Littérature scientifique sur le sujet « Cementitious hydrates »
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Articles de revues sur le sujet "Cementitious hydrates"
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Awan, Muhammad Maqbool Sadiq, Parviz Soroushian, Arshad Ali et Muhammad Yousaf Saqid Awan. « High-Performance Cementitious Matrix using Carbon Nanofibers ». Indonesian Journal of Science and Technology 2, no 1 (1 avril 2017) : 57. http://dx.doi.org/10.17509/ijost.v2i1.5989.
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Graphite nanomaterials would realize their reinforcement potential within cement-based materials when they are thoroughly dispersed and effectively bonded to cement hydrates. Thorough dispersion of graphite nanomaterials in the fresh cementitious matrix encounters challenges associated with the hydrophobic nature of nanomaterial surfaces and their strong tendency towards agglomeration via attractive van der Waals forces. Effective interfacial interactions with cement hydrates are further challenged by the relatively inert nature of nanomaterial surfaces. An experimental program was conducted with the objective of effectively utilizing both acid-oxidized and pristine carbon nanofibers towards reinforcement of high-performance cementitious pastes. Hybrid reinforcement systems comprising optimum volume fraction of carbon nanofibers and micro-scale fibers were also evaluated in cementitious matrices. The improvements in nanofiber dispersion and interfacial interactions resulting from acid-oxidation and use of proper dispersion techniques were found to bring about significant gains in the engineering properties of high-performance cementitious materials.
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Al-Fakih, Amin, Ali Odeh, Mohammed Abdul Azeez Mahamood, Madyan A. Al-Shugaa, Mohammed A. Al-Osta et Shamsad Ahmad. « Review of the Properties of Sustainable Cementitious Systems Incorporating Ceramic Waste ». Buildings 13, no 8 (20 août 2023) : 2105. http://dx.doi.org/10.3390/buildings13082105.
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Global carbon dioxide emissions can be attributed to Portland cement production; thus, an alternative cementitious system is essential to reduce cement demand. Ceramic waste powder (CWP), which contains high proportions of silica and alumina, has emerged as a promising alternative because of its chemical composition. This review discusses the potential of CWP as an alternative cementitious system and its effects on the physical, mechanical, and durability properties of cementitious systems. The findings revealed that the utilization of CWP in cementitious systems has positive effects on their physical, mechanical, and durability properties owing to the chemical composition of CWP, which can act as a filler material or contribute to the pozzolanic reaction. A pozzolanic reaction occurs between the silica and alumina in the CWP and calcium hydroxide in the cement, resulting in the production of additional cementitious materials such as calcium silicate hydrates and calcium aluminate hydrates. These additional materials can improve the strength and durability of cementitious systems. Various studies have demonstrated that CWP can be effectively used as a partial replacement for cement in cementitious systems. This can reduce the carbon footprint of construction activities by reducing the demand for Portland cement. However, the optimal amount and particle size of CWP have not been fully determined, and further research is required to optimize its use in cementitious systems. In addition, the technical and economic challenges associated with the use of CWP in construction must be further investigated to ensure its effective implementation.
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Zhu, Zheyu, Zhongping Wang, Yue Zhou, Yuting Chen et Kai Wu. « Identification of Chemical Bonds and Microstructure of Hydrated Tricalcium Silicate (C3S) by a Coupled Micro-Raman/BSE-EDS Evaluation ». Materials 14, no 18 (8 septembre 2021) : 5144. http://dx.doi.org/10.3390/ma14185144.
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Identifying the phase evolution and revealing the chemical bonds of hydrated cements accurately is crucial to regulate the performance of cementitious materials. In this paper, a coupled Raman/BSE-EDS analysis was proposed to determine the chemical bonds of tricalcium silicate hydrates and the interface transition zone (ITZ) between inner C-S-H and anhydrates. The results show that the Raman/BSE-EDS method can accurately identify the chemical bonds of inner C-S-H and inner ITZ regions, which confirms the mixed structure of inner C-S-H and nano calcium hydroxide (CH). The inner ITZ shows a lattice change region with a thickness of 700–1000 nm, which can be attributed to the pre-disassembly process of C3S crystal. The successful application of coupled Raman/BSE-EDS provides new insight into the hydration process and multi-structure features of traditional cementitious materials.
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Takahashi, Keisuke, et Mari Kobayashi. « Utilization of Cement and Concrete for Deep Sea Infrastructure ». ce/papers 6, no 6 (décembre 2023) : 1291–94. http://dx.doi.org/10.1002/cepa.2996.
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AbstractThe use of cementitious materials in deep sea environments, focusing on the durability challenges of low‐temperature seawater and hydraulic pressure, are presented in this paper. The authors conducted laboratory and deep‐sea field experiments, thermodynamic calculation, and evaluated the performance of different types of binders in deep sea conditions. Durability of rebar in cementitious materials was investigated. In situ construction methods using cementitious materials was demonstrated on the deep‐sea field. Testing results revealed that deep sea conditions, especially low‐temperature seawater, can accelerate the disintegration of cement hydrates, and the use of pozzolanic admixture and calcium aluminate cement can improve its resistance. Our study provides valuable insights and applicability of cementitious materials to deep sea infrastructure construction.
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Oproiu, Carmen-Lidia, Georgeta Voicu, Alina Bădănoiu et Adrian-Ionuţ Nicoară. « The Solidification/Stabilization of Wastewater (From a Landfill Leachate) in Specially Designed Binders Based on Coal Ash ». Materials 14, no 19 (27 septembre 2021) : 5610. http://dx.doi.org/10.3390/ma14195610.
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The aim of this study is to assess the possibility to solidify/stabilize a liquid waste from a municipal waste landfill using binders based on coal ash (fly ash and bottom ash) and specially designed cements for waste treatment (INERCEM). The leaching test proved that all cementitious systems are efficient for the solidification/stabilization of the studied wastes and can reduce the leaching potential of heavy metals present in both liquid waste and coal ash. Therefore, these wastes cease to be a source of environmental pollution. X-ray diffraction (XRD) and thermal complex analysis (DTA-TG) were used to assess the nature and amount of compounds formed in these cementitious systems during the hydration and hardening processes; ettringite, calcium silicate hydrates and CaCO3 were the main compounds formed in these systems assessed by these methods. The microstructure of hardened specimens was assessed by scanning electronic microscopy (SEM); the presence of hydrate phases, at the surface of cenospheres present in fly ash, proved the high pozzolanic reactivity of this phase.
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Lee, Heeyoung, Jongkyeong Seong et Wonseok Chung. « Correlation Analysis of Heat Curing and Compressive Strength of Carbon Nanotube–Cement Mortar Composites at Sub-Zero Temperatures ». Crystals 11, no 10 (28 septembre 2021) : 1182. http://dx.doi.org/10.3390/cryst11101182.
