O agregado de trióxido mineral (MTA) tem-se demonstrado aplicável em diversas situações que exigem reparação dos tecidos dentais e periapicais. Contudo, desvantagens relacionadas ao seu elevado custo, propriedades físico-químicas e dificuldade de manuseio têm limitado sua utilização. Neste sentido, um novo cimento de aluminato de cálcio e aditivos (CAC+) foi desenvolvido para superar algumas características negativas do MTA, mantendo, no entanto, suas propriedades satisfatórias. O objetivo deste estudo foi avaliar a progressão de culturas de células osteogênicas e de células indiferenciadas da polpa dental (linhagem OD-21) expostas ao CAC+, utilizando MTA como controle, ou a preparações alternativas do CAC+, com maior conteúdo de cloreto de cálcio (CaCl2) e/ou com substituição do óxido de zinco por óxido de bismuto como radiopacificador. Para isso, células osteogênicas derivadas de calvárias de ratos ou células da linhagem OD-21 foram crescidas sobre Thermanox® por 24 h e expostas, por períodos de até 14 dias, a amostras dos diferentes materiais, posicionadas sobre Transwell®. Em células osteogênicas, apesar de a proximidade com as amostras de CAC+ e MTA inibir o crescimento celular, nas áreas periféricas das lamínulas, foram observados proliferação, viabilidade celular e expressão de marcadores-chave da diferenciação osteoblástica, que precederam a mineralização da matriz extracelular. Culturas expostas ao CAC+, comparativamente ao MTA, exibiram aumentos na viabilidade celular, atividade de fosfatase alcalina e na expressão de marcadores de diferenciação, o que não se repetiu para células OD-21. Além disso, demonstrou-se que os efeitos destes cimentos sobre a osteogênese in vitro variaram de acordo com o período de exposição das culturas, sendo mais favoráveis durante sua fase proliferativa. Entre as preparações de CAC+, verificou-se que o aumento no teor de CaCl2 promoveu maior disponibilização de Ca2+ no meio de cultura, o que correspondeu a maior diferenciação celular e formação de matriz mineralizada em culturas de células osteogênicas e OD-21, e à redução de efeitos negativos da adição de óxido de bismuto sobre osteoblastos. Conclui-se que o CAC+ favorece o desenvolvimento do fenótipo osteogênico, atuando principalmente em células em estágios iniciais de diferenciação e que a adição de CaCl2, independentemente do agente radiopacificador, potencializa os efeitos benéficos sobre células osteogênicas e favorece o desenvolvimento e diferenciação de células indiferenciadas derivadas do tecido pulpar, podendo ser considerado como material alternativo ao MTA. / Mineral trioxide aggregate (MTA) has been successfully applied in endodontic procedures in which dental and periapical tissue repair are required. However, some drawbacks of MTA as high cost, physicochemical properties and difficulty in handling have limited its use. In this context, a novel calcium aluminate cement plus additives (CAC+) has been developed to overcome some negative features of MTA. The aim of this study was to evaluate the progression of either osteogenic cell cultures or undifferentiated dental pulp-derived ones (OD-21 cell line) exposed to CAC+ or to alternative formulations of CAC+ with a higher content of calcium chloride (CaCl2) and/or replacement of zinc oxide by bismuth oxide as radiopacifier agent. Rat calvaria-derived cells or OD-21 cells were grown on Thermanox® coverslips for 24 h and exposed to samples of CAC+ or MTA (control) placed on Transwell® for periods of up to 14 days. In osteogenic cell cultures, the proximity to MTA or CAC+ samples inhibited cell growth, whereas at distance it was observed cell proliferation, cell viability and expression of differentition markers prior to mineralization of the extracellular matrix. Comparatively to MTA, osteogenic cell cultures exposed to CAC+ exhibited higher cell viability, alkaline phosphatase activity and expression of key osteoblast markers, contrary to what was observed for OD-21 cells. Furthermore, it was demonstrated that the effects of these cements on in vitro osteogenesis varied according to the timing of exposure, with a more favorable impact during the proliferative phase of cultures. Among the diverse formulations of CAC+, it was found that the increase in the CaCl2 content promoted greater availability of Ca2+ in the culture medium, which corresponded to higher cell differentiation and mineralized matrix formation in osteoblastic cell cultures and OD-21 cells, while reducing the negative effects of bismuth oxide on osteoblasts. In conclusion, CAC+ supported the acquisition of the osteogenic cell phenotype, mostly for cells in early stages of differentiation. Additionaly, the increase in the CaCl2 content, regardless of the radiopacifier agent, potentiates the beneficial effects on osteogenic cells and promotes the growth and differentiation of OD-21 cells, rendering CAC+ a potential alternative material to replace MTA in endodontic procedures.

