除冰盐冻融作用下混凝土界面粘结强度与界面过渡区细观力学性能的关系

Relationship Between Bond Strength of Concrete Interface and Meso-mechanical Properties of Interface Transition Zone Under Freezing-thawing Action of Deicing Salt

界面过渡区(Interfacial transition zone, ITZ)是混凝土内部结构的薄弱环节,也是外界侵蚀性离子向内扩散渗透的通道。通过除冰盐快速冻融实验研究了在除冰盐冻融环境下混凝土界面宏观和细观力学性能的变化规律。结果表明,混凝土粗骨料与砂浆的界面粘结强度和ITZ显微硬度在盐冻过程中均呈现出典型的两段式线性变化,即随着盐冻循环次数增加而增强的初始强化阶段和随着盐冻循环次数增加而降低的后期劣化阶段;初始界面粘结强度或ITZ显微硬度随着水胶比的增大而减小,初始强化速率减慢,后期劣化速率加快,且低水胶比的混凝土有着较好的抗盐冻性能;盐冻过程中混凝土粗骨料和砂浆的界面粘结强度与ITZ显微硬度之间具有较明显的相关性。此研究结果为盐冻环境下混凝土细观力学分析提供了基础数据。

Interfacial transition zone(ITZ)is the concrete internal structure of the weak link,it is also a channel for external erosive ions to diffuse and penetrate inward.In this work,the macroscopic and meso-mechanical properties of concrete interface under freezing-thawing environment of deicing salt were studied by rapid freezing-thawing experiment.The results show that the interface bond strength and ITZ microhardness of concrete aggregate and mortar show a typical two-stage linear change during the salt freezing process.The initial strengthening stage increased with the increase of salt freezing cycles and the later deterioration stage decreased with the increase of salt freezing cycles.The initial interface bond strength or ITZ microhardness will decrease with the increase of water-binder ratio,the initial strengthening rate will slow down,and the later deterioration rate will accelerate.The concrete with lower water-binder ratio has better salt freeze resistance.There is an obvious correlation between the bonding strength and ITZ microhardness of coarse aggregate in concrete during salt-freezing process.It provides basic data for meso-mechanical analysis of concrete in salt-frozen environment.