Some aspects of cellulose ethers influence on water transport and porous structure of cement-based materials

International audienceThis paper evaluates and compares the impact of cellulose ethers (CE) on water transport and porous structure of cement-based materials in both fresh and hardened state. Investigations of the porous network (mercury intrusion porosimetry, apparent density, 2D and 3D observations) emphasize an air-entrained stabilisation depending on CE chemistry. We also highlight that CE chemistry leads to a gradual effect on characteristics of the water transport. The global tendencies brought by CE are: higher water retention, lower capillarity water absorption, lower liquid water permeability as well as higher water vapour permeability. All things considered, we demonstrate that CE chemistry is an important controlling factor on water transport and porous structure evolution

Traditional Medicine in Madagascar - Current Situation and the Institutional Context of Promotion

Following WHO recommandations and in order to improve medical coverage, Madagascar officially recognized in 2007 its traditional medicine as a legitimate practice.UNESCO, to sustain traditional healers in the Indian Ocean, wanted to use anthropological tools to explore the current situation in Madagascar.Despit a plurality of practices, data collected for three months in the Southeast of the Island, allowed us to identify some fundamental aspects of Malagasy traditional medicine, such as the omnipresence of symbolism or the complexity of healers’ roles at the crossroads of social, sacred and therapeutic registries.The study shows that the national policy on traditional medicine improves gradually the promotion of these practices too often undervalued. Nevertheless, the institutional context exposes weaknesses which might explain the difficulty encountered by some tradipractitioners to find their place in this new regulation. Indeed, regarding the current context, a reducing process of the healers' practices is likely to emerge

Current understanding of cellulose ethers impact on the hydration of C3A and C3A-sulphate systems

International audienceThe impact of cellulose ethers (CE) on C3A hydration was examined to support the understanding of the retarding effect of CE on cement hydration. In this sense, we successively studied the CE adsorption on ettringite and calcium hydroaluminates, and then the CE influence during C3A hydration in presence or absence of calcium sulphate. We emphasized a phase-specific adsorption of CE depending on CE chemistry. Besides, in addition of CE, we highlighted a gradual slowing down of C3A dissolution as well as ettringite and calcium hydroaluminates precipitation. Again, a great impact of CE chemistry and CE adsorption behaviour were noticed. Thus, HECs induce always a stronger adsorption on calcium hydroaluminates and a longer C3A hydration delay that HPMC

Changes in C3S hydration in presence of cellulose ethers

International audienceThe influence of cellulose ethers (CE) on C3S hydration processes was examined in order to improve our knowledge of the retarding effect of cellulose ethers on the cement hydration kinetics. In this frame, the impacts of various cellulose ethers on C3S dissolution, C-S-H nucleation-growth process and portlandite precipitation were investigated. A weak influence of cellulose ethers on the dissolution kinetics of pure C3S phase was observed. In contrast, a significant decrease of the initial amount of C-S-H nuclei and a strong modification of the growth rate of C-S-H were noticed. A slowing down of the portlandite precipitation was also demonstrated in the case of both cement and C3S hydration. CE adsorption behavior clearly highlighted a chemical structure dependence as well as a cement phase dependence. Finally, we supported the conclusion that CE adsorption is doubtless responsible for the various retarding effect observed as a function of CE types

« C’est qui TGV ? » Contextualisation de l’enseignement dans le premier degré à La Réunion

L’académie de La Réunion compte en 2009, quarante sept enseignants possédant l’habilitation Langue et Culture Régionale. Outre quelques enseignants itinérants, le seul dispositif présent dans l’Académie est celui des classes bilingues et seuls dix professeurs des écoles exercent en classes bilingues expérimentales sur un total de 6434 enseignants du premier degré, soit 0,1% de l’effectif des professeurs des écoles. Malgré le terme pompeux d’habilitation Langue ET Culture régionale, dans les faits et dans la pédagogie, la culture est absente. A aucun moment, n’est évoquée, dans l’Académie, la question d’une quelconque prise en compte de la culture réunionnaise, la possibilité d’une contextualisation de l’enseignement. Cet article s’appuie sur des observations et des engagements, notamment pédagogiques, vieux de vingt années. Il tente de montrer que sans contextualisation de l’enseignement, sans réelle prise en compte de la culture réunionnaise, sans formation des enseignants à cette culture, sans opérationnalisation des connaissances transmises, les « classes bilingues », au nombre anecdotique, n’ont, au mieux, qu’un rôle de vitrine, de bonne conscience institutionnelle dans un département dont, faute de formation, beaucoup, enseignants, comme membres des corps d’inspection, disent qu’il n’est pas différent d’un département métropolitain.In 2009, the regional education authority of Reunion Island counts fortyseven teachers holding the capacitation allowing them to officially teach «Regional Language and Culture ». The only existing implement for so doing in the area is the few bilingual classes. Only ten primary school teachers practice in experimental bilingual classes on a total of 6434 teachers of the first degree, that is 0.1 % of the total number of the primary school teachers. In spite of the pompous term « capacitation to Regional Language and Culture», the culture is factually and pedagogically absent from the syllabus. Never have the Regional education authority evoked the question of the Reunion Island culture, or the possibility of a contextualisation of the teaching. The present paper lies on observations and commitments made twenty years ago. It tries to show that without contextualising the teaching, without real consideration for the Reunion Island culture, without training of the teachers in this culture, without an educational application of the knowledge, " bilingual classes ", the bilingual classes, whose number is ridiculous, are doomed to, at best, hold the role of glass window, giving the institution good consciousness. Many teachers and inspectons as well, say, that french department is not different from the department in Metropolitan France, whereas in fact, the problem is that of teachers’ training

