Alain Baronnet

Despite its ubiquitous presence in the built environment, concrete’s molecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete’s environmental footprint have provided strong motivation to develop new concrete with greater specific stiffness or strength (for structures with less material). Herein, a combinatorial approach is described to optimize properties of cement hydrates. The method entails screening a computationally generated database of atomic structures of calcium-silicate-hydrate, the binding phase of concrete, against a set of three defect attributes: calcium-to-silicon ratio as compositional index and two correlation distances describing medium-range silicon-oxygen and calcium-oxygen environments. Although structural and mechanical properties correlate well with calcium-to-silicon ratio, the cross-correlation between all three defect attributes reveals an indentation modulus-to-hardness ratio extremum, analogous to identifying optimum network connectivity in glass rheology. We also comment on implications of the present findings for a novel route to optimize the nanoscale mechanical properties of cement hydrate. Concrete is a vital material in meeting present day construction demands. Here, the authors report a computational combinatorial approach to understand how molecular level characteristics influence the mechanical properties of cement hydrates, via screening against distinct defect types.

Research Article| April 01, 2013 Serpentinite: What, Why, Where? Bernard W. Evans; Bernard W. Evans 1Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, USAE-mail: bwevans@u.washington.edu Search for other works by this author on: GSW Google Scholar Keiko Hattori; Keiko Hattori 2Department of Earth Sciences, University of OttawaOttawa, ON K1N 6N5, CanadaE-mail: khattori@uottawa.ca Search for other works by this author on: GSW Google Scholar Alain Baronnet Alain Baronnet 3Centre Interdisciplinaire de Nanosciences de Marseille, CNRS, Aix-Marseille Université, 13288, Marseille, FranceE-mail: baronnet@cinam.univ-mrs.fr Search for other works by this author on: GSW Google Scholar Author and Article Information Bernard W. Evans 1Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, USAE-mail: bwevans@u.washington.edu Keiko Hattori 2Department of Earth Sciences, University of OttawaOttawa, ON K1N 6N5, CanadaE-mail: khattori@uottawa.ca Alain Baronnet 3Centre Interdisciplinaire de Nanosciences de Marseille, CNRS, Aix-Marseille Université, 13288, Marseille, FranceE-mail: baronnet@cinam.univ-mrs.fr Publisher: Mineralogical Society of America First Online: 09 Mar 2017 Online ISSN: 1811-5217 Print ISSN: 1811-5209 © 2013 by the Mineralogical Society of America Elements (2013) 9 (2): 99–106. https://doi.org/10.2113/gselements.9.2.99 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Bernard W. Evans, Keiko Hattori, Alain Baronnet; Serpentinite: What, Why, Where?. Elements 2013;; 9 (2): 99–106. doi: https://doi.org/10.2113/gselements.9.2.99 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract Rock-forming serpentine minerals form flat, cylindrical, and corrugated crystal microstructures, which reflect energetically efficient layering of alternate tetrahedral and octahedral sheets. Serpentinization of peridotite involves internal buffering of the pore fluid, reduction of oxygen fugacity, and partial oxidation of Fe2+ to Fe3+. Sluggish MgFe diffusion in olivine causes precipitation of magnetite and release of H2. The tectonic environment of the serpentinization process dictates the abundance of fluid-mobile elements in serpentinites. Similar enrichment patterns of fluid-mobile elements in mantle-wedge serpentinites and arc magmas suggest a linkage between the dehydration of serpentinite and arc magmatism. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

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We report on microstructural data obtained by optical microscopy and transmission electron microscopy concerning the crystallographic relationships of serpentine minerals with their host olivine in two contrasting situations. In the first case, mesh-textured lizardite (liz) is developed in a standard 60% serpentinized oceanic harzburgite from the Oman ophiolite where olivine converts to columnar lizardite. The joined columns are perpendicular to the basal plane (001)liz, corresponding to the pseudofibres observed optically. The plane (001)liz is locally parallel to the narrow boundary ol–liz; thus column orientations register the interface of serpentinization. The ol–liz relationships are not strictly topotactic, but reflect preferred cracking orientations in olivine, parallel to (010)ol. In the second case, antigorite (atg) develops in a rare sample of antigorite schist in a kimberlite from Moses Rock (Colorado Plateau), representative of a suprasubduction-zone mantle wedge. High-resolution transmission electron microscopy (HRTEM) images along [010]atg show domains of very regular modulation with a 43·5 Å wavelength (m = 17, where m is the number of silicate tetrahedra along the wave), with few defects, indicative of HP–HT antigorite, and also heavily kinked regions as fingerprints of strong tectonic shear. TEM imaging and electron diffraction patterns reveal two topotactic relationships between antigorite and olivine: [100]atg//[010]ol and <100>atg//<100>ol; the planes in contact are (001)atg//(100)ol and (001)atg//(010)ol, respectively. The [010]atg//[001]ol and antigorite lamellae are parallel to the forsterite b-axis. In both cases, the topography of olivine–serpentine interfaces is controlled by open fluid pathways along microcracks oriented according to the anisotropy of the olivine aggregate. In the cases studied, the serpentine aggregate exhibits a preferred orientation inherited from that of the peridotite. These results have some relevance to the seismic anisotropy of serpentinized mantle. Anisotropy of propagation of seismic waves as a result of the olivine fabric is maintained and reinforced with the development of lizardite. Conversely, the development of antigorite produces a trench-parallel fast S-wave polarization and an anisotropy that is lowered at low degrees of serpentinization and then increased with increasing serpentinization.