Academic literature on the topic 'Cement hydrates'
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Journal articles on the topic "Cement hydrates"
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Fitzgerald, Richard J. "Modeling cement hydrates." Physics Today 62, no. 11 (November 2009): 23. http://dx.doi.org/10.1063/1.4797014.
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Guo, Wei Juan, Gao Xiang Du, Qiang Xue, and Jing Hui Liao. "Effect of Naphthalene Based Superplasticizers on Performance of Ultrafine White Cement." Advanced Materials Research 250-253 (May 2011): 182–87. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.182.
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The compressive strength of ultrafine white cement samples at three ages: 3, 7 and 28 days and micro appearance of hydrates were tested. The influence of the usage of superplasticizers on the compressive strength of ultrafine white cement paste and hydrates were investigated. The results indicated that the 28d compressive strength of ultrafine white cement with 3% naphthalene based superplasticizers added was 92.9 MPa, 22.9% of that of pure ultrafine white cements (75.6 MPa). The addition of superplasticizers was beneficial to the density of white cement paste. A large number of hydrates (AFt, C-H-S, and so on) were generated in the capillary pores, which would improve the structure of capillary pores of hardened cement paste, increase the density and strength.
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Gou, Mi Feng, and Xue Mao Guan. "Performance of Chloride Binding by Aluminate Hydrates in Cement-Based Composite Materials." Advanced Materials Research 583 (October 2012): 211–14. http://dx.doi.org/10.4028/www.scientific.net/amr.583.211.
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The chloride binding capacity of aluminate hydrates in cement-based composite materials is investigated. The total chloride contents and free chloride contents were analyzed by acid-soluble method and water-soluble method. The chemical interaction of chloride with the hydrates of aluminate phases in cement was also studied by X-ray diffraction. Test results show that the monosulfate hydrate has chloride binding capacities, whereas ettringite has no capacity to bind chloride. The chloride binding by monosulfate hydrate is attributed to the formation of Friedel’s salt and Kuzel’s salt by the ion exchange of SO42- with Cl- and the nonlinear relationship can be represented best by a Freundlich isotherm.
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SHINOBE, Kan, Nobukazu NITO, Yutaka AIKAWA, and Etsuo SAKAI. "HYDRATES AND MORPHOLOGY OF HYDRATED HIGH VOLUME BLAST FURNACE SLAG CEMENT." Cement Science and Concrete Technology 71, no. 1 (2017): 68–73. http://dx.doi.org/10.14250/cement.71.68.
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Hlobil, Michal. "DISTRIBUTION OF HYDRATION PRODUCTS IN THE MICROSTRUCTURE OF CEMENT PASTES." Acta Polytechnica CTU Proceedings 27 (June 11, 2020): 84–89. http://dx.doi.org/10.14311/app.2020.27.0084.
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This case study focuses on the quantification of the amorphous hydrate distribution in the microstructure of hardened cement paste. Microtomographic scans of the hardenend cement paste were thresholded based on histogram image analysis combined with microstructural composition obtained from CEMHYD3D hydration model, to separate unhydrated cement grains, crystalline and amorphous hydrates, and capillary pores. The observed spatial distribution of the amorphous hydrate exhibited a strong spatial gradient as the amorphous gel tended to concentrate around dissolving cement grains rather than precipitate uniformly in the available space. A comparative numerical study was carried out to highlight the effect of the spatially (non)uniform hydrate distribution on the compressive strength of the hardened cement paste.
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Krivoborodov, Yury R., and Svetlana V. Samchenko. "The Increase of Hydration Activity of Portland Cement by Additives of Crystalline Hydrates." Materials Science Forum 974 (December 2019): 195–200. http://dx.doi.org/10.4028/www.scientific.net/msf.974.195.
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The article presents the results of a study of the effect of synthesized microdisperse additives of crystalline hydrates based on calcium sulfoaluminates on the properties of cement stone. The effectiveness of the use of a rotary pulsation apparatus (RPA) to obtain microdispersed additives is identified. The possibility of accelerating the hardening of cement stone by entering microdispersed additives into its composition is shown. It has been established that in the presence of microdispersed additives of crystalline hydrates in the cement stone, the phase composition of hydrate tumors changes, the amount of calcium hydrosilicates and ettringite increases, the porosity decreases and the strength of the cement stone increases. This provision is confirmed by the increase in the degree of cement hydration, the amount of bound water in all periods of hardening of the stone. It is proposed to use microdisperse additives, which play the role of primers for the crystallization of ettringite and calcium hydrosilicates, to increase the strength of cement stone in the early stages of hardening.
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Madej, Dominika. "Strontium Retention of Calcium Zirconium Aluminate Cement Paste Studied by NMR, XRD and SEM-EDS." Materials 13, no. 10 (May 21, 2020): 2366. http://dx.doi.org/10.3390/ma13102366.
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This work concerns the hydration mechanism of calcium zirconium aluminate as a ternary compound appearing in the CaO-Al2O3-ZrO2 diagram besides the calcium aluminates commonly used as the main constitutes of calcium aluminate cements (CACs). Moreover, a state-of-the-art approach towards significant changes in hydraulic properties was implemented for the first time in this work, where the effect of structural modification on the hydration behavior of calcium zirconium aluminate was proved by XRD, 27Al MAS NMR and SEM-EDS. The substitution of Sr2+ for Ca2+ in the Ca7ZrAl6O18 lattice decreases the reactivity of Sr-substituted Ca7ZrAl6O18 in the presence of water. Since the original cement grains remain unhydrated up to 3 h (Ca7ZrAl6O18) or 72 h (Sr1.25Ca5.75ZrAl6O18) of curing period in the hardened cement paste structures, strontium can be considered as an inhibition agent for cement hydration. The complete conversion from anhydrous 27AlIV to hydrated 27AlVI species was achieved during the first 24 h (Ca7ZrAl6O18) or 7 d(Sr1.25Ca5.75ZrAl6O18) of hydration. Simultaneously, the chemical shift in the range of octahedral aluminum from ca. 4 ppm to ca. 6 ppm was attributed to the transformation of the hexagonal calcium aluminate hydrates and Sr-rich (Sr,C)3AH6 hydrate into the cubic phase Ca-rich (Sr,C)3AH6 or pure C3AH6 in the hardened Sr-doped cement paste at the age of 7 d. The same 27Al NMR chemical shift was detected at the age of 24 h for the reference hardened undoped Ca7ZrAl6O18 cement paste.
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Liu, Yan Jun, Bo Tian Chen, and Yong Chao Zheng. "Thermodynamic Interpretation of Carbonation Process of Portland Cement Hydration Products." Advanced Materials Research 753-755 (August 2013): 543–57. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.543.
