Dans une démarche de valorisation des déchets, les granulats recyclés sont introduits dans la formulation des bétons pour donner naissance à de nouveaux bétons recyclés qui représentent l’objet du projet national RECYBETON et du projet ANR ECOREB. Cette thèse se concentre sur l’étude du béton frais et en particulier la maîtrise du retrait plastique et l’effet du degré de saturation initial des gravillons recyclés sur le comportement des bétons recyclés. Deux familles de bétons avec des rapports eau/ciment respectifs de 0,6 et 0,45 ont été testés en conditions endogènes ainsi qu’en dessiccation (Vvent = 8 m/s). Chaque famille de bétons est constituée d’un béton naturel de référence et de deux bétons recyclés différenciés pas le degré initial de saturation des gravillons recyclés (50 et 120 % de l’absorption nominale). Les résultats expérimentaux soulignent la capacité des gravillons recyclés initialement partiellement saturés à capter rapidement l’eau contenue dans la pâte de ciment, modifiant ainsi le rapport E/C, les propriétés rhéologiques du béton frais et les résistances mécaniques du béton durci. Après saturation en eau, si les conditions de séchage conduisent à un manque d’eau dans le béton, les gravillons recyclés peuvent fournir de l’eau à la pâte. Ils constituent donc un potentiel de cure interne. Le retrait plastique sous vent est explicitement lié au ressuage, au développement de la pression capillaire et à la fissuration. Le temps d’initiation de la fissuration dépend de la quantité d’eau totale dans le béton et de sa capacité à ressuer tandis que l’ouverture de fissure varie avec la valeur de retrait plastique mesurée. Dans cette étude, le développement de la pression capillaire est la cause de la fissuration qui apparaît dès l’entrée d’air dans le matériau poreux. Les différences de comportements les plus importantes sont observées entre bétons ayant une quantité d’eau totale différente plutôt qu’entre bétons naturel et recyclé. La compilation des résultats expérimentaux a permis de mettre sur pied des modélisations qui illustrent les comportements observés. Les pores concernés par l’entrée d’air dans les bétons recyclés et naturels au moment de la fissuration sont les plus gros pores de la pâte. Enfin, un couplage hygrothermique séchage-température du béton peut influer sur le démarrage de l’hydratation. / In the context of sustainable development, the reuse of construction and demolition waste is necessary to conserve nonrenewable natural aggregate resources, so recycled aggregates are introduced in concrete mix design. This is the aim of the national projet RECYBETON and the research project ECOREB. This study deals with the fresh concrete and more specifically with shrinkage control and the effects of the initial saturation degrees of recycled coarse aggregates on concrete behavior.Two concrete families, with two different water/cement ratios 0,60 and 0,45, are tested under endogenous and drying (wind speed equal to 8 m/s) conditions. Each concrete family contains a reference natural concrete and two recycled concretes. The initial saturation degree is the difference between them (recycled coarse aggregates saturated or semi saturated).Experimental results underline the capacity of non-saturated aggregates to quickly absorb water from cement paste, modifying the W/C ratio, rheological properties of the fresh concrete and the mechanical strength (at 28 days) of recycled concretes. After saturation in water, recycled aggregates can release water into the cement paste if the undergone drying conditions lead to a lack of water in the cement matrix. The recycled coarse aggregates can be seen as an internal curing potential.Experimental plastic shrinkage studies carried out under drying conditions highlight a link between bleeding, capillary pressure, plastic shrinkage and cracking. It should be pointed out that the initial cracking is dependent on the total quantity of water in the concrete and on its bleeding capacity. The opening cracks vary with the plastic shrinkage values measured during the test. The analysis of the results emphasize that the capillary pressure is the determining parameter and that the air entry value matches the cracks. The major behavior differences are found between concretes with different volumes of water rather than between natural and recycled concretes.Finally, the analysis of all the experimental results have allowed concrete modelling and understanding why concretes do not behave in the same way. When it cracks, the air come in the biggest pores of the concrete paste. Moreover, a hygrothermal coupling exists between the drying and the temperature in concrete. It can affect hydration start up.