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Concrete curing under sub-zero temperatures causes various problems, such as initial cracking and a decrease in mechanical strength. This study investigated the effect of sub-zero ambient temperature and multi-walled carbon nanotube (MWCNT) content on the heat and strength characteristics of heat-cured MWCNT cementitious composites. The experimental parameters were the application of heat curing, MWCNT content, use of an insulation box to achieve a closed system, and ambient temperature. The results showed that the internal temperature change of the MWCNT cementitious composite increased with the ambient temperature and MWCNT content. When an insulation box was installed, the maximum temperature change of the MWCNT cementitious composite during curing increased. Furthermore, heat curing increased the compressive strength of the cementitious composite. Moreover, a microstructure analysis using field-emission scanning electron microscopy verified the formation of a MWCNT network among the cement hydrates.
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Renaudin, Guillaume, Adel Mesbah, Belay Dilnesa, Michel Francois et Barbara Lothenbach. « Crystal Chemistry of Iron Containing Cementitious AFm Layered Hydrates ». Current Inorganic Chemistry 5, no 3 (14 juillet 2015) : 184–93. http://dx.doi.org/10.2174/1877944105666150420235831.
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Xu, Yue, Jian Xi Li et Li Li Kan. « Investigation on a New Hydraulic Cementitious Binder Made from Phosphogypsum ». Advanced Materials Research 864-867 (décembre 2013) : 1923–28. http://dx.doi.org/10.4028/www.scientific.net/amr.864-867.1923.
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A new kind of high strength cementitious material is made from phosphogypsum (PG), active carbon and fly-ash. Through the orthogonal research, it was showed that the calcination temperature, retention time, dosage of active carbon and fly ash on the compressive strength of cementitious binder are the most important. The result also showed that, in the conditions of temperature 1200°C, time retention 30 min, dosage of active carbon 10%, dosage of fly ash 5%, the compressive strength of the cementitious material for 3d and 28d could reach to 46.35MPa and 92.70MPa, the content of sulfur trioxide was 11.60% accordingly. A lot of active mineral materials, such as dicalcium silicate, tricalcium silicate, tricalcium aluminate were formed in the calcination. The C-S-H gel, calcium hydroxide and ettringite were found in 3d and 28d hydrates. It is found that the lime saturation ratio and silica modulus need to be control between 0.40~0.65 and 4~8 in order to produce high strength cementitious material.
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Kaminskas, Rimvydas, et Brigita Savickaite. « Expanded Clay Production Waste as Supplementary Cementitious Material ». Sustainability 15, no 15 (1 août 2023) : 11850. http://dx.doi.org/10.3390/su151511850.
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Global warming stands as one of the most significant challenges facing our planet, primarily due to the substantial emissions of greenhouse gases into the atmosphere. Among the major contributors to these emissions is the cement industry, which ranks as one of the largest sources of CO2 pollutants. To address this issue, a potential solution involves partially substituting cement with alternative materials, particularly waste generated by other industries. The aim of this study was to investigate the opportunity of using an industrial waste which originates from the cleaning of flue gas in the production of expanded clay as a supplementary cementitious material. The influence of expanded clay kiln dust on the properties of Portland cement was estimated by XRD, thermal, calorimetry and compressive strength analysis. The expanded clay kiln dust was used as received and it was additionally thermally activated at 600 °C. It was determined that the original dust can be distinguished by average pozzolanic activity; meanwhile, the pozzolanic activity of additionally activated waste increased by one third. Portland cement was replaced with both types of waste in various proportions. It was found that the additive of the investigated waste accelerates the primary hydration of Portland cement, generates the pozzolanic reaction, and incites the formation of calcium silicate hydrates and hydrates containing aluminum compounds. The addition of up to 25 wt.% of activated expanded clay kiln dust leads to a higher compressive strength of samples of Portland cement.
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Bernard, Ellina. « Research progress on magnesium silicate hydrate phases and future opportunities ». RILEM Technical Letters 7 (1 septembre 2022) : 47–57. http://dx.doi.org/10.21809/rilemtechlett.2022.162.
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This short letter summaries the latest research on the structure and thermodynamic modelling of the magnesium silicate hydrates (M-S-H) phases. M-S-H structure is comparable to hydrated clays, with a smaller and rounder microstructures compared to clay platelets. Similar to clay minerals, M-S-H can incorporate ions such as aluminium and hydrated exchangeable cations to compensate the negative surface charge. This fundamental understanding of M-S-H structure allowed to develop structure-based thermodynamic models, which can further help to optimise the conditions for M-S-H formation and its use as cementitious materials. Optimized binders containing M-S-H have the advantages of presenting: i) good mechanical properties, ii) dense microstructure and potentially good resistances to leaching and iii) low pH values. These types of binders could therefore be used for cement products with non-steel reinforcement, for the encapsulation of specific wastes, for products containing natural fibres or for the clay stabilisation, etc.
Thèses sur le sujet "Cementitious hydrates"
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Hérin, Thibaut. « Mécanismes de la radiolyse dans les hydrates cimentaires et conséquence sur la formation de dihydrogène dans les matériaux irradiés ». Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF010.
