Nanoscale Characterization of Expansion Due to Delayed Ettringite Formation

这项研究的主要目的是研究晚龄期钙矾石形成的纳米和微观机制，以及这些机制如何与混凝土材料的宏观膨胀相关，从而实现可能的缓解钙矾石晚龄期形成造成的损害的策略。这项研究将考察反应物和产物的化学和物理结构以及孔结构的演变，这些结构涉及到晚期钙矾石的形成和随后的膨胀和破裂过程。通过纳米压痕和残余应力分析等分析技术改进现有的模型，可以更彻底地理解微观结构上的结晶压力。混凝土是世界上应用最广泛的工程材料，但在许多方面仍然缺乏了解。防止钙矾石延迟形成会导致混凝土开裂，这将显著提高美国和国外的基础设施寿命。教育活动将包括前往当地的初中和高中提供动手实验，让学生真实地了解工程是如何成为现代世界的重要组成部分。当地的小学团体将被邀请到校园参加田纳西理工S STEM中心的实践学习体验。除教育活动外，还提议在项目结束时举办一个残余应力分析讲习班，向其他水泥和混凝土研究人员传播田纳西理工学院在这一领域的强大背景；从而扩大到传统的K-12外联范围。

The primary objective of this research is to investigate the nano- and micro-scale mechanisms of late age ettringite formation and how these mechanisms relate to macro-scale expansion in concrete materials, enabling possible mitigation strategies for damage due to the late age formation of ettringite. This research will examine the chemical and physical structure of the reactants and products, as well as the pore structure evolution, involved in the process of late age ettringite formation and subsequent expansion and cracking. A more thorough understanding of the crystalline pressures induced on the microstructure will result by refining existing models with analytical techniques such as nanoindentation and residual stress analyses.Concrete is the most widely used engineering material in the world, yet is still poorly understand in many regards. The prevention of delayed ettringite formation, which is known to cause concrete cracking, would significantly improve the infrastructure life span of the United States and abroad. Educational activities will include traveling to local middle and high schools to provide hands-on experiments that give the students a real-life view of how engineering is an important part of the modern world. Local primary school groups will be invited to campus to participate in hands-on learning experiences at Tennessee Tech?s STEM Center. In addition to the educational activities, a residual stress analysis workshop is proposed at the end of the project to disseminate the strong background in this field at Tennessee Tech to other cement and concrete researchers; thus, expanding beyond traditional K-12 outreach.