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Cement hydration products carbonation is not only blamed for the carbonation-induced hardened cement paste or concrete cracking, also attributed to the pore water PH-value decrease, which causes the reinforcement corrosion under the existence of water and oxygen due to removal of oxide film passivating rebar surface, in hardened cement paste and concrete. Based on chemical thermodynamics, this paper presents the susceptibility of different cement hydration products to carbonation through calculating their Standard Gibbs Free Energy respectively, Gibbs free energy under temperature variation and the minimum equilibrium pressure of carbon dioxide triggering the carbonation process. The calculated results show that, under standard state (25°C, 100kpa), the minimum equilibrium pressure of carbon dioxide triggering carbonation process is significantly variable for different types of cement hydration products. For example, mono-sulfate sulfoferrite hydrates (3CaOFe2O3CaSO412H2O) is the most susceptible to carbonation, followed by mono-sulfate aluminate hydrates (3CaOAl2O3CaSO412H2O), while multi-sulfate sulfoaluminate hydrates (3CaOAl2O33CaSO432H2O) is the least vulnerable to carbonation, followed by silicate hydrates (5CaO6SiO25.5H2O). The findings in this paper are significant in understanding thermodynamic mechanism of cement hydrates carbonation and seeking the solution to prevent cement hydrates from carbonation-induced deterioration.
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Wang, Feng, Pingan Chen, Xiangcheng Li, and Boquan Zhu. "Effect of Colloidal Silica on the Hydration Behavior of Calcium Aluminate Cement." Materials 11, no. 10 (September 28, 2018): 1849. http://dx.doi.org/10.3390/ma11101849.
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The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO2 nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO2 nanoparticles.
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Tang, Shengwen, Yang Wang, Zhicheng Geng, Xiaofei Xu, Wenzhi Yu, Hubao A, and Jingtao Chen. "Structure, Fractality, Mechanics and Durability of Calcium Silicate Hydrates." Fractal and Fractional 5, no. 2 (May 17, 2021): 47. http://dx.doi.org/10.3390/fractalfract5020047.
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Cement-based materials are widely utilized in infrastructure. The main product of hydrated products of cement-based materials is calcium silicate hydrate (C-S-H) gels that are considered as the binding phase of cement paste. C-S-H gels in Portland cement paste account for 60–70% of hydrated products by volume, which has profound influence on the mechanical properties and durability of cement-based materials. The preparation method of C-S-H gels has been well documented, but the quality of the prepared C-S-H affects experimental results; therefore, this review studies the preparation method of C-S-H under different conditions and materials. The progress related to C-S-H microstructure is explored from the theoretical and computational point of view. The fractality of C-S-H is discussed. An evaluation of the mechanical properties of C-S-H has also been included in this review. Finally, there is a discussion of the durability of C-S-H, with special reference to the carbonization and chloride/sulfate attacks.
Dissertations / Theses on the topic "Cement hydrates"
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Rheinheimer, Vanessa. "A nanoscale study of dissolution and growth processes in cement hydrates." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/285965.
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This thesis aims at providing new knowledge on the, otherwise poorly known, molecular-scale mechanisms that operate during hydration of cement phases and dissolution of their hydrates. In order to pursue this objective, a novel approach has been followed, including the development of a new procedure to synthesize thin films of calcium silicates, real time characterization of grain growth and dissolution with liquid-cell atomic force microscopy, and monitoring of their chemical evolution by X-ray photoelectron spectroscopy of thin films hydrated in-situ, avoiding atmospheric contamination. Nanometer-sized films of clinker phases have been prepared using electron-beam evaporation methods. After deposition on silicon substrates, film thicknesses and mineralogical composition were characterized by atomic force microscopy (AFM) or mechanical profilometry and grazing-angle X-ray diffraction (GAXRD), respectively. Chemical composition was determined by X-ray photoelectron spectroscopy (XPS). Results from the GAXRD and XPS analysis show that aluminates phases are not suitable to be evaporated by electron beam technique. However
quantitative analysis of calcium silicates samples shows that the Ca:Si ratio of the deposited film is the same as in the bulk starting material, confirming the suitability of the technique for the synthesis of these materials. Calcium silicate thin films with different thicknesses were submitted to hydration in different ways. XPS results describe clear chemical changes when samples are exposed to water vapor by shifts on the silicon peak, broadening on the calcium peak and decreasing on the Ca:Si ratio, related to the silicon polymerization due to the C-S-H formation. In situ hydration in fluid cell followed by AFM in water and calcium hydroxide saturated solution allows observing the formation of C-S-H particles, that happens very fast in C3S, which is dissolved later, and slower in C2S. Finally, Scanning transmission X-ray microscopy (STXM) of samples hydrated in situ with water allows observing the formation of particles with different concentration of calcium and silicon, and different chemical state at some point. The development of this technique of synthesis and the results obtained on the hydration allow improving the knowledge of early stage clinker phase hydration at the molecular level and to better understand the behavior of these materials, shedding some additional light on the complex problem of the hydration mechanisms of cementitious materials.Aquesta tesi té per objectiu proporcionar nous coneixements sobre els mecanismes, abans poc coneguts, que operen durant la hidratació de les fases de ciment i la dissolució dels seus hidrats a escala molecular. Per tal d'aconseguir aquest objectiu, un nou enfocament ha estat seguit amb l'elaboració d'un nou procediment per sintetitzar pel·lícules primes de silicats de calci, la seva caracterització en temps real del creixement del gra i de la dissolució amb les cel·les de líquid al microscopi de forces atòmiques i el seguiment de l'evolució de la seva composició química per espectroscòpia de fotoelectrons de raigs X de pel·lícules primes hidratades in-situ, evitant la seva contaminació atmosfèrica. S'han preparat pel·lícules nanomètriques de les fases del clínquer utilitzant l'evaporació per feix d'electrons. Després de la deposició en substrats de silici, es van caracteritzar el gruix mitjançant la microscòpia de forces atòmiques (AFM) i la perfilometria mecànica i la composició mineralògica amb la difracció de raigs X d'angle rasant (GAXRD). La composició química es va determinar per espectroscòpia fotoelectrònica de raigs X (XPS). Els resultats del GAXRD i d'XPS mostren que els aluminats no són adequats per a ser evaporats utilitzant l'evaporació assistida amb feix d'electrons. No obstant això, anàlisis quantitatives de les mostres de silicats de calci mostren que la relació Ca:Si de la pel·lícula dipositada és la mateixa que en el material de partida, el que confirma la idoneïtat de la tècnica per a la síntesi d'aquests materials. Les pel·lícules primes de silicat càlcic de gruixos diferents van ser sotmeses a hidratació de diferents maneres. Els resultats d`XPS descriuen canvis químics clars quan les mostres estan exposades al vapor d'aigua com s'infereix dels canvis en el pic del silici, l'eixamplament del pic del calci i la disminució en la relació Ca:Si, que es relaciona amb la polimerització del silici degut ala formació de C-S-H. La hidratació in situ en aigua o solució saturada d'hidròxid de calci a la cel·la de fluid de l'AFM permet observar la formació de partícules de C-S-H. La hidratació ocorre molt ràpidament en el C3S, que després es dissol, i és més lenta en el C2S. Finalment, la microscòpia de transmissió i escaneig de raigs X (STXM) de les mostres hidratades in situ amb aigua permet observar la formació de partícules amb diferents concentracions de calci i silici i, en alguns casos, la variació de l'estat químic . El desenvolupament d'aquesta tècnica de síntesi i els resultats obtinguts en la hidratació permeten millorar el coneixement de la hidratació de les fases del clínquer en estadis inicials a nivell molecular i entendre millor el comportament d'aquests materials, ajudant a aclarir el complex problema dels mecanismes d'hidratació dels materials del ciment
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Acher, Loren. "Etude du comportement sous irradiation γ et électronique de matrices cimentaires et de leurs hydrates constitutifs." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX045/document.
