L'objectif de cette thèse était de modéliser à partir des expériences de percolation-réactive, les processus hydrodynamique et réactionnel qui gouvernent l'altération des ciments de puits. Différentes expériences ont été réalisées dans des conditions représentatives de celles du stockage du CO2. Des échantillons fracturés ont été utilisés pour injecter une saumure enrichie en CO2 à 60°C et 10MPa et à différentes pressions partielles de CO2. Le débit d'injection variait en fonction des propriétés hydrauliques de l'échantillon exposé. L'injection d'une saumure enrichie en CO2 à débit constant à travers une fracture supposée plane a permis d'étudier les modifications des propriétés hydrodynamiques et ces conséquences sur la géochimie et la microstructure du ciment altérée. L'impact dynamique de l'évolution microstructurale a été mis en évidence. Les expériences conduites sur des échantillons présentant de larges ouvertures, réalisées sur une durée de 5 h, ont montré que la perméabilité était maintenue constante le long de l'expérience. Trois couches d'altération se sont développées consécutivement à la dissolution de la portlandite et la décalcification des CSH. L'altération a entrainé la précipitation des carbonates et de la silice amorphe à proximité de la fracture. Dans le cas d'une expérience longue durée appliquant les mêmes conditions que précédemment on a observé que la croissance de la silice amorphe a entrainé la diminution de la perméabilité. Par ailleurs les expériences effectuées sur des échantillons présentant de faibles ouvertures, ont indiqué que la conversion de la portlandite en calcite conduit au colmatage de la fracture. L'évolution des assemblages de phases conduisant à la formation des carbonates et de la silice amorphe ont été modélisés à partir du code géochimique GEMS. Les mécanismes de diffusion et les processus de mise en place des couches d'altération ont été étudiés à partir d'un modèle analytique et d'un modèle de transport réactif à partir du code géochimique PHREEQC. Mots-clés Percolation-réactive, processus hydrodynamique et thermochimique, altération, ciments de puits, stockage du CO2, modélisation. / Title: “Experimental characterization and modelling of the alteration of fractured cement under CO2 storage conditions.”The main purpose of this thesis was to characterize and to model the hydrodynamic and thermochemical processes leading to the alteration of the wellbore cement materials under borehole conditions. Percolation experiments were performed on fractured cement samples under CO2 storage conditions (60°C and 10MPa). Injection flow rate was dictated by the fracture aperture of each sample. CO2 enriched brine was flowed along the fracture aperture, and permeability changes as well as chemical evolution of major cations were continuously acquired during the experiment time. Reaction paths developed by the alteration of the cement were characterized using microtomography and ESEM images. The experiments conducted using samples presenting large fracture apertures during 5h showed that permeability was maintained constant during the experiment time. Three reacted layers were displaying by the alteration of portlandite and CSH. Long term experiment conducted with large initial fracture aperture showed a decrease of the permeability after 15hours of CO2 exposure. Otherwise, experiments performed on samples presenting narrow apertures indicated the conversion of portlandite and CSH to calcite leading to the permeability reduction and the fracture clogging. Assemblages of phases and chemical changes were modelled using GEMS-PSI speciation code. We studied also using a coupled transport-reactive model the conditions leading to the cement alteration and the formation of associated layers.Key words: Hydrodynamic and thermochemical processes, alteration, wellbore cement, CO2 storage, percolation experiments, numerical modeling.

