Research article summary (published 6 Sep 2009):

A realistic molecular model of cement hydrates.

Full Abstract

Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this "liquid stone" gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm(3)) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)(1.65)(SiO2)(H2O)(1.75), also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking.

Author information

Author/s: Pellenq, Roland J-M (RJ); Kushima, Akihiro (A); Shahsavari, Rouzbeh (R); Van Vliet, Krystyn J (KJ); Buehler, Markus J (MJ); Yip, Sidney (S); Ulm, Franz-Josef (FJ);

Affiliation: Centre Interdisciplinaire des Nanosciences de Marseille, Centre National de la Recherche Scientifique and Marseille Université, Campus de Luminy, Marseille, 13288 Cedex 09, France.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A), published in United States. (Language: eng)

Reference: 2009-Sep; vol 106 (issue 38) : pp 16102-7

Dates: Created 2009/10/06; Completed 2009/11/06;

PMID: 19805265, status: MEDLINE (last retrieval date: 11/6/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adsorption Algorithms Calcium Compounds - chemistry Computer Simulation Elasticity Microscopy, Electron, Transmission Models, Molecular Monte Carlo Method

Monte Carlo Method Oxides - chemistry Particle Size Reproducibility of Results Silicon Dioxide - chemistry Thermodynamics Water - chemistry X-Ray Diffraction

Associated Chemicals: Calcium Compounds (0) ; Oxides (0) ; lime (1305-78-8) ; Silicon Dioxide (7631-86-9) ; Water (7732-18-5)

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