Letteratura scientifica selezionata sul tema "Ciment – Propriétés physico-chimiques"
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Tesi sul tema "Ciment – Propriétés physico-chimiques":
Yapi, Amoncou Fidel. "Etude de la corrosion des armatures dans les mortiers composes : Influence du milieu de conservation : Apport de la chronopotentiométrie". Lyon, INSA, 1991. http://www.theses.fr/1991ISAL0075.
One of the most important damages of reinforced concrete constructions is the corrosion of steel reinforcement ; this last is aggravated by the presence of aggressive agents: acids, chlorides… Our research concern the study of corrosion possibility of steel reinforcement in motars made with different types of binders. We used artificial protland cement (CPA 55) as reference and the others binders are mixture of 70% CPA55 and 30 % of artificial pouzzolanic materials mainly calcined clay, fly ash, metakaolin, and slag. The specimens are cured in water or in solution containing 5% of MgCl 2 in order to study the influence of chlorides. Two methods are used to study the corrosion: voltamperometrical and chronopotentiometrical methods. In order to interpret electrochemical results, the evolution of microstructure is studied with physico chemical methods (ATD,IR, porosimetry. ) Chronopotentiometrical method give better informations with regard to steel corrosion in mortar. In solution containing MgC12, only the binder with 30% of metakaolin don't depassivate the reinforcement
Platel, David. "Impact de l'architecture macromoléculaire des polymères sur les propriétés physico-chimiques des coulis de ciment". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://pastel.archives-ouvertes.fr/pastel-00001497.
Le, Rouzic Mathieu. "Étude des propriétés physico-chimiques et mécaniques des matériaux cimentaires à base d’oxyde de magnésium". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1082/document.
Magnesium phosphate cements are the most representative cements of the activated-by-acid cements family. Despite the fact that they are known since the early 20th century, their use in civil engineering is fairly limited. These materials are used for road repairs where the fast compressive strength development is an advantage. Recently they have also been used in wastes stabilization/solidification (S/S), especially with wastes incompatible with Portland cement. The challenges of the use of these cements are related to the nature of their formation reaction: fast, very exothermic, with a very short setting time (only a few minutes).The bonding phase, k-struvite (MgKPO4.6H2O), is obtained from magnesium oxide mixed in water with monopotassium phosphate (KH2PO4).MgO + KH2PO4 + 5H2O MgKPO4.6H2OThe setting mechanisms are still poorly known and various theories, involving or not secondary product formation, have been suggested. Our researches have aimed to understand the setting mechanisms, as well as the influence of the formulation parameters on the properties of the magnesium phosphate cement. Results show that the formation of k-struvite involved a precipitation-dissolution reaction of an intermediate product, the newberyite (MgHPO4.3H2O). Formation reactions of these two products are controlled by the supersaturation rate and the pH of the solution. The study highlights the strong effect of water on the properties of fresh cement paste. With a low mass ratio e/c in comparison of Portland cement (ratio e/c between 0,1 and 0,25), a slight modification of the ratio (0,02) leads to a segregation and a surface heterogeneity of the cement paste. Among the formulation parameters, the molar ratio MgO/KH2PO4 (Mg/P) seems the most important parameter. Indeed, it impacts most of the properties of the magnesium phosphate cement (compressive strength, setting time, reaction heat, paste fluidity …). Low Mg/P ratios lead to poor water resistance, to crystals formation inside the microstructure that can be seen on the surface of the sample (an efflorescence appearance), and to important swelling of the paste, leading to the cracking of the samples. After the parametric study, a magnesium phosphate cement paste has been defined. Dimensional changes and chemical shrinkage measurement were conducted to understand the mechanisms involved in this swelling phenomenon. In support, microstructural analyses (SEM, XRD, TGA) and leaching tests complete the experimental campaign. The results confirm the influence of a low Mg/P ratio on cement swelling and water resistance. Finally, a study on various additions to the paste has been conducted, with the purpose of improving the cement paste performances. It shows that the addition of an inert filler (siliceous sand or fly ashes) has a retarding effect and reduced the reaction heat
Sedan, David. "Etude des interactions physico-chimiques aux interfaces fibres de chanvre/ciment : influence sur les propriétés mécaniques du composite". Limoges, 2007. http://aurore.unilim.fr/theses/nxfile/default/84a25f18-1c55-4565-bd8f-a95fa2e7ea73/blobholder:0/2007LIMO4055.pdf.