On appelle clinker le matériau obtenu par cuisson de calcaire et d'argile et qui constitue le principal ingrédient du ciment Portland, composant essentiel de la majorité des bétons produits dans le monde. Ce clinker doit être finement broyé avant de pouvoir présenter une réactivité suffisante. La maîtrise des procédés de broyage représente un enjeu considérable pour l'industrie cimentière : il s'agit du premier poste en termes de consommation électrique d'une usine, en partie du fait de l'inefficacité des procédés employés. Les techniques de broyage par compression, apparues au cours des années 80, ont constitué un progrès majeur du point de vue de l'efficacité énergétique, mais la généralisation de leur utilisation a été freinée par des problèmes de maîtrise du procédé, en particulier pour des finesses importantes. L'enjeu de cette thèse est une meilleure compréhension des phénomènes en jeu lors du broyage par compression du clinker, en vue d'un meilleur contrôle des installations industrielles lors de la fabrication de produits fins. Nous nous sommes intéressés en particulier au comportement, du point de vue fondamental, d'un matériau granulaire subissant une fragmentation de ses grains, en nous appuyant sur la simulation numérique d'un Volume Elémentaire Représentatif de matière par les éléments discrets (DEM). Nous avons aussi recherché une loi de comportement permettant de relier contraintes, déformation, et évolution de la taille des particules pour le matériau broyé, en nous appuyant à la fois sur la micromécanique et les techniques d'homogénéisation, et un modèle semi-empirique de bilans de masses. Enfin, un premier pas vers la modélisation du procédé industriel et notamment sa simulation par éléments finis a été esquissé, afin de résorber les difficultés rencontrées en pratique par les industriels / Noindent Clinker is the material obtained by calcination of a mix of clay and limestone, and it is the main component of Portland cement, a crucial ingredient for the majority of concrete used around the world. This clinker must be finely ground to have a sufficient reactivity. Mastering the grinding process is a key issue in the cement industry: it is the first source of expense in terms of electric consumption in a factory, partially because of the overall inefficiency of the process. Compressive grinding techniques, first appeared during the 80's, allow major improvements in terms of energy efficiency, but the general implementation is yet to come, hindered by process control issues, especially for high fineness. The goal of this study is a better understanding of phenomenons occurring during compressive grinding of clinker, in order to provide better process control for industrial installations when dealing with fine products. We particularly choose to study the behaviour, on a fundamental point of view, of a granular material subjected to grain fragmentation, using the numerical simulation of an Elementary Representative Volume of material through Discrete Element Method (DEM). We also looked for a behaviour law able to provide a link between stress, strain, and grain size evolution for the ground material, using at the same time micromechanics and homogenization technique, and a semi-empirical mass balance model. Finally, we made first efforts in the direction of modelling the whole process through numerical simulation by Finite Element Method (FEM), in order to tackle the issue met by the industrials in operations

54 Summary In this experimental study, selected Devonian limestones of the Prague Basin (i.e. samples from the historic quarry of Branické skály) were examined to find their suitability for production of hydraulic limes or for natural cement. Four representative samples of the dvorecko-prokopské limestone were sampled in the form of blocks weighing approximately 10 kg each, from the layer of the quarry wall that had been chosen based on literature research. A detailed mineralogical-petrographic examination of samples was the first step, in an attempt to obtain their mineralogical composition, microstructure and texture. Samples were analysed by polarizing microscopy and cathodoluminescence of thin sections, and X-ray diffraction of insoluble residues determined by treatment with both the hydrochloric acid and the acetic acid solution. Mineralogical composition of the insoluble residuals was illite, kaolinite, quartz and Na-plagioclase (albite). Two samples contained among above mentioned mineral phases also chlorite. The utility of studied limestones for the production of hydraulic binders (hydraulic limes and natural cement) was derived from both the calculations based on obtained chemical analyses (included standard cement and lime indexes and modules) and the firing experiments. The firing experiments...