Comportements alimentaires, petite enfance et grande distribution

Du peuplement de l’île de La Réunion, peuplement pluriel initié durant la seconde partie du XVIIe siècle, sont issues des conduites alimentaires spécifiques à ce département français de l’Océan indien. Ces pratiques se sont, tout au long de l’histoire, construites à partir des modèles de référence fournis par ceux qui, de diverses origines, sont venus peupler cette île initialement déserte. Il s’agira ici d’examiner la manière dont se sont constitués les usages alimentaires par emprunts aux cultures d’origine des habitants de l’île et syncrétismes entre les divers modèles. Ces processus d’intégration de nouvelles pratiques seront confrontés aux phénomènes engendrés par l’installation dans l’île, depuis une vingtaine d’années, de la grande distribution. Quels bouleversements se sont opérés dans les modes de consommation ? Comment l’arrivée de nouveaux produits modifie‑t‑elle les conduites préexistantes ? Nous étudierons plus particulièrement le changement des normes et pratiques alimentaires dans l’enfance.Initiated during the second part of the 17th century and involving diverse groups, the populating of Reunion Island has resulted in food behaviours that are specific to this French département in the Indian Ocean. Throughout history, these practices have been constructed on the basis of reference models provided by those people of diverse origins who came to live on this initially uninhabited island. The article will examine the way in which, throughout history, food practices were built up through borrowings from the island inhabitants’ cultures of origin, by syncretism between different models. These integration processes of new practices will be compared with phenomena produced by the setting up on the island in the last twenty years of large volume distribution. How have modes of consumption been disrupted? How has the arrival of new products from large volume distribution modified pre‑existing behaviours? Due to the great anthropological richness of the theme, we will study more specifically changing food norms and practices in childhood

Impact des éthers de cellulose sur l'hydratation du silicate tricalcique

National audienceLes mécanismes d'hydratation du ciment en présence de molécules organiques restent assez mal élucidés. Les éthers de cellulose sont systématiquement introduits dans les formulations des mortiers industriels. Leurs conséquences macroscopiques sur la réaction d'hydratation du ciment sont parfaitement connues, notamment en terme de ralentissement de la cinétique d'hydratation, mais elles n'en restent pas moins inexpliquées. Par conséquent, l'interaction des éthers de cellulose avec la matrice cimentaire a été examinée. Les résultats tendent à montrer que les éthers de cellulose ont un impact mineur sur la dissolution des différentes phases anhydres. Au contraire, ces adjuvants présentent un effet important sur la germination-croissance de certains hydrates comme l'hydrosilicate de calcium et la portlandite

Impact of cellulose ethers on the cement paste microstructure

ISBN = 3-87264-022-4 7 pagesInternational audienceComplementary investigation tools (2D and 3D observations by optical microscopy and fast X-ray microtomography and then image analysis) were developed in order to examine the effects of cellulose ethers on the cement paste microstructure. The obtained results show that the presence of cellulose ether may induce an increase of both 50-250 µm-diameter air voids. The chemistry of the cellulose ethers appears as a main controlling factor of this porous media modification. In particular, cellulose ethers seems to play an important role on the air bubbles morphological characteristics, the content of air volume and the stabilisation of the porosity from the fresh cement paste to the hardened cement paste

Les plantes de l’amour à La Réunion

On Reunion Island, phytotherapy is omnipresent and the plants found on the island are frequently associated with everyday use. More specifically, some plants are used for intimate reasons, which are split among masculine and feminine uses based on their supposed effects. As such, we can distinguish between two types of love plant usage: more feminine uses tend towards the preparation of witchcraft type love philtres that manipulate or aim to encourage the emotional attachment of someone, whereas male uses are more associated with a direct effect on sexual performance. Although the use of love philtres on unsuspecting romantic interests is well established in memoirs, the creation of certain aphrodisiacs sheds more light on the varying dynamics of creole society. These aphrodisiacs reveal an adaptation of traditional knowledge to modern methods in a globalized context which includes the integration of molecules used in allopathic medicine, ethnobotanical traditions found outside the Mascarene Islands, as well as trends communicated through advertising and other media

L’apport de l’haïtianiste André Marcel d’Ans à l’anthropologie en général et à l’anthropologie des mondes créoles en particulier

André Marcel d’Ans ne s’est jamais positionné comme un spécialiste de l’anthropologie réflexive. Pour autant, son apport à l’épistémologie de la discipline, peu, voire non reconnu, mérite d’être développé. A la suite de Roger Bastide, qui, dès la fin des années 1940, a mis en évidence l’intérêt anthropologique de l’étude des sociétés créoles, en interrogeant tant la notion de culture que l’anthropologie elle-même, André Marcel d’Ans questionne non seulement les structures de la société haïtienne mais aussi, et c’est le point qui nous intéresse ici, l’interprétation que peut en faire le chercheur. Ses réflexions sur les préjugés susceptibles d’être véhiculés par les chercheurs interrogent chaque aspect de la recherche, tant pour les sociétés créoles que pour les autres sociétés étudiées. Elles questionnent tant la manière dont sont conduites les enquêtes de terrain (la méthodologie employée), que l’interprétation des données ou la réécriture du réel qui s’opère lors de la phase de rédaction de la recherche.André Marcel d'Ans has never been a specialist in reflexive anthropology. However, his contribution to the epistemology of the discipline, not enough recognized, deserves to be developed. Following Roger Bastide, who, from the late 1940s, highlighted the anthropological interest of the study of Creole societies, by exploring both the notion of culture and anthropology itself, André Marcel d’Ans studies not only the structures of Haitian society but also, and this is our focus point here, the interpretation that the researcher can make. His questions on prejudices that can be conveyed by researchers question every aspect of the research, both for Creole societies and for the other societies studied. They question both the way the fieldwork is conducted (the methodology used), the interpretation of the data, and the rewriting of reality that occurs during the research writing phase