of corrosive medium in the environment, accelerate the corrosion of steel bar in concrete and the corrosion cracking of concrete protective layer, and affect the normal use of concrete structure. The durability of concrete in salt frozen environment is studied. It has important theoretical significance and engineering value for durability design of new concrete structure engineering and durability evaluation and maintenance of existing concrete structure engineering. In this paper, the reinforced concrete structure in deicing salt environment and marine environment in cold area is taken as the research object, the influence of salt freezing damage on concrete durability is studied, and the durability service life of concrete structure in salt frozen environment is predicted. The main contents of the study are as follows: 1) through rapid salt freezing test of fly ash concrete with 3.5 NaCl solution as freeze-thawing medium, the effect of salt freezing cycle on concrete damage is studied. In this paper, the influence of reinforcement on the change of salt freezing damage of concrete is analyzed. The static elastic modulus of fly ash concrete subjected to salt freezing is studied, and the relation model between static elastic modulus of concrete and damage degree of salt freezing is established. It lays a foundation for durability research and load-bearing performance evaluation of reinforced concrete members in salt-frozen environment. (2) the experimental study on chloride ion diffusion of reinforced concrete members subjected to salt freezing is carried out. Based on the effect of freeze-thaw action on the surface structure of fly ash concrete. The influence of salt freezing damage on the free chloride diffusion process in concrete was studied, and the relationship model between chloride diffusion coefficient and salt freezing damage degree was established based on Fick's second law. Considering the effect of salt freezing damage on chloride diffusion in concrete, a chloride diffusion model in salt frozen concrete was established. Based on the analysis of the effect of reinforcing bar on chloride ion diffusion in concrete, the method of calculating chloride ion concentration on reinforced bar surface in salt frozen concrete is put forward. 3) through analyzing the process control of reinforcement corrosion in concrete in salt freezing environment, considering the influence of salt freezing damage on chloride ion diffusion and reinforcement corrosion in concrete. The prediction model of steel bar corrosion rate before corrosion expansion cracking of concrete cover in salt frozen environment was established, and the influence of various factors on steel bar corrosion rate before corrosion expansion and cracking of concrete cover layer was analyzed. The prediction model is verified by engineering. 4) based on the accelerated test of corrosion expansion cracking of concrete cover in salt freezing environment, the damage degree of concrete salt frost, the ratio of concrete cover thickness to diameter of steel bar and other factors on the form of corrosion cracking of concrete are analyzed. The model of corrosion rate of steel bar in salt frozen environment is established, which provides a theoretical basis for the durability life prediction of concrete structure under salt frozen environment. 5) the durability life prediction of corroded reinforced concrete structures in salt freezing environment is studied. The relationship between freeze-thaw cycle life and freeze-thaw cycle fatigue of concrete is analyzed. The probabilistic distribution characteristics of freeze-thaw damage life of concrete are obtained, and the prediction method of durability life of concrete in freezing and thawing environment is put forward. By analyzing the initial corrosion condition of steel bar in concrete, the condition of corrosion heaving and cracking of protective layer is analyzed. Based on the reliability theory, the prediction method of initial corrosion life of reinforced bars in salt frozen environment and the life prediction method of corrosion cracking of concrete cover are proposed, which provides a reference for the durability design of concrete structures.
【学位授予单位】：西安建筑科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU375

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