Les superplastifiants sont des adjuvants développés pour conférer aux matériaux cimentaires une plus grande fluidité pour un même rapport eau/ciment (E/C) en favorisant la dispersion des particules. De nombreuses études ont été réalisées pour approfondir la compréhension de leur mode d'action. La plupart du temps, elles relient directement la quantité adsorbée au comportement rhéologique des matériaux dans lesquels ils sont incorporés. Cependant, à une échelle intermédiaire, l'organisation mésostructurale de la pâte cimentaire contrôle non seulement sa fluidité, mais également son homogénéité et sa stabilité physicochimique.Ces travaux de thèse portent sur une dernière génération de superplastifiant : les polycarboxylates (PCE). Une approche expérimentale multi-échelles a été développée en intégrant les caractéristiques mésostructurales de la pâte de façon à faire le lien entre les interactions organo-minérales, notamment l'adsorption des PCE, et les propriétés macroscopiques (comportements en sédimentation et rhéologique). L'identification et la caractérisation granulaire de la pâte a été abordée à l'échelle de la particule, par une approche morpho-granulométrique. Des indices de dispersion ont été définis de façon à quantifier l'influence des PCE sur l'organisation mésostructurale des particules (particules unitaires ou agglomérées). Dans un second temps, l'évolution de cette organisation a été étudiée par l'analyse des colonnes de sédimentation. Un indice de séparation de phase a été défini, mettant en évidence l'existence de plages de stabilité en fonction du dosage et de la structure moléculaire du PCE incorporé.La mise en relation de ces observations avec l'étude des interactions organo-minérales a permis d'approfondir la compréhension du mode d'action et de l'influence des PCE. Cette démarche analytique représente un outil potentiel au développement de superplastifiants novateurs. / Superplasticizers are admixtures developed to give the cementitious materials greater fluidity for the same water to cement ratio (w/c), promoting the particles dispersion. Many studies were conducted to deepen the understanding of their mode of action. Usually, they connect directly the amount adsorbed with the rheological behavior of the materials in which they are incorporated. However, at an intermediate scale, mesostructurale organization of the cement paste controls not only its fluidity, but also its homogeneity and physicochemical stability.This work focuses on a new generation of superplasticizers: polycarboxylates (PCE). A multi-scale experimental approach has been developed by integrating mesostructural characteristics of cement paste to make the link between the organo-mineral interactions, particularly PCE adsorption, and the macroscopic properties (sedimentation and rheological behavior). Identification and granular characterization of cement paste was discussed, at the level of the particle, by a morpho-granulometric approach. Dispersion indices were defined to quantify the influence of PCE on mesostructural organization of particles (unit particles or agglomerates). In a second step, the evolution of this organization has been studied by analysis of sedimentation columns. A phase separation index has been defined, highlighting the existence of stability ranges as a function of the dosage and molecular structure of the PCE incorporated.Linking these observations with study of organo-mineral interactions has allowed to deepen the understanding of the mode of action and influence of PCE. This analytical approach is a potential tool to the development of innovative superplasticizers.

Les bétons de chanvre associent un granulat végétal issu du chanvre, appelé « chènevotte », et une matrice minérale. Ce sont des matériaux isolants répondant particulièrement bien aux nouvelles problématiques environnementales du secteur du bâtiment. Pourtant, leur développement est freiné par d'occasionnels désordres de mise en œuvre et des propriétés mécaniques relativement faibles qui pourraient résulter d'interactions complexes développées entre la chènevotte et le liant. Dans ce contexte, l'objectif des travaux a été de préciser la nature de ces interactions et d'identifier par quels mécanismes celles-ci peuvent modifier la prise du liant et les propriétés finales du matériau. Pour cela, l'évolution de mélanges de matières premières (chènevottes et liants) de natures différentes a été étudiée par des techniques de biochimie, de spectroscopie, de physico-chimie et de mécanique. Cette approche multi-échelle a ainsi permis de mettre en évidence le puissant