A reação álcali-silica (RAS) ocorre entre certas formas de sílica, estruturalmente distorcidas ou amorfas, e soluções de hidróxido alcalino, como KOH e NaOH. O produto da RAS é um gel de silicato e álcalis, susceptível de expansão pela absorção de água. Quando a RAS ocorre nos agregados minerais utilizados no concreto, o processo de reação e expansão do gel compromete a resistência mecânica da estrutura. Neste trabalho, foram estudados os efeitos sobre o gel de dois processos propostos respectivamente para mitigar a expansão e prevenir a ocorrência da RAS: o tratamento do gel com LiNO3 e a aplicação de metiltrimetoxisilano (MTMS, Si(OCH3)3CH3). Também foi analisada a reatividade de minerais utilizados como agregados (basalto, granito e quartzito), simulando a RAS em condições de laboratório. Utilizando técnicas de ressonância Magnética Nuclear (RMN) de 29Si, 7Li, 23Na, 13C e 1H, foi analisada a estrutura do gel, dos minerais e dos produtos resultantes dos tratamentos e de ataques com soluções alcalinas. Os resultados mostram que a estrutura de silicatos no gel é lamelar formada principalmente por silicatos do tipo Q3 e a aplicação de soluções de LiNO3 provoca uma transformação para um silicato de tipo linear. Esta alteração, eliminado os espaços interlamelares capazes de absorver água e causar expansão coletiva da estrutura, explica o efeito observado de redução da expansão pelos tratamentos com Li. Por outro lado, após exposição ao MTMS não foi detectada interação dos silicatos pertencentes ao gel com os grupos SiCH3, indicando autocondensaçao dos silanos. Com relação ao ataque dos minerais reativos, foram detectadas mudanças na distribuição de espécie de silicatos Qn nas três rochas. No basalto e no granito existe um aumento da fração de espécies Q1 e Q4 com relação ao mineral original. No quartzito as diferenças são maiores em magnitude e dependem dos parâmetros do ataque: temperatura e tempo de ataque. O aumento da temperatura dissolve os silicatos amorfos de conectividade baixa e média (Q0, Q1 e Q2) e produz um silicato altamente conexo formado por espécies Q3 e Q4. O aumento do tempo de ataque à temperatura ambiente não produz transformações apreciáveis na parte amorfa, mas sim dissolução de silicatos Q4 pertencentes a grãos de quartzo de maior tamanho. / The alkali-silica reaction (ASR) occurs between structurally distorted or disordered silica and aqueous solutions of alkaline hydroxides, as KOH or NaOH. The product of the ASR is an alkali-silicate gel, which may expand upon water absorption. When the ASR occurs in mineral aggregate used in concrete, the process of reaction and expansion cause the decrease in the mechanical resistance of the structure. In this work, a structural study was carried out to analyze the effect on the gel of two processes proposed respectively to mitigate the expansion and prevent the ASR: the treatment with LiNO3 and the application of methyltrimethoxysilane (MTSM, Si(OCH3)3CH3). Also, the reactivity of three minerals (basalt, granite and quartzite) commonly used as aggregates was analyzed, simulating the ASR in laboratory conditions. Nuclear Magnetic Resonance (NMR) techniques of 29Si, 7Li, 23Na, 13C e 1H in the solid state were applied to analyze the structure of the gel, the minerals and the products resulting from treatments and the attack with alkaline solutions (KOH). The results show that the silicate network in the gel is a lamellar structure, composed mainly by Q3 silicates, which is transformed into a linear structure upon the treatment with LiNO3 solutions. This modification, eliminating the inter-lamellar spaces capable to host water and cause the collective expansion of the structure, explain the reduction in the expansion observed in mortar or concrete structures treated with Li. On the other hand, after exposing gel samples to MTMS aqueous solutions, no interaction of the silicate groups in the gel with SiCH3 groups were detected, indicating auto-condensation of silane in these samples. With respect to the attack of the reactive minerals, some changes were detected in the distribution of Qn silicate species in the three rocks. In attacked basalt and granite there is an increase in the fraction of Q1 and Q4with respect to the original minerals. In attacked quartzite the differences are mores strong and depend on the reaction parameters: temperature and time of attack. The increment in temperature dissolve the amorphous silicates of low and medium connectivity (Q0, Q1 and Q2) resulting in a highly connected silicate with Q3 and Q4. Conversely, no appreciable transformation in the amorphous silicates were observed during longer attack times at room temperature, but the dissolution of bigger silica particles with well defined Q4 species was observed.

