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Cementitious materials (cement paste) are highlyheterogeneous and hierarchical material systems. Processes and features at thenanometer sized morphological structures affect the performance,deformation/failure behavior at larger length scales.  Further,cement paste undergo chemical and morphological changes gaining strengthduring transient hydration process. Mechanical properties, deformation andfailure are thus influenced by starting material genome chemistry structures,their evolution to microstructures and engineering scale.Molecular Dynamics (MD) modeling methods built uponmaterial chemistry level molecular models provide a viable methodology to studyand characterize material systems based on nanoscale and chemistry levelfeatures. The present paper presents our work on the material modeling ofdeformation and failure of nanoscale hydrated calcium silicate hydrate (CSH) incement paste. In particular, MD modeling shear and compression deformation ofhydrated cement paste constituent calcium-silicate-hydrate (CSH) is discussed.Computational CSH molecular structure (Jennite) is subjected to shear andcompressive deformation resulting in the predicted shear stress - strainbehavior along its main crystalline orientations, and an estimation of shearmodulus and strength. In the case of shear deformation, simulation resultsindicated that the nanoscale CSH Jennite under shear deformation displays alinear elastic behavior up to shear stress of approximately 1.0 GPa, and sheardeformation of about 0.08 radians, after which point yielding and plasticdeformation occurs. The shear modulus determined from the simulations was 11.2± 0.7 GPa. The deformation-induced displacements in molecular structures wereanalyzed dividing the system in regions representing calcium oxide layers. Thedisplacement/deformation of the layers of calcium oxide forming the structureof nanoscale CSH Jennite was analyzed. The non-linear stress-strain behavior inthe molecular structure was attributed to a non-linear increase in thedisplacement due to sliding of the calcium oxide layers on top of each otherwith higher shearing. These results support the idea that by controlling thechemical reactions, the tailored morphologies can be used to increase theinterlinking between the calcium oxide layers, thus minimizing the shearing ofthe layers and leading to molecular structures that can withstand largerdeformation and have improved failure behavior.In addition, recent results from compression deformation,material chemistry changes and macro-molecular systems with multiple cementmaterial phases emulating the material scale and features captured innanoindentation will be discussed.

Material chemistry level modeling, molecular dynamics, nanoscale mechanics, deformation, failure