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

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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.