A reação álcali-silica (RAS) ocorre entre certas formas de sílica, estruturalmente distorcidas ou amorfas, e soluções de hidróxido alcalino, como KOH e NaOH. O produto da RAS é um gel de silicato e álcalis, susceptível de expansão pela absorção de água. Quando a RAS ocorre nos agregados minerais utilizados no concreto, o processo de reação e expansão do gel compromete a resistência mecânica da estrutura. Neste trabalho, foram estudados os efeitos sobre o gel de dois processos propostos respectivamente para mitigar a expansão e prevenir a ocorrência da RAS: o tratamento do gel com LiNO3 e a aplicação de metiltrimetoxisilano (MTMS, Si(OCH3)3CH3). Também foi analisada a reatividade de minerais utilizados como agregados (basalto, granito e quartzito), simulando a RAS em condições de laboratório. Utilizando técnicas de ressonância Magnética Nuclear (RMN) de 29Si, 7Li, 23Na, 13C e 1H, foi analisada a estrutura do gel, dos minerais e dos produtos resultantes dos tratamentos e de ataques com soluções alcalinas. Os resultados mostram que a estrutura de silicatos no gel é lamelar formada principalmente por silicatos do tipo Q3 e a aplicação de soluções de LiNO3 provoca uma transformação para um silicato de tipo linear. Esta alteração, eliminado os espaços interlamelares capazes de absorver água e causar expansão coletiva da estrutura, explica o efeito observado de redução da expansão pelos tratamentos com Li. Por outro lado, após exposição ao MTMS não foi detectada interação dos silicatos pertencentes ao gel com os grupos SiCH3, indicando autocondensaçao dos silanos. Com relação ao ataque dos minerais reativos, foram detectadas mudanças na distribuição de espécie de silicatos Qn nas três rochas. No basalto e no granito existe um aumento da fração de espécies Q1 e Q4 com relação ao mineral original. No quartzito as diferenças são maiores em magnitude e dependem dos parâmetros do ataque: temperatura e tempo de ataque. O aumento da temperatura dissolve os silicatos amorfos de conectividade baixa e média (Q0, Q1 e Q2) e produz um silicato altamente conexo formado por espécies Q3 e Q4. O aumento do tempo de ataque à temperatura ambiente não produz transformações apreciáveis na parte amorfa, mas sim dissolução de silicatos Q4 pertencentes a grãos de quartzo de maior tamanho. / The alkali-silica reaction (ASR) occurs between structurally distorted or disordered silica and aqueous solutions of alkaline hydroxides, as KOH or NaOH. The product of the ASR is an alkali-silicate gel, which may expand upon water absorption. When the ASR occurs in mineral aggregate used in concrete, the process of reaction and expansion cause the decrease in the mechanical resistance of the structure. In this work, a structural study was carried out to analyze the effect on the gel of two processes proposed respectively to mitigate the expansion and prevent the ASR: the treatment with LiNO3 and the application of methyltrimethoxysilane (MTSM, Si(OCH3)3CH3). Also, the reactivity of three minerals (basalt, granite and quartzite) commonly used as aggregates was analyzed, simulating the ASR in laboratory conditions. Nuclear Magnetic Resonance (NMR) techniques of 29Si, 7Li, 23Na, 13C e 1H in the solid state were applied to analyze the structure of the gel, the minerals and the products resulting from treatments and the attack with alkaline solutions (KOH). The results show that the silicate network in the gel is a lamellar structure, composed mainly by Q3 silicates, which is transformed into a linear structure upon the treatment with LiNO3 solutions. This modification, eliminating the inter-lamellar spaces capable to host water and cause the collective expansion of the structure, explain the reduction in the expansion observed in mortar or concrete structures treated with Li. On the other hand, after exposing gel samples to MTMS aqueous solutions, no interaction of the silicate groups in the gel with SiCH3 groups were detected, indicating auto-condensation of silane in these samples. With respect to the attack of the reactive minerals, some changes were detected in the distribution of Qn silicate species in the three rocks. In attacked basalt and granite there is an increase in the fraction of Q1 and Q4with respect to the original minerals. In attacked quartzite the differences are mores strong and depend on the reaction parameters: temperature and time of attack. The increment in temperature dissolve the amorphous silicates of low and medium connectivity (Q0, Q1 and Q2) resulting in a highly connected silicate with Q3 and Q4. Conversely, no appreciable transformation in the amorphous silicates were observed during longer attack times at room temperature, but the dissolution of bigger silica particles with well defined Q4 species was observed.

