Shear Deformations of Tobermorite 14 A using Atomic Scale Simulations:Towards Understanding the Molecular Mechanism of Creep

【Author】

Hegoi Manzano;Enrico Masoero;Inigo Lopez-Arbeloa;

【Abstract】

<正>Atomistic simulations are a great complementary tool to experimental techniques.They we can provide very detailed information of the molecular structure and processes, helping to understand and predict macroscopic properties of materials.In this work we apply atomistic simulation to the study of creep in cement.We have investigate the shear strength of lobermorite 14 A,a crystalline calcium silicate hydrate related to the C-S-H gel,the main component of cement.A shear strain parallel the calcium silicate layers has been applied,monitoring the developed stress,relaxation events,and the local deformations to dissipate the stress.The study has been carried out for systems with different water content to explore the impact of water in the mechanical response of the material. Our results confirm the key role of water in the shear strength of the material.Depending on the water content,the system behaves like a brittle crystal or a plastic glass.Water acts as a "lubricant" allowing the sliding between calcium silicate layers as solid blocks without internal deformation.Therefore,when water is not present,the calcium silicate layers have to deform the relax the accumulated stress.After our results we can suggest thai the relaxation in the C-S-H gel that originates creep will take place in the water rich regions.During the stress dissipation the particles will not suffer internal deformation, and the gel might behave as a plastic glass. These results are the first information about the molecular mechanism behind creep in cement,and will be used in a close future as input for mesoscale modeling of the C-S-H gel mechanical properties. Originality The nanoscale structure and properties of the C-S-H gel.main component of cement,are elusive.Its heterogenous chemistry and morphology makes difficult its experimental characterization.Atomistic simulation methods are a great complememary tool to the experiments.These methods provide very detailed information of the fundamental mechanisms at the atomic scale,and help us to understand and predict experimental data. However,these atomistic simulation have been used scarcely to investigate the C-S-H gel. This work is one of the first attempts to understand the complex mechanics of the C-S-H gel at the atomic-nano scales beyond the elastic limit using modeling techniques.We have employed atomic scale simulations to investigate the mechanical response of lobermorite under shear strain.Special attention has been paid to the impact of water content on the structure and properties.The results are qualitatively related to creep in cement.

【Keywords】

C-S-H gel;;tobermorite;;shear deformation;;atomic scale simulations;;creep;;water

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