L’étude menée s’attache à évaluer le potentiel d’activation du laitier de haut fourneau dans un liant ternaire constitué de ciment alumineux, de sulfate de calcium et de laitier. Dans ce système ternaire, le constituant majoritaire est le sulfate de calcium. Le potentiel d’un tel système n’est pas encore connu mais cette étude vise à renseigner sur les principaux avantages et limites d’utilisation. D’un point de vue des propriétés d’usage de ce liant, la prise, le durcissement rapide et la montée des résistances sont assurés par le liant ettringitique. Ensuite, et uniquement si la dessiccation est évitée, le laitier de haut fourneau réagit et dans ce cas, l’apport du laitier dans de tels systèmes est double. Il contribue à l’augmentation des performances mécaniques à moyen et long terme et à limiter l’expansion sous eau. D’un point de vue de la compréhension des mécanismes d’hydratation, une démarche expérimentale originale est mise en place et dévoile le potentiel du laitier. Elle est basée sur la comparaison des performances obtenues avec différentes cures. Le potentiel d’hydratation du laitier est amplifié lorsque le système subit un séchage puis une réhydratation. Cependant, les techniques utilisées (diffraction des rayons X et calorimétrie différentielle à balayage) ne sont pas adaptées au suivi et à la quantification de laitier consommé. Ainsi, la compréhension de l’hydratation s’appuie sur des techniques dites indirectes. Une semi-quantification par diffraction des rayons X est réalisée pour le suivi et l’évaluation de la mayénite, le sulfate de calcium (anhydre ou dihydraté), la syngénite et l’ettringite, l’analyse thermogravimétrique permet de mesurer le degré d’hydratation du système, et la porosimétrie mercure informe sur les changements microstructuraux. La plus grosse difficulté dans ces travaux a porté sur le suivi et la quantification des phases amorphes (anhydres ou hydratées), telles que le laitier, les gels de C-S-H et d’AH3, et c’est pour cette raison qu’une approche par modélisation a été mise en place afin d’identifier le rôle de chaque constituant du système ternaire [Ciment Alumineux – Sulfate de Calcium – Laitier] et particulièrement du laitier lors de l’essai de réhydratation. L’approche par modélisation permet de mieux identifier les phénomènes chimiques et physiques ayant lieu lors de l’hydratation du liant. Elle est utilisée pour expliquer les observations macroscopiques (comme les performances mécaniques) et aide à déterminer les cinétique d’hydratation dans le milieu poreux. Le modèle utilisé n’est pas encore parfaitement au point mais il a permis d’identifier les différentes séquences d’hydratation (à savoir que le liant ettringitique réagit dans les premiers instants et qu’ensuite, l’hydratation de l’anhydrite entraine la formation de gypse et l’hydratation du laitier est effective à long terme) et de confirmer que la réaction du laitier est lente. / The potential of activation of a Ground Granulated Blast Furnace Slag has been evaluated into a ternary system comprising of a Calcium Sulfate as major component and a Calcium Aluminate Cement. This system is not well known and the main goal of this study is to determine its main advantages and limitations. From the usage properties point of view, fast setting and initial strengths are governed by the ettringitic binder. Then, and only if the dehydration is avoided, slag reacts. In this case, slag contributes to the increase of mechanical performances at medium and long terms and to limit the expansion under water. From an understanding point of view, the original experimental approach reveals the potential of the slag. It is based on a comparison of performances with different types of curing methods. The potential of hydration of the slag is amplified when the system is dehydrated during a few days and then rehydrated. However, slag contribution is complex to establish because analytical methods to follow-up slag consumption (such as X-ray Diffraction and Differential Scanning Calorimetry analysis) are not well adapted. So, to understand the hydration mechanisms, indirect approaches are used. Semi-quantitative methods by X-ray Diffraction to follow-up the mayenite, calcium sulfate, syngenite and ettringite, ThermoGravimetric Analysis to measure degree of hydration and Mercury Intrusion Porosimetry to identify microstructural changes have been carried. The most important difficulty concerns the identification and quantification of amorphous phases such as slag, C-S-H and AH3. That is why a modelling approach is necessary to understand the role of each compound in the ternary mixture and in particular the obvious contribution of slag during rehydration test. This modelling approach increases knowledge of the physical and chemical phenomena in this ternary binder. It is useful to explain the observed macroscopic properties such as strength and helps to determine the kinetics of hydration in porous environment. Even if this model is still under development, it has allowed identifying the sequences of hydration (ettringitic binder reacts at very initial time, then anhydrite transforms into gypsum and slag reacts at long term) and confirms therefore that the reaction of slag is slow.