Ce travail s'intéresse à la fonctionnalisation de nanoparticules de silice par des organosilanes,<br />en milieu hydroalcoolique et en milieu aqueux, ainsi qu'à la nature des liens formés avec la<br />surface.<br />Une étude bibliographique est consacrée à la nature chimique de la surface de la silice et la<br />réactivité des organosilanes.<br />Le chapitre II est consacré à l'étude par RMN 29Si en solution de la réactivité des précurseurs<br />triméthylétoxysilane (TMES), diméthyldiéthoxysilane (DMDES), méthyltriéthoxysilane<br />(MTES) et mercaptopropyltriéthoxysilane (SHPTES). Une séquence performante, le 29Si-1H<br />DEPT, a été adaptée à ces systèmes.<br />Le chapitre III traite du coeur de la problématique; à savoir, la modification chimique de la<br />surface des silices par les organoalcoxysilanes. Après avoir mis en évidence le caractère<br />covalent de la liaison formée, l'influence de nombreux paramètres expérimentaux sur le<br />greffage ainsi que les propriétés hydrophobes des particules a été étudiée.

Gegenstand dieser Arbeit ist die Untersuchung der Medium Range Order in binären Alkalisilicatgläsern mittels 29Si-Festkörper-NMR-Spektroskopie. Die Medium Range Order kann durch die Qn,jklm-Verknüpfungen beschrieben werden. Die experimentelle Ermittlung der Qn,jklm-Verknüpfungen ermöglicht Aussagen über die kontrovers diskutierte topologische Verteilung der Qn-Gruppen im Glas, d.h. ob im Glas eine homogene oder inhomogene Qn-Verteilung vorliegt. Es wurden 29Si-angereicherte binäre Natrium- und Lithiumsilicatgläser verschiedener Zusammensetzungen NMR-spektroskopisch untersucht. Die Anreicherung mit dem 29Si-Isotop führte einerseits zu einer signifikanten Verbesserung des Signal / Rausch-Verhältnisses der 1D-Spektren und ermöglichte andererseits die Anwendung von 2D-NMR-Experimenten. Aus der Kombination der verschiedenen NMR-Methoden konnten Erkenntnisse über die Qn,jklm-Verknüpfungen gewonnen werden. In allen untersuchten Gläsern wurden Abweichungen von einer homogenen Qn-Verteilung gefunden.

In this work 23Na MAS NMR was validated as a successful quantitative method for studies of exchanging sodium in bentonites useful, in particular, for studies of ion-exchange kinetics. Na-enriched bentonites equilibrated in a re-circulated process water at iron-oxide pelletizing plants may acquire properties of Ca-bentonites after already 20 minutes of the equilibration time, since &gt;50 % of sodium ions will be exchanged by calcium ions during first minutes of bentonite placed in contact with the process water. It was shown that all sodium activated bentonites used in this study exchange &gt;50% of sodium in Na+/Ca2+ and ca 20 % of sodium in binary Na+/Mg2+ systems with the same bentonite/solution ratio and same concentrations of these ions in aqueous solutions as in the process water at a pelletizing plant. In total, approximately 50 % of the exchangeable sodium in original bentonites was exchanged after equilibrating of bentonites in the process water already after 20 minutes. Experimental Na+/Ca2+ exchange curves for ‘model’ Ca2+(aq) solutions and for process water are very similar as Ca2+ is the dominant constituent in the process water. Since bivalent ions (Ca2+ and Mg2+) that present in the process water readily replace Na+ ions, Na-bentonite transforms into Ca- or Mg- bentonite, which have worse rheological, swelling and, therefore, binding properties. This ion-exchange process can influence the binder performance in the pelletizing process. Taking into account that fluorapatite is one of the components present in a blend of minerals processed, possible interactions between orthophosphate (the principal anionic component of apatites) and bentonites in aqueous suspensions are considered. It was found that sorption of orthophosphate on Ca-montmorillonite follows a different pattern from sorption of orthophosphate on aluminum oxides and kaolinite. While there is a small amount of sorption below pH 7, which may involve inner-sphere complexation and precipitation of AlPO4 to Al-OH edge sites on the montmorillonite crystals, most sorption of orthophosphate occurs at higher pH. Both macroscopic sorption measurements and solid-state 31P MAS NMR suggest that above pH 7 there is precipitation of proton depleted calcium phosphate phases. Based on both 31P chemical shifts and 31P chemical shift anisotropies it was concluded that the principal precipitated phased are most likely ‘brushite-like’ phases. Very short spin-lattice T2(31P) relaxation times (≤100 μs) for the orthophosphate/bentonite systems can possibly be explained by the presence of paramagnetic Fe in bentonites. Since there are insufficient concentrations of soluble Fe species in the supernatant solution that may give rise to the observed effects, it is likely that orthophosphate is precipitated as thin layers on the surfaces of montmorillonite crystals, where phosphorus may interact with Fe atoms present in the crystal lattice. PO4-tetrahedra in sorbed species can be also distorted giving rise to a larger 31P CSA than for pure ‘apatite-like phases’. 