pouvoir retardateur des produits extraits de la chènevotte sur la prise des liants hydrauliques. Ce retard peut conduire à une absence totale de prise du liant, lorsque celui-ci est couplé à des phénomènes de dégradation de la chènevotte, de migration de ces produits dans la matrice et d'évaporation d'eau. En outre, il a été démontré que les caractéristiques de la chènevotte (composition chimique), la nature du liant (ciment pur ou additionné de chaux), ainsi que les conditions de cure (présence ou non de CO2) sont des facteurs pouvant moduler les effets délétères sur la prise et les propriétés mécaniques du matériau formé. Ils constituent donc des paramètres potentiels d'optimisation des bétons de chanvre. / The hemp concretes, combine a plant aggregate, called “shiv” with a mineral binder. They are insulating materials particularly suited to face the new environmental problems of the building sector. However, their development is hampered by the occasional implementation problems and their relatively low mechanical properties that could result from complex interactions between the shiv and the binder. In this context, the objective of the presented work was to clarify the nature of these interactions and to identify the mechanisms by which they can impact the setting of the binder and the final properties of the material. To do so, the evolution of mixtures of the initial components (shiv and binders) differing by their nature was studied by biochemical, spectroscopic, physical chemistry and mechanical techniques. This multi-scale approach enabled us to highlight the powerful set retarding action of shiv-extractable products on hydraulic binders. This delay can even lead to a total failure of the binder setting when this one is coupled to simultaneous degradation of the hemp aggregate, migration of the formed products in the matrix and water evaporation. Finally, it has been demonstrated that the characteristics of the shiv (chemical composition), the nature of the binder (pure cement or lime added), and the curing conditions (presence or absence of CO2) represent factors that may modulate the deleterious effects on the setting and the mechanical properties of the formed material. They hence constitute potential parameters for the optimization of hemp concretes.

Durant la phase de construction des puits pétrolier, le ciment est coulé dans l'espace annulaire entre le cuvelage et la roche environnante. La gaine de ciment a pour but de tenir le cuvelage, garantir l'étanchéité des puits pétroliers, ou des réservoirs de stockage de CO2, et de protéger le cuvelage de la corrosion. Au cours de la vie du puits, cette gaine de ciment est soumise tout le long du puits à des sollicitations thermiques et mécaniques qui varient au cours du temps et qui peuvent modifier ses propriétés et altérer son étanchéité. L'objet de cette thèse est d'étudier l'effet de la température et des contraintes sur les propriétés mécaniques de la pâte de ciment en cours de prise et de la pâte de ciment durcie. L'approche est basée sur une étude expérimentale qui combine des essais calorimétriques, des mesures de vitesse des ondes et des essais oedométriques avec le système des cellules STCA (Slurry To Cement Analyzer) sur le ciment en cours de prise ainsi que des essais de compression uniaxiale et triaxiale sur la pâte de ciment durcie. Les résultats expérimentaux ont montré que la température et la pression accélèrent la cinétique d'hydratation et que la température affecte significativement les propriétés élastiques du matériau tandis que la pression ne les influence pas pour une gamme de pression limitée à 20MPa. Une modélisation de la cinétique d'hydratation associée à une technique d'homogénéisation est proposée afin d'interpréter les essais. On a mis aussi en évidence que lorsque la prise se fait sous contraintes mécaniques, des déformations irréversibles peuvent se développer dans la pâte de ciment, ce qui peut conduire à la formation d'un micro-annulaire entre la gaine ciment, le cuvelage et la formation géologique. Le comportement différé de la pâte de ciment durcie a été étudié à partir d'essais de fluage uniaxiaux et d'essais de compression isotrope. Les essais ont mis en évidence que le fluage sous chargement uniaxial est plus important pour un ciment hydraté à une température plus élevée, ce qui est attribué à une microstructure plus hétérogène. Un modèle visco-endommageable permettant de reproduire les phases de fluage primaire et tertiaire a été développé. Les essais de compression isotrope drainés et non-drainé isothermes sous forte contrainte ont