Identification and Modeling of Interphase in Cementitious Mixtures through Integrated Experimental-Computational Multiscale Approach

水泥混合物的有效性能和结构性能基本上取决于界面区域的质量，因为它充当在骨料和粘结基质之间传递力的桥梁，并且通常容易受到损坏。尽管在过去的几十年里取得了进步，理解和模拟水泥混合物的界面区域仍然提出了重要的挑战。随着非传统添加剂如再生骨料和替代粘合剂的使用越来越频繁，人们越来越需要基础知识来揭示界面形成机制和预测界面性质的模型。本研究的目的是发展一种实验-计算方法来识别和模拟胶凝材料的界面区域。研究成果的成功应用和传播有望通过推广非水泥粘合剂和二次骨料，在不损害机械性能和结构性能的情况下，大幅降低成本、自然资源和二氧化碳排放。该项目将改善代表性不足的学生的教育和培训机会，并影响当前的土木工程实践，从而能够开发更具成本效益的混合物产品，显着提高各种结构材料的性能和可持续性。为了实现这一目标，该研究系统地整合了多尺度测试和两个-方法耦合多尺度计算模拟有以下四个具体目标：1）发展多尺度实验方法来识别水泥混合物中界面区的微观结构细节和性能; 2）建立了一个包含非线性-非弹性材料行为的双向耦合计算多尺度模型; 3）将实验研究与计算建模相结合以确定界面区域的有效材料性质; 4）验证-校准建模方法并将其扩展到混合物设计变量变化的其他情况。这项研究将推进对水泥混合物的基本理解，特别是界面对整个混合物性质和性能的力学影响。该研究包含了多个智力意义，包括多个长度-时间尺度的微机械-纳米机械材料表征和非线性-非弹性材料行为的双向链接多尺度计算。该项目的成功完成将提供重要的关键信息，将推进当前的技术和知识的广泛的多相颗粒固体，其中非弹性-非线性变形，界面和多物理载荷涉及作为主要的能量耗散和性能控制现象。

Effective properties and structural performance of cementitious mixtures are substantially governed by the quality of the interphase region, because it acts as a bridge transferring forces between aggregates and a binding matrix, and is generally susceptible to damage. In spite of advancements made over the last several decades, understanding and modeling the interfacial region of cementitious mixtures still presents important challenges. As non-traditional additives such as recycled aggregates and alternative binding agents are more often used today, there is a growing need of fundamental knowledge to uncover interphase formation mechanisms and a resulting model to predict interphase properties. The goal of this research is to develop an experimental-computational method to identify and model the interphase region of cementitious materials. The successful application and dissemination of research findings is expected to significantly reduce costs, natural resources, and carbon dioxide emissions through the promotion of non-cement binding agents and secondary aggregates without compromising mechanical properties and structural performance. This project will improve education and training opportunities of underrepresented students and also impact current civil engineering practices, allowing for the development of more cost-effective mixture products that significantly increase the performance and sustainability of a wide range of structural materials.To meet the goal, this research systematically integrates multiscale tests and the two-way coupled multiscale computational modeling with the following four specific objectives: 1) develop a multiscale experimental method to identify microstructure details and properties of the interphase zone in cementitious mixtures; 2) develop a two-way coupled computational multiscale model that involves nonlinear-inelastic material behavior; 3) integrate the experimental efforts with computational modeling to determine effective material properties of interphase region; and 4) validate-calibrate the modeling approach and extend it to other cases where mixture design variables are varied. This research will advance the fundamental understanding of cementitious mixtures, specifically the mechanical effects of interphase on entire mixture properties and performance. This research incorporates several intellectual significances including micromechanical-nanomechanical material characterization in multiple length-time scales and the two-way linked multiscale computation with nonlinear-inelastic material behavior. Successful completion of the project will provide significant key information that will advance current technology and knowledge on a broad range of multiphase particulate solids in which inelastic-nonlinear deformation, interface, and multiphysical loads are involved as primary energy dissipation and performance-controlling phenomena.