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Les matrices cimentaires envisagées pour le conditionnement des déchets radioactifs de moyenne activité à vie longue sont soumises aux rayonnements ionisants, ce qui entraîne la production de dihydrogène radiolytique et implique la prise en compte de ce risque. Jusqu’à présent, l’évaluation du risque H₂ reposait sur l’hypothèse d’une radiolyse de l’eau porale majoritaire et une radiolyse des phases solides négligeable. Cependant, les hydrates constitutifs de la pâte cimentaire contiennent beaucoup d’eau chimiquement liée et la décomposition radiolytique de cette dernière pourrait conduire à un terme source H₂ supplémentaire qu’il convient d’évaluer.Dans un souci de simplification, l’étude de la pâte cimentaire a été réalisée en recourant à quatre minéraux modèles, sélectionnés pour leur représentativité ou leur qualité démonstrative : la portlandite, la tobermorite 11 Å, la tobermorite 9 Å et la méta-jennite. Cette sélection conserve une grande proximité avec le matériau cimentaire et permet d’étudier distinctement, sous irradiation, le comportement de l’eau de cristallisation et/ou de l’eau de constitution (liaisons OH) qui représentent les deux types d’eau chimiquement liée. Afin d’éviter une contribution parasite de l’eau adsorbée, dont la présence indésirable peut conduire à surestimer la contribution des phases solides, un soin particulier a été accordé à la désorption des échantillons de cette étude.L’exposition des minéraux, à des sources de rayonnement ionisants (électrons accélérés et rayonnement γ) génère une production de H₂ variable selon le minéral. La portlandite présente une production de H₂ fortement dépendante de la surface spécifique des échantillons irradiés. Des expériences de résonance paramagnétique électronique ont permis d’identifier deux voies de production de H₂ dans ce minéral.Un premier mécanisme, localisé en surface, induit une production importante de H₂ dans les échantillons de forte surface spécifique. Un second mécanisme provoque la création de H₂ dans le volume du matériau. Ce H₂ est alors capable de migrer du volume vers la surface via un mécanisme de transport par subdiffusion. Cet effet donne lieu à un relâchement progressif de H₂ dans les échantillons irradiés.Concernant les C-S-H cristallisés, la tobermorite 9 Å qui est le minéral contenant le moins d’eau chimiquement liée est paradoxalement celui produisant le plus de H₂. Cette production semble néanmoins exclusivement issue des sites de surface du minéral. Les irradiations menées sur la méta-jennite et la tobermorite 11 Å montrent au contraire que la radiolyse de l’eau de cristallisation de ces minéraux ne contribue pas à la production de H₂. Si une dissociation de molécules d’eau de cristallisation a bien été observée dans la tobermorite 11 Å, il semblerait que les radicaux formés conduisent à la formation de liaisons SiO-H, initialement absentes, plutôt qu’à la formation de H₂. L’irradiation d’échantillons de méta-jennite, présentant différentes quantités d’eau de cristallisation, a montré que la production de H₂ est indépendante de ce paramètre. Cela implique ici aussi que l’eau de cristallisation ne permet pas de produire H₂ et que seule l’eau de constitution est responsable de la formation de H₂ observée dans ce minéral.Dans l’ensemble, la production de H₂ des minéraux est fortement gouvernée par des phénomènes de surface. Il apparaît probable que dans le cas d’un milieu cimentaire, constitué de matériaux non pulvérulents, la prévalence de ces mécanismes diminue au profit de la radiolyse de l’eau porale ordinairement prise en compte. Ce scénario conduit à une contribution existante, mais limitée, des phases solides à la production de H₂ radiolytiqueThe cementitious matrices considered for the conditioning of long-lived intermediate-level radioactive waste are subject to ionising radiation, which leads to the production of radiolytic dihydrogen and requires this risk to be taken into account. Until now, H₂ risk assessment has been based on the assumption that radiolysis of pore water is predominant and radiolysis of solid phases negligible. However, the hydrates making up the cementitious paste contain a lot of chemically bound water and the radiolytic decomposition of the latter could lead to an additional H₂ source term that needs to be assessed.In order simplify the system, the cement paste was studied using four model minerals, selected for their representativeness or demonstrative quality: portlandite, 11 Å tobermorite, 9 Å tobermorite and meta-jennite. This selection maintains close proximity to the cementitious material and enables the behaviour of the water of crystallisation and/or the water of constitution (OH bonds), which represent the two types of chemically bound water, to be studied separately under irradiation. In order to avoid a parasitic contribution from adsorbed water, the undesirable presence of which could lead to an overestimation of the contribution of the solid phases, particular care was taken with the desorption of the samples in this study.Exposure of minerals to sources of ionising radiation (accelerated electrons and γ-radiation) generates H₂ production that varies according to the mineral. The production of H₂ in portlandite is highly dependent on the specific surface area of irradiated samples. Electron paramagnetic resonance experiments have identified two H₂ production pathways in this mineral.A first mechanism, localised at the surface, induces significant H₂ production in samples with a high specific surface area. A second mechanism leads to the creation of H₂ in the volume of the material. This H₂ is then able to migrate from the volume to the surface via a subdiffusion transport mechanism. This effect results in a progressive release of H₂ in the irradiated samples.Concerning crystallised C-S-H, tobermorite 9 Å, which is the mineral containing the least chemically bound water, is paradoxically the one producing the most H₂. However, this production seems to come exclusively from the mineral's surface sites. The irradiations carried out on meta-jennite and 11 Å tobermorite show, on the contrary, that radiolysis of the water of crystallisation in these minerals does not contribute to H₂ production. While dissociation of water of crystallisation molecules was indeed observed in 11 Å tobermorite, it would appear that the radicals formed lead to the formation of SiO-H bonds, which were initially absent, rather than to the formation of H₂. Irradiation of meta-jennite samples with different amounts of water of crystallisation showed that H₂ production is independent of this parameter. This again implies that water of crystallisation does not produce H₂ and that only water of constitution is responsible for the formation of H₂ observed in this mineral.Overall, H₂ production in minerals is strongly governed by surface phenomena. It seems likely that in the case of a cementitious medium, made up of non-powdery materials, the prevalence of these mechanisms decreases in favour of the radiolysis of pore water, which is usually taken into account. This scenario leads to an existing, but limited, contribution of the solid phases to the production of radiolytic H₂
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Ectors, Dominique [Verfasser], et Jürgen [Gutachter] Neubauer. « Advances in the analysis of cementitious reactions and hydrate phases / Dominique Ectors. Gutachter : Jürgen Neubauer ». Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1102529214/34.
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Wilson, William. « Chemo-mechanical characterization of microstructure phases in cementitious systems by a novel NI-QEDS technique ». Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11620.
Texte intégralRésumé :
