【作者】 范宏；

【导师】 赵铁军； F H Wittmann；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2009， 博士

【摘要】 氯离子侵蚀是导致混凝土结构发生耐久性破坏的最主要原因,对氯离子扩散性能的研究是目前国内外研究的重点问题。本文基于使用环境,针对长期暴露混凝土结构的氯离子侵入性能,在以下几个方面做了探索性和创新性研究工作:（1）对青岛市现存钢筋混凝土结构的耐久性状况进行了调查,对暴露环境和混凝土结构耐久性能进行了分析。结果表明,引起钢筋混凝土结构耐久性失效的原因存在于结构设计、施工及维护的各个环节。在结构使用过程中,未进行合理维护所造成的结构耐久性降低是不容忽视的。（2）通过对典型工程钻芯取样和实验室化学分析,对氯离子环境下混凝土结构由于材料因素和环境因素导致的耐久性不足的原因进行了分析和讨论。研究表明,实际暴露混凝土中氯离子的分布存在不同形态;表面氯离子浓度差异较大,由氯离子浓度曲线外推得到的理论上的表面氯离子浓度比较稳定;局部环境对氯离子侵入有十分显著的影响;经过二十多年时间暴露的普通硅酸盐水泥混凝土的氯离子扩散系数在10^-13m²/s数量级;氯离子的扩散性能在混凝土表层和内部存在明显差异。（3）海洋环境下,混凝土碳化十分有限,混凝土的碳化区以部分碳化区为主。处在浪溅区和潮汐区长期暴露的混凝土结构,混凝土表层发生碳化的深度不超过12mm,虽然化学分析表明存在钙的溶出,但混凝土碳化和表层盐结晶堵塞了混凝土表面区域的毛细孔,使混凝土表层的孔隙率减小,对氯离子的侵入有阻碍作用。（4）采用氯离子分布曲线法、自然浸泡法、RCM法、自然扩散室等方法对实际混凝土结构和实验室混凝土的氯离子扩散性能进行了评价。RCM法得到的扩散系数比较高,扩散室法与自然浸泡试验的结果比较接近和适中,氯离子分布曲线拟合法得到的扩散系数最低,与RCM法得到的结果相差在十倍以上,且低于对比试验和海边暴露试验的数值。在海洋浪溅区,长期暴露的普通硅酸盐水泥混凝土氯离子扩散系数的衰减指数α为0.525,该指数不仅受水化作用控制,而且受环境因素的影响。（5）以不同试验方法获得的氯离子扩散系数对混凝土结构进行寿命预测,得到的结果有显著差异;实验室混凝土和实际暴露混凝土的氯离子扩散系数衰减指数差异明显;对氯离子扩散系数的衰减进行评价时,不仅应考虑水化因子还应考虑环境因子;氯离子扩散在空间上可划分为对流区和扩散区进行评价。（6）探讨了氯离子环境下混凝土结构耐久寿命影响因素的概率分布特征,分析了耐久可靠性的发展规律。建立了考虑氯离子扩散系数空间差异性和时间依赖性的基于可靠度的寿命预测模型。通过具体的算例和与其它模型的比较,阐述了这一方法的有效性和实用性。本文通过实验室试验、现场暴露试验和长期暴露的混凝土结构钻芯取样对氯离子在混凝土结构中的扩散性能进行了评价;研究了不同因素对氯离子侵入的影响;建立了实验室耐久性指标与实际暴露结构性能指标之间的定量关系;建立了考虑氯离子扩散系数时间、空间依赖性的基于可靠度的寿命预测模型,为氯离子环境下混凝土结构的耐久性设计提供了理论基础和具体方法。更多还原

【Abstract】 Chloride is the most important cause which induces damage to the durability of concrete structures.Chloride diffusion properties are currently the focus of the investigation at home and abroad.This paper carries on the exploratory and innovative research work in the following areas:1) The of durability of existing reinforced concrete structures in Qingdao City were investigated,the exposure condition and the durable performance of concrete structures were analyzed.Results show that factors inducing durability degradation for reinforced concrete structures exist in design,construction and maintenance.At the process of using construction,the fact that durability of the structure will be are reduced by scarce of reasonable maintenance should not be ignored.2) The insufficient of durability for concrete structure under chloride environment induced by material and environmental factors were analyzed and discussed.Results show thatthe forms of chloride profiles are different in actual exposure conditions,the surface chloride concentration of concrete in theory obtained by extrapolation from chloride profile are relatively stable,local environment has significant impact on chloride ingress,the chloride diffusion coefficient is in the order of 10^-13m²/s magnitude to normal portland cement concrete after more than two decades exposure,significant differences of the diffusion property exist in inner and outer region of concrete.3) Under marine environment,the carbonation is very limited and the carbonation is dominated by incomplete carbonation zone.Depth of carbonation in the surface layer of concrete is not exceeding 12mm to concrete construction in splash and tide zone. Although chemical analysis shows that leaching of calcium exist,salt crystallization and carbonation block the pores in surface area of concrete induce the decreasing of porosity and reduce the chloride ingress.4) The diffusion properties of actual concrete structure and laboratory concrete were evaluated by methods of chloride profiles fitting,natural immersion,RCM and diffusion sell.Diffusion coefficient obtained by RCM is the highest,and that of natural immersion and natural diffusion sell are moderate and similar;the value of diffusion coefficient obtained by fitting is the lowest,which is ten times less than the result of RCM method and lower than which obtained by laboratory test and exposure test at seashore.The attenuation index of chloride diffusion coefficient is 0.525 to ordinary portland cement concrete after long-term exposure in splash zone5) Significant differences exist in life prediction with chloride diffusion coefficient obtained from different methods.Obvious differences exist in attenuation index of diffusion coefficient to concrete in laboratory and exposed conditions.Not only the hydration but also environmental factors should be considered when evaluate changes of the chloride diffusion coefficient.Differences of diffusion coefficient in space should be considered and concrete should be divided into diffusion zone and convection zone. Characteristics of probability distribution of influencing factors to durable life of concrete structures under chloride environment were explored.The law of development of durable reliability was analyzed.The life prediction model under chloride ion environment was set up in considering differences in space and time-dependent of the chloride ion diffusion coefficient.Effectiveness and practicality of this method was expounded through specific example and comparing with other models.The diffuse performance of chloride ions in concrete structures were evaluated though laboratory test,exposing test and cores drilling from concrete after long time exposing. The quantitative relationship between durability indexes in laboratory and performance indexes of actual exposure construction was established.Life prediction model based on reliability was set up in considering time and spatial dependence of the chloride ion diffusion coefficient.Theoretical basis and specific methods for the durability design and construction of concrete structure under chloride environment were provided.更多还原