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Afin de conditionner les déchets technologiques issus du démantèlement de l’Atelier de Vitrification de Marcoule au Commissariat à l’Energie Atomique et aux énergies alternatives (CEA), leur blocage dans une matrice cimentaire est envisagé. Dans ce contexte, l’effet des rayonnements ionisants issus des déchets nucléaires sur la matrice de confinement doit être examiné afin de garantir d’une part l’intégrité du colis, et d’autre part une production de gaz de radiolyse limitée. Ce travail de thèse s’intéresse au comportement sous irradiation gamma et électronique de trois types de matériaux cimentaires aux constituants différents et se focalise sur la production de gaz de radiolyse et sur l’évaluation de la résistance physique à travers l’observation des modifications structurales. Le sujet est traité par une double approche à la fois sur pâte de ciment et sur phases modèles, c’est-à-dire sur les hydrates constitutifs des pâtes de ciment synthétisés indépendamment. Il apparaît clairement que l’eau porale ainsi que les hydrates constitutifs contribuent à la production d’hydrogène radiolytique, avec une forte variation selon la nature des matériaux cimentaires. Ainsi, les ciments à base d’aluminates de calcium et les ciments phospho-magnésiens présentent un intérêt notable par rapport aux ciments silico-calciques usuels quant à la production d’hydrogène. Aux très fortes doses (plusieurs GGy) la résistance structurale sous irradiation électronique a été évaluée par diffraction de rayons X. Les hydrates constitutifs des trois familles de ciment étudiées présentent une bonne résistance structurale. Malgré la présence de variations dimensionnelles et microstructurales, ils ne s’amorphisent pas sous irradiation, ce qui s’avère positif en vue de l’application industrielle envisagéeIn order to treat the technological waste arising from the dismantling of the Marcoule Vitrification facility of the French Atomic Energy Commission (CEA), conditioning in a cement matrix is being put forward. Within this context, the impact of ionizing radiation produced by the nuclear waste on the confinement matrix ought to be investigated in order to ensure both the integrity of the package and the limitation of the radiolytic gas production. This thesis investigates the behavior of three types of cement compounds with distinct constituents under gamma and electronic radiation. This study deals with both the radiolytic gas production and the physical resistance of the materials using a structural modification examination. A double and complementary approach is used treating cement pastes and synthetic cement compounds together. It clearly appears that the pore water and the hydrates themselves both contribute to the radiolytic hydrogen production, with a significant variation depending on the nature of the materials. As far as radiolysis is concerned, calcium aluminate-based cements and magnesium phosphate cements are of considerable interest in comparison with the usual calcium silicate cements. At very high doses (GGy range), the structural resistance under electron irradiation was evaluated by X-ray diffraction. The constituent hydrates of the three cement types studied exhibit a good structural resistance. Despite the presence of dimensional variations at the unit cell scale as well as microstructural evolution, no amorphization is observed under irradiation, which is an interesting result with respect to the intended industrial application
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Constantinides, Georgios 1978. "Invariant mechanical properties of calcium-silicate-hydrates (C-H-S) in cement-based materials : instrumented nanoindentation and microporomechanical modeling." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34377.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.Includes bibliographical references (p. 455-478).
Random porous solids such as bone and geomaterials exhibit a multiphase composite nature, characterized by water-filled pores of nm- to m-scale diameter. The natural synthesis and operating environments of such materials significantly alters phase composition and multiscale structural heterogeneities throughout the material lifetime, defining significant changes in macroscopic mechanical performance for applications ranging from multispan bridges to calcium-phosphate bone replacement cements. However, the nanoscale phases formed within the unique chemical environment of pores cannot be recapitulated ex situ in bulk form, and imaging of the composite microstructure is obfuscated by the size, environmental fragility, and nonconductive nature of such geomaterials and natural composites. Thus, there is an increasing drive to develop new approaches to image, quantify the mechanical contributions of, and understand the chemomechanical coupling of distinct phases in such composites. In this thesis, we utilize recent advances in experimentation namely instrumented indentation, and micromechanical modeling namely homogenization techniques, in an attempt to quantify the mutli-phase, multi-scale heterogeneity observed in all cement-based materials. We report a systematic framework for mechanically enabled imaging, measuring and modeling of structural evolution for cement based materials (CBM), porous geocomposites, at length scales on the order of constituent phase diameters (10-8 - 10-6 m), and thus identify two structurally distinct but compositionally similar phases heretofore hypothesized to exist.
(cont.) The presented experimental and modeling results culminated in micromechanical models for elasticity and strength that can predict the macroscopic mechanical behavior for a range of CBM systems. The models directly correlate the changes in chemical and mechanical state to predict the experimentally observed range of macroscopic mechanical properties. This general framework is equally applicable to other man-made and natural composites, and enables accurate prediction of natural composite microstructure and mechanical performance directly from knowledge of material composition.
by Georgios Constantinides
Ph.D.
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Nguyen, Dan-Tam. "Microindentation Creep of Calcium-Silicate-Hydrate and Secondary Hydrated Cement Systems." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31519.
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The nanostructure, physical properties and mechanical performance of C-S-H, 1.4 nm tobermorite, jennite, and ettringite were studied. C-S-H of variable stoichiometries was examined as a model system in comparison with that produced in the hydration of Portland cement. The current Master’s thesis is comprised of four research papers designed to improve the current understanding of the nanostructure and engineering properties of C-S-H systems and modified C-S-H systems. Many of the controversial issues in cement science were identified and were addressed in a comprehensive research study, which examined the key features of the C-S-H systems at the nano-structure level. In Chapter 4, each paper presented new evidence for a number of mechanical aspects of C-S-H materials. Numerous advanced analytical tools were used in order to verify the observations made in each section. The major achievements of the current work are mentioned briefly as follows:
1. It was determined that microindentation is a useful method for determining the creep behavior of C-S-H of various stoichiometries, 1.4 tobermorite, jennite, and ettringite.
2. Microindentation parameters i.e. creep modulus, indentation modulus and indentation hardness are porosity dependent.
3. Microindentation creep measurements on C-S-H (C/S = 0.80 and 1.20) demonstrated that creep modulus, indentation modulus, and indentation hardness are all dependent on mass-loss from the 11%RH condition.
4. Evidence was presented that the nanostructural role of interlayer water in C-S-H has a significant influence on the creep process.
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Bordy, Arthur. "Influence des conditions thermo-hydriques de conservation sur l'hydratation de matériaux cimentaires à base d’une fine recyclée." Thesis, Cergy-Pontoise, 2016. http://www.theses.fr/2016CERG0876/document.
