This paper addresses multiscale stiffness homogenization methodology to extract macroscale elastic mechanical properties of four types of sustainable concretes from their nanoscale mechanical properties. Nine different sustainable concrete mixtures were studied. A model based on micromechanics was used to homogenize the elastic properties. The hardened cement pastes were homogenized by three analytical methods based on Self-Consistent and Mori-Tanaka schemes. The proposed multiscale method combines advanced experimental and analytical methods in a systematic way so that the inputs are nanoscale phases properties extracted from statistical nanoindentation technique and mechanical properties of mixture ingredient. Predicted elastic properties were consistent with traditional experimental results. Linking homogenized mechanical properties of sustainable concrete to volume proportions through an analytical approach provides a critical first step towards rational optimization of these materials. 1. Introduction Concrete is a complex heterogeneous material whose mechanical properties can vary substantially from point to point. Predicting the mechanical behavior of such materials always has been a challenge confronting scientists. However, progress in both experimentation and continuum micromechanics has provided the required foundations for the development of multiscale models for complex heterogeneous materials such as concrete. These upscaling schemes work as ways to exchange information about mechanical properties between different scales of a model. Furthermore, performance-oriented optimization of the homogenized properties becomes possible by considering modifications to the material chemistry, composition, processes, and their related impacts on microstructure. 2. Background 2.1. Sustainable Concrete Concrete containing fly ash and blast furnace slag, kenaf fiber reinforced concrete (KFRC), and lightweight aggregate concrete (LWAC) can be categorized as sustainable concrete, by achieving concrete with high strength while reducing cement consumption. Plant-based natural fibers, such as kenaf bast fibers, can be used in concrete to obtain a new lighter weight and yet tougher concrete while maintaining desirable material properties will directly enhance the merits of precast concrete [1]. CO2 sequestration is another positive impact of kenaf. One acre of kenaf captures as much CO2 as three acres of rain forest, and much of the captured CO2 can be permanently trapped inside structures used in construction [2]. Additionally, the lighter weight and better
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