Face à la finitude des ressources de la terre et de sa capacité d’absorption de la pollution, le développement d’écobétons pour un futur industrialisé durable représente un défi majeur de la science du béton moderne. En raison de sa nature hétérogène complexe, les propriétés macroscopiques du béton dépendent fortement des constituants de sa microstructure (ex. silicates de calcium hydratés [C–S–H], Portlandite, inclusions anhydres, porosité, agrégats, etc.). De plus, la nécessité d’une exploitation rapide et optimale des matériaux cimentaires émergents dans les applications industrielles demande de nos jours une meilleure compréhension de leurs particularités chimico-mécaniques à l’échelle micrométrique. Cette thèse vise à développer une méthode de pointe de couplage de la nanoindentation et de la spectroscopie quantitative aux rayons X à dispersion d'énergie (NI-QEDS), puis à fournir une caractérisation chimico-mécanique originale des phases microstructurales présentes dans les matrices réelles de ciments mélangés. La combinaison d’analyses NI-QEDS statistiques et déterministes a ainsi permis d’élargir la compréhension des systèmes avec ciment Portland et ajouts cimentaires (ACs) conventionnels ou alternatifs. Plus spécifiquement, l’étude des C–(A)–S–H (C–S–H incluant l’aluminium ou non) dans différents systèmes à base de ciments mélangés a montré des compositions différentes pour cet hydrate (variations dans les taux de Ca, Si, Al, S et Mg), mais ses propriétés mécaniques n’ont pas été significativement affectées par l’incorporation des ACs dans des dosages typiques. Les résultats présentés ont aussi démontré le rôle important des autres phases imbriquées dans la matrice de C–(A)–S–H, soit les inclusions anhydres dures (ex. le clinker et les ACs) et les autres hydrates tels que la Portlandite et les hydrates riches en aluminium (ex. les carboaluminates) avec des propriétés mécaniques plus élevées que celles des C–(A)–S–H. La thèse est basée sur cinq articles couvrant : (1) une analyse NI-EDS de systèmes incorporant des volumes élevés de pouzzolanes naturelles; (2) le développement de la méthode NI-QEDS; des analyses statistiques NI-QEDS (3) de systèmes avec cendres volantes et laitier, et (4) d’un système combinant ciment, calcaire et argile calcinée; et (5) une exploration déterministe NI-QEDS de systèmes conventionnels et alternatifs incorporant la poudre de verre, le métakaolin, le laitier ou la cendre volante. Finalement, en plus d’avancer les derniers modèles et méthodes micromécaniques, l’outil développé a fourni une perception chimico-mécanique originale des phases microstructurales et de leur arrangement. Le dévoilement de la signature chimico-mécanique de ces pâtes de ciments mélangés particulièrement complexes offre un savoir unique pour l’ingénierie des bétons de demain.Abstract : Facing the limitedness of the earth’s resources and pollution absorption capacity, the development of eco-concrete for a sustainable industrialized future is one of the major challenges of modern concrete science. Due to its complex heterogeneous nature, the macro-scale properties of concrete strongly depend on the microstructure constituents (e.g., calcium-silicate-hydrates [C–S–H], Portlandite, anhydrous inclusions, porosity, aggregates, etc.). Moreover, the need for rapid and optimal exploitation of emerging binding materials in industrial applications urges today a better understanding of their chemo-mechanical features at the micrometer scale. This thesis aims at developing a state-of-the-art method coupling NanoIndentation and Quantitative Energy-Dispersive Spectroscopy (NI-QEDS), and providing an original chemo-mechanical characterization of the microstructure phases in highly heterogeneous matrices of real blended-cement pastes. The combination of statistical and deterministic NI-QEDS analysis approaches opened new research horizons in the understanding of Portland-cement systems incorporating conventional and alternative supplementary cementitious materials (SCMs). More specifically, the investigations of C–(A)–S–H (C–S–H including aluminum or not) in different blended-cement systems showed variable compositions for this hydrate (i.e., Ca, Si, Al, S and Mg contents), but the mechanical properties were not significantly affected by the incorporation of SCMs in typical dosages. The presented results also showed the important role of the other phases embedded in the C–(A)–S–H matrix, i.e., hard anhydrous inclusions (e.g., clinker and SCMs) and other hydrates such as Portlandite and Al-rich hydrates (e.g., carboaluminates) with mechanical properties higher than those of the C–(A)–S–H. The thesis is based on five articles focusing on: (1) the NI-EDS investigation of high-volume natural pozzolan systems; (2) the development of the NI-QEDS method; the statistical NI-QEDS analyses of (3) fly ash and slag blended-cement systems and of (4) a limestone-calcined-clay system; and (5) the deterministic NI-QEDS exploration of alternative and conventional systems incorporating glass powder, metakaolin, slag or fly ash. Finally, the developed tool not only advanced the latest micromechanical methods and models, but also provided original chemo-mechanical insights on the microstructure phases and their arrangement. Unveiling the chemo-mechanical signature of these highly-complex blended cement pastes further provided unique knowledge for engineering concretes for tomorrow.
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Maddalena, Riccardo. « Synthesis of Calcium Silicate Hydrate (C-S-H) and novel cementitious materials : characterisation, engineering applications and environmental aspects ». Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=29561.
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Jagannathan, Deepak. « Calcium-Silicate-Hydrate in cementitious systems : chemomechanical correlations, extreme temperature behavior, and kinetics and morphology of in-situ formation ». Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/92651.
Texte intégralRésumé :
Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 96-102).
Concrete, the second most used material on the planet, is a multi-scale heterogeneous material. A fundamental component known as Calcium-Silicate-Hydrate which forms from the reaction between cement and water is the binding phase in concrete. Curiously, this is the least understood component of concrete because of its porous amorphous structure. Further, beyond mere scientific curiosity, cementS̆s industry large carbon footprint due to its volume of usage sets up a practical context to seek improvements in concrete performance and equip concrete with additional functionalities. It is our contention that we can better understand the least known and crucial component of concrete, Calcium-Silicate-Hydrate, to inform the design of next generation of high performance concrete. With this broad theme, this thesis presents three different aspects of properties of Calcium Silicate Hydrate: chemomechanical correlations, behavior under extreme temperature and pressures, and kinetics and nanostructure of in-situ formation. Calcium Silicate Hydrate (C-S-H) formed in-situ in concrete is believed to have a layered structure with silicate chains similar to crystal structures of Tobermorite and Jennite. Its chemical composition, characterized by Ca/Si ratio, must therefore influence its silicate chain structure and thus its mechanical properties. We explore the correlation between CS- H composition and its mechanical properties. By varying chemical composition of cement clinkers and supplementary cementitious materials, water/cement ratios, and hydration temperatures, we prepare cement pastes with different C-S-H of different C/S ratios. We use nanoindentation and X-ray spectroscopy to respectively measure the mechanical properties and composition of C-S-H. We then study the mechanical performance of C-S-H at elevated temperatures. This is relevant in the design of infrastructure that can sustain extreme events such as blasts and high velocity impacts. As a starting point for concrete that would enable such infrastructure, we use ultra high performance concrete (UHPC). We use nanoindentation and X-ray spectroscopy to respectively measure mechanical properties and composition of individual components of UHPC. We compare the composition and properties of C-S-H found in UHPC to that found in ordinary cement pastes (OPC). Our grid nanoindentation experiments also reveal an artifacts created by the incorporation of steel fiber reinforcements in UHPC. We find that steel fiber reinforcements disrupt the perfect packing of constituent materials in UHPC to create capillary porosity at microscale. Further, we study the mechanical properties of C-S-H in concrete specimens subjected to high temperatures of 400°C and 1000°C. As a product of the reaction between cement and water, the properties of C-S-H are ultimately controlled by the reaction. To obtain quantitative kinetics, we use time-lapse optical microscopy to study hydration of micron sized monoclinic C₃S particles with in droplets of water of 50 [mu]m. Using Raman spectroscopy, we characterize the hydration product growing inside these droplets.
by Deepak Jagannathan.
S.M.
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Zhu, Xiaodong. « Étude à l'échelle nanométrique du nano-revêtement organique efficace sur la surface de la pâte de ciment dans un environnement agressif pour des matériaux de construction durables ». Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDENGSYS/2023/2023ULILN035.pdf.