The use of hemp fibres in a cement material gives interesting properties to composites. The understanding of the interactions between the fibres and the cement matrix is essential to study mechanical behaviour of such composites. Hemp fibres, by a high content of pectins, fix calcium Ca2+ and hydroxyle OH- ions on their surface. A lack of hydroxyle and calcium ions is observed in the interstitial phase, which implies an inhibition of calcium silicate hydrates (CSH) responsible for the delay in setting time. Chemical attack of the fibres surface by an alkaline and calcium rich media, as cement paste, degrades hemicelluloses contained in the fibres and seems to roughen the surface. Quantities of sugars or uronic acids released by the fibres are too little to have an effect on the chemical properties of the solutions. Calcium ions fixation on hemp fibres surface implies a strong adhesion between them and cement matrix. So, an improvement of the mechanical properties of the composite is observed. The fibres network in composites permits an increase of the flexural strength associated to a rise of the displacement to rupture. Such composites could be consequently interesting in building applications
Guillon, Emmanuel. "Durabilité des matériaux cimentaires : modélisation de l'influence des équilibres physico-chimiques sur la microstructure et les propriétés mécaniques résiduelles". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2004. http://tel.archives-ouvertes.fr/tel-00133395.
Serraj, Siham. "Mise au point et études mécaniques et physicochimiques d'un ciment hydrolique phosphocalcique à usage orthopédique et odontologique". Montpellier 1, 1999. http://www.theses.fr/1999MON13504.
Hadj-Aissa, Aurélie. "Corrélations entre les propriétés physico-chimiques et l’efficacité photocatalytique d’un matériau cimentaire enrichi en TiO2". Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10056.
More than half of the world population is exposed to urban air pollution which poses problems for the environment and human health. To reduce the background of the pollution in cities, an innovative cementitious material has been developed and used to degrade pollutants thanks to its photocatalytic properties induced by the addition of TiO2. This work was focused on the correlation between physicochemical properties and the photocatalytic efficiency of a mortar enriched with TiO2 during the degradation of two volatile organic compounds (VOCs), formaldehyde and toluene as well as a mixture of nitrogen oxides (NOx). The occurence rate of of titanium dioxide on the surface, the relative percentage of titanium and the absorptance of UV photons by TiO2, respectively, were determined by Raman spectroscopy, scanning electron microscopy coupled with X-ray analysis and UV-visible diffuse refectance spectroscopy. Proportionality between these three variables has been demonstrated. The photocatalytic efficiency of TiO2-rich cementitious materials has been demonstrated for the degradation of the 2 VOCs and also for NOx. The photocatalytic efficiency is related to the presence of TiO2 on the surface and the ability of TiO2 to absorb UV photons. The cement matrix can also, in the dark, reduced significantly the concentration of formaldehyde. The study of the influence of materials and environmental parameters showed the importance of the TiO2 content, the luminous flux and relative humidity on the photocatalytic properties of the mortar and allowed to contribute to a better understanding of the reactions occurring during the degradation of pollutants by a photocatalytic cementitious material
Tadier, Solène. "Étude des propriétés physico-chimiques et biologiques de ciments biomédicaux à base de carbonate de calcium : apport du procédé de co-broyage". Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT045H/document.
