@article {679, title = {Multiscale poromechanics of wet cement paste}, journal = {Proceedings of the National Academy of Sciences}, volume = {2}, year = {2019}, month = {May-09-2019}, pages = {201901160}, abstract = {

Capillary effects, such as imbibition drying cycles, impact the mechanics of granular systems over time. A multiscale poromechanics framework was applied to cement paste, which is the most common building material, experiencing broad humidity variations over the lifetime of infrastructure. First, the liquid density distribution at intermediate to high relative humidity is obtained using a lattice gas density functional method together with a realistic nanogranular model of cement hydrates. The calculated adsorption/desorption isotherms and pore size distributions are discussed and compare well with nitrogen and water experiments. The standard method for pore size distribution determination from desorption data is evaluated. Second, the integration of the Korteweg liquid stress field around each cement hydrate particle provided the capillary forces at the nanoscale. The cement mesoscale structure was relaxed under the action of the capillary forces. Local irreversible deformations of the cement nanograins assembly were identified due to liquid\–solid interactions. The spatial correlations of the nonaffine displacements extend to a few tens of nanometers. Third, the Love\–Weber method provided the homogenized liquid stress at the micrometer scale. The homogenization length coincided with the spatial correlation length of nonaffine displacements. Our results on the solid response to capillary stress field suggest that the micrometer-scale texture is not affected by mild drying, while nanoscale irreversible deformations still occur. These results pave the way for understanding capillary phenomena-induced stresses in heterogeneous porous media ranging from construction materials to hydrogels and living systems.

}, issn = {0027-8424}, doi = {10.1073/pnas.1901160116}, url = {http://www.pnas.org/lookup/doi/10.1073/pnas.1901160116}, author = {Zhou, Tingtao and Katerina Ioannidou and Franz-Josef Ulm and Bazant, Martin Z. and Roland Jean-Marc Pellenq} } @article {532, title = {Phase separation of stable colloidal clusters}, journal = {Physical Review Materials}, volume = {2}, year = {2018}, month = {Sep-25-2018}, abstract = {

This article presents a nonequilibrium thermodynamic theory for the mean-field precipitation, aggregation, and pattern formation of colloidal clusters. A variable gradient energy coefficient and the arrest of particle diffusion upon \“jamming\” of cluster aggregates in the spinodal region predicts observable gel patterns that, at high intercluster attraction, form system-spanning, out-of-equilibrium networks with glasslike, quasistatic structural relaxation. For reactive systems, we incorporate the free energy landscape of stable prenucleation clusters into the Allen-Cahn reaction equation. We show that pattern formation is dominantly controlled by the Damk\öhler number and the stability of the clusters, which modifies the autocatalytic rate of precipitation. As clusters individually become more stable, bulk phase separation is suppressed.

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}, doi = {10.1103/PhysRevMaterials.2.095602}, url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.095602}, author = {Petersen, Thomas and Bazant, Martin Z. and Roland Jean-Marc Pellenq and Franz-Josef Ulm} }