Fracture of the reinforcing bars and deterioration mechanism due to Alkali Silica Reaction

碱硅反应引起的钢筋断裂及劣化机理

基本信息

批准号：
17360216
负责人：
KOSA Kenji
金额：
$ 6.62万
依托单位：
Kyushu Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17360216/
关键词：
Concrete Durability Alkali aggregate reaction Reinforcing bar Fracture of reinforcing bar Load-carrying capacity

项目摘要

The following conclusions were drawn from the experiment and analysis focusing on the alkali aggregate reaction :(1) Research on the expansion characteristics of cores sampled from alkali silica reaction (ASR)-affected structuresAnalysis was conducted on 21ASR-affected piers having seriously-deteriorated appearances. Of the 21 piers, six had a core expansion of over 1000×10^6. They showed serious damage exceeding a cumulative crack density of 1m/m^2 or more. Therefore, the core expansion of 1000×10^6 can be used as the reference value for the management and evaluation of deterioration of ASR-affected structures.(2) Quantitative evaluation of ASR damage to actual structuresThe relationship between cracking behavior and compressive strength of cores was obtained from ASR-affected actual structures. It was found that the crack density increased up to 8.0 m/m2, but about 80% of the design compressive strength was retained.(3) Experiment simulating fracture of reinforcing bars due to alkali aggregate reactionsAn experiment simulating ASR expansion was conducted using 1/8 scale specimens modeling actual structures and containing expansion concrete within the specimens. Fracturing of reinforcing bars was well reproduced and the fractured planes showed brittle fracturing similar to that observed in the fractured planes of actual structures. It was also found that the rib shape of reinforcing bars has a significant effect on the crack propagation of those bars. According to the comparison of present bars (8φ) and the former bars (2φ) having different rib shape, cracks caused by concrete expansion propagated for less than 5.0% of the bar diameter in the case of present-reinforcing bars, but that of former reinforcing bars was as large as 80%.

从实验和分析中得出以下结论，重点是碱总反应：（1）对从碱二氧化硅反应（ASR）受影响的结构分析采样的核心的扩展特征进行研究，对受到严重偏置外观的受影响的21ASR影响的托架进行了研究。在21个码头中，有6个核心膨胀超过1000×10^6。他们显示出严重的损害，超过1m/m^2或更多的累积裂纹密度。因此，1000×10^6的核心膨胀可以用作管理和评估受ASR影响结构的确定的参考值。（2）对ASR损伤的定量评估是从ASR影响的实际结构中获得对裂纹行为和核心核心的实际结构关系的定量评估。发现裂纹密度增加到8.0 m/m2，但保留了大约80％的设计压缩强度。（3）通过使用1/8级标本模拟的实际结构和包含扩展的表量在1/8级标本中进行了模拟ASR扩展的实验，模拟了由于碱骨料反应而模拟加强杆的裂缝实验。钢筋的破裂被很好地繁殖，并且骨折的平面显示出与实际结构断裂平面相似的脆性裂缝。还发现，加固条的肋骨形状对这些条的裂纹繁殖具有显着影响。根据当前条（8φ）和以前的条形（2φ）的比较，在现有的固定条的情况下，由混凝土膨胀引起的裂缝散布了不到5.0％的条形直径，但以前的加固棒的裂纹高达80％。