摘 要
冻融循环作用是影响混凝土耐久性的关键环境因素之一，尤其在寒冷地区对基础设施的长期性能构成严重威胁。本文旨在系统分析冻融循环下混凝土耐久性退化机理，揭示其微观结构演化与宏观性能衰减之间的内在联系。通过设计多轮次冻融试验，结合超声波测试、质量损失率、相对动弹性模量等指标评估混凝土性能变化，并利用扫描电子显微镜（SEM）和X射线衍射（XRD）技术观察微观结构演变。研究结果表明，随着冻融次数增加，混凝土内部微裂缝逐渐扩展，孔隙率显著上升，导致密实度下降和力学性能劣化；同时，水泥石中氢氧化钙等成分发生分解，进一步削弱界面过渡区稳定性。本研究的创新点在于构建了基于多尺度观测的耐久性退化模型，实现了从宏观性能到微观机制的系统映射，为评估和预测混凝土在严寒环境下的服役寿命提供了理论依据和技术支撑。研究成果对于提升寒区工程材料的耐久性设计水平具有重要应用价值。
关键词：冻融循环；混凝土耐久性；微观结构演化；性能退化模型；多尺度观测
ABSTRACT
Freeze-thaw cycling is one of the key environmental factors affecting the durability of concrete, particularly posing a serious threat to the long-term performance of infrastructure in cold regions. This study aims to systematically analyze the mechanisms of durability degradation in concrete under freeze-thaw cycles and to reveal the intrinsic relationship between microstructural evolution and macroscopic performance deterioration. Through multi-cycle freeze-thaw experiments combined with ultrasonic testing, mass loss rate, and relative dynamic elastic modulus as evaluation indicators, this research assesses changes in concrete properties, while employing scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques to observe microstructural evolution. The results indicate that with an increasing number of freeze-thaw cycles, internal microcracks in concrete gradually expand and porosity rises significantly, leading to reduced density and degradation of mechanical properties. At the same time, components such as calcium hydroxide in the cement paste undergo decomposition, further weakening the stability of the interfacial transition zone. The innovation of this study lies in constructing a durability degradation model based on multi-scale observation, achieving a systematic mapping from macroscopic performance to microscopic mechanisms, thereby providing theoretical foundations and technical support for evaluating and predicting the service life of concrete in harsh cold environments. The findings of this research hold significant application value for improving the durability design standards of engineering materials used in cold regions.
Keywords: Freeze-Thaw Cycles; Concrete Durability; Microstructure Evolution; Performance Degradation Model; Multi-Scale Observation
目 录
摘 要 I
ABSTRACT II
第1章 绪论 2
1.1 研究背景和意义 2
1.2 研究现状 2
1.3 本文研究方法 2
第2章 冻融循环作用下混凝土内部损伤演化特征 4
2.1 混凝土孔隙结构在冻融循环中的变化规律 4
2.2 冻融引起的微观裂缝扩展机制分析 4
2.3 冻融对混凝土界面过渡区的影响研究 5
第3章 冻融循环对混凝土力学性能的退化影响 2
3.1 冻融循环后混凝土抗压强度的变化趋势 2
3.2 抗拉与抗折性能在冻融环境下的退化规律 2
3.3 力学性能退化与损伤累积的关系模型 3
第4章 冻融循环与其他环境因素耦合作用下的耐久性退化 4
4.1 冻融-盐侵蚀耦合作用下的混凝土劣化机理 4
4.2 冻融-碳化协同作用对混凝土耐久性的影响 4
4.3 多因素耦合环境下混凝土耐久性的综合评估方法 5
结论 6
参考文献 7
致 谢 8