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La valorisation, comme granulats, des matériaux issus du recyclage du béton de démolition contribueà diminuer les surfaces dédiées au stockage des déchets et à limiter le recours systématique auxressources naturelles. L’emploi de fines recyclées à partir de béton de déconstruction s’inscrit danscette démarche et permet par ailleurs, quand la fine est utilisée en substitution partielle du cimentlors de la fabrication de nouveaux matériaux cimentaires, de réduire l’impact sur l’environnement deces matériaux.Cet usage conduit à mettre en présence dans la pâte à l’état frais du ciment anhydre et du cimenthydraté, ce qui pose la question de l’impact de cette situation sur le matériau. Pour y répondre enpartie, les travaux de recherche présentés dans cette thèse ont pour objectifs principaux d’étudier leprocessus d’hydratation d’une phase anhydre en présence d’autres phases hydratées, et d’analyserl’influence des conditions thermo-hydriques de conservation (HR et T°) sur les cinétiquesd’hydratation des matériaux cimentaires.Pour ce faire, une campagne expérimentale a été menée sur des mortiers et leurs pâtes de cimentéquivalentes fabriqués en remplaçant une partie de leur ciment Portland par une fine issue durecyclage d’une pâte de ciment durcie et bien hydratée. Un suivi au cours du temps des teneurs enPortlandite, de la porosité totale, de la résistance à la compression ainsi que de la résistance à lacarbonatation accélérée des matériaux a été réalisé. Les résultats obtenus montrent qu’il est possiblede fabriquer des mortiers en substituant le ciment par une fine obtenue uniquement par concassageet broyage d’une pâte de ciment durcie. Cependant, l’augmentation du taux de substitution massiquedu ciment par la fine recyclée s’accompagne d’une altération des propriétés et performances desmortiers. Les résultats du suivi d’hydratation couplés aux résultats d’analyse de la microstructure ontmontré que l’effet des conditions thermo-hydriques de conservation sur les cinétiques d’hydratationdes différentes pâtes de ciment dépend de leurs propriétés intrinsèques (microstructure). Celapourrait expliquer l’absence de consensus dans la littérature sur la valeur de l’humidité relativeambiante conduisant à l’arrêt de l’hydratation.En parallèle à l’étude expérimentale, une étude numérique de l’influence des conditions thermohydriquesde conservation sur l’hydratation des pâtes de ciment a été menée. Pour les besoins del’étude, une réadaptation du code de calcul utilisé, CEMHYD3D, a été nécessaire. Les résultatsobtenus montrent que, lors de l’hydratation, la Portlandite initialement présente dans le matériau(apportée par la fine recyclée) se dissout au contact de l’eau alors que la phase encore anhydre enproduit. Cette étude a également permis de conforter les résultats expérimentaux quant à l’influencede l’humidité relative ambiante sur l’hydratationThe use, as aggregates, of recycled materials from demolished concrete contributes to limit landfill and the systematic use of natural resources. Using recycled fines from the deconstruction concrete is an extension of this approach. When used as a partial substitution for cement in cementitious materials, it may also be a solution to reduce the environmental impact of these materials.This specific use induces the presence of anhydrous cement particles and hydrated cement phases in the fresh material. This raises the question whether and how it can impact the hydration process. With the aim to answer, at least partially, to this question, the thesis presents a study of the hydration process of an anhydrous phase in the presence of other hydrated phases, and analyzes the influence of the conservation conditions (RH and T°) on the hydration kinetics of cementitious materials.An experimental campaign was conducted on mortars and their equivalent cement pastes designed by replacing a part of their Portland cement by a recycled cement paste fine. The monitoring of the Portlandite content, the total porosity, the compressive strength and the accelerated carbonation of the materials was achieved. The obtained results show that it is possible to design mortars by substituting their cement by a fine obtained only from crushing and grinding of a hardened cement paste. However, increasing the substitution ratio of the cement by the recycled fine was find to be accompanied by a deterioration of the mortars properties and performances. The results of the hydration monitoring coupled to investigations of the microstructure showed that the effect of conservation conditions on the hydration kinetics of the different cement pastes depends on their intrinsic properties (microstructure). This could explain the lack of consensus in the literature on the drying conditions under which hydration kinetics are strongly affected.In parallel to the experimental study, a numerical study of the influence of the conservation conditions on the hydration of cement pastes was conducted. Readjustments of the parameters of the used code (CEMHYD3D) were necessary. The obtained results show that, during hydration, the Portlandite originally present in the material (provided by the recycled fine) dissolves in contact with water, while the anhydrous phase produces new Portlandite. This study consolidated moreover the experimental results on the influence of the ambient relative humidity on hydration
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Roosz, Cédric. "Propriétés thermodynamiques des phases cimentaires hydratées : C-S-H, C-A-S-H et M-S-H." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2264/document.
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Le béton est l'un des matériaux de construction les plus utilisés au monde. Sa durabilité, ses propriétés mécaniques et chimiques en ont fait un matériau de choix dans les concepts de stockage proposés par l'Agence Nationale pour la gestion des Déchets RadioActifs (Andra), notamment pour la réalisation des ouvrages de soutènement, bouchons d'alvéoles, massifs d'appuis ou encore conditionnement des déchets. L'étude de la stabilité des phases constitutives des matériaux cimentaires est donc nécessaire au vu des quantités envisagées et de la pérennité des ouvrages, et doit considérer (i) des gammes de températures adaptées aux matrices cimentaires de confinement en contact avec des déchets exothermiques (25 à 80°C), et (ii) une échelle de temps représentative de la durée de vie d'un stockage.Le projet ThermoChimie de l'Andra vise donc à développer une base de données (BDD) thermodynamiques cohérente, permettant de modéliser l'évolution chimique des matériaux cimentaires dans l'environnement du stockage de déchets radioactifs. Toutefois, dans l'état actuel, la base de données ne propose que des données thermodynamiques sur les phases cimentaires bien cristallisées, ainsi que sur un jeu de données limité à trois compositions chimiques différentes pour les C-S-H nanocristallins, ne permettant pas de reproduire la dégradation des matériaux cimentaires, ni de modéliser la dégradation des nouvelles formulations telles que les bétons "bas-pH".L'objectif est donc d'acquérir un jeu de données thermodynamiques complémentaire, sur les phases telles que les C-S-H (Silicates de Calcium Hydratés), C-A-S-H (Silicates de Calcium Alumineux Hydratés) et M-S-H (Silicates de Magnésium Hydratés), pour les intégrer à la base de données Thermo-Chimie. Cette étude s'appuie sur un travail expérimental, analytique et numérique dans le but d'obtenir un jeu de données thermodynamiques (ΔfG0, ΔfH0, Cp(T), S0) suffisamment représentatif de la variabilité chimiques de ce type de phases. Enfin, cet ensemble de donnée permet le développement d'un modèle de prédiction de données thermodynamiques dans des espaces de compositions et de températures étendues.Le développement de ce modèle de prédiction requiert (i) l'acquisition de propriétés thermodynamiques sur des phases représentatives du système chimique étudié, et (ii) une connaissance précise de la structure et des formules chimiques de ces phases. Trois types d'hydrates ont donc été synthétisés puis caractérisés : les C-S-H, les C-A-S-H et les M-S-H. Des méthodes analytiques telles que la DRX, l’ATG et la RMN du solide (29Si, 27Al) permettent d'établir des similitudes entre la structure des C-(A-)S-H et celle de la tobermorite d'une part, et entre la structure des M-S-H et celle des phyllosilicates Mg-Si 2:1 