29Si MAS and 1H-29Si CP/MAS NMR experiments on bentonite samples also performed in this work provide information about impurities of quartz in bentonites, a level of substitution of aluminum by iron atoms in the structure of montmorillonite and about the degree of hydration of montmorillonite. 29Si NMR experiments on bentonite incubated with waterglass in aqueous suspensions at concentrations of sodium silicates as in the process water demonstrated that one can follow the process of polymerization of waterglass in solutions and also detect sodium silicates polymerized on surfaces of bentonites already after 1 hour of incubation. Polymerized waterglass sorbed on bentonite surfaces may also alter rheological, swelling and, therefore, binding properties of sodium-activated bentonites used in pelletization of iron-oxide ores.

L’objectif de ce travail de thèse est d’établir les relations entre les propriétés structurales et les conditions d’élaboration d’un vitrifiat de déchets amiantés (nom commercial Cofalit®), dans la perspective de fabriquer un prototype de module de stockage thermique d’énergie solaire. Malgré des provenances de déchets très diverses, les variations de compositions du vitrifiat restent limitées. Les conditions d’élaboration (de refroidissement en particulier) induisent par contre d’importantes disparités dans la microstructure. L’analyse d’une carotte de Cofalit nous a permis de déterminer les mécanismes de cristallisation lors de la fabrication du Cofalit (refroidissement non contrôlé), conduisant à un mélange de phases cristallisées et vitreuse. Nous avons étudié les propriétés structurales (par DRX et RMN) et de cristallisation d’échantillons modèles représentatifs du matériau industriel. Les variations de composition observées sur celui-ci ont été simulées par des ajouts de silice ou de chaux. L’influence de la teneur en fer sur les propriétés radiatives, structurales (verres et céramiques) et de cristallisation a également été quantifiée. Le suivi de la cristallisation séquentielle des céramiques a été effectué par DRX in situ à haute température, à partir de l’état vitreux et à partir de l’état liquide lors du refroidissement. Ces essais ont montré que le Cofalit cristallise complètement pour des vitesses de refroidissement inférieures à 10 K/min. La stabilité du Cofalit (au niveau structural) lors de recuits à hautes températures a également été démontrée. / The aim of this work is to establish relationships between structural properties and production conditions of a vitrified asbestos-containing wastes ceramics (commercially named Cofalit®), with the goal of elaborating a prototype for thermal energy storage of solar energy. Despite various waste sources, the variations of composition observed for this material are limited. On the contrary, the production conditions (cooling stage in particular) induce important differences in the material microstructure. The analysis of a Cofalit core sample allowed us to determine the crystallisation mechanisms during its fabrication process (uncontrolled cooling), leading to a mixture of vitreous and crystalline phases. We propose a structural study (by XRD and NMR) and crystallization properties analyses of synthetic samples, representative of the industrial material. Observed variations of composition on the latter are simulated by additions of silica and lime. The influence of iron oxide content on radiative, structural and crystallization properties (of both glass and ceramic samples) have also been investigated. The following of the sequential crystallisation of ceramic samples has finally been performed using in situ high temperature XRD, from glassy state and during cooling from liquid state. These tests show that the Cofalit crystallizes completely for rates lower than 10 K/min. The high temperature stability on a structural level has also been demonstrated during annealings.

