荷载与氯离子耦合作用下混凝土耐久性试验方法与装置的研究进展

Research Progress of Concrete Durability Testing Method and Device Under the Coupling Effect of Load and Chloride Ion

20世纪20年代初,随着设计理论和施工技术的不断成熟,钢筋混凝土开始被大规模应用于基础建设中。钢筋混凝土兼具钢与混凝土的优点——坚固又耐用,但是人们却低估了环境因素对它的影响并为此付出了巨大的代价,氯离子、碳化、冻融、硫酸盐、化学侵蚀等环境因素均可导致钢筋混凝土的耐久性劣化。其中,氯离子引起的钢筋锈蚀问题最为突出,空气或水中的氯离子可穿透混凝土保护层到达钢筋表面,从而引起钢筋锈蚀。针对这一问题,学者们集中研究了氯离子如何穿透混凝土,并取得了相当丰硕的成果。然而,服役中的钢筋混凝土需时刻承受荷载的作用,复杂的应力状态会引起混凝土材料内部细观结构的变化,从而影响甚至改变氯离子的扩散行为。上述研究忽略了荷载因素,难以应用于实际工程。此外,氯离子扩散行为还与应力在材料内累积的损伤有关。因此,近年来,荷载与氯离子侵蚀耦合的耐久性研究越来越受到重视,且已成为重大工程项目中不可缺少的一部分。针对实际工程中钢筋混凝土的荷载形式,研究人员开发了大量耦合试验方法与装置,较为成熟的有单轴拉伸、单轴压缩、静力弯曲分别与氯离子耦合。但研究人员在运用上述方法时所采用的实验制度不同,导致其结果没有可比性。此外,还有部分研究人员探索了更为复杂的耦合因素(劈裂拉伸、偏心压缩、疲劳弯曲、静力剪切分别与氯离子耦合),复杂耦合因素更符合实际工程状态,也是近年来研究的趋势,但关于它的研究仍处在起步阶段。本文归纳了拉伸、压缩、弯曲、剪切荷载作用下混凝土的抗氯离子侵蚀耐久性试验方法,对存在的问题进行了讨论,并提出了改进建议和进一步的研究方向,以期为制定统一、标准化的耦合耐久性试验方法与装置提供参考。

In the early 1920 s,with the development of design theory and construction technology,reinforced concrete began to be widely used in infrastructure construction. Reinforced concrete combined the advantages of both steel and concrete-strong and durable. However,the impact of environmental factors was underestimated and a huge price was paid for it. Environmental factors such as chloride ion,carbonization,freezethaw,sulfate,chemical erosion and so on can lead to deterioration of reinforced concrete durability. Amongst,chloride induced steel corrosion is the most prominent in all durability problems. In air or water,chloride ion can penetrate the protective layer of concrete and reach the reinforcing bar’s surface,causing corrosion. A large number of theoretical and experimental studies focused on describing chloride ion penetration through concrete,and achieved considerable results.However,the in-service reinforced concrete bears load all the time,complex stress state causes the internal meso-structure change of concrete materials,and affects or even changes the diffusion behavior of chloride,the above study of chloride ion diffusion neglecting the load factors,which makes it difficult to transform the above research results from laboratory to practical engineering. In addition,the chloride ion diffusion behavior is also related to the cumulative damage of stress history. Therefore,in recent years,more and more attention has been paid to the durability study about the coupling of load and chloride ion,and it has become an indispensable part of major engineering projects.According to the load state in practical projects,researchers have developed a large number of coupling test methods and devices. The relative mature ones are uniaxial tension,uniaxial compression and static bending,coupled with chloride respectively. However,different experimental details used by different researchers lead to incomparable experimental results. Besides,some researchers have explored more complex coupling factors( splitting tension,eccentric compression,fatigue bending,static shear coupled with chloride respectively). Complex coupling factors are more similar with the practical projects,and are also the trend of recent research,but they are still in the initial stage.In this paper,the test methods of chlorideion corrosion resistance of concrete under tension,compression,bending and shear loads are summarized. The existing problems are discussed,suggestions for improvement and directions for further study are put forward,in order to provide reference for formulating unified and standardized coupling durability test methods and devices.