【作者】 吴庆令；

【导师】 余红发；

【作者基本信息】 南京航空航天大学 ， 道路与铁道工程， 2010， 博士

【摘要】 当今世界各国均面临着海工混凝土耐久性不良的严重问题,政府不得不付出大量的“人力物力财力”来维护或加固工程,造成的经济损失巨大,因此研究海洋环境锈蚀混凝土构件的耐久性评估和寿命预测方法,具有重要的社会意义和工程应用价值。本文以海洋区域环境下腐蚀混凝土和锈蚀混凝土构件为研究对象,通过对我国沿海地区的海工混凝土实地调查分析和耐久性试验研究,重点探讨海洋浪溅区、水下区、潮汐区和盐雾区等混凝土耐久性损伤失效过程及其规律,深入分析海工混凝土的损伤劣化过程与劣化机理,包括氯离子扩散规律,混凝土的相对动弹性模量变化、混凝土损伤劣化等规律,混凝土在海水腐蚀、干湿循环等作用下的耐久性评估,最终建立海洋环境下锈蚀钢筋混凝土构件的耐久性预测模型,研究成果可为海洋混凝土结构工程的安全性和耐久性评估提供较重要的依据,为最终实现海工混凝土结构的耐久性设计奠定基础。本文的主要研究内容与结果如下:第一章综述了海工混凝土耐久性与使用寿命预测方法的研究意义和国内外研究动态以及研究进展,指出了当前研究中存在的问题,在此基础上确定了本文的研究方案和研究内容。第二章首先针对氯离子对海工混凝土结构的危害,分析了海工混凝土或海工混凝土结构在我国南北方沿海地区的耐久性和服役寿命,然后探索了海工混凝土中钢筋锈蚀的基本条件、机理及其影响因素;最后探讨了海工混凝土在大气区、水下区、盐雾区、潮汐区与浪溅区的劣化机制;从而为建立与使用环境相适应的海工混凝土使用寿命预测模型奠定了基础。第三章初步优选了几种掺加矿物掺合料混凝土的配合比,试验研究了普通混凝土、高性能混凝土、矿物掺合料混凝土等的制备方法和基本性能。为了研究混凝土材料和钢筋混凝土构件在海洋水下区、潮汐区、浪溅区、大气区以及浪溅区等海洋区域环境中的耐久性异同,重点设计了海工混凝土耐久性的现场暴露试验和实验室模拟试验,包括:(1)混凝土材料在海洋环境中的暴露试验及室内常温海水浸泡的腐蚀试验;(2)钢筋混凝土构件海洋环境中的暴露试验及室内模拟海洋环境的加速试验。第四章模拟海洋水下区、潮汐区、盐雾区和盐雾碳化区,在实验室进行了混凝土材料与钢筋混凝土构件的腐蚀损伤对比试验,并结合现场海洋环境钢筋混凝土构件的非破损检测和对比分析,测定了混凝土的相对动弹性模量和质量损失率,同时观测了试件的外观剥落表征情况,研究了海工混凝土的损伤规律与劣化特性;最后探讨了混凝土材料和混凝土构件的损伤对比。第五章主要在现场暴露试验和实验室模拟试验的基础上,分别测定了混凝土试件不同深度的总氯离子浓度和自由氯离子浓度,深入研究了普通混凝土、高性能混凝土、掺矿物掺合料混凝土在海洋大气区、水下区、潮汐区和浪溅区等海洋区域环境中混凝土的Cl-扩散规律,然后针对不同海洋区域环境和不同混凝土种类,探讨了海工混凝土的氯离子扩散特性。第六章以锈蚀钢筋混凝土构件为研究对象,根据现场海洋区域环境自然暴露法和实验室加速腐蚀法,对锈蚀后钢筋混凝土构件的弯曲承载能力试验结果和破坏形态进行了详尽的分析与探讨;同时建立了基于海洋区域环境的钢筋锈蚀率的分析模型,讨论了矿物掺合料掺量及混凝土强度对钢筋锈蚀率的影响,给出了钢筋锈蚀率与钢筋表面氯离子含量的关系;最后综合考虑钢筋锈蚀率对混凝土构件中钢筋性能和钢筋与混凝土粘结性能的影响,在现行结构设计规范基础上提出了锈蚀钢筋混凝土构件的抗弯承载力评估模型,并与试验结果进行对比验证,结果表明本文提出的锈蚀钢筋混凝土构件的承载力计算评估模型与试验结果有很好的一致性,证明本文建立的评估模型具有较高的使用价值,可以将该模型应用于实际海洋混凝土结构工程中。第七章基于改进的Tuutti模型,分析了海工混凝土结构的破坏过程与使用寿命的定义,研究了基于氯离子侵入的锈蚀海工混凝土构件的2个阶段的使用寿命预测方法,两者相加即为最终的使用寿命。(1)第一阶段:考虑混凝土在海洋Cl-环境使用过程中氯离子扩散系数及其时间依赖性,氯离子结合能力、临界氯离子浓度、混凝土内部初始氯离子浓度和混凝土氯离子扩散性能的劣化效应系数的影响,本文引用了改进的寿命计算模型评估第一阶段寿命。(2)第二阶段:假定寿命为钢筋锈蚀率达到5%经历的时间,这期间因钢筋锈蚀而导致抗弯承载能力下降,致使锈蚀钢筋混凝土的抗弯承载力小于弯矩设计值而失效。当钢筋锈蚀率超过5%时,混凝土与钢筋的粘结力大幅度减少,混凝土结构的耐久性失效,即为海工混凝土第二阶段的耐久性寿命终结标志。最后根据混凝土结构可靠度设计统一标准,初步提出了基于可靠度理论的锈蚀海工混凝土寿命预测模型,并指出可靠度模型的有效性与问题。结果表明,无论是在海洋潮汐区、浪溅区还是水下区中,F20C70混凝土构件的寿命均大于其他混凝土,基本在100a以上。第八章归纳了本文的主要工作和结论,提出了进一步研究的建议。更多还原

