06 Mai2016
Written by romainadmin. Posted in News
Title: Simulation of the cement strength retrogration
organised by Dr. Moon Ju Hyuk
Abstract
Cementitious materials are widely used by the mankind. Research is made to reduce its production costs, its environmental impact and to increase its durability. For this, several approaches are used including experiments and theoretical works. At the DIPC/CFM we are simulating the different phases of the cement paste at the atomic scale using advanced methods. In a collaborative project with Tecnalia Research and Innovation and INTEVEP‐PDVSA, we study the C‐S‐H gel which is the most common phase of cements. This phase is important because it gives the strength to the cement and glue its structure. At high temperature, the C‐S‐H gel goes through an irreversible phase transition that reduces the lifetime of the cement. The product of the phase transition is a crystal (see figure) that is more compact than the C‐S‐H gel; cracks appears in the cement due to the contraction of this phase. We investigate if this transition can be avoided looking at the mechanism of transition and at the energetical properties of the system. In this presentation, we will briefly present methods that we use to study the C‐S‐H gel. Using those, we understood the mechanism of transition which consist in multiple dissociations of Si‐O‐Si bonds. Moreover, we can suggest a way to push back the dissociation and consequently the phase transition.
21 Jan2016
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19/01/2016 – Ce séminaire à été donné à l’INSP (Institut des NanoSciences de Paris) afin de présenter l’importance de prendre en compte les effets nucléaires quantiques lorsque l’on s’intéresse à des systèmes composés d’atomes légers (H, Li) ou sous contraintes. La méthode des intégrales des chemins a été présentée puis ses points forts ont été mis en évidence au travers de deux exemples : le fractionnement isotopique du Li entre un minéral et une solution ; le déplacement des atomes d’hydrogène dans la Portlandite (hydroxyde) sous très haute pression.
24 Nov2015
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1/ Title: Quantum Nuclear Effects in Portlandite under Pressure
2/ Title: Strength retrogression in cements: stability of alpha-C2SH
21 Juil2015
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Titled: Hydrogen tunnelling in Portlandite [Ca(OH)2] under pressure
10 Déc2014
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Invited PhD at the DIPC (San Sebastian, Spain) from september 2014 to december 2014.
Postdoc at the DIPC (San Sebastian, Spain) from january 2015 to may 2018.
Postdoctoral contract at DIPC starting from 10 Dec. 2014 on the study of cementitious materials with ab initio calculations.
15 Juil2014
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Seminar titled : Realistic calculations of the isotopic fractionation factors of Si and Li for equilibriums involving liquid phases on the 17th of July at the DIPC of Donostia.
Homepage of the DIPC : http://dipc.ehu.es/
29 Août2013
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Silicon isotope fractionation implying liquid phases at 300K: importance of configurational disorder
http://goldschmidt.info/2013/abstracts/finalPDFs/1020.pdf
15 Août2012
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DFT summer school
25 Juin2012
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Summer school, lien vers programme