d'autre part. Les hydrates présentent toutefois une nanocristallinité ainsi que des défauts tant au niveau de la polymérisation du silicium tétraédrique qu'au niveau de l'empilement de leurs feuillets.Une approche multi-techniques est également utilisée, couplant isothermes d'adsorption (eau et azote) et RMN 1H aux résultats de DRX et ATG, pour discriminer les différents types d'eau plus ou moins liés à la structure des C-(A-)S-H. Cette étude a permis de mettre en évidence et de quantifier les différents types d'eau composant la structure des C-(A-)S-H. L'impact des méthodes de préparation a également été mis en évidence sur la quantification des différents types d'eau et notamment l'eau interfoliaire. L'acquisition des paramètres thermodynamiques sur les phases synthétisées est réalisée à partir de l'analyse des solutions d'équilibre pour le calcul des log K et ΔfG0, alors que des acquisitions calorimétriques permettent l'obtention des capacités calorifiques ainsi que le calcul de S0. Enfin, l'enthalpie de formation de ces phases est calculée à partir des enthalpies libres et des entropies. Le modèle de prédiction des données thermodynamiques est développé sur la base des propriétés acquisesConcrete is one of the most widely used building materials in the world. Durability, mechanical and chemical properties have made it a material of choice in storage concepts proposed by the French National Agency for Radioactive Waste Management (Andra), including the achievement of retaining structures, cell plugs, massive supports or conditioning waste. The study of the stability of the constituent phases of cementitious materials is needed in view of the planned quantities and the durability of the structures, andmust consider (i) temperature ranges suitable for cement matrices containment in contact with exothermic waste (25-80°C), and (ii) a representative time scale of the lifetime of the storage.The Andra ThermoChimie project therefore aims to develop a consistent thermodynamic database, to model the chemical evolution of cement materials in the environment of radioactive waste. However, in the present state, the database offers only thermodynamic data of cementitious crystalline phases, as well as a limited data set of three different chemical compositions for nanocrystalline C-S-H. This does not allow to reproduce the degradation of cementitious materials, or model the degradation of the new formulations, such as "Low pH" concretes.The objective is therefore to acquire a thermodynamic complementary data set on phases such as C-S-H (Calcium Silicate Hydrates) C-A-S-H (Calcium Aluminate Silicate Hydrates) and M-S-H (Magnesium Silicate Hydrates), to complete the ThermoChimie database. This study is based on experimental, analytical and digital work, in order to obtain a set of thermodynamic data (ΔfG0, ΔfH0, Cp(T), S0) sufficiently representative of the chemical variability of these phases. Finally, this set of data allows the development of a thermodynamic predictive model in extended spaces of compositions and temperatures.Development of this predictive model requires (i) The acquisition of thermodynamic properties on representative phases of the studied chemical system, and (ii) a precise knowledge of the structure and chemical formulas of these phases. Three types of hydrates were therefore synthesized and characterized: C-S-H, C-A-S-H and M-S-H. Analytical methods such as XRD, TGA and solid state NMR (29Si, 27Al) are used to ascertain similarities between the structure of C-(A-)S-H and that of tobermorite, and between the structure of M-S-H and that of Mg-Si phyllosilicates 2:1. Hydrates, however, have a lower crystallinity, with defects in the polymerization of silica chains, and random stacking faults (turbostratism).A multi-technique approach is also used, combining adsorption isotherm (water and nitrogen) and 1HNMR with XRDand TGA, and allows characterization of different types of water more or less bound to the structure of C-(A-)S-H.This study allowed to highlight and quantify the different types of water in the C-(A-)S-H structure. The impact of the drying process was also highlighted on the quantification of different types of water, including interlayer water. The acquisition of thermodynamic parameters of the synthesized phases is carried out from the analysis of equilibrium solutions for the calculation of log K and ΔfG0, while calorimetric acquisitions permit obtaining heat capacities and the calculation of S0. Finally, enthalpy of formation of these phases is calculated from the Gibbs free energy of formation and entropies.The predictive model is developed fromthe acquired thermodynamic properties.The Gibbs free energy of formation ΔfG0 is predicted from an electronegativity model, while Cp and S0 are predicted through polyhedral decomposition model. Finally, a comparison of data obtained with those published in the literature, and the realization of predominance diagrams generalized to the whole CaO-MgO-Al2O3-SiO2-H2O system assess the reliability of the proposed model
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Okoronkwo, Monday Uchenna. "Phase development in cement hydrate systems." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215261.
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Much progress has been made in understanding the physicomechanical properties of blended cement pastes of various formulations. However, unanswered questions abound, particularly as it concerns the long term chemistry of mineral distribution as clinker is diluted with progressively more supplementary cementitious materials (SCM's) and as a greater fraction of blending agent reacts with cement with time. This Thesis describes progress towards elucidating the mineralogical evolution mainly by isothermal equilibrium of known compositions. The evolution of mineralogy of two major systems: the calcium-alumina-silica-water (CASH) system and sodium-calcium-alumina-silica-water (NCASH) systems were studied at 20 – 85 °C, using ~70 compositions. Phase assemblage models have been developed for the systems, demonstrating the mode of occurrence and coexistence of phases with respect to temperature and composition. The coexistence of gels, one based on calcium silicate hydrate (C-S-H), the other based on aluminosilicate hydrate (A-S-H), and crystalline phases such as hydrogarnet solid solution, strätlingite and gismondine-Ca in the CASH system at 20 – 85°C, are illustrated. Transformation of gels to their corresponding crystalline phases has been predicted. Similarly, models are presented showing the mode of occurrence and coexistence of portlandite, alumina hydrate, silica, tobermorite, strätlingite, hydrogarnet solid solution, gismondine- type zeolite (Na,Ca)P solid solution, zeolite A, zeolite X, sodalite, etc., at temperatures 20 – 85 °C for the NCASH system. The stability and properties of the various crystalline CASH phases such as, hydrogarnet solid solution, strätlingite and gismondine, in relation to other phases relevant to cement hydration – such as C-S-H, AFts, AFms, gypsum and calcite – are characterized. The impact of sulfate, carbonate, alkali and solid solution on phase stability in systems relevant to aluminosilicate substituted cement paste are investigated. Concerns on long-term evolution of pH and its consequences to the passivation of cement-steel composite are discussed.
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Rassineux, François. "Altération des mortiers : étude expérimentale et analogues anciens." Poitiers, 1987. http://www.theses.fr/1987POIT2314.
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Etude de l'evolution de matrices cimentes soumise a une lixiviation par des solutions diluees. La stabilite des deux mortiers de compositions mineralogiques differentes depend du ph et de la pression en co::(2). Le mecanisme de dissolution est le processus dominant durant la lixiviation. L'identification du phases sur les liants modernes et ceuxs de l'epoque gallo romaine permet de connaitre la durabilite a long terme. Une simulation thermodynamique du processus ete realisee
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Shahsavari, Rouzbeh. "Hierarchical modeling of structure and mechanics of cement hydrate." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/64567.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2011."February 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 236-251).