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Améliorer la durée de vie de la pâte de ciment constitue un enjeu important dans le secteur de construction. Des recherches expérimentales indiquent que le revêtement de surface, agissant comme une barrière physique, est un moyen efficace d'améliorer la durabilité des matériaux en évitant la pénétration de l'eau ou de substances dangereuses. En raison des limites de l'observation expérimentale, il est important d'approfondir les études au niveau atomique pour comprendre le mécanisme à l'origine du comportement hydrophobe de la surface du ciment modifiée avec un traitement de nano-revêtement.Par conséquent, cette thèse adopte une étude à l'échelle nanométrique pour comprendre et contrôler le processus de nano-revêtement afin de concevoir une surface hydrophobe imperméable de silicate de calcium hydraté (CSH) grâce au nano-revêtement par un film d'époxy et de caoutchouc dans un environnement agressif. À cette fin, des simulations de dynamique moléculaire (MD) basées sur une combinaison potentielle d'un champ de force général (CLAYFF) et du champ de force à valence constante (CVFF) ont été utilisées pour représenter les interactions interatomiques entre le CSH et les films époxy ou en caoutchouc. Un modèle réaliste a été utilisé pour représenter la nanostructure CSH.La thèse est consacrée, dans un premier temps, à étudier en profondeur les propriétés de surface hydratée de la pâte CSH afin de bien comprendre la nature hydrophile de la surface (001) de CSH. Ensuite, une étude approfondie a été réalisée sur l'interaction interfaciale et les propriétés d'adhésion entre le nano-revêtement de résines époxy et la surface CSH. Pour cela, nous utilisons l'éther diglycidylique du bisphénol A (DGEBA) comme monomère époxy et la m-phénylènediamine (MPD) comme durcisseur. Par la suite, une analyse approfondie du processus de nano-revêtement de caoutchouc hydrophobe sur une surface CSH est explorée. Quatre types de caoutchouc sont utilisés, comme le TPI (1,4-trans-Polyisoprène), le CPI (1,4-cis-Polyisoprène), le TPB (1,4-trans-Polybutadiène) et le CPB (1,4-cis-Polyisoprène). Polybutadiène). Enfin, le présent travail s'intéresse à l'analyse du processus de détérioration de l'interface entre les films de époxy/caoutchouc et la surface de CSH dans un environnement agressif, comme l'eau salée (4% en poids de NaCl).Les résultats obtenus indiquent que l'énergie de surface des CSH recouverts de films d'époxy et de caoutchouc est considérablement réduite et sa valeur est de 33.7 mJ/m2 à 48.4 mJ/m2. Ceci réduit considérablement le caractère hydrophile de la surface du CSH. L'angle de contact moyen entre la nano-gouttelette d'eau et la surface CSH recouverte de caoutchouc se situe entre 92.85° et 98.11°. L'adhésion interfaciale calculée entre les revêtements organiques (époxy et caoutchouc) et le CSH est comprise entre 49.42 mJ/m2 et 102.81 mJ/m2. De plus, les résultats montrent que la m-phénylènediamine (MPD) améliorerait considérablement l'efficacité du nano-revêtement époxy. Concernant le nano-revêtement de caoutchouc, on constate que le processus de revêtement avec du TPI (1,4-trans-Polyisoprène) et du CPB (1,4-cis-Polybutadiène) améliorera efficacement l'imperméabilité de la pâte CSH. Dans des conditions agressives, le nano-revêtement partiel par l'époxy se détache de manière plus déformée dans une solution à 4 % en poids de NaCl en raison des ions chlore qui sont responsables de l'attaque de la surface CSH. Un nano-revêtement de caoutchouc continu et bien réparti est capable de rendre le CSH imperméable dans des environnements difficiles, ouvrant la voie à un avenir prometteur pour les matériaux cimentaires durables.La thèse de doctorat conclut la faisabilité et la fiabilité du nano-revêtement par un film en caoutchouc pour prévenir la détérioration interfaciale des surfaces CSH dans un environnement agressif et pour améliorer l'imperméabilité de la surface CSH nano-revêtue pour des matériaux cimentaires plus durablesImproving the life-time of cement paste is a significant challenge in construction sector. Surface treatment approaches, such as surface coating, surface pore sealing, and surface impregnation, have been playing a significant role to improve the durability of cement-based structures especially in preventing surface deterioration and damage. Experimental investigations indicate that surface coating, acting as a physical barrier, is an effective way for enhancing the durability of materials by avoiding the penetration either of water or hazards substances. Due to the experimental observation limitations, there is an urgency need to deeper delve the atomic level to understand the mechanism behind the success hydrophobic behavior of cement surface modified with a nano-coating treatment.Therefore, this dissertation adopts a nano-scale level study to understand and control the nano-coating process to engineer an impermeable hydrophobic Calcium-Silicate-Hydrate (CSH) surface through nano-coating of epoxy and rubber films under aggressive environment. To this end, Molecular Dynamics (MD) simulations based on a combination potential of a general force field (CLAYFF) and the consistent-valence force field (CVFF) have been employed to represent the interatomic interactions between CSH and epoxy or rubber films. A developed realistic model has been used to represent the CSH nanostructure.The thesis is dedicated, first, to study deeply the hydrated surface properties of CSH paste in order to thoroughly understand the hydrophilic nature of the (001) CSH surface. Then, a fully investigation has been performed on the interfacial interaction and adhesion properties between epoxy resins nano-coating and CSH surface. For that, we use diglycidyl ether of bisphenol A (DGEBA) as epoxy monomer and m-phenylenediamine (MPD) as hardener. Thereafter, an in-depth analysis of a hydrophobic rubber nano-coating process onto CSH surface is explored. Four types of rubber are employed, as TPI (1,4-trans-Polyisoprene), CPI (1,4-cis-Polyisoprene), TPB (1,4-trans-Polybutadiene), and CPB (1,4-cis-Polybutadiene). Finally, the present work is devoted to analyze the interfacial deterioration process between epoxy/rubber nano-coating of CSH surfaces under aggressive environment, like a salty water (4 wt.% of NaCl).Results obtained indicate that epoxy and rubber coated CSH surface energy are drastically dropped to the range of 33.7 mJ/m2- 48.4 mJ/m2, which extremely reduces the hydrophilicity of the CSH surface. The averaged contact angle between water-nanodroplet and rubber coated CSH surface is found in range of 92.85° and 98.11°. The calculated interfacial adhesion between organic-coatings (epoxy and rubber) and CSH is in range of 49.42 mJ/m2 to 102.81 mJ/m2. Additionally, m-phenylenediamine (MPD) would highly improve the epoxy nano-coating efficiency. Regarding rubber nano-coating, it is found that coating process with TPI (1,4-trans-Polyisoprene) and CPB (1,4-cis-Polybutadiene) than CPI (1,4-cis-Polyisoprene) and TPB (1,4-trans-Polybutadiene) will enhance efficiently the impermeability of CSH paste. Under aggressive conditions, non-fully epoxy nano-coating is detached more distorted in 4 wt.% of NaCl solution due to the chlorine ions, which are responsible to attack the CSH surface. A continuous well-distributed rubber nano-coating is capable to make CSH impermeable under harsh environment leading to a promising future for sustainable cementitious materials.The doctoral thesis concludes the feasibility and reliability of nano-coating by rubber film to prevent the interfacial deterioration of CSH surfaces in aggressive environment and to improve the impermeability of nano-coated CSH surfaces for more durable cementitious materials
Chapitres de livres sur le sujet "Cementitious hydrates"
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Ahn, Ji Whan, Kwang Suk You, Gi Chun Han et Kye Hong Cho. « Stabilization Behavior of Heavy Metals Derived from Wastes on Cementitious Minerals and Hydrates ». Dans Materials Science Forum, 630–33. Stafa : Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-995-4.630.