The cement being used in the construction industry is the result of a chemical process<p>linked to the decarbonation of limestone conducted at high temperature and results in a<p>significant release of CO2. This thesis is part of the project EcoBéton (Green concrete) funded<p>by the French National Research Agency (ANR), with a purpose to show the feasibility of<p>high substitution of cement by mineral additions such as blast furnaces slag, fly ash and<p>limestone fillers. Generally for high percentages of replacements, the early age strength is<p>lower than Portland cement concrete. To cope with this problem, an optimisation method for<p>mix design of concrete using Bolomey’s law has been proposed. Following the encouraging<p>results obtained from mortar, a series of tests on concretes with different substitution<p>percentages were carried out to validate the optimisation method. To meet the requirements of<p>the construction industry related to performance of concrete at early age, which determine<p>their durability, a complete experimental study was carried out. Standard tests for the<p>characterization of the mechanical properties (compressive strength, tensile strength, and<p>setting) allowed to validate the choice of mix design on the basis of equivalent performance.<p>We focused on the hydration process to understand the evolution of the mechanical<p>properties. Setting time measurement by ultrasound device at different temperatures (10°C,<p>20°C and 30°C) showed that ground granulated blast furnace slag (GGBFS) and fly ash<p>delayed the setting process, while use of limestone filler may accelerate this process.<p>Calorimetric studies over mortars and concretes made possible to calculate the activation<p>energy of the different mixtures and a decrease in heat of hydration of concretes with mineral<p>additions was observed which is beneficial for use in mega projects of concrete. Scanning<p>Electron Microscopy observations and thermal analysis have given enough information about<p>the hydration process. It was observed that the hydration products are similar for different<p>concrete mixtures, but the time of their appearance and quantity in the cement matrix varies<p>for each concrete mix.<p>Last part of the thesis was dedicated to the study of main types of shrinkage. First of all,<p>deformations measured were correlated to hydration, capillary depression and porosity<p>evolution. Results allowed concluding that the use of mineral additions has an actual effect on<p>the plastic shrinkage behaviour, but its impact is not proportional to the percentage of<p>additions. Substitution of cement by the additions seems to have a marked influence on the<p>kinetics of the shrinkage without any effect on its long term amplitude. The study of<p>restrained shrinkage under drying conditions by means of ring tests showed that concretes<p>with high percentage of slag addition seem more prone to cracking than the Portland cement<p>concretes. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

As ações presentes durante a construção de estruturas de edifícios em concreto armado são significantemente influenciadas pelo processo construtivo e podem ultrapassar a capacidade resistente definida no projeto estrutural. Os pavimentos recém concretados são suportados por pavimentos previamente concretados, através de um sistema de fôrmas, escoras e reescoras. Se houver fissuração prematura os pavimentos terão maiores deformações ao longo do tempo. Assim sendo, o trabalho apresenta um procedimento de análise estrutural que leva em conta a seqüência natural de construção. A definição das ações nos pavimentos durante a construção estabelece a história de carregamentos dos elementos estruturais do início ao fim da obra. Os modelos tridimensionais (utilizando o método dos elementos finitos) aqui apresentados consideram que o tempo altera as propriedades de resistência e deformabilidade do concreto antes dos 28 dias. Com isso, é definido um novo método para a determinação da distribuição das ações de construção entre o sistema de escoramento e os pavimentos interligados (Método Aproximado). Além disso, propõe-se uma nova metodologia para verificação dos estados limites considerando a existência das etapas de construção. / The loads during construction of multistory reinforced concrete structures are significantly influenced by the construction schedule and can exceed the supporting structure\'s design capacity. The fresh floors are supported by previously cast floors, through a system of forms, shores and reshores. If cracked prematurely, the floors will have larger time-dependent deflections. Then, the text presents a procedure for structural analysis that takes into account the natural sequence of construction. Definition of the loads on floors during construction provides a view of the history of structural element loads from the beginning to the end of construction work. The tridimensional models (using the finite element method) presented herein considers that the time affects the strenght and deformability properties of concrete before 28 days. Then, a new method for determining how the construction loads are distributed among the shoring system and the interconnected floors is defined (Approximated Method). Further, a new methodology for the limit states verification taking into account the construction phases is proposed.