With an annual production of more than 20 billion tons a year, concrete continues to be the world's dominating manufacturing material for a foreseeable future. However, this ubiquity comes with a large ecological price as concrete stands as the third largest culprit to the torrent of CO2 after transportation and electricity generation. Despite several decades of studies, fundamental questions are still unsettled on the structure and properties of the smallest building block of concrete, Calcium- Silicate-Hydrate (C-S-H). Given the variable stoichiometry and morphology of C-S-H, no accurate models were ever developed that could link electronic information at one end to the C-S-H molecular properties at the other end. This thesis develops a new modeling toolbox that enables unraveling the interplay between structure, composition, morphology and mechanical properties of this "liquid stone" gel. First, using ab-initio calculations we characterize the structural and mechanical properties of several mineral analogs of CS- H (tobermorite family and jennite). We show tobermorite as a class of layered materials that unlike the common intuition, is not softest along the interlayer direction. Instead, the mechanically softest directions are two inclined regions forming a hinge mechanism. This feature sheds light on the complex mechanics of the realistic C-S-H layers. It occurs when the electrostatic interlayer interactions become comparable to the iono-covalent intralayer interactions. Next, to pass information to the next hierarchical level, we start by benchmarking the predictive capabilities of two commonly used force field potentials for C-S-H minerals against ab-initio calculations. While both potentials seem to give structural properties in reasonable agreement with the ab-initio results, the higher order properties such as elastic constants are more discriminating in comparing potentials with regards to predicting mechanical properties. Based on this finding, we use ab-initio structural and elasticity data in tandem to develop a new force field potential, CSH-FF, well customized and substantiated for the C-S-H family. This simple, yet efficient force-field is used in conjunction with statistical mechanics to analyze a series of molecular C-S-H models. Our simulation results predict a range of compositions and corresponding mechanical properties of solid C-S-H molecules that are consistent with real cement paste samples. This confirms our bottom-up multiscale approach with the model parameters linked to electronic structure calculations. The combination of these techniques and findings paves a path toward a predictive computational design strategy to improve the core properties of cement hydrate while reducing its negative environmental impact.
by Rouzbeh Shahsavari.
Ph.D.
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Chen, Quanyuan. "Examination of hydrated and accelerated carbonated cement-heavy metal mixtures." Thesis, University of Greenwich, 2003. http://gala.gre.ac.uk/6132/.
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Cement -based solidification/stabilisation (s/s) has been applied to the disposal of heavy metal bearing contaminated soil and wastes for approximately 50 years. This work studies the interactions of cement and heavy metals and provides further insight into encapsulation of heavy metals in cement matrices. The pastes and suspensions of calcium oxide, calcium hydroxide, pure cement phases ( 38, C}A, C4AF, Ci 2A7 and CA) and Portland cement with or without heavy metals (Zn2+ , Pb2+, Cu2+ and Cr3+) were examined by a number of analytical techniques. These techniques were X-ray powder diffraction (XRD), solid state magic angle spinning/nuclear magnetic resonance (MAS/NMR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), differential thermal analysis (DTA) and thermogravimetry (TG). Thermodynamic modelling using a geochemical code, PHREEQC, and the edited database, was carried out to elucidate the chemical reactions occurring in cement/heavy metal systems. Heavy metals acted as accelerators for hydration of CaO, CaS and Portland cement except that Zn2+ retarded the early-age hydration of Cfi and Portland cement. This work confirmed that the precipitation of portlandite was retarded due to the hydrolysis of heavy metals. Calcium ions resulting from the decomposition of cement phases combined with heavy metals to form calcium-heavy metal double hydroxides, including CaZn2(OH)6.2H2O, Ca2(OH)4Cu(OH)2.mH2O and Ca2Cr(OH)7 .3H2O. The carbonation of CaS and Portland cement resulted in the formation of calcium carbonate and the condensation of silicates from single tetrahedra to branching sites and three-dimensional frameworks (low Ca/Si ratio C-S-H gel). The polymerisation of C-S-H gel, and the polymorphism conversion and decomposition temperature of calcium carbonate were influenced by heavy metals. The incorporation of heavy metal cations in C-S-H gel is similar to that seen in glass. Heavy metals acted as network modifiers or network intermediates. In hydrated Portland cement pastes, aluminium was partitioned in ettringite or calcium carboaluminate. After carbonation, this work revealed that aluminium was in the tetrahedral form, forming mixed AlCVSiC^ branching or three-dimensional networks. This thesis presents the new structural models for C-S-H gel and the chemical mechanisms of 38 reactions with water and carbon dioxide in the presence or absence of heavy metals. In the absence of gypsum, the reaction products detected in the pastes of C3A, C4AF, Ci2A? and CA were gehlenite hydrate, calcium carboaluminate, C4AH X and hydrogarnet. Heavy metals, especially Zn 2+ , inhibited the formation of hydrogarnet and promoted the conversion of C-A-H to calcium carboaluminate and calcium carbonate. In the presence of gypsum, the major hydration product of C^A was ettringite. During carbonation, COs'" substituted for SO 4 2 " and formed calcium carboaluminate, and eventually transformed into calcium carbonate and gibbsite. The conversion of metastable calcium carbonate polymorphs (aragonite and vaterite) to calcite through Ostwald ripening occurred very slowly in the carbonated pastes containing gypsum. The reactivity of C 3 A, C^Ay, CA and C4AF during carbonation was much lower than seen during hydration. Heavy metals influenced the rates and products of hydration or carbonation of CsA, Ci2A7, CA and C4 AF and were completely incorporated in the reaction products of these phases. Thermodynamic modelling confirmed that accelerated carbonation could be beneficially employed to cement-based s/s to improve its effectiveness. Calculations of solubility and equilibrium phase assemblage are consistent with the experimental examination obtained in this work.
Books on the topic "Cement hydrates"
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Strienitz, Rolf. Bildung und quantitative Bestimmung von tobermoritischen Phasen in dampfgehärteten Baustoffen mittels Röntgenverfahren nach RIETVELD. Freiberg: Technische Universität Bergakademie Freiberg, 2006.
Find full textBook chapters on the topic "Cement hydrates"
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Ioannidou, K. "Heterogeneity in Cement Hydrates." In ACS Symposium Series, 357–71. Washington, DC: American Chemical Society, 2018. http://dx.doi.org/10.1021/bk-2018-1296.ch018.
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Lequeux, Nicolas, and Nathalie Richard. "Structural Investigation of Calcium Silicate Hydrates by X-Ray Absorption Spectroscopy." In Nuclear Magnetic Resonance Spectroscopy of Cement-Based Materials, 181–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-642-80432-8_12.
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Faugère, M. P., M. Crespin, P. Dion, F. Bergaya, A. Feylessoufi, and H. Van Damme. "Influence of Heat Treatment Kinetics on Calcium Silicate Hydrates Phase Evolution." In Nuclear Magnetic Resonance Spectroscopy of Cement-Based Materials, 217–25. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-642-80432-8_16.
