Vers une utilisation rationnelle des métakaolins flash : application aux bétons

The objective of the present thesis was to promote the use of metakaolin as substitute for cement in cementitious matrix by unlocking several scientific challenges. The use of mineral additions modifies the properties of concrete in the fresh state, the hardening state and the durability state. In the fresh state, rheology was studied by adapting a formulation method for self-compacting concretes. This application was then further developed to be used at an industrial scale. In the hardening state, the hydration phases were analysed with a focus on the effect of the cement nature on the metakaolin reactivity. Finally in the durability state, two particular features were studied:1) the metakaolin effect on the carbonation kinetic and 2) the effect of the metakaolin on the chloride diffusion.L'objectif de ce travail est de contribuer à la valorisation du métakaolin en substitution du ciment dans les matrices cimentaires en levant certains verrous scientifiques. En effet l'utilisation d'additions minérales modifie les propriétés des bétons, que cela soit à l'état frais, à l'état durcissant ou à l'état durci. A l'état frais, la rhéologie a été étudiée avec l'adaptation et l'application d'une méthode de formulation pour béton auto-plaçant. Cette application a été développée jusqu'à l'échelle industrielle. A l'état durcissant, la phase d'hydratation a été étudiée en s'attardant particulièrement sur l'effet de la nature du ciment substitué sur la réactivité du métakaolin. Enfin à l'état durci deux caractéristiques de durabilité ont été explorées, à savoir l'effet du métakaolin sur la carbonatation dans une première partie, puis sur la diffusion des chlorures dans une deuxième partie

Publishing Reference Geodata on the Web : Opportunities and Challenges for IGN France

International audienceThe French national mapping agency (IGN) produces several different but complementary geographic vector reference databases delivered in traditional GIS formats. However, linked data users have different expectations and habits, such as the need to browse an entire data catalogue in RDF using the "follow-your-nose" navigation capacity from one graph to another. Besides, traditional GIS data formats are not interoperable with RDF. Yet, all these geographic datasets could be used with benefits on the Web of data, either with direct georeferencing through geographic primitives, or indirect one through postal addresses. In this paper, we aim to contribute to the georeferencing of datasets published on the Web of data by providing such resources for French context. Firstly, we propose two vocabularies designed for representing structured geometries defined with coordinates expressed in any Coordinates Reference System (CRS). Secondly, we reuse these vocabularies and the CRSs' dataset to publish a reference dataset on administrative units that can also be reused for indirect georeferencing purposes. Finally , we also propose two vocabularies for describing geographic feature types. In addition to these resources, we also present a comprehensive workflow for easily publishing geographic data on the Web of data

Development and application of a 2-step methodology to select a reference society providing Dietary Reference Values for national implementation

Objective: To describe and discuss a 2-step methodology developed to select a reference society that provides Dietary Reference Values (DRVs) for national implementation and to illustrate its application in Switzerland with one macronutrient and one micronutrient.Design: During Step 1, we searched and compared DRVs and methodologies used to define DRVs from eight European societies for seven selected nutrients. We repeated this procedure during Step 2 for DRVs from two preselected societies for 44 nutrients.Setting: The 2-step methodology applied here for Switzerland may be used in other countriesParticipants: The research team commissioned six external experts from three linguistic regions of Switzerland, who provided their opinions through two online surveys, individual interviews, and a focus group.Results: After Step 1, we excluded five societies because of old publication dates, irrelevant publication languages for Switzerland, difficulty in accessing documents, or because their DRVs were mainly based on another society. After Step 2, the two societies were qualified based on the analysis of the values and methodologies used. The need for free and easily accessible scientific background information favored the European Food Safety Authority (EFSA). We chose alternative societies for nine nutrients for the overall population or subgroups, and for elderly.Conclusions: To manage heterogeneous and complex data from several societies, adopting a 2-step methodology including fewer nutrients and more societies during Step 1, and fewer societies but all nutrients in Step 2, was very helpful. With some exceptions, we selected EFSA as the main society to provide DRVs for Switzerland

Dataset interlinking module

euzenat2011eThis report presents the first version of the interlinking module for the Datalift platform as well as strategies for future developments