Lors du forage des puits d'hydrocarbure, une pâte de ciment est coulée dans l'espace annulaire entre le cuvelage en acier et les formations géologiques traversées. Pompée à l'état liquide, cette pâte de ciment fait sa prise le long du puits sous différentes conditions de température et de pression. La gaine de ciment ainsi mise en place a pour principales fonctions de promouvoir l'étanchéité pour protéger le casing contre la corrosion, de fournir le support mécanique pour assurer la stabilité du puits et d'isoler les différents fluides dans les couches traversées. Au cours de sa vie dans le puits, depuis le forage à la complétion et de la production à l'abandon, la gaine de ciment est soumise à différentes sollicitations mécaniques et thermiques qui peuvent l'endommager et altérer ses principales fonctions. La réponse de la pâte de ciment soumis à ces sollicitations dépend non seulement des conditions d'hydratation mais aussi de l'histoire des chargements précédemment appliqués. La prédiction du comportement de la gaine de ciment doit donc se faire à l'aide d'une modélisation numérique qui nécessite une loi de comportement pour la pâte de ciment. Le but de cette thèse est d'établir une loi de comportement de la pâte de ciment en cours d'hydratation pendant le jeune-âge (les 144 premières heures). Pour ce faire, des essais calorimétriques, de mesures de vitesse des ondes et des essais œdométriques ont été réalisés sur une pâte de ciment pétrolier classe G (w/c = 0,44) en cours de prise. Les conditions d'hydratation explorées vont de 7 à 30°C pour les températures et de 0,3 à 45MPa pour les pressions. Les résultats expérimentaux ont montré que les déformations volumiques de la pâte de ciment dues à son hydratation (retrait macroscopique) sont considérablement influencées par la contrainte sous laquelle la pâte de ciment s'hydrate. Plus la contrainte d'hydratation est élevée, plus élevé est le retrait macroscopique à 144 heures. Inversement, les déformations irréversibles dues à un cycle de chargement mécanique à cet âge sont moins importantes pour les contraintes plus élevées. Les résultats ont également montrés qu'au cours de la prise du ciment, il existe un temps critique à partir duquel l'application des cycles de chargement mécanique crée des déformations résiduelles dans la pâte de ciment. Ce temps critique arrive à un degré d'hydratation relativement constant, compris entre 0,18 et 0,20. Le modèle « Boundary Nucleation and Growth » a été utilisé pour étudier la dépendance de ce temps critique à la pression et à la température. Pour la modélisation du retrait macroscopique et de la réponse contrainte – déformation de la pâte de ciment, un modèle élasto-plastique chemo-poro-mécanique couplé, prenant en compte la désaturation du milieu, a été développé. Ce modèle utilise une surface de charge fermée de type Cam-Clay et une loi plastique associée. La loi d'écrouissage dépend des déformations volumiques plastiques et du degré d'hydratation. Les paramètres du modèle ont été évalués pour simuler le retrait macroscopique de la pâte de ciment hydratée sous différentes contraintes et températures. A un degré d'hydratation donnée, le modèle permet également de simuler la réponse contrainte-déformation due à un chargement mécanique / When drilling oil & gas well, cement slurry is pumped between the casing and the rock formation. This cement slurry sets at different conditions of temperature and pressure. The role of this cement sheath is to provide zonal isolation of different fluid along the well, to protect the casing against corrosion and to provide mechanical support. During the life of the well, from drilling to completion, production and P&A (plug and abandonment), the cement sheath is submitted to various mechanical and thermal loading that can potentially damage its properties and alter its performance. The behavior of cement paste submitted to theses solicitations depends both on the hydration condition and the loadings previously applied on the cement paste. The prediction of cement sheath behavior should be done by numerical modeling, which needs a constitutive law for cement paste. The purpose of the present work is to establish a constitutive law of cement paste during its hydration at early age (first 144 hours). The approach is based on combined calorimetric, wave velocities and oedometric tests on an oil-well class G cement paste with water-to-cement ratio equals 0.44. The hydration conditions explored are 7 to 30°C for temperature and 0.3 to 45MPa for pressure. The experimental results showed that the volumetric strain due to cement hydration (macroscopic shrinkage) depends considerably on the hydration pressure. At 144 hours of hydration, the macroscopic shrinkage increases with the hydration pressure increase. But, the residual strain due to application of mechanical cycle at this age is less for cement hydrated under higher pressure. The experimental results revealed that during the hydration there is a critical time after which, the application of mechanical loading can potentially induce residual strain in cement paste. This time is reached at constant hydration degree between 0.18 and 0.20. The Boundary Nucleation and Growth model was used to model the pressure and temperature dependence of this critical time. A coupled elasto-plastic chemo-poro-mechanical model is developed to simulate the macroscopic shrinkage of cement paste hydrated at different conditions of temperature and pressure. A modified Cam-Clay type yield surface with associate flow rule is used. The hardening law depends both on the degree of hydration and on the plastic volumetric strain. At constant degree of hydration, the developed model permits to simulate the stress – strain behavior of cement paste due to the mechanical loading

The main idea of my thesis is to describe the influence of institutional care and education on the early development of a child. The theoretical part analyzes a child younger than three years, especially the child's personality development. Special attention is devoted to the development of communication and language skills of a child of this age, also the basic terms are defined there. The thesis observes the early age institutional care and education in the Czech Republic and abroad, describes its historical background and current situation. Related research studies and future trends and visions are also included. The aim of the research is to compare a group of children in early institutional care with a group of children growing exclusively in a family environment and check if the stay in the institutional care has positive effects on the development of communication skills.

