冻融循环下混凝土细观结构演化及力学损伤特性研究进展

Review of Meso-structural Evolution and Mechanical Damage Characteristic of Concrete Subjected to Freeze-thaw Cycles

周期性冻融循环会对季冻区混凝土材料的细观结构产生不可逆损伤,进而劣化其承载能力与耐久性能。混凝土的冻融破坏本质上是内部孔/裂隙等初始缺陷在周期性冻胀力的作用下发生的疲劳损伤累积。因此,开展冻融循环条件下混凝土材料细观结构损伤演化特性的研究对于评估寒区在役混凝土结构的安全性具有重要的意义。围绕冻融循环条件下混凝土细观结构演化及力学损伤特性两个核心内容,针对混凝土细观结构获取与表征技术、混凝土冻融循环室内物理试验与数值模拟方法,以及混凝土力学损伤特性与耐久性评估等方面的研究现状进行了系统的总结与分析。传统的冻融研究主要集中于宏观尺度下混凝土局部损伤演化,从细观尺度入手,研究了冻融循环下混凝土细观结构演化与力学损伤特性,有助于更加深入地了解宏观力学性能与耐久性劣化背后的冻融破坏机制与初始孔/裂隙缺陷扩展-聚并-贯通的发展规律。在此基础上,建立考虑冻融参数的细观结构演化与宏观损伤特性之间的内在联系,实现冻融环境下混凝土材料宏观物理力学特性的准确分析。为寒区工程结构服役期的损伤特性识别、稳定性与耐久性分析提供参考。

In seasonally frozen areas,the bearing capacity and durability of the concrete could be deteriorated with irreversible damage of the meso-structure under the periodic freeze-thaw cycles.The freeze-thaw damage of concrete is essentially the accumulation of fatigue damage caused by initial defects including internal pores and cracks under the action of periodic frost heave force.Therefore,it is of great significance to evaluate the safety of in-service concrete structures in cold regions by studying the damage evolution characteristics of the meso-structure of concrete under freeze-thaw cycles.The meso-structure evolution and mechanical damage characteristics of concrete under freeze-thaw cycle were main concerns.The research status of meso-structure acquisition and characterization technologies,laboratory physical test and numerical simulation approaches of concrete under freeze-thaw cycles,and mechanical damage characteristics and durability evaluation were systematically summarized and analyzed.Previous studies mainly focused on the local damage evolution of concrete at the macro-scale.The meso-structure evolution and damage characteristics of concrete under freeze-thaw cycles were studied from the meso-scale.In this way,the freeze-thaw failure mechanism behind the macro-mechanical properties and durability deterioration could be deeply analyzed,as well as the development law of the propagation,coalescence and penetration of the initial defects of pores and cracks.Furthermore,the inherent relationships between the meso-structure evolution and the macroscopic damage characteristics considering the different freeze-thaw cycle parameters could be established.Finally,the accurate analysis and prediction of the macroscopic physical and mechanical characteristics of concrete materials under the freeze-thaw environment could be achieved.A reference of the identification of damage characteristics,stability and durability analysis of engineering structures in cold regions during service could be provided by the correlational research.