Permeability of C-S-H

International audienc

Influence of the flexibility of the calcium silicate hydrates layers on the mesotexture: coarse grained simulations accounting for three-body interactions

International audienceCalcium silicate hydrates exhibit various mesotextures, composed of fundamental pieces presenting with different morphologies. The structuration of nanolayer (2D) and nanofibrillar (1D) materials is a result of the interplay between intermolecular forces involving the fundamental pieces (layers or fibrils) and the pore fluid as well as the flexibility of each piece. In this paper, coarse-grained simulations are performed to simulate the differences in the mesotexture of crystalline calcium silicate hydrate with a fibril morphology taking into account the flexibility of these fibrils. The resulting pore size distributions of the gel are computed and exhibit a dependence on the size of the fibril. These results are a contribution to a better understating of C-S-H nanostructuration

Interactions between crystalline calcium silicate hydrates: grand canonical simulation of pressure and temperature effects

International audienceThe interactions between calcium silicate hydrates and pore solution at the nanoscale are crucial in physical phenomena related to the thermo-hydro-mechanical behaviour of cement-based materials. In this paper, these interactions are studied using grand canonical Monte Carlo simulations according to various temperatures and pressures. A nanocrystalline structure of calcium silicate hydrate (tobermorite) is considered. Micro-instabilities of snap-through type are identified. The corresponding potential of mean force, accounting for the interactions of the solid layers in drained conditions, is provided, which leaves rooms to upscale the behaviour of calcium silicate hydrates to the mesoscale

Einstein Explains Water Transport in C-S-H

International audienc

Modélisation Multi-Échelle Multi-Physique MultiTechnique pour la corrélation composition-(micro)structure-propriétés des matériaux cimentaires

The central paradigm of materials science and materials engineering involves establishing processing- (micro)structure-property-performance correlations for materials. These correlations, in particular structure-property relationships, are fundamental in the study of cement-based materials, being a critical strategy for coping with the rise in the complexity of the mineralogical and chemical compositions of cement systems. Modeling and simulation approaches arise as important tools in establishing these correlations, especially when they are based on fundamental scientific principles. In this work, I present modeling and simulation techniques used in a multiscale and multi-physics framework with the goal of establishing composition-property correlations in cement systems. This manuscript follows a scale-wise organization, with the first chapter devoted to information from the molecular scale, followed by a chapter on how to upscale nanoscale information up to the scale of Civil Engineering applications. First, it is shown how molecular simulations can be used to calculate the elastic constants, thermal properties, mass transport properties, electromagnetic properties, and coupling properties of phases relevant to cement systems. It is also shown how molecular simulations help unveil the physical processes associated with sorption and hygro-thermo-mechanical couplings bottom-up. Then, a discussion on the mesoscale(s) of interest in the passage atomistic-to-continuum and in the realm of continuum mechanics up to the macroscopic scale (of industrial applications) of cement-based materials is presented. It is shown how Micromechanics theory provides estimates of effective properties in a multi-physics context but also information about local fields. Ongoing research and perspectives extending the multiscale multi-physics and multi-technique strategy to new phenomena and applications are finally presented

Thermal conductivity, heat capacity and thermal expansion of ettringite and metaettringite: Effects of the relative humidity and temperature

International audienc

Influence of the flexibility of the calcium silicate hydrates layers on the mesotexture: coarse grained simulations accounting for three-body interactions

International audienceCalcium silicate hydrates exhibit various mesotextures, composed of fundamental pieces presenting with different morphologies. The structuration of nanolayer (2D) and nanofibrillar (1D) materials is a result of the interplay between intermolecular forces involving the fundamental pieces (layers or fibrils) and the pore fluid as well as the flexibility of each piece. In this paper, coarse-grained simulations are performed to simulate the differences in the mesotexture of crystalline calcium silicate hydrate with a fibril morphology taking into account the flexibility of these fibrils. The resulting pore size distributions of the gel are computed and exhibit a dependence on the size of the fibril. These results are a contribution to a better understating of C-S-H nanostructuration

Quantifying the Processes at the Origin of the Dielectric Response of Cement-Based Materials with Molecular Dynamics Simulations

International audienceThe pore phase determines the dielectric and electrical responses of cement-based materials. Porosity is hierarchical in these materials with pore classes including macro, capillary, and nanopores. This work shows how molecular dynamics simulations provide quantitative information about the complex dielectric and electrical response for free water and ions, surface water and physically bound ions species, water and ions confined in nanopores, and also OH groups in the pore wall

Mécanique des matériaux nanogranulaires

International audienceLes matériaux cimentaires (ainsi que d'autres matériaux nanoporeux comme les argiles et l'os) présentent une échelle mésoscopique qui peut bien être représentée par des grains interagissant via des forces colloïdales. Dans ce papier, je discute comment des phénomènes comme l'asymétrie tension/compression, l'expansion thermique et l'hystérésis associée à des chargements thermomécaniques émergent des systèmes qui interagissent par le bias des potentiels de force moyenne anharmoniques. Dans ce papier, je me concentre sur l'étude des silicates de calcium hydratés (C-S-H), qui sont le principal produit issu des processus d'hydratation des ciments Portland. L'objectif est d'identifier l'origine physique des phénomènes mentionnés ci-dessus afin de mieux comprendre le comportement des C-S-H