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Tits, J., X. Gaona, N. Macé, D. Kulik, T. Stumpf, C. Walther, G. Geipel et E. Wieland. « Immobilisation of Uraniumvi in Cementitious Materials : Evidence for Structural Incorporation in Calcium–Silicate–Hydrates and Solid Solution Formation ». Dans Proceedings of the 10th International Congress for Applied Mineralogy (ICAM), 699–706. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27682-8_84.
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Chen, W., J. Xiang, Y. Gao et Z. Zhang. « Effects of Graphene Oxide Content on the Reinforcing Efficiency of C–S–H Composites : A Molecular Dynamics Study ». Dans Lecture Notes in Civil Engineering, 521–26. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3330-3_55.
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AbstractDetermining the graphene oxide (GO) content is the key to applying GO to reinforce the mechanical performance and durability of cementitious composites. However, most of the previous studies are conducted from the perspective of experiments and lack elaboration on the mechanism of the GO-reinforced cementitious composite under different GO content. Hence, we investigated the effect of GO content on the reinforcing efficiency of calcium–silicate–hydrate (C–S–H) to trade off the enhancement of GO in cementitious composites and the corresponding economic benefits. The results demonstrated that an appropriate number of GO nanosheets can reinforce the cementitious composite with simultaneous high enhancing efficiency and economic benefits. The microdamage evolution of GO/C–S–H composites and the GO reinforcing mechanisms are reported. Our findings deepen the understanding of the enhancing mechanisms of GO embedded in C–S–H nanocomposites and help to determine the suitable GO content in practical engineering.
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Ramu, Yogesh Kumar, Paul Stephen Thomas, Kirk Vessalas et Vute Sirivivatnanon. « Submicroscopic Evaluation Studies to Minimize Delayed Ettringite Formation in Concrete for a Sustainable Industry and Circular Economy ». Dans Lecture Notes in Civil Engineering, 445–55. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3330-3_45.
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AbstractThe high cost of maintenance, repair and retrofitting of concrete infrastructure to keep these structures durable and serviceable is not sustainable, so the design process needs to consider all aspects of deterioration mechanism/s that can potentially occur in a concrete structure. The ideal solution should contribute to sustainability by enhancing the durability of concrete elements and supporting a circular economy. We studied delayed ettringite formation (DEF), a potential deterioration mechanism, including mitigation measures, in various heat-cured cementitious systems. The results showed that continuously connected pore/crack paths at the submicroscopic level favor the transportation of DEF-causing ions in heat-cured systems. DEF increases the chance of developing cracks, which is a durability concern. To mitigate DEF, fly ash produced from an Australian bituminous coal-burning power station was incorporated in the binder to support the circular economy concept. Changes in heat-cured cementitious systems were evaluated using expansion, electrical resistivity, dynamic modulus, and microstructural studies. The pozzolanicity of fly ash was found to greatly enhance the formation of denser calcium-silica-hydrate, which in turn restricted the transportation of DEF-causing ions at the submicron level, leading to less DEF occurrence and enhancement of the durability and sustainability of concrete in field structures.
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Duan, W., Y. Zhuge et Y. Liu. « Effect of Blending Alum Sludge and Ground Granulated Blast-Furnace Slag as Cement Replacement to Mitigate Alkali-Silica Reaction ». Dans Lecture Notes in Civil Engineering, 93–102. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3330-3_12.
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AbstractThe alkali–silica reaction (ASR) is a severe durability issue in cement-based materials. Although using calcium-rich supplementary cementitious materials (SCMs) such as ground granulated blast-furnace slag (GGBS) is beneficial for improving mechanical performance, it can lead to critical ASR-induced damage, primarily when high-reactive aggregates are used. We used alum sludge, a byproduct of drinking water treatment processes, and found it to have high efficiency in mitigating ASR in mortars containing GGBS as cement replacement and waste glass as high-reactive aggregate. The raw alum sludge was calcined for 2 h at 800 ℃ and ground to pass a 75-µm sieve. Ternary blended binders were made by replacing 10, 20 and 30% of cement with the mixture of alum sludge and GGBS (ratio 1:1). The mortar samples exhibited a considerable compressive strength and significant ASR resistance when 30% of cement was replaced with the mixture of alum sludge and GGBS compared with the reference samples. Microstructural characterization using X-ray diffraction, backscattered electron images and energy-dispersive X-ray spectroscopy indicated that increasing the aluminum content of the alum sludge could prevent the formation of detrimental Ca-rich and low-flowable ASR gels. The hindering effect was attributed to the alkaline binding ability and the extra precipitation of calcium aluminum silicate hydrate phases due to the abundant Al in the binder.
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Rivas Murillo, J., R. Mohan et A. Mohamed. « Constitutive Material Models for High Strain Rate Behavior of Cementitious Materials from Material Chemistry—Molecular Dynamics Modeling Methodology with Illustrative Application to Hydrated Calcium Silicate Hydrate Jennite ». Dans Blast Mitigation Strategies in Marine Composite and Sandwich Structures, 423–42. Singapore : Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-7170-6_22.
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HERFORT, DUNCAN, et BARBARA LOTHENBACH. « Ternary phase diagrams applied to hydrated cement ». Dans A Practical Guide to Microstructural Analysis of Cementitious Materials, 485–502. CRC Press, 2015. http://dx.doi.org/10.1201/b19074-12.
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Ghosh, Aditya Shankar, et Dr Tapash Kumar Roy. « EFFECT OF RICE HUSK ASH AS SUPPLEMENTARY CEMENTITIOUS MATERIAL FOR RIGID PAVEMENT CONSTRUCTION ». Dans Futuristic Trends in Construction Materials & ; Civil Engineering Volume 3 Book 4, 193–204. Iterative International Publishers, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3bice4p7ch1.
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The calorific value of the agricultural waste in the form of Rice Husk is very close to the calorific value of coal. Therefore it finds its use as fuel for boilers in cement production. This saves 5% of the country’s coal which is the non-renewable resource of fuel. The resultant Rice Husk Ash (RHA) produced is mostly used in land filing which is an environmentally hazardous way to deposit this agro-industrial by product. Researchers have observed the RHA produced has high silica content which makes it a suitable Supplementary Cementitious Material (SCM). This not only reduces the use of coal but also reduces the cement manufacturing cost. The manuscript here is keen to achieve sustainability in industry as well as innovation and infrastructure by not only reducing the usage of non-renewable energy resources but also effectively addressing the environmental and economic concerns. In this study the properties of hydrated cements are investigated when mixed with the RHA. This not only improved the properties of the concrete but also made them sustainable for high grade concrete construction, conventionally used for the construction of rigid pavements. The activity of the RHA made variation in the mortar properties which was analyzed by X-Ray Diffraction (XRD). Experimental results confirmed increased compressive strength of high grade RHA mixed cement concrete by replacement up to 15% and 5% of Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC) respectively by weight compared to high grade virgin cement concrete. The incorporation of RHA also reduced the pH value and consequently the Alkali Aggregate Reaction (AAR).