Implantation of bone substitute materials using minimally invasive surgical techniques requires specific properties for the material including resorbability, injectability and adequate radio-opacity. The control of such properties of the material is of prime importance to meet a surgeon's requirements. In this context, this study deals with two different mineral cements: the first one is only composed of calcium carbonate phases and the second one is a mixture of equal amount of calcium phosphate and calcium carbonate phases. An original methodology involving complementary analytical techniques was implemented to thoroughly investigate the grinding mechanism of separated or mixed reactive powders constituting the solid phase and its effects on cement reactivity and properties. We show that co-grinding the solid phase decreases the mean size of the particles and favours both a homogeneous mixing and good contact between the components, leading to a decrease in the setting time. We also set two original protocols designed to evaluate paste injectability and phase separation during paste extrusion. Co-grinding leads to synergistic positive effects on cement injectability and radio-opacity. It allows maintaining a low and constant load during the extrusion of paste, which composition remains constant. Moreover, the cement's mechanical properties can be enhanced by lowering the L/S ratio because of the lower plastic limit. To be able to follow in situ the injection of the bone cement using X-ray radiography, strontium has been introduced as a contrast agent in the cement composition. Two different routes have been investigated: SrCO3 has been added to the solid phase or SrCl2 has been dissolved in the liquid phase. We show that co-grinding process permits to homogenise strontium distribution in the cement allowing us to optimise the minimum amount of strontium to add into the cement paste to reach the radio-opacity required by ISO 9917-1 standard. Moreover, adding SrCl2 in the liquid phase makes the cement paste more viscous and diminishes its injectability. Release tests performed on Sr-loaded cements show a sustained release of strontium at 37°C and pH 7.4. Finally, in-vitro cell tests have shown the excellent behaviour of osteoprogenitor cells, especially on cements including SrCO3. The last part of this work deals with the study of the crystallization of aragonite CaCO3 in the presence of phosphate ions, naturally present in biological fluids, to better understand the setting ability of calcium carbonate cements in-vivo. Using the constant composition crystal growth technique, we show that the presence of phosphate ions, even in very low amount (concentration < 0.5 µM) diminishes both the nucleation and the crystal growth rates of aragonite. This work contributes to the optimization of the properties of calcium carbonate-based cements and a better understanding and control of their behaviours during implantation and their evolution in-vivo. From a fundamental point of view, this multidisciplinary work performed in model conditions in-vitro and completed by preliminary in-vivo experiments have underlined the interest in combining these two approaches to identify and understand the phenomena and the chemical reactions involved during the setting of biomedical cements
Tlaiji, Tala. "Développement et caractérisation du comportement thermomécanique des matériaux composites TRC". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1116/document.
In order to strengthen and protect civil engineering structures from fires, a research program was undertaken for the development of new TRC composite materials. The TRC composite generally consists of two components, the textile reinforcement and the cement matrix. The new composites of the project are formulated with an inorganic phosphate cement or an aluminous matrix with continuous textile reinforcements using glass, carbon or hybrids. The purpose of this work is to examine and develop TRC that meets the thermomechanical performance criteria. The first level of design is to define a characterization methodology, which identifies the thermomechanical characteristics and physicochemical properties of TRC subjected to high temperature. Several coupled thermal and mechanical loading regimes as well as thermal analyses were applied and taken into account for different TRC formulations. In a first experimental part, the nature of the matrix and the cooling effect on the thermomechanical behaviour of TRC were studied. The second part of the experimental work explores the thermomechanical and thermo-physico-chemical behaviour of two families of TRC. The first family of TRC was formed of a phosphate cement and E-glass textile. It examines the bond that can be developed through the fibre-matrix interface by two different geometries of textile. The effectiveness of the reinforcement is then improved by a pre-impregnation by a resin epoxy. The second family of TRC deals with the reinforcement of an aluminous matrix by carbon grids. This family has undergone several changes. Filling of the matrix with alumina and micron glass was not sufficient to improve the behaviour of TRC. A new carbon grid was then used and layers of Mat AR glass fibres were inserted into the matrix. These layers of Mat AR created good thermal insulation but presented a delamination problem. Finally, the addition of polypropylene fibres in an aluminous mortar with graded granulometry showed satisfactory results. After the search and validation of the most efficient TRC, the "heat shield" function of insulating materials was processed to improve the thermomechanical stability of TRC
Auriol, Mélodie. "Influence des interactions physico-chimiques entre particules et composés organiques sur la stabilité de mousses minérales". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0241/document.
Cement-based mineral foams are solid porous materials and presentvery interesting insulating properties. Such materials are used in the constructionsector in order to reduce the energy consumption of houses. However, theproduction of these materials can be difficult because of the kinetic competitionbetween foam stability and cement setting. Cement-based mineral foams areextremely complex materials because of the number of components and all theirinteractions. The objective of our study is to get insight into the interactions betweenmineral and organic compounds and to understand their role in the stabilizingmechanisms. Our strategy was to study a model system, sufficiently close the realone to be representative, and sufficiently simple to identify the contribution of thedifferent components. We used as a foaming agent a surfactant exhibiting acharacteristic peak in UV-visible spectroscopy in order to determine its function andposition in the complex system. We first worked on unfoamed slurries, then westudied thin liquid films and the foamed materials