题目：混凝土碱硅反应-在纳米尺度中的新发现
Alkali Silica Reaction – Recent Findings at Nanoscale.
时间：2021年12月24日周五10：00－11：00
地点：腾讯会议 ID：42265298356
腾讯直播间：https://meeting.tencent.com/l/QALGLWoVMAcS
报告人：耿国庆（新加坡国立大学，土木与环境工程系）
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土木与交通学院
2021年12月22日
报告人简介：
耿国庆老师于2010年在东南大学获得学士学位，随后分别于2013年和2017年在加州大学伯克利分校土木与环境工程系（CEE）获得硕士和博士学位，研究领域为胶凝材料的微观化学和矿物学。他获得了Paul Scherer研究所（瑞士）的博士后奖学金，期间研究了混凝土作为建筑材料和支撑放射性废料材料的耐久性。自2019年以来，耿老师在新加坡国立大学土木与环境工程系任助理教授，成立课题组，专注于建筑材料的可持续性和基于性能的设计，以及预测和提高建筑材料的长期耐用性等方面的研究。耿老师是美国混凝土学会新加坡分会、新加坡混凝土学会的成员，同时也是RILEM东亚区召集人和技术委员会成员。
Dr. Guoqing Geng received his PhD degree in Department of Civil and Environmental Engineering (CEE) of UC Berkeley in 2017, with research interests on the microscale chemistry and mineralogy of cementitious materials. He was awarded a postdoctoral fellowship in Paul Scherer Institute (Switzerland), where he studied the durability of concrete both as a construction material and hosting material for radioactive wastes. Since 2019, Dr. Geng leads a research group in CEE of National University of Singapore and focuses on the sustainability and performance based designing of construction materials, as well as predicting and enhancing their long-term durability. He is a board member of the American Concrete Institute – Singapore Chapter, Singapore Concrete Institute. He is also the East Asian Region Convener and technical committee members of RILEM.
报告摘要：
碱硅反应(ASR)引起的劣化显著缩短了混凝土基础设施的使用寿命。越来越多的微观形态证据揭示了骨料内部反应产物的纳米片形貌，表明它与在骨料和水泥浆之间的界面附近观察到的非晶态ASR 产物相比，具有结晶性。然而，这种晶状ASR产物的晶体结构和性质尚未得到充分研究。本次报告中，耿老师将总结其课题组使用基于同步加速器的微X射线吸收光谱(micro-XAS)、高压XRD (HP-XRD)以及层析micro-XRD对ASR产物进行研究的最新发现。他们首次证明了结晶ASR产物中钾和钙的化学环境类似于它们在天然矿物石板岩中的化学环境。X射线衍射数据进一步验证了它们的结构相似性。他们确定了结晶ASR产物各向相异的不可压缩性，以及它们的体积模量。他们还揭示了结晶ASR的膨胀并不能解释微观尺度的 ASR 损伤。这些研究结果为了解ASR产物的形成，和损伤过程的多尺度力学建模提供了参考。
Deterioration induced by alkali silica reaction (ASR) significantly shortens the service life of concrete infrastructure globally. Increasing micro-morphological evidences have unveiled the nano-platy morphology of the reaction product inside the aggregate, indicating its crystalline nature in contrast to the amorphous ASR product observed adjacent to the interface between aggregate and cement paste. However, the crystal structure and the property of this crystalline ASR product have not been sufficiently investigated. The presentation is a summary of our recent findings about the ASR product using synchrotron-based micro X-ray absorption spectroscopy (micro-XAS) and high pressure XRD (HP-XRD), and tomographic micro-XRD. For the first time, we demonstrated that the chemical environment of K and Ca in the crystalline ASR products resembles that in the natural mineral shlykovite. Their structural similarity is further validated by the comparable X-ray diffraction data. We determined the anisotropic incompressibility of the crystalline ASR products, as well as their bulk modulus. We also revealed that the swelling of crystalline ASR does not provide an explanation to the ASR damage at microscale. The results provide fundamental input for understanding the formation of the ASR product, and for multi-scale mechanical modeling of the damage process.