Actes de conférences sur le sujet "Cementitious hydrates"
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Owada, Hitoshi, Tomoko Ishii, Mayumi Takazawa, Hiroyasu Kato, Hiroyuki Sakamoto et Masahito Shibata. « Modeling of Alteration Behavior on Blended Cementitious Materials ». Dans 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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Ozbulut, Osman E., Zhangfan Jiang et Guohua Xing. « Evaluation of Various Factors on Electrical Properties of GNP-Reinforced Mortar Composites ». Dans 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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John, Emerson E., W. Micah Hale et R. Panneer Selvam. « Effect of High Temperatures and Heating Rates on High Strength Concrete for Use as Thermal Energy Storage ». Dans ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90096.
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In recent years due to rising energy costs as well as an increased interest in the reduction of greenhouse gas emissions, there is great interest in developing alternative sources of energy. One of the most viable alternative energy resources is solar energy. Concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. Areas where CSP technologies can be improved are improved heat transfer fluid (HTF) and improved methods of thermal energy storage (TES). One viable option for TES storage media is concrete. The material costs of concrete can be very inexpensive and the costs/ kWhthermal, which is based on the operating temperature, are reported to be approximately $1. Researchers using concrete as a TES storage media have achieved maximum operating temperatures of 400°C. However, there are concerns for using concrete as the TES medium, and these concerns center on the effects and the limitations that the high temperatures may have on the concrete. As the concrete temperature increases, decomposition of the calcium hydroxide (CH) occurs at 500°C, and there is significant strength loss due to degeneration of the calcium silicate hydrates (C-S-H). Additionally concrete exposed to high temperatures has a propensity to spall explosively. This proposed paper examines the effect of heating rates on high performance concrete mixtures. Concrete mixtures with water to cementitious material ratios (w/cm) of 0.15 to 0.30 and compressive strengths of up to 180 MPa (26 ksi) were cast and subjected to heating rates of 3, 5, 7, and 9° C/min. These concrete mixtures are to be used in tests modules where molten salt is used as the heat transfer fluid. Molten salt becomes liquid at temperatures exceeding 220°C and therefore the concrete will be exposed to high initial temperatures and subsequently at controlled heating rates up to desired operating temperatures. Preliminary results consistently show that concrete mixtures without polypropylene fibres (PP) cannot resist temperatures beyond 500° C, regardless of the heating rate employed. These mixtures spall at higher temperatures when heated at a faster rate (7° C/min). Additionally, mixtures which incorporate PP fibres can withstand temperatures up to 600° C without spalling irrespective of the heating rate.
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Thienoosan, S., D. J. C. Y. Goonewardena et G. Tharmarajah. « Physical and Mechanical Characteristics of Lime-based Cementitious Grout ». Dans SLIIT 2nd International Conference on Engineering and Technology. SLIIT, 2023. http://dx.doi.org/10.54389/hdst9141.
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Grout is an essential part in soil and rock anchoring while large amount of grout is consumed in anchoring process and capacity of anchoring can be increased by strengthening the grout. Increasing the strength of the grout or achieving the strength of the cement-based grout by partially replacing the cement with hydrated lime and by adding coir fiber can produce sustainable and structurally acceptable grout. This research study investigates grout with water/solid (w/s) ratio of 0.45, 0.7 while replacing the blended Hydraulic cement (BHC) content with hydrated lime by 35%, 50% and 65% with 1% coir fiber, superplasticizer and silica fume. The results show that flow of the grout is reduced with the addition of lime, fiber. Bleeding is improved in the lime-based grout. Compressive strength reduces with the addition of lime while grout achieves improved strength in long term. Compositions with 35% Lime content showed better performance and w/s ratio of 0.45 had the best compositions comparing the physical and mechanical characteristics. The fiber grout sample with w/s = 0.45 and 35% lime content had the best results with flow of 135mm, final bleeding of 3.75%, bleeding settlement in less than one hour and compressive strength at 7days, 28days are 10.4Mpa, 21.75Mpa respectively. KEYWORDS: Soil Anchoring, Lime-based grout, Coconut coir fiber, Mechanical characteristics, Physical properties.
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Chuang, Li, Tomohiro Kajio, Eiji Owaki, Yuka Morinaga, Yogarajah Elakeswaran et Toyoharu Nawa. « Sulphate attack in slag-blended cementitious materials hydrated wth sodium sulphate ». Dans Fifth International Conference on Sustainable Construction Materials and Technologies. Coventry University and The University of Wisconsin Milwaukee Centre for By-products Utilization, 2019. http://dx.doi.org/10.18552/2019/idscmt5110.
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« On the Occurrence of CAH10 in Hydrated Calcium Sulfoaluminate Cements ». Dans SP-349 : 11th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete. American Concrete Institute, 2021. http://dx.doi.org/10.14359/51732744.
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Paiva, Rayane de Lima Moura, Lucas Rosse Caldas, Patrícia Brandão Souza, Giulia Fea Oliveira et Romildo Dias Toledo Filho. « Evaluation of Bio-Based Earth Engineered Mortars for Low Energy and Carbon Buildings in Tropical and Subtropical Climates ». Dans 4th International Conference on Bio-Based Building Materials. Switzerland : Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.203.
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Improving the thermal performance of low-income housing in developing countries, located in tropical and subtropical regions, is one of the main challenges of the building sector. The use of mortars as building cladding is a current practice in many developing countries. Bio-based (such as bamboo particles) and earth materials have shown interesting potential for improving some thermal properties of covering mortars. In addition, bio-based earth mortars can have a lower carbon footprint than conventional mortars (typically made of cement or cement with lime) used in the building sector. The aim of this study is the evaluation of the life cycle GHG emissions of different mixtures of an engineered bio-based earth mortar mixed with bamboo particles, earth, and different cementitious materials (Portland cement, hydrated lime, metakaolin, and fly ash) and water. Four mixtures are evaluated: without bamboo particles, with 3%, 6%, and 9% of bamboo particles in volume. The thermal energy performance and carbon footprint of these mortars are evaluated. From physical tests carried out in the laboratory, thermal energy simulations are carried out in DesignBuilder software considering a case study of a social housing project in Brazil, evaluating tropical and subtropical climates. Finally, the carbon footprint was performed, using the Life Cycle Assessment (LCA) methodology considering a cradle-to-gate scope. When compared with two conventional mortars (made of cement and hydrated lime), the bio-based earth mortar presents better thermal energy performance and a lower carbon footprint. We can conclude that there is a potential to improve the thermal energy performance in low-income housing and, at the same time, to reduce the mortar carbon footprint. This mortar can be produced where bamboo and cementitious materials are available, which is the case in several developing countries that are expected to have a substantial housing demand for new buildings in the coming years.