【Abstract】 The study of durability evaluation and life prediction method of RC components in marine environments has important social significance and application value. The research object is durability and service life prediction of RC components exposed to marine environments in the thesis. Based on on-the-spot investigation and durability experimental study, durability failure process and its regularity of concretes in marine splash zone, submerged zone, tidal zone and salt-spray zone are discussed. Degradation process and degradation mechanism of marine concretes exposed to seawater are analysis, including chloride ion diffusion law, relative dynamic modulus loss, mass loss. Main contents of each chapter are mentioned as follows:In Chaper 1, durability of concrete exposed to marine environments and service life predicting methods were summarinzed and the research progress are reviewed. Problems remaining to be investigated were also proposed, and on the basis of this study research scheme and content are determined.According to the widely existence of chloride ion in marine environments and its harm to marine concrete, analysis on the durability and service life of RC structures exposed to southern and northern coastal areas in china has been carried out in Chaper 2. Then the basic conditions, mechanism and influencing factors of rebar corrosion in marine concretes are explored. Finally the basic transmission mechanism and degradation mechanism of marine concrete are mainly discussed. Thus it can lay a foundation for establishing life prediction model of concretes exposed to different marine regional environment.In Chaper 3, first preliminarily selected several mineral admixtures mixing proportion of concrete, ordinary concrete, high-performance concrete, and the mineral admixtures concrete methods of preparation and basic properties are briefly introduced. In order to study the durability of the concrete materials and RC components in marine environment, field exposure test and laboratory tests of marine concrete durability and designed, including: (1) field exposure test and indoor temperature soak corrosion test of concrete materials; (2) field exposure test environment and indoor simulation accelerated tests of RC components.In Chaper 4, comparative experiments of concrete materials and RC components are conducted in laboratory by simulating marine environments, and combining with non-destructive detection and analysis, the relative dynamic modulus and mass loss rate are determined, and the spalling appearance of specimens are observed. Damage rules and characteristics of marine concrete are investigated. Lastly, the damage relationship of concrete materials and RC components are studied. In Chaper 5, based on field exposure tests and indoor simulation tests, the total and free chloride ion concentrations at different depth of concrete specimens were measured. Chloride ion diffusion law of concretes exposed to marine environments and the relationship are studied. Then according to different marine environments and different concrete types, the concrete chloride diffusion characteristics are probed into.In Chaper 6, adopting corroded RC components as research object, the test results of bending bearing capacity and the destruction mode of RC components are analyzed and discussed according to the natural exposure method in field marine environment and the accelerated corrosion in laboratory. Meanwhile, based on marine regional environment, an analytical model of rebar corrosion rate is established, and the influencing of mineral admixture on rebar corrosion rate is discussed, also the relationship between rate corrosion rate and steel surface chlorine ion concentration is given. Finally, considering the influence of rebar corrosion rate on performance of rebar and stick performance of rebar and concrete, the flexural capacity evaluation model of corroded RC components is put forward based on current structure design codes, and the model has clear concept, wide serviceability and more reasonable. Furthermore, the results show that there is a good agreement between measured value and calculated value, which indicates that the evaluation model has high value; it can be applied to reality RC engineerings.In Chaper 7, based on the residual life of rust RC structure, analyzes the research status of the damage process of RC are analyed, and the definition of service life are given, then put forward the service life prediction model of two stages. (1)The first stage: On the basis of Khatri’s model, an improved model for calculating service life of marine concrete is proposed. Influencing factors of chloride diffusivity, chloride binding capacity, critical chloride concentration, structural defects are taken into consideration. The result from the improved model is in good agreement with those of Clear’s experimental model. (2)The second stage: definite the bearing capacity drops to certain scope as the end mark of the durability life of corroded RC components. After derived, when rebar corrosion rate from 0 to 5%, t corcan be calculated.A summarization of this main work and conclusions was presented in chapter 8. Suggestions for further researches were put forward.更多还原