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Noma, Hiroaki, Yoshio Adachi, Hideo Yamada, Tadashi Nishino, Yoshihisa Matsuda, and Takushi Yokoyama. "29Si MAS NMR Spectroscopy of Poorly-Crystalline Calcium Silicate Hydrates (C-S-H)." In Nuclear Magnetic Resonance Spectroscopy of Cement-Based Materials, 159–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-642-80432-8_10.
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Kim, Chang Bum, Byoung Kwon Kim, and Sung Churl Choi. "Characteristics of Calcium Trisulphoaluminate Hydrates for Rapid Hardening of Cement Composites." In Materials Science Forum, 669–72. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-431-6.669.
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Nagesh, Ashwin Konanur, and Pijush Ghosh. "Interfacial Performance of Coating Polymer on Calcium–Silicate–Hydrates During Different Stages of Cement Hydration." In RILEM Bookseries, 69–77. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-76547-7_7.
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Hou, Dongshuai. "Introduction to Modeling of Cement Hydrate at Nanoscale." In Molecular Simulation on Cement-Based Materials, 7–33. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8711-1_2.
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Hou, Dongshuai. "Modeling the Calcium Silicate Hydrate by Molecular Simulation." In Molecular Simulation on Cement-Based Materials, 55–86. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8711-1_4.
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Parrott, Leslie J. "Mathematical Modelling of Microstructure and Properties of Hydrated Cement." In Problems in Service Life Prediction of Building and Construction Materials, 213–28. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5125-9_13.
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Zhutovsky, Semion, and Andrei Shishkin. "Recovering of Clinker Minerals from Hydrated Portland Cement Paste." In RILEM Bookseries, 63–73. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-76543-9_7.
Full textConference papers on the topic "Cement hydrates"
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Hayashi, Akihiko, Yuko Ogawa, and Kenji Kawai. "Heavy Metal Desorption From Cement Hydrates Caused by Chloride Solutions." In International Conference on the Durability of Concrete Structures. Purdue University Libraries Scholarly Publishing Services, 2014. http://dx.doi.org/10.5703/1288284315405.
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Ravi, Krishna, and Seth Moore. "Cement Slurry Design to Prevent Destabilization of Hydrates in Deepwater Environment." In SPE Indian Oil and Gas Technical Conference and Exhibition. Society of Petroleum Engineers, 2008. http://dx.doi.org/10.2118/113631-ms.
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Yaphary, Yohannes L., Shuhuan Hu, Denvid Lau, and Raymond H. W. Lam. "Piezoelectricity of Portland cement hydrates cured under the influence of electric field." In 2016 IEEE 16th International Conference on Nanotechnology (IEEE-NANO). IEEE, 2016. http://dx.doi.org/10.1109/nano.2016.7751344.
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Owada, Hitoshi, Tomoko Ishii, Mayumi Takazawa, Hiroyasu Kato, Hiroyuki Sakamoto, and Masahito Shibata. "Modeling of Alteration Behavior on Blended Cementitious Materials." In ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2011. http://dx.doi.org/10.1115/icem2011-59096.
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A “realistic alteration model” is needed for various cementitious materials. Hypothetical settings of mineral composition calculated based on the chemical composition of cement, such as Atkins’s model, have been used to estimate the alteration of cementitious material. However, model estimates for the concentration of certain elements such as Al and S in leachate have been different from experimental values. In a previous study, we created settings for a mineralogical alteration model by taking the initial chemical composition of cementitious materials from analysis results in experiments and applying their ratios to certain hydrated cement minerals, then added settings for secondary generated minerals in order to account for Ca leaching. This study of alteration estimates for ordinary portland cement (OPC) in groundwater showed that the change in Al and S concentrations in simulated leachate approached values for actual leachate[1]. In the present study, we develop an appropriate mineral alteration model for blended cementitious materials and conduct batch-type leaching experiments that use crushed samples of blast furnace slag cement (BFSC), silica cement (SC), and fly ash cement (FAC). The cement blends in these experiments used OPC blended with blast furnace slag of 70 wt.%, silica cement consisting of an amorphous silica fine powder of 20 wt.%, and fly ash of 30 wt.%. De-ionized water was used as the leaching solution. The solid-liquid ratios in the leaching tests were varied in order to simulate the alteration process of cement hydrates. The compositions of leachate and minerals obtained from leaching tests were compared with those obtained from models using hypothetical settings of mineral composition. We also consider an alteration model that corresponds to the diversity of these materials. As a result of applying the conventional OPC model to blended cementitious materials, the estimated Al concentration in the aqueous solution was significantly different from the measured concentration. We therefore propose an improved model that takes better account of Al behavior by using a more reliable initial mineral model for Al concentration in the solution.
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Huang, Shun, Julien Sanahuja, Luc Dormieux, Benoit Bary, Eric Lemarchand, and Myriam Hervé. "Double Scale Model of the Aging Creep of Low Density Hydrates of Cement Paste." In Sixth Biot Conference on Poromechanics. Reston, VA: American Society of Civil Engineers, 2017. http://dx.doi.org/10.1061/9780784480779.127.
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Feng, Ming, and Catalin Teodoriu. "A Simplified Temperature Prediction of Circulation and Simulator Development Under Steady-State Heat Transfer in the Deepwater Wellbore." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62536.
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One of the critical factors in the deepwater exploration and development is the temperature during the drilling process. Temperature in the wellbore will induce the wellbore instability, which means the bottom hole pressure will change according to the accumulated thermal effects on the density, viscosity of the fluid during the circulation. Unpredicted bottom hole pressure will lead to unknown well control risks, which make the deepwater drilling is in great danger and unacceptable for the engineers. In the casing design, the thermal effects were ignored in the past but with drilling deeper subsea wells, the thermal effects will exist inevitably. The extreme values observed at the seafloor could be as low as 40°F and as high as 150∼200°F at the wellbore annulus. Unfortunately, deepwater environments combine low temperatures, high pressures, gas and water that can induce hydrate formation. Hydrates can lead to drillpipe blockages and affect BOP operation. The low temperatures due to the hydrate or ocean current affect the properties of cement, which indicates to redesign cement slurry composition required. Except the effects on the density and viscosity of fluid, the rising temperature in the annulus between the drill pipe and casing will make the trapped pressure increase in the annulus between outside casings. If the annulus build-up pressure can’t be released without rapture disks, otherwise the trapped pressure is beyond the initial design pressure, and the potential damage will happen. This paper provides a simplified method to predict the circulation temperature under steady-state heat transfer in the deepwater rissssserswellbore, and a simulator is developed.
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Kang, Seungmin, Hyunju Kang, and Myongshin Song. "A Study on the Change of Cement Hydrates and Residual Strength of Concrete Due to Fire Exposure." In Research, Development and Practice in Structural Engineering and Construction. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-08-7920-4_cs-9-0273.
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Ozbulut, Osman E., Zhangfan Jiang, and Guohua Xing. "Evaluation of Various Factors on Electrical Properties of GNP-Reinforced Mortar Composites." In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8062.