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Sharp, J. H., J. Hill, N. B. Milestone et E. W. Miller. « Cementitious Systems for Encapsualation of Intermediate Level Waste ». Dans ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4554.
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Encapsulation in cement is the favoured method in the UK for disposal of intermediate and low level radioactive wastes. It is usual to use composite cement systems incorporating blast furnace slag (BFS) or pulverised fuel ash (PFA) as these offer several advantages over Portland cement, notably a lower heat of hydration. The use of these mineral additions utilises a waste product which would itself need a disposal route and, because of the decreased amount of Portland cement used, provides a reduction in cost and energy consumption. Cementitious systems have many attributes which make them suitable for encapsulation and immobilisation, including: • Inexpensive and readily available; • Assist immobilisation of radionuclides by: a) acting as a diffusion barrier, b) providing sorption and reaction sites, c) maintaining a high pH which in turn decreases radionuclide solubility; • Provide radiation shielding which is not degraded by the radiation; • Controllable permeation and diffusion characteristics over a wide range via selection of constituents and components. Where physical adsorption is a significant factor for immobilisation, the calcium silicate hydrate gel (C-S-H) formed on hydration of a Portland cement is advantageous as it has a high surface area and large micropore volume. Composite cements based on blast furnace slag will produce a higher proportion of C-S-H than ordinary Portland cement increasing the sorption capacity, and reducing the capillary porosity so that the diffusion resistance is increased. Intermediate level waste covers a wide range of materials, for example, metals and ion exchangers, each with differing chemical properties. It is, therefore, necessary to access the ability of the cementitious system to immobilise different wastes and to characterise the products formed. It is also necessary that alternative encapsulant materials be considered for immobilising wastes not suited to the composite cements already being used. The techniques employed to do this include x-ray diffraction (XRD), to identify standard and non-standard hydration products, isothermal conduction calorimetry (ICC) and scanning electron microscopy (SEM).
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« Optimization Performance of High Volume Fly Ash Self-Consolidating Mixtures with Hydrated Lime (Mortar Component) ». Dans SP-320:10th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete. American Concrete Institute, 2017. http://dx.doi.org/10.14359/51701084.
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Paiva, Rayane de Lima Moura, Adriana Paiva Souza Martins, Lucas Rosse Caldas, Oscar A. M. Reales et Romildo Dias Toledo Filho. « Earth-Based Mortars : Mix Design, Mechanical Characterization and Environmental Performance Assessment ». Dans 4th International Conference on Bio-Based Building Materials. Switzerland : Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.271.
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The incorporation of sustainable materials in the civil construction sector has grown in recent years to minimize environmental impacts. Among these materials, the use of earth, a local raw material that does not require much energy for its processing, appears as an advantageous and promising alternative. Earth mortars stabilized with natural binders, when compared to conventional mortars, can have technological, economic and environmental advantages. The objective of this work was to develop an earth-based mortar stabilized with mineral binders using a 1:3 binder to aggregate mass proportion, and to evaluate its fresh and hardened state properties, as well as its environmental impacts using Life Cycle Assessment (LCA) with a cradle to gate scope. The selected materials were divided in four groups: (i) cement, hydrated lime, fly ash and metakaolinite (binders), (ii) natural sand and coarse fraction of the earth (aggregates), (iii) calcium chloride and superplasticizer (additives) and (iv) water. In the matrix formulation the clay fraction from earth constituted the majority of the binder. The selection of supplementary cementitious materials as additional binders provided improvements in workability and mechanical properties of the mortar. A mix design was carried out using different cement (5; 7.5 and 10%) and fly ash (11; 13.5 and 16%) mass percentages. The water/binder material ratio, superplasticizer content and calcium chloride content were 0.65; 2% and 1%, respectively. The results showed that an increase in fly ash content combined with a decrease in cement content provided an increase in workability and a decrease in mechanical properties of mortars. Nevertheless, the mechanical performance of the mortars remained above the minimum values prescribed in Brazilian construction codes. From the results analysis it was concluded that partial replacement of cement by fly ash provided greater workability in the fresh state and reduced the environmental impacts of the earth-based mortar.
Rapports d'organisations sur le sujet "Cementitious hydrates"
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Ucak-Astarlioglu, Mine, Jedadiah Burroughs, Charles Weiss, Kyle Klaus, Stephen Murrell, Samuel Craig, Jameson Shannon, Robert Moser, Kevin Wyss et James Tour. Graphene in cementitious materials. Engineer Research and Development Center (U.S.), décembre 2023. http://dx.doi.org/10.21079/11681/48033.
Texte intégralRésumé :
This project aims to determine the influence of laboratory-generated graphene (LGG) and commercial-grade graphene (CGG) on the chemical structure and compressive strength of graphene-cement mixtures. Determining the graphene-cement structure/processing/property relationships provides the most useful information for attaining the highest compressive strength. Graphene dose and particle size, speed of mixing, and dispersant agent were found to have important roles in graphene dispersion by affecting the adhesion forces between calcium silicate hydrate (CSH) gels and graphene surfaces that result in the enhanced strength of cement-graphene mixtures. X-ray diffraction (XRD), Raman, and scanning electron microscope (SEM) analyses were used to determine chemical microstructure, and compression testing for mechanical properties characterization, respectively. Based on observed results both LGG and CGG graphene cement mixtures showed an increase in the compressive strength over 7-, 14-, and 28-day age curing periods. Preliminary dispersion studies were performed to determine the most effective surfactant for graphene dispersion. Future studies will continue to research graphene—cement mortar and graphene—concrete composites using the most feasible graphene materials. These studies will prove invaluable for military programs, warfighter support, climate change, and civil works.
2
Qadri, Faisal, et Nishant Garg. Reducing Concrete Cure Times for Bridge Substructure Components and Box Culverts. Illinois Center for Transportation, septembre 2023. http://dx.doi.org/10.36501/0197-9191/23-018.
Texte intégralRésumé :
This report investigated pathways to reduce concrete curing time while maintaining mechanical and durability performance. Among several options such as admixtures, supplementary cementitious materials, and low water-to-cement ratio, researchers explored two mix designs in a field demonstration project. For Stage I of the project, a low water-to-cement ratio concrete mixture was used. For Stage II, the use of calcium-silicate-hydrate (C-S-H) based seeds was explored. Concrete laboratory mixtures containing C-S-H seeds X1 and X2 exhibited increased early-age strength and reduced permeability. Based on these findings and the Illinois Department of Transportation acceptance of X2 as a Type S admixture, a field demonstration project was conducted on a box culvert near Armstrong, Illinois. The X2 concrete mix design was compared to a low water-to-cement ratio concrete mix design. Results showed that the X2 mixture with C-S-H seeds consistently demonstrated higher strength than the low water-to-cement concrete mixture, suggesting that seed-based admixtures can provide additional benefits for reducing curing times. The recommended dosage of X2 is 5 fl oz/cwt for optimal performance in reducing cure time.