不同类盐蚀对混凝土的宏-细观损伤机理

发布时间：2018-05-19 20:26

本文选题：混凝土 + 盐蚀　；参考：《吉林大学》2017年硕士论文

【摘要】：混凝土遭受盐类侵蚀是引起混凝土结构失效的一种耐久性破坏方式。在不同类盐蚀作用下,混凝土构筑物往往在远未达到设计使用年限的情况下就失效破坏,其服役期工作性能也大幅降低,这必将严重制约水泥基复合材料在侵蚀性环境中的实际工程应用。在我国东北盐渍土地区、西北盐湖地区以及东南沿海地区,混凝土结构受到盐渍土、侵蚀性地表水以及海水侵蚀,导致混凝土结构发生耐久性破坏的工程实例已经屡见不鲜。这些区域混凝土构筑物受耐久性破坏的侵蚀性离子主要是SO42-、Cl-和HCO3-离子。不同类盐蚀引起混凝土细观损伤、结构性能劣化、耐久性破坏的作用机理和效果截然不同,因此开展混凝土受不同盐类侵蚀的宏-细观损伤机理研究是混凝土结构耐久性研究中亟待解决的科学问题,具有十分重要的研究前景。在实际工程结构中,由于混凝土内部结构孔隙的存在,各种盐离子的侵蚀渗入会对其物理力学性能产生巨大影响。侵蚀环境中混凝土的细观结构变化决定了混凝土宏观的物理力学性能,由于盐类随水分在混凝土内部迁移、析出、结晶、膨胀导致混凝土细观结构破坏,从而引起宏观的耐久性破坏,故必须将宏观物理现象和细观结构损伤联系起来进行研究。本文依托国家自然科学基金重点项目(41430642)、国家自然科学基金青年项目(51108207)、中国博士后科学基金项目(2015M581403)和冻土工程国家重点实验室开放基金(SKLFSE201514)的资助,针对东北盐渍土地区独特的土壤环境,首次将碳酸氢根作为混凝土主要的侵蚀性离子,进行了碳酸氢盐侵蚀下的混凝土宏-细观损伤机理研究。通过混凝土受SO42-、HCO3-侵蚀的干湿循环试验、长期浸泡试验和SEM试验,将宏观物理力学性能与细观结构分析相结合,对不同类盐蚀混凝土的宏-细观损伤机理进行深入分析。试验考虑的影响因素包括侵蚀性阴离子类别、侵蚀溶液浓度、混凝土水胶比、侵蚀时间、含气量等,在试验中观测混凝土相对动弹性模量、质量损失等指标。通过试验分析,混凝土结构处于侵蚀性土壤与空气交界面或侵蚀性地下水及地表水与空气交界处侵蚀破坏最严重。复合盐(SO42-和HCO3-)对混凝土的耐久性破坏最严重,SO42-对混凝土的耐久性破坏次之,HCO3-最弱。拟合得出了干湿循环环境中混凝土相对动弹性模量与侵蚀时间之间的函数关系,从而能够对盐蚀环境下混凝土材料的寿命进行有效预测。另外,通过大量SEM试验,对单盐侵蚀及复合盐侵蚀状态下的混凝土的细观结构损伤进行了研究,并将受盐蚀混凝土的宏观物理力学性能与细观结构分析相结合,为揭示混凝土结构受盐类侵蚀破坏的本质做了有益尝试。
[Abstract]:Salt erosion of concrete is a kind of durability failure mode that causes failure of concrete structure. Under the action of different kinds of salt corrosion, concrete structures often fail and destroy under the circumstances of far less than the design life, and the service performance of concrete structures is also greatly reduced. This will seriously restrict the practical engineering application of cement-based composites in erosive environment. In the saline soil area of northeast China, the northwest salt lake area and the southeast coastal area, the concrete structure has been eroded by saline soil, erosive surface water and sea water, which has caused the durability damage of concrete structure. The erosive ions of concrete structures in these regions are mainly so _ 42-O _ (Cl-) and HCO _ 3- ions. The mechanism and effect of concrete meso-damage, structural performance deterioration and durability damage caused by different kinds of salt corrosion are very different. Therefore, it is an urgent scientific problem to study the macro-meso damage mechanism of concrete subjected to different salt erosion, which has a very important research prospect. In practical engineering structures, the physical and mechanical properties of concrete are greatly influenced by the erosion and infiltration of various salt ions due to the existence of pores in the internal structure of concrete. The macroscopic physical and mechanical properties of concrete are determined by the variation of the meso-structure of concrete in the erosive environment. Because the salts migrate, precipitate, crystallize and expand with the water in the concrete, the micro-structure of the concrete is destroyed. So it is necessary to study the macroscopic physical phenomena and the damage of mesoscopic structures. This paper relies on the support of the key projects of the National Natural Science Foundation of China 41430642U, the Youth Project of the National Natural Science Foundation of China 51108207U, the China Post-doctoral Science Foundation Project (2015M581403) and the State key Laboratory of Frozen soil Engineering (SKLFSE201514). In view of the special soil environment in the saline soil area of Northeast China, the mechanism of macro- meso-damage of concrete under bicarbonate erosion was studied by using bicarbonate as the main corrosive ion of concrete for the first time. Through dry-wet cycle test, long-term immersion test and SEM test of concrete corroded by so _ 42-HCO _ 3-, macroscopical physical and mechanical properties were combined with meso-structure analysis to deeply analyze the macro-meso-damage mechanism of different kinds of salt corroded concrete. The influencing factors considered in the experiment include the category of erosive anions, the concentration of erosive solution, the ratio of water to binder of concrete, the time of erosion and the amount of air. The relative dynamic modulus of elasticity and mass loss of concrete are observed in the test. Through experimental analysis, the erosion damage of concrete structure is the most serious at the interface between soil and air or erosive groundwater and the interface between surface water and air. Composite salt so _ 42- and HCO _ 3) have the most serious durability damage to concrete (so _ 42-) and HCO _ 3- is the weakest. The functional relationship between the relative dynamic elastic modulus and the erosion time of concrete in dry-wet cycle environment is obtained, which can effectively predict the life of concrete materials under salt corrosion environment. In addition, through a large number of SEM tests, the microstructural damage of concrete under the condition of single salt erosion and complex salt erosion is studied, and the macroscopic physical and mechanical properties of the concrete subjected to salt corrosion are combined with the meso-structure analysis. A useful attempt has been made to reveal the nature of concrete structure damaged by salt erosion.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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