Le verre SON68 est dans un premier temps altéré en mode dynamique dans l’eau de COx riche en silicium (42mg/L) à pH 8, à fort S/V (14000 m⁻¹) et à 35, 50 et 90°C. Les résultats montrent que l’altération du verre semble être gouvernée par un mélange de processus de diffusion et de réaction de surface. La vitesse résiduelle à 90°C est de l’ordre de 10⁻⁴ g.m⁻².j⁻¹, l’énergie d’activation est de l’ordre de 70 kJ.mol⁻¹. Un mécanisme de dissolution/précipitation et d’hydrolyse/condensation sont responsables du développement de la couche d’altération. Les silicates de Mg et la calcite précipitent à 35 et 50°C, mais en plus la powellite et l’apatite ont été identifiées à90°C. Les résultats de la modélisation géochimique reproduisent les données expérimentales. Le verre est ensuite hydraté à des températures allant de 35 à 125°C et des valeurs d’humidité relative (HR) entre 92 et 99,9%. L’hydratation du verre augmente avec la température et l’HR. L’énergie d’hydratation est de l’ordre de 34,2 kJ.mol⁻¹. Les épaisseurs des couches d’altération varient entre 0,3μm à 35°C et 5μm à 125°C. La couche d’altération est appauvrie en (B, Li, Na) et enrichie en (Si, Al, Fe, Ca, Zn et Ni). Les principales phases secondaires formées sont la calcite, la powellite, l’apatite, la tobermorite et un gel hydraté.L’influence des matériaux en champ proche sur l’altération du verre SON68 dopé en ²⁹Si a été étudiée. La présence d’acier augmente le pH et diminue la concentration en Si et en Mo sans modifier la vitesse globale de corrosion du verre. Le Si est retenu sur les produits de corrosion d’acier, sa concentration en solution semble être contrôlée par la dissolution de l’argilite. La corrosion du verre en présence d’acier et d’argile à 90°C conduit à la formation de magnétite, sidérite, ferrosilicates, silice pure, sulfures de fer (pyrite, troïlite, pyrrhotite etmackinawite), calcite, apatite, powellite et silicates de Mg. Les résultats de modélisation sont en bon accord avec les données expérimentales. / The SON68 glass is initially altered in dynamic mode under silica rich COx water (42 mg/L) at pH8, high S/V ratio (14000 m⁻¹) and at 35, 50 and 90°C. The results showed that the glass alteration seems to be governed by both diffusion and surface reaction process. The residual rate at 90°C is around 10-4 g.m⁻².d⁻¹. The activation energy is about 70 kJ.mol⁻¹. The dissolution /precipitation and hydrolysis/condensation mechanisms are responsible for the development of the alteration layer. Mg silicates and calcites precipitate at 35 and 50°C, the same phases in addition to powellite and apatite precipitate at 90°C. The results predicted by the model reproduce well experimental data. The glass is then hydrated at temperatures ranging from 35 to 125°C and relative humidity values (RH) between 92 an 99.9%. The glass hydration increases with the temperature and RH, the hydration energy is about 34.2 kJ.mol⁻¹. The alteration layers thicknesses vary between 0.3μm at 35°C and 5μm at 125°C. The alteration layer is depleted in (B, Li, Na) and enriched in (Si, Al, Fe, Zn and Ni). The secondary phases are calcite, powellite, apatite and tobermorite in adition to a hydration gel. The effect of near field materials on the ²⁹Si doped SON68 glass alteration was studied. The presence of steel increases the pH and decreases the Si and Mo concentrations without changing the overall rate of glass corrosion. The Si is retained on the steel corrosion products, its concentration in solution seems to be controlled by the clay dissolution. The glass corrosion in the presence of steel and clay at 90°C leads to the formation of magnetite, siderite, ironsilicates, pure silica, iron sulphur (pyrite, troilite,pyrrhotite and mackinawite), calcite, apatite, powellite and Mg silicates. The modelling results agree well with the experimental data.