montré un comportement différé avec hystérésis lors de cycles décharge-recharge. Ces essais ont été analysés à partir d'un modèle de comportement poro-visco-plastique. Le comportement élastoplastique à court terme a été abordé à l'aide des essais triaxiaux sous chargement déviatorique drainé. Ces essais ont mis en évidence que la température d'essai affecte fortement la surface de charge initiale et les déformations tandis qu'elle ne modifie pas significativement la surface de rupture. Un modèle de plasticité avec une surface de charge fermée et un écrouissage dépendant des déformations plastiques accumulées a été développé pour décrire ces essais. Enfin, une étude préliminaire sur les effets des cycles mécaniques et thermiques a été menée. Des cycles thermiques ne dépassant pas la température d'hydratation ne semblent pas affecter les propriétés mécaniques du matériau. Cependant, une dégradation très rapide avec le nombre de cycles mécaniques a été mise en évidence lorsque la contrainte dépasse 60% de la résistance en compression simple / During the construction phase of oil wells, a cement slurry is pumped into the annular space between the casing and the rock. The cement sheath aims to support the casing, provide zonal isolation in the well and reservoirs of CO2 storage and protect the casing against corrosion. During the life of the well, the cement is submitted to various thermal and mechanical solicitations along the well that can modify its mechanical properties and damage its sealing performance. The aim of this thesis is to study the effect of temperature and stresses on the mechanical properties of cement paste during hydration and in the hardened state. The used approach is based on an experimental study that combine the calorimetric tests, waves velocity measurement and oedometric tests in STCA system (Slurry To Cement Analyzer) on cement paste during hydration as well as the uniaxial and triaxial compression tests on hardened cement paste. The experimental results showed that temperature and pressure accelerate the kinetics of hydration. Temperature affects significantly the elastic properties of the material whereas the pressure does not modify them for a range of pressure limited to 20MPa. A hydration kinetics modelling associated to a homogenization method is used to interpret the tests. It is shown that for hydration under stress, the irreversible strains can evolve in the cement paste and conduct to the formation of a micro-annular between the cement sheath, the casing and geological formation. The time-dependent behaviour of hardened cement paste is studied using creep tests under uniaxial loading and also from the results of isotropic compression tests. The results show that the uniaxial creep is more important for cements hydrated at higher temperatures, which is attributed to a more heterogeneous microstructure. A visco-damaged model allowing to reproduce the primary creep and tertiary creep is developed and calibrated. Isothermal isotropic drained and undrained compression tests show a time-dependent behaviour with hysteresis during unloading-reloading cycles. These tests are analyzed on the basis of a poro-visco-plastic model. The elastoplastic behaviour in short terms is studied from triaxial tests under drained deviatoric loading. These tests bring to light that the test temperature affects highly the initial yield surface and the strains but it does not significantly modify the failure surface. A model of plasticity with a closed yield surface and hardening, depending on the accumulated plastic strains is developed to describe these tests. Finally, a preliminary study on the effect of mechanical and thermal loading cycles is performed. The thermal loading cycles with temperatures lower than the hydration temperature seem to do not affect the mechanical properties of the material. The mechanical loading cycles show a rapid degradation with the number of loading cycles when the axial stress exceeds 60% of the uniaxial strength