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Graphene nanoplatelets (GNPs) have the same chemical structures as carbon nanotubes but their internal structure consists of multiple layers of graphene with thicknesses of only a few nanometers. Due to their increased thickness, GNPs are less prone to agglomeration and entanglement when they are used as nanofillers in composite materials. Although it has been shown that self-sensing cementitious composites can be fabricated using GNPs, further studies are needed to reveal effect of various factors on the performance of such composites. Here, a fabrication method that mainly employs polycarboxylate-based superplasticizers together with high-speed shear mixing to disperse GNPs in cement composites is used to prepare GNP-reinforced mortar composites. The molecular structure of polycarboxylate-based superplasticizer can considerably affect the performance of GNP-cement composites. Therefore, two commercially available polycarboxylate-based superplasticizers that possess varying backbone and side-chain lengths are systematically incorporated to prepare GNP-reinforced multifunctional composites. In addition, the effects of mixing durations on the electrical properties of the developed composites are assessed. Another essential challenge in the development of multifunctional cement composites is to improve the interfacial interaction between GNPs and the hydration products of cement such as calcium-silicate-hydrates (CSH). Here, incorporation of supplementary materials such as silica fume into the matrix is studied to improve the bond between a cementitious matrix and nano reinforcement. The bulk resistivity of the mortar specimens is measured using the four-probe measurement method. The piezoresistive behavior and sensing ability of the GNP-reinforced mortar composites are investigated through compressive tests at quasi-static.
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Niibori, Yuichi, Masayuki Narita, Akira Kirishima, Taiji Chida, and Hitoshi Mimura. "Fluorescence Emission Behavior of Eu(III) Sorbed on Calcium Silicate Hydrates Formed With No Dried Process." In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-16524.
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Calcium silicate hydrate (CSH) is a main component of cement-based material required for constructing the geological repository. As in many countries, since the repository in Japan is constructed below water table, we must consider the interaction of radionuclide with cement materials altered around the repository after the backfill. Using fluorescence emission spectra, so far, the authors have investigated the interaction of Eu(III) (as a chemical analog of Am(III)) with CSH gels formed with no dried process, considering a condition saturated with groundwater. However, in such fluorescence emission behaviors, a deexcitation process of OH vibrators of light water and a quenching effect caused by Eu-Eu energy transfer between Eu atoms incorporated in the CSH gel must be considered. This study examined the fluorescence emission behavior of Eu(III) sorbed on CSH gels formed with no dried process, by using La(III) (non-fluorescent ions) as a diluent of Eu(III). Furthermore, the CSH samples were synthesized with CaO, SiO2, and heavy water (D2O) as a solvent in order to avoid the obvious deexcitation process of OH vibrators of light water. This study prepared CSH samples with the Ca/Si ratio set to 1.6, 1.0, and 0.5. A 1 mM solution of a given combination of Eu(III) and La(III) (Eu(III) content: 100%, 67%, 50% or 33%) was added into CSH gel sample. The contact time-period of the CSH gel with the Eu(III)/La(III) solution was set to 60 days. In the results, the peak around 618 nm was split into two peaks of 613 nm and 622 nm in the cases of Ca/Si = 1.0 and 1.6. Then, the peak of 613 nm decreased with increment of Eu(III)/La(III) ratio. This means that the relative intensity of 613 nm is useful to quantify the amount of Eu(III) incorporated in CSH gel. Besides, the intensity peak of 584 nm decayed with increment of Eu/La ratio, suggesting a quenching effect due to Eu-Eu energy transfer. However, the decay behavior of the fluorescence emission did not depend on the Eu/La concentration ratio. That is, such a quenching effect is neglectable. Additionally, the low Ca/Si ratio samples underwent slow attenuation of fluorescence and showed profiles similar to those of high Ca/Si ratio samples. Therefore, low Ca/Si ratio samples also include the reaction forming a complex on the surface of CSH gel with Eu(III). In other words, even if Ca/Si ratio is lower than 1.0, CSH gels would retard the migration of radionuclides released from the repository.
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Meng, Meng, Luke Frash, James Carey, Wenfeng Li, Nathan Welch, and Hongtao Zhang. "Measurement of Cement in Situ Stresses and Mechanical Properties Without Cooling or Depressurization." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206139-ms.
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Abstract Accurate characterization of oilwell cement mechanical properties is a prerequisite for maintaining long-term wellbore integrity. The drawback of the most widely used technique is unable to measure the mechanical property under in situ curing environment. We developed a high pressure and high temperature vessel that can hydrate cement under downhole conditions and directly measure its elastic modulus and Poisson's ratio at any interested time point without cooling or depressurization. The equipment has been validated by using water and a reasonable bulk modulus of 2.37 GPa was captured. Neat Class G cement was hydrated in this equipment for seven days under axial stress of 40 MPa, and an in situ measurement in the elastic range shows elastic modulus of 37.3 GPa and Poisson's ratio of 0.15. After that, the specimen was taken out from the vessel, and setted up in the triaxial compression platform. Under a similar confining pressure condition, elastic modulus was 23.6 GPa and Possion's ratio was 0.26. We also measured the properties of cement with the same batch of the slurry but cured under ambient conditions. The elastic modulus was 1.63 GPa, and Poisson's ratio was 0.085. Therefore, we found that the curing condition is significant to cement mechanical property, and the traditional cooling or depressurization method could provide mechanical properties that were quite different (50% difference) from the in situ measurement.
Reports on the topic "Cement hydrates"
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Guthrie, George Drake Jr, Rajesh J. Pawar, James William Carey, Satish Karra, Dylan Robert Harp, and Hari S. Viswanathan. Hydrated Ordinary Portland Cement as a Carbonic Cement: The Mechanisms, Dynamics, and Implications of Self-Sealing and CO2 Resistance in Wellbore Cements. Office of Scientific and Technical Information (OSTI), July 2017. http://dx.doi.org/10.2172/1373519.
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Jawed, I., G. Childs, A. Ritter, S. Winzer, and D. B. Barker. High-Strain-Rate behavior of Hydrated Cement Paste. Fort Belvoir, VA: Defense Technical Information Center, January 1987. http://dx.doi.org/10.21236/ada179488.
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Snyder, Kenneth A., and Paul E. Stutzman. Hydrated Phases in Blended Cement Systems and Synthetic Saltstone Grouts. Gaithersburg, MD: National Bureau of Standards, June 2013. http://dx.doi.org/10.6028/nist.ir.7947.
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Poole, T., L. Wakeley, and C. Young. Individual and combined effects of chloride, sulfate, and magnesium ions on hydrated Portland-cement paste. Office of Scientific and Technical Information (OSTI), March 1994. http://dx.doi.org/10.2172/10147904.
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Keener, T. C., S. J. Khang, and G. R. Meyers. Evaluation of Ohio fly ash/hydrated lime slurries and Type 1 cement sorbent slurries in the U.C. Pilot spray dryer facility. Final report, September 1, 1993--August 31, 1994. Office of Scientific and Technical Information (OSTI), February 1995. http://dx.doi.org/10.2172/57880.
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