冻融环境下钢筋混凝土间粘结界面的显微结构

Microstructure of Bonding Interface Between Reinforcement and Concrete in Freeze-thaw Environment

为了分析冻融环境对钢筋与混凝土间粘结界面显微结构的影响,利用扫描电镜对取自冻融作用前后钢筋周围不同位置处的界面样品进行了观察,并通过宏观力学试验验证了粘结性能随冻融作用的退化规律。研究结果表明:冻融作用对粘结界面的显微结构和力学性能有很大影响,且影响效果与界面相对于钢筋位置有关。原本较为致密的钢筋顶部界面区内出现了细小的冻胀裂纹,而比较酥松的钢筋底部界面区内进一步生长出取向程度更高的凝胶体。粘结界面显微结构的变化导致钢筋混凝土间宏观粘结性能不断退化,具体体现于粘结强度不断损失和粘结破坏形式的劣化。

Influence of freeze-thaw action on the microstructure of bonding interface between reinforcement and concrete was studied by means of SEM. The morphologies of interfacial samples taken from different regions around reinforced rebar were observed. Further, bond deterioration between reinforcement and concrete resulted from freeze-thaw action was verified by means of pullout test. The results show that there are obvious effects of freeze-thaw environment on the microstructure and mechanical properties of bonding interface, and the influence depends on the location of bonding interface around the rebar. Due to freeze- thaw action, some fine cracks appear in the initial compact interface near the top of rebar, on the other hand, a new hydrated layer with more orientation develops from the initial loose interface near the bottom of rebar. Therefore, the deterioration of bonding properties of reinforced concrete results in the degeneration of microstructure of bonding interface, and the loss of bond strength attributed to freeze-thaw action, as well as the degradation of bond failure mode.