Luc Nicoleau

Identification of binding peptides on calcium silicate hydrate: a novel view on cement additives.

Phage display experiments on industrially important calcium silicate hydrates (C-S-H), the main hydration product of ordinary Portland cement, suggest fundamentally different specific binding motifs compared to hitherto existing commercial cement additives. According to that, a strong and specific adsorbing additive on C-S-H should have three features which are a negative charge, H-bond formers (especially amide functions) and a hydrophobic part.

Revised atomistic models of the crystal structure of C-S-H with high C/S ratio

Abstract The atomic structure of calcium-silicate-hydrate (C1.67–S–Hx) has been studied. Atomistic C–S–H models suggested in our previous study have been revised in order to perform a direct comparison of energetic stability of the different structures. An extensive set of periodic structures of C–S–H with variation of water content was created, and then optimized using molecular dynamics with reactive force field ReaxFF and quantum chemical semiempirical method PM6. All models show organization of water molecules inside the structure of C–S–H. The new geometries of C–S–H, reported in this paper, show lower relative energy with respect to the geometries from the original definition of C–S–H models. Model that corresponds to calcium enriched tobermorite structure has the lowest relative energy and the density closest to the experimental values.

Mesocrystalline calcium silicate hydrate: A bioinspired route toward elastic concrete materials

Controlled aggregation of polymer-stabilized calcium silicate hydrate nanoparticles leads to elastic cementitious materials. Calcium silicate hydrate (C-S-H) is the binder in concrete, the most used synthetic material in the world. The main weakness of concrete is the lack of elasticity and poor flexural strength considerably limiting its potential, making reinforcing steel constructions necessary. Although the properties of C-S-H could be significantly improved in organic hybrids, the full potential of this approach could not be reached because of the random C-S-H nanoplatelet structure. Taking inspiration from a sea urchin spine with highly ordered nanoparticles in the biomineral mesocrystal, we report a bioinspired route toward a C-S-H mesocrystal with highly aligned C-S-H nanoplatelets interspaced with a polymeric binder. A material with a bending strength similar to nacre is obtained, outperforming all C-S-H–based materials known to date. This strategy could greatly benefit future construction processes because fracture toughness and elasticity of brittle cementitious materials can be largely enhanced on the nanoscale.

Atomistic modeling of crystal structure of Ca{sub 1.67}SiH{sub x}

The atomic structure of calcium-silicate-hydrate (C-1.67-S-H-x) has been investigated by theoretical methods in order to establish a better insight into its structure. Three models for C-S-H all derived from tobermorite are proposed and a large number of structures were created within each model by making a random distribution of silica oligomers of different size within each structure. These structures were subjected to structural relaxation by geometry optimization and molecular dynamics steps. That resulted in a set of energies within each model. Despite an energy distribution between individual structures within each model, significant energy differences are observed between the three models. The C-S-H model related to the lowest energy is considered as the most probable. It turns out to be characterized by the distribution of dimeric and pentameric silicates and the absence of monomers. This model has mass density which is closest to the experimental one