The diploma thesis focuses on the communication skills development of a girl who underwent cochlear implantation at an early age. This thesis is divided into theoretical and empirical parts. The first chapter defines the hearing impairment in the sense of classification ways, diagnostics methods, and its consequences. The second chapter describes the speech development of intact and hearing-impaired children. The choice of the therapeutic method is described as well. The third chapter is focused on cochlear implantation and explains the functioning mechanism. Also, the thesis mentions the history and current manufacturers of cochlear implants. The following part of this chapter is devoted to the comprehensive care of cochlear implant users, specifically the therapeutic process. The last section contains the list of diagnostic materials used for the communication skills assessment of implanted children. The research part aims to explore the process of communication skills development of a girl implanted due to the bilateral congenital deafness via a longitudinal case study. For data collection, the methods of medical reports analysis, interview with the parents and early care counselor and observation at home were used. The anamnesis in the pre and postoperative phases is compiled based on the...

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In order to avoid the occurrence of early-age damage, cement-treated base (CTB) materials must be allowed to cure for a period of time before the pavement can be opened to traffic. Trafficking of a CTB before sufficient strength gain has occurred can lead to marring or rutting of the treated layer. The specific objectives of this research were to examine the correlation between Clegg impact values (CIVs) determined using a heavy Clegg impact soil tester and rut depths measured in newly constructed CTB and subsequently establish a threshold CIV at which rutting should not occur.The experimental work included field testing at several locations along United States Highway 91 near Smithfield, Utah, and laboratory testing at the Brigham Young University (BYU) Highway Materials Laboratory. In both the field and laboratory test programs, ruts were created in CTB layers using a specially manufactured heavy wheeled rutting device (HWRD). In the field, ruts caused by repeated passes of a standard pickup and a water truck were also evaluated. The collected data were analyzed using regression to identify a threshold CIV above which the CTB should not be susceptible to unacceptable rutting. From the collected data, one may conclude that successive wheel passes each cause less incremental rutting than previous passes and that CTB similar to the material tested in this research should experience only negligible rutting at CIVs greater than about 35. The maximum rut depth measured in either field or laboratory rutting tests was less than 0.35 in. in this research, probably due to the high quality limestone base material utilized to construct the CTB. In identifying a recommended threshold CIV at which CTB layers may be opened to early trafficking, researchers proposed a maximum tolerable rut depth of 0.10 in. for this project, which corresponds to a CIV of approximately 25. Because a CIV of 25 is associated with an acceptably minimal rut depth even after 100 passes of the HWRD, is achievable within a reasonable amount of time under normal curing conditions, and is consistent with earlier research, this threshold is recommended as the minimum average value that must be attained by a given CTB construction section before it can be opened to early trafficking. Use of the proposed threshold CIV should then ensure satisfactory performance of the CTB under even heavy construction traffic to the extent that the material properties do not differ greatly from those of the CTB evaluated in this research.

This thesis deals with actual topic in the Czech Republic - pre-school education of children younger than three years in kindergartens. With regards to social, health educational and family policies development, education and care of children under three years of age have shifted to kindergartens. The aims of this thesis are to describe recent changes concerning family, current state of pre-school education system in the Czech Republic with regard to children younger than three years of age needs and analyze and specific these needs by a contemporary young child. On such substantial data base we would like to define specific conditions of pre-school education of such young children. To follow the aims, an inquiry was conducted to examine whether or not the needs of children younger than three years are fulfilled at some kindergartens. Following that, the inquiry outputs from individual school have been compared to one another and to a model of an optimal praxis of a pre-school institution. Based on this thesis outcomes it is obvious that pre-school education of children of age up to three years in kindergartens is possible. In further detail, to maintain current quality of pre- school education also in case of inclusion of such children into kindergartens it is necessary to adopt specific legal...