La synthèse de matériaux zéolithiques est régie par de nombreux paramètres, en particulier la nature de l'hétéroélément associé au silicium et celle de l'agent organique structurant. Ainsi, l'introduction de germanium dans les milieux réactionnels ainsi que l'utilisation de structurants dérivés d'imidazole, les cations 1-éthyl-3-méthylimidazolium et 1-butyl-3-méthylimidazolium, ont permis la découverte de deux nouveaux solides microporeux nommés respectivement IM-16 et IM-20 et présentant des topologies de charpente inédites (respectivement UOS et UWY). De plus, un troisième germanosilicate poreux nommé IM-17 a été obtenu en présence du cation décaméthonium. Chacun de ces trois matériaux possède un système tridimensionnel de canaux avec des ouvertures de 8 et 10 atomes T (IM-16) ou de 10 et 12 atomes T (IM-17 et IM-20), ainsi que des unités de construction composites d4r au sein de leur charpente. Enfin, une partie importante du travail a été consacrée à l'élaboration de molécules structurantes originales (dérivés du décahydro-dicyclopenta[b,d]pyrrole) puis de leur emploi en synthèse hydrothermale. Ces essais ont permis d'obtenir divers matériaux déjà connus, parmi lesquels les zéolithes IM-12 (UTL), ITQ-7 (ISV), ITQ-17 (BEC) et ITQ-21. / The synthesis of zeolitic materials is ruled by numerous parameters, particularly the nature of the heteroelement associated with silicon and of the organic structure-directing agent (SDA). The introduction of germanium into the synthesis gels and the use of imidazole-derived SDAs, the cations 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, allowed us to discover two new microporous solids named IM-16 and IM-20 and exhibiting novel framework structures (respectively UOS and UWY). Furthermore, a third porous germanosilicate named IM-17 was obtained in the presence of the decamethonium cation. Each of these materials possesses a three-dimensional channel system with 8- and 10-ring pores (IM-16) or 10- and 12-ring pores (IM-17 and IM-20), as well as double-4-ring (d4r) composite building units in their framework. Finally, an important part of this work was dedicated to the elaboration of original SDAs (decahydro-dicyclopenta[b,d]pyrrole derivatives) and their use in hydrothermal synthesis. This led to the synthesis of several known zeolites such as IM-12 (UTL), ITQ-7 (ISV), ITQ-17 (BEC) and ITQ-21.

L'objectif de ce travail de thèse est double : d'une part mesurer les propriétés mécaniques de couches hybrides à base d'organosiloxanes et de silice colloïdale et ensuite de lier ces caractéristiques mécaniques à leur structure.<br />La partie bibliographique est divisée en deux chapitres : le premier porte sur la description de la technique de nanoindentation et son utilisation pour obtenir les propriétés mécaniques des matériaux élastoplastiques. Le second est consacré aux matériaux hybrides organiques-inorganiques, à leur élaboration sous forme de couches et enfin à leur caractérisation structurale par spectroscopie dans le domaine de l'infrarouge et Résonance Magnétique Nucléaire du 29Si.<br />L'étude expérimentale est également divisée en deux chapitres : le chapitre I est consacré à l'élaboration des sols permettant la fabrication des couches et à la caractérisation structurale à la fois des sols (par RMN du 29Si en phase liquide) et des dépôts (par spectroscopie IR et RMN du 29Si en phase solide). Chaque système étudié est composé d'un organosiloxane différent R'nSi(OR)4-n et de silice colloïdale. Le chapitre II présente les caractérisations mécaniques par nanoindentation de ces différents systèmes qui sont analysées en relation avec leurs structures. Le but est ainsi de mettre en évidence plusieurs effets : celui de la fonctionnalité de l'alcoxyde, celui de la nature du groupement R' non polymérisable, l'effet de charge et d'encombrement stérique et enfin celui de la teneur et de la taille des particules de silice.

Les géopolymères apparaissent comme une alternative potentielle aux liants hydrauliques classiques. Ces aluminosilicates alcalins sont des matériaux amorphes produits à partir de métakaolin, ou de cendres volantes réagissant avec une liqueur d'hydroxyde, ou de silicate alcalin. Cette thèse a pour but d'évaluer le potentiel des géopolymères pour la construction des puits de pétrole. Il s'agit de combler un déficit de caractérisation et de compréhension sur le comportement rhéologique, et sur l'évolution mécanique et chimique, du gâchage à la prise des géopolymères. Pour ce faire, des méthodes aussi diverses que la RMN, le SAXS, la DLS et l'USWR ont été mobilisées pour expliquer les observations rhéologiques et mécaniques. Dans un premier temps, nous avons étudié la viscosité d'un des réactifs de la géopolymérisation : la liqueur alcaline. Nous avons montré que les variations de viscosité peuvent être expliquées par des considérations de volumes effectifs des espèces en solution. Les variations de ces volumes effectifs en fonction de la composition peuvent être rationalisées en invoquant le phénomène de volume d'excès molaire, lié à la solvatation des ions, ainsi que l'organisation de la liqueur en paires d'ions. Une fois la viscosité de la liqueur connue, il est possible de suivre l'évolution des propriétés rhéologiques de la suspension de métakaolin lors des premières heures de la réaction, en fonction de la composition et de la température. Finalement, un suivi combiné de la dissolution du métakaolin par RMN du solide et du développement des propriétés mécaniques de la matrice géopolymère du gâchage au durcissement par USWR nous a permis de conclure au caractère limitant de l'étape de dissolution du métakaolin.