[pt] O objetivo deste trabalho foi a análise macro-mecânica do comportamento da terra como argamassa para revestimentos de terra. Não foram encontradas referências a estudos semelhantes a este, tratando-se portanto de um estudo pioneiro, no Brasil e no exterior. Os revestimentos foram aplicados em um substrato de terra batida de 50 e 30 cm de altura e de largura, respectivamente. Foram analisados revestimentos fabricados com 17,5%, 12%, 9% e 6% em peso de argila em relação ao material seco para dois solos distintos: Tassin (ilítico) e Rochechinard (caulinítico). Como revestimento de referência, foi fabricada uma argamassa de cal e areia (1:3). Além disso, foi avaliado o efeito da inclusão de duas fibras existentes no mercado: fibras curtas de sisal (Agave sisalana), naturais do Brasil, e resíduos de fabricação de fibras curtas de cânhamo (Cannabis sativa), provenientes da França. Tais fibras foram empregadas somente em corpos-deprova de Rochechinard com 17,5% e 12% em peso de argila em relação ao material seco, e adicionadas ao solo em uma porcentagem de 0,5% do peso do solo seco, com as mãos. Sisal possui seção circular com valores médios de 0,15 mm de diâmetro e 40 mm de comprimento; cânhamo é considerado como seção retangular de 2x5 mm de área e comprimento de 20 mm. Para todos os revestimentos foram realizadas observações visuais in situ da retração. Em seguida, os revestimentos foram ensaiados ao cisalhamento através da adição de 250 g, até a ruptura, a cada 30 s em um quadro retangular de madeira, que era pendurado nas amostras. No laboratório, a retração restringida em 4 lados e a resistência à flexão foram testadas em amostras prismáticas. Foi observado que tanto a retração quanto a resistência à flexão aumentam com o teor de argila. Além disso, os compósitos de solo com sisal apresentaram, em geral, maiores resistências àqueles em que houve emprego de cânhamo. / [en] This work analyzes the macro-mechanical behavior of earth when it is used as a raw material for finishing. It is a pioneer study in Brazil and abroad. The finishings were applied on a rammed earth wall of 50 of height and 30 cm of width. Finishings fabricated with four different clay contents (17,5%, 12%, 9% and 6% by weight of clay in relation to the dry material) were analyzed for two different soils. Each one of these soils has a predominant type of clay: Tassin (with illite in greater quantity) and Rochechinard (with kaolinite in greater quantity). As a reference finishing, it was fabricated a mortar of lime and sand (1:3). Furthermore, the behavior of two fibers was evaluated: short sisal fibers (Agave sisalana), natural from Brazil, and residue from the manufacture of short hemp fibers (Cannabis sativa), from France. These fibers were used only in samples of Rochechinard with two clay contents (17.5% and 12% by weight of clay in relation to the dry material). The fibers were added to the soil on a percentage of 0.5% by weight of dry soil, manually. Sisal has circular section with average values of 0.15 mm of diameter and 40 mm long; hemp fiber is considered as a rectangular section with 2 mm of height, 5 mm of width and 20 mm long. For all finishings, visual observations of shrinkage were performed in situ. Those finishings with higher clay content dropped from the support. The finishings which did not fell were tested in shear. For this, a load of 250 g was added, until rupture, in every 30s on a rectangular wood frame (600 g weight), that was hung in the samples. In laboratory, linear shrinkage and flexural strength were tested on prismatic samples. It was observed that both shrinkage and flexural strength increase with clay content. Regarding the addition of fibers, it was found that the composites fabricated with sisal had generally better results than those with hemp.

Esta investigación comprende el potencial de resistencia y la expansión que presenta el suelo, dicha evaluación es realizada mediante ensayos CBR. Se utiliza la técnica de suelo cemento para mejorar las características físicas y mecánicas, este proceso consiste en mezclar al material con cemento Portland Tipo I formando suelo cemento 10%, 15% y 20%, los cuales presentan un incremento del CBR (máximo: 138.7% y mínimo: 91.9%) logrando un tipo de subrasante extraordinaria para resistir la estructura del pavimento y una reducción de 7.18% en la expansión de las muestras. / This research includes the potential for resistance and the expansion that the soil presents, this evaluation is carried out through CBR tests. The soil cement technique is used to improve the physical and mechanical characteristics, this process consists in mixing the material with Portland cement type I. That combination forms soil cement 10%, 15% y 20%, which present an increase of the CBR (max: 138.7% y min: 91.9%) achieving a type of extraordinary subgrade to resist the structure of the pavement and a reduction of 7.18% in the expansion of the samples. / Tesis

