Collaborative Research: Coupling System Chemistry and Time-Dependent Deformation of Cementitious Materials through Evolving Thermodynamic States

最近的研究表明，应力诱导溶解是各种矿物的主要随时间变化的变形机制。基于最近的建模工作，有理由相信应力诱导的溶解也是胶凝材料中的一种重要的变形机制。因此，在胶凝材料内部的化学演化、微结构发展和应力和应变状态之间存在着预期的耦合。这个项目的一个主要目标是开发一个基本的热力学模型框架，将胶凝材料的演化系统化学和力学联系起来，并通过一种计算方法来实现该模型，该方法预测材料的微观结构和粘弹性/粘塑性性质的完全耦合的演化。在与基本模型的协同中，将使用应力试件的时间步进微计算机层析成像进行新的实验，以验证应力诱导胶凝材料溶解的假设。该项目的成果将导致在理解本构性质的演变和潜在的变形机制方面取得重要进展；这最终将有助于设计出具有更高强度、韧性、耐久性和可持续性的混凝土。混凝土是世界上第二大使用商品，存在许多结构和耐久性问题，导致巨大的经济和环境成本。混凝土等胶凝材料的缺陷可能部分归因于与缺乏有效预测材料结构和性能演变的可用建模工具相关的设计限制。该项目的成果将提供先进的建模、实验和计算工具，帮助提高胶凝材料的经济性、耐久性和可持续性，从而带来社会效益。此外，其他研究人员最终将能够自由实施在该项目中开发的工具，以解决与混凝土有关的一系列重要问题，如冻融循环和化学侵蚀造成的退化。一种涉及基础理论以及化学和力学过程(如变形)之间的耦合的建模方法能够最终改变我们对混凝土等胶凝材料行为的理解。

Recent research indicates that stress induced dissolution is a primary time-dependent deformation mechanism of various minerals. Based on recent modeling efforts, there is reason to believe that stress induced dissolution is also a significant deformation mechanism in cementitious materials. Thus, there is an expected coupling between the evolution of chemistry, microstructure development, and stress and strain states within cementitious materials. A primary objective of this project is to develop a fundamental thermodynamic model framework that links evolving system chemistry and mechanics of cementitious materials, and to implement the model through a computational method that predicts the fully coupled evolution of microstructure and viscoelastic/viscoplastic properties of the materials. In synergy with the fundamental modeling, novel experiments using time-stepping micro-computed tomography of stressed specimens will be performed to test the hypothesis that stress induces dissolution in cementitious materials. The results of this project will lead to important advances in understanding the evolution of constitutive properties and the underlying deformation mechanisms; this will ultimately help enable design of concrete with greater strength, toughness, durability, and sustainability. Concrete, the second most used commodity in the world, suffers from many structural and durability issues that result in substantial economic and environmental costs. The drawbacks of cementitious materials such as concrete may be attributed in part to design limitations associated with the lack of available modeling tools for effectively predicting the evolution of the material structure and properties. The results of this project will provide societal benefit by providing advanced modeling, experimental, and computational tools to help improve the economy, durability and sustainability of cementitious materials. Furthermore, other researchers will ultimately be able to freely implement the tools developed in this project to address a host of important issues with respect to concrete, such as degradation due to freeze-thaw cycling and chemical attack. A modeling approach that involves fundamental theory and coupling between chemistry and mechanical processes (such as deformation) has the capability to ultimately transform our understanding of the behavior of cementitious materials such as concrete.