: exemple du couple métakaolin flash et addition calcaire

International audienceAfin d'abaisser l'impact carbone des bétons, la réduction du facteur clinker est essentielle. Ce travail montre l'impact d'une réduction du dosage en clinker (moins de 50% du liant) sur les caractéristiques du béton (résistances mécaniques et performances de durabilité). Il s'attarde particulièrement à l'utilisation couplée de métakaolin flash et d'addition calcaire en complément d'un CEM I. Trois bétons ont ainsi été formulés avec 50% de CEM I ; le complément a été est apporté par le couplage d'additions minérales. Des mélanges ne contenant plus que 40 ou 30% de CEM I ont également été évalués. Toutes les compositions citées ont été comparées à un ciment CEM II/A, qui correspond à lui seul à plus de 50% des volumes de ciments consommés en France. Avec une baisse d'au moins 30% de l'impact carbone par rapport à un CEM II/A-LL, l'utilisation de la bi-addition est une solution viable pour la formulation des bétons dits bas carbone. A dosages en liant et en eau équivalents, les bétons à base de bi-addition ont tous respectés la résistance mécanique de la classe d'exposition visée

Performance-based evaluation of flash-metakaolin as cement replacement in marine structures – Case of chloride migration and corrosion

International audienc

Carbonation of Blended Binders Containing Metakaolin

WOS:000380463000004International audienceThe pozzolanic materials are often recommended for their very good durability in aggressive environment. Unfortunately, this is not always true and particularly in the case of carbonation by the atmospheric CO2. Although cement replacement by pozzolanic materials causes a decrease in pore size, the pozzolanic reaction consumes portlandite and decreases the protection potential against CO2 ingress. This is the case for most pozzolanic materials, including metakaolin. The aim of this study is first to confirm the literature results of carbonation by using flash metakaolin in partial replacement of cements (CEM I, CEM II A-LL and CEM II A-V). Then the concretes with a metakaolin are compared with concretes based on standardized cement in order to assess the carbonation depth of metakaolin-based concretes and concretes used today in the building construction. Even though the cement replacement of CEM I and CEM II A-V by metakaolin increases the carbonation depth, results are not the same with the CEM II A-LL cement. The interaction of metakaolin with the cement limestone filler can explain this better performance, certainly because the hemicarboaluminate allows slowing down the CO2 propagation through the matrix

Carbonation of Blended Binders Containing Metakaolin

WOS:000380463000004International audienceThe pozzolanic materials are often recommended for their very good durability in aggressive environment. Unfortunately, this is not always true and particularly in the case of carbonation by the atmospheric CO2. Although cement replacement by pozzolanic materials causes a decrease in pore size, the pozzolanic reaction consumes portlandite and decreases the protection potential against CO2 ingress. This is the case for most pozzolanic materials, including metakaolin. The aim of this study is first to confirm the literature results of carbonation by using flash metakaolin in partial replacement of cements (CEM I, CEM II A-LL and CEM II A-V). Then the concretes with a metakaolin are compared with concretes based on standardized cement in order to assess the carbonation depth of metakaolin-based concretes and concretes used today in the building construction. Even though the cement replacement of CEM I and CEM II A-V by metakaolin increases the carbonation depth, results are not the same with the CEM II A-LL cement. The interaction of metakaolin with the cement limestone filler can explain this better performance, certainly because the hemicarboaluminate allows slowing down the CO2 propagation through the matrix

Les valeurs nutritionnelles de référence suisses

Les valeurs nutritionnelles de référence (VNR) sont importantes pour la promotion de la santé, l’élaboration de règlements relatifs à l’étiquetage des denrées alimentaires et l’identification des populations à risque d’excès ou d’insuffisance d’apports. Les VNR sont des repères quantitatifs concernant les apports nutritionnels ; elles sont calculées pour différents groupes de population selon des critères de santé définis. Elles fournissent aux professionnels des indications utiles sur les quantités d’énergie et de nutriments théoriquement nécessaires pour assurer la croissance, le développement et la santé de l’organisme, tout en limitant les risques de carences et de maladies non transmissibles, comme les cancers ou les maladies cardiovasculaires. Il est important pour la Suisse de disposer de VNR harmonisées à l’échelle nationale, basées sur des données scientifiques solides, fiables et reconnues dans tout le pays. Les VNR permettent, par exemple, d’évaluer l’état nutritionnel de la population et de mettre à jour les recommandations alimentaires illustrées par la pyramide alimentaire suisse. Dans ce contexte, l’Office fédéral de la sécurit

Randomized Controlled Trial of Enhanced Recovery Program Dedicated to Elderly Patients After Colorectal Surgery

Enhanced recovery program is a multimodal, multidisciplinary-team, evidence-based care approach to reduce perioperative surgical stress, decrease morbidity and hospital stay, and improve recovery after surgery. This program may be most beneficial for elderly (≥70 y), but sparse series have investigated this question