This study is to compare the performance of recycled aggregate concrete and the impact of up to 50% cement replacement with fly ash on durability. Water content, sieve analysis, standard and modified compaction tests were performed to assess the physical properties of the recycled aggregate concrete. Accelerated aging tests were performed to predict the long term durability of the recycled aggregate concrete. Following Arrhenius modeling and TTS and SIM accelerated aging protocols, a time versus stiffness master curve was created. This allowed the prediction of equivalent age using experimental data and theoretical analysis. To account for environmental exposure, the specimens underwent 24 and 48 hours of wet-dry cycling and subjected. Overall there was an increase in stiffness and strength from the specimens containing fly ash. All tests performed predicted equivalent age beyond the testing period of 144 hrs. and up to 7 years. Specimens containing fly maintained a constant and higher density to environmental exposure. / by Lillian Gonzalez. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Os finos de resíduos cimentícios (previamente hidratados) podem ser reciclados através de tratamento térmico, tornando-se um ligante alternativo. Quando tratados termicamente em temperaturas inferiores a 550ºC, o processo não gera emissões de CO2 relativas à descarbonatação do calcário. Esta pesquisa teve como objetivo reativar o cimento Portland de alto forno (CP III) previamente hidratado, desidratando-o em temperatura de 500°C com patamar de 2h e reidratando-o com teores de água e de dispersante variados. Inicialmente foram realizadas caracterizações a fim de comparar as características físico-químicas do cimento desidratado com o cimento anidro. Posteriormente, foram analisadas as transformações de fases observadas com a hidratação, desidratação e reidratação do cimento. A segunda parte do estudo foi de otimização das pastas reidratadas e hidratadas, onde foram definidas condições ideais de dispersão, com a saturação ideal de dispersantes e teores mínimos de água resultado em pastas com volume de poros menores e consequentemente resistências mais elevadas. Os resultados obtidos comprovaram que o cimento desidratado se reidrata e forma fases similares às fases formadas na hidratação, como C-S-H, portlandita, hidrotalcita, etc. O cimento de alto forno carbonata mais do que o cimento Portland (CP V). Devido à área superficial elevada (14 vezes superior ao do cimento anidro), o cimento desidratado libera calor de molhagem elevado, consequencia da recombinação da água com as fases desidratadas. Observou-se ainda que, é possível controlar a resistência à compressão da pasta reidratada, otimizando o volume de poros presentes nas pastas. As resistências das pastas reidratadas com dispersante aos 28 dias foram 2,37 vezes maiores quando comparados com sistemas aglomerados. Com relação a porosidade, há indícios que é possível obter níveis de porosidade para as pastas reidratadas semelhantes com a pasta hidratada. / The fines of cementitious wastes (previously hydrated) can be recycled through heat treatment, becoming an alternative binder. When heat treated at temperatures below 550°C, the process does not generate CO2 emissions relative to limestone decarbonation. The objective of this research was to reactivate the previously hydrated Portland cement (CP III), dehydrating it at a temperature of 500°C with a 2-hours plateau and rehydrating it with varying water and dispersant contents. Characterization was initially performed to compare the physicochemical characteristics of dehydrated cement (DC) with anhydrous cement (AC). Subsequently, the AC-HP phase transformations for DC-RP were analyzed. The second part of the study was the optimization of rehydrated (RP) and hydrated (HP) pastes, where ideal dispersion conditions were defined, with optimum dispersant and water minimum contents, resulting in pastes with smaller pore volumes and consequently more compressive strength high. The results confirm that the DC rehydrates and forms phases similar to the phases formed in the hydration, such as C-S-H, portlandite, hydrotalcite, etc. The blast furnace cement carbonate more than Portland cement (no additions). Due to the high surface area (14 times higher than that of the AC), the DC releases high wetting heat, due to the recombination of the water with the dehydrated phases. It was also observed that it is possible to control the compressive strength of the rehydrated paste by optimizing the pore volume present in the pastes. The strengths of dispersed pastes with additives at 28 days were 2.37 times higher when compared to agglomerated systems. With respect to porosity, there are indications that it is possible to obtain porosity levels for the similar rehydrated pastes with the hydrated paste.