In theory, this work is devoted to the principles and methods of measurement of volume changes of mortars and concretes. Emphasis is placed on cement self-levelling screeds with initial shrinkage compensation. In the practical part of the work is devoted to the development of prototype measuring system designed for non-contact detection of volume changes hydrating silicate. Using the new measurement method is also practically examined the influence of boundary conditions on hydration volume changes of selected silicate binders, cement mortar and cement levelling compound based on four different connective concepts. In the calculation, this work focuses on the numerical modelling of volume changes of the examined compounds.

Ces travaux de thèse visent à trouver des solutions pour minimiser autant que possible la présence de microporosités dans les alliages aéronautiques conventionnels et nouveaux. Ces microporosités résultent notamment de la réaction de l’aluminium liquide, durant la phase de coulée, avec l’hydrogène apportée par la vapeur d’eau contenue dans les réfractaires. La plupart de ces produits sont des bétons hydrauliques à matrice cimentaire alumineuse. Dans une première étape, l’identification physico-chimique et minéralogique des matériaux et des produits élaborés a été réalisée. Le comportement thermo-hydrique de différentes de bétons et de pâtes cimentaires durcies a ensuite été étudié par des essais de reprise d'humidité réalisés dans diverses conditions hygrothermiques, y compris à températures élevées (300°C). On montre ainsi que les variations hydriques dépendent fortement de la nature du liant, en particulier de sa teneur en alumine. Les phénomènes de physisorption et chimisorption sont mobilisés. Parallèlement, le comportement thermique d'une goulotte réfractaire a été modélisé, première étape pour quantifier les transferts de vapeur d’eau au sein des matériaux. Des mesures continues de température et de pression ont été obtenues sur des éprouvettes de pâtes et de bétons diversement conditionnées, placées au contact d’une frette métallique maintenue à 700°C. D’autres mesures ont été faites. Elles ont consisté à immerger des échantillons (pâtes et bétons), préalablement conservés dans différentes conditions hygrothermiques, dans l’aluminium liquide, afin de comparer leur réactivité en termes de relargage d’hydrogène, d’oxygène et de vapeur d’eau / This thesis aims to find solutions to minimize as much as possible the presence of micro-porosities in conventional and new aerospace alloys. These micro-porosities resulting especially from the reaction of the molten aluminum, during the casting phase, with the hydrogen provided by the steam contained in the refractory castables. Most of these castables are composites obtained with hydraulic binders based on aluminous cements. Firstly, a physico-chemical and mineralogical characterization of the basic materials and processed products was performed. Then, the thermo-hydric behavior of different castables and hardened cement pastes (principal source of the physical water and the chemical water) was then studied by moisture pick up tests made in various hygrothermal conditions, including at high temperatures (300 °C). It was shown that the hydric variations amplitudes strongly depend on the binder’s nature, in particular on its alumina content. The phenomena of physisorption and chemisorption are mobilized. Meanwhile, the transient thermal behavior in the time through the thickness of a refractory launder was modeled as a first step to quantify the water vapor transfer in the materials. Continuous measurements of temperature and pressure were obtained on pastes and concretes samples variously packged, placed in contact with a heated metal band maintained at 700 °C. Other measurements were made. They consisted into immersing samples (cement pastes and castables), previously stored in different hygrothermal conditions in liquid aluminum, in order to compare their reactivity in terms of release of hydrogen, oxygen and water vapor