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

胶凝混合物的有效性能和结构性能在很大程度上取决于相间区域的质量，因为它在集料和结合基质之间充当传递力的桥梁，并且通常容易受到破坏。尽管在过去的几十年里取得了进步，但对胶凝混合物界面区域的理解和建模仍然面临着重要的挑战。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，越来越需要基础知识来揭示间相形成机制，并由此建立预测间相性质的模型。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相间区域。研究成果的成功应用和传播有望通过推广非水泥粘结剂和二次骨料，在不影响机械性能和结构性能的情况下，显著降低成本、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，允许开发更具成本效益的混合产品，从而显著提高各种结构材料的性能和可持续性。为了实现这一目标，本研究系统地将多尺度试验和双向耦合多尺度计算模型结合起来，实现以下四个具体目标：1)建立一种多尺度实验方法来识别胶凝混合物中相间带的微观结构细节和特性；2)建立涉及非线性非弹性材料行为的双向耦合计算多尺度模型；3)将实验结果与计算模型相结合，确定相间区的有效材料性能；4)验证和校准建模方法，并将其扩展到混合设计变量变化的其他情况。本研究将促进对胶凝混合物的基本认识，特别是间相对整个混合物性质和性能的力学影响。本研究包含了多个长度-时间尺度的微-纳米材料表征以及非线性非弹性材料行为的双向链接多尺度计算等几个知识意义。该项目的成功完成将提供重要的关键信息，将推动当前多相颗粒固体的广泛技术和知识，其中非弹性非线性变形、界面和多物理载荷是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.