Evaluation of transport properties of deteriorated concrete due to calcium leaching with coupled CT image analysis and random walk simulation
Evaluation of transport properties of deteriorated concrete due to calcium leaching with coupled CT image analysis and random walk simulation
复制标题
通过耦合 CT 图像分析和随机行走模拟评估钙浸出导致的劣化混凝土的传输特性
DOI：
10.1016/j.conbuildmat.2023.130526
复制
发表时间：
2023
影响因子：
7.4
通讯作者：
Katsufumi Hashimoto
中科院分区：
文献类型：
--
作者：
Yingyao Tan;Takafumi Sugiyama;Katsufumi Hashimoto
由于钙离子的浸出，混凝土长期与水接触可能会变质。本研究采用直径3mm、高6mm的微小圆柱形试样对钙离子进行自然扩散试验，测定在20℃和80℃条件下33天的浸出情况。在每个试样中插入一块石灰石作为骨料，以研究界面过渡区（ITZ）的影响。采用同步加速器x射线计算机断层扫描（CT）以微米为单位对大块水泥膏体中浸出和非浸出区域的传质变化进行了评估。在高温浸出试验中，观察到Ca(OH)2在试样内部有较深的溶解前缘。通过随机游走仿真得到扩散参数。结果表明，未变质ITZ区钙离子扩散系数约为未浸出区钙离子扩散系数的10倍。在20℃和80℃时，浸出区扩散系数分别约为非浸出区扩散系数的50倍和100倍。此外，在聚集体靠近或暴露于溶解前沿的方向，由于ITZ作用，Ca(OH)2溶解前沿在试样内部出现更深。
Concrete may deteriorate when chronically in contact with water due to the leaching of calcium ions. This study conducted a natural diffusion test for calcium ions with a minute cylindrical specimen of 3 mm in diameter and 6 mm in height to determine leaching at 20 and 80 °C in 33 days. One piece of limestone as aggregate was inserted inside each specimen to investigate the effect of the interfacial transition zone (ITZ). Changes in mass transfer in the leaching and non-leaching regions in bulk cement paste were evaluated using synchrotron X-ray computed tomography (CT) in a micrometer order. A deeper dissolution front of Ca(OH)2inside the specimen was observed for a higher temperature leaching test. Random walk simulation was performed to obtain diffusion parameters. Results showed that the calcium diffusion coefficient of non-deteriorated ITZ is about ten times as high as that of the non-leaching region. For the leaching region, the diffusion coefficient is about 50 times and 100 times as high as that of the non-leaching region at 20 °C and 80 °C, respectively. In addition, the Ca(OH)2dissolution front appeared deeper inside the specimen in the direction where aggregate is close or exposed to the dissolution front because of ITZ.