Дисертації з теми "Cementious materials"
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Danché, Valentine. "Impression 3D par liaison sélective de béton de chanvre." Electronic Thesis or Diss., CY Cergy Paris Université, 2024. http://www.theses.fr/2024CYUN1286.
Повний текст джерела3D printing is experiencing a significant rise in the construction industry, paving the way for the expected digitalization of the sector. As new techniques are explored to combine technical optimization and CO2 emission reduction, this study focuses on powder-bed 3D printing. Despite still being relatively niche, this method could facilitate printing with a high natural fiber content, thus taking a further step towards carbon neutrality. The process is simple, involving three iterative steps : depositing a layer of reactive powder, compacting it, and then injecting water onto the surface.Hence, controlling water penetration into the powder is crucial to improve print quality. The objective is to confine the available water to the desired area, ensuring optimal binder hydration and preventing leaching from previous layers. Several factors may limit penetration depth, including the physical properties of the powder (compactness, permeability) and those of the injected fluid (surface tension, viscosity, yield stress) to study their impact on the kinetics of water propagation on the surface and within the powder. Consequently, we examined the vertical water propagation kinetics in compacted cementitious powder samples. To better simulate the phenomena occurring within the printer, vertical imbibition in both penetration directions was monitored through image analysis and MRI, providing additional insights into the quantity and distribution of water in the samples.Following the development of a versatile setup, we investigated pure powders (such as cement, calcite, metakaolin, sand) and those containing porous aggregates (recycled cement paste or micronized hemp shives) to better understand their impact on water penetration in a bio-sourced printable powder. Indeed, this technique sheds new light with a saturation sensibility and, when combined with MRI, water transfers between the matrix and porous aggregates. Natural porous aggregates like hemp are well-known to affect water distribution as they absorb and swell on contact with water. The results indicate that kinetics do not always slow down over time which opens discussions on the validity of Washburn's Law, commonly used to describe water propagation phenomena in porous media.Finally, the complete development of a powder-bed 3D printer has enabled the printing of cubes, which will facilitate the study of the influence of printing parameter choices (injection type and compactness) on part geometry. We will then be able to consider biobased materials as a possible tool for improving printing precision
Houk, Alexander Nicholas. "SELF-SENSING CEMENTITIOUS MATERIALS." UKnowledge, 2017. https://uknowledge.uky.edu/ce_etds/58.
Повний текст джерелаIsaacs, Ben. "Self-healing cementitious materials." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54220/.
Повний текст джерелаPheeraphan, Thanakorn. "Microwave curing of cementitious materials." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12174.
Повний текст джерелаPeach, Benjamin. "Laser scabbling of cementitious materials." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/11853/.
Повний текст джерелаBrown, Nicholas John. "Discrete element modelling of cementitious materials." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8011.
Повний текст джерелаRad, Taghi. "Microstructural characteristics of recycled cementitious materials." Thesis, University of Hertfordshire, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340038.
Повний текст джерелаBolton, Mark William. "Soil Improvement Using Optimised Cementitous Materilas Design." Thesis, Griffith University, 2014. http://hdl.handle.net/10072/365243.
Повний текст джерелаThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text
Mihai, Iulia. "Micromechanical constitutive models for cementitious composite materials." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/24624/.
Повний текст джерелаValori, Andrea. "Characterisation of cementitious materials by 1H NMR." Thesis, University of Surrey, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510562.
Повний текст джерелаUnsworth, Hugh P. "Cementitious materials in waste containment, leach studies." Thesis, University of Dundee, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337409.
Повний текст джерелаGoldthorpe, Kathryn. "Stability of cementitious materials in saline environments." Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361798.
Повний текст джерелаDavies, Robert Elfed. "Micromechanical modelling of self-healing cementitious materials." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/70424/.
Повний текст джерелаYu, Shu W. "Ionic and molecular diffusion in cementitious materials." Thesis, Aston University, 1990. http://publications.aston.ac.uk/14273/.
Повний текст джерелаRound, Robert. "Evaluation of reaction kinetics and material properties of cementitious ceramic materials using ultrasonic velocity and attenuation measurements." Thesis, Brunel University, 1996. http://bura.brunel.ac.uk/handle/2438/6512.
Повний текст джерелаNeithalath, Narayanan. "Development and characterization of acoustically efficient cementitious materials." Skokie, Ill. : Portland Cement Association, 2004. http://www.cement.org/bookstore/profile.asp?itemid=SN2924.
Повний текст джерелаSun, Ruting (Michelle). "Characterization of the acoustic properties of cementitious materials." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/27308.
Повний текст джерелаZhou, Ding. "Developing supplementary cementitious materials from waste London clay." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44528.
Повний текст джерелаMarchetti, Ezio. "Use of Agricultural Wastes as Supplementary Cementitious Materials." Thesis, KTH, Byggvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284110.
Повний текст джерелаDen globala cementproduktionen ökar från 1990 till 2050 och växer särskilt snabbt i utvecklingsländer, där den utgör en viktig del för infrastrukturutveckling och industrialisering. Varje ton vanligt portlandcement (OPC) släpper i genomsnitt ut cirka 800 kg koldioxid i atmosfären, och, totalt, representerar den totala cementproduktionen ungefär 7% av alla koldioxidutsläpp från mänsklig verksamhet. Det här examensarbetet syftar till att fördjupa kunskapen om och därmed i förlängningen återanvändningen av fasta avfallsmaterial från jordbruket som delvis ersättning av OPC, vilket kan bidra till hållbarheten i betongindustrin på grund av deras tillgänglighet och miljövänlighet. I synnerhet kan risskalaska (RHA) och havreskalaska (OHA), som bränns under rätt process, ha en hög reaktiv kiseldioxidhalt, vilket representerar mycket potentiella puzzolaner. De mekaniska och fysiska egenskaperna hos båda materialen har undersökts för att utvärdera deras inverkan på betongegenskaper. Därefter presenteras en jämförande miljökonsekvensanalys mellan RHA-betong och OPC-betong med samma motståndsklass med användning av miljövarudeklaration (EPD) för det använda materialet. Man drar slutsatsen att användningen av RHA som alternativt bindemedel (SCM) till OPC kan hjälpa till att minska koldioxidutsläppen och den globala uppvärmningspotentialen.
Zhang, Jie. "Microstructure study of cementitious materials using resistivity measurement /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20ZHANG.
Повний текст джерелаJustice, Joy Melissa. "Evaluation of Metakaolins for Use as Supplementary Cementitious Materials." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6936.
Повний текст джерелаVerganelakis, Dimitris A. "Fringe-field imaging and NMR studies of cementitious materials." Thesis, University of Kent, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267400.
Повний текст джерелаKhalifa, Abdalla. "Processing and characterisation of cementitious materials reinforced with fibres." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/69959/.
Повний текст джерелаTyrer, M. J. "Stabilisation of clay type soils with cementitious material." Thesis, Teesside University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382206.
Повний текст джерелаOjedokun, Olalekan. "Durability properties of an alkali activated cementitious material." Thesis, Sheffield Hallam University, 2018. http://shura.shu.ac.uk/21933/.
Повний текст джерелаVikan, Hedda Vestøl. "Rheology and Reactivity of Cementitious Binders with Plasticizers." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-689.
Повний текст джерелаThe rheological behaviour of cementitious pastes has been studied by various means. Six different cements have been studied in main parts of the work and all of them have been characterized according to the Rietveld method in order to determine the exact content of minerals. Easily soluble alkalis were measured by plasma-emission- spectroscopy of the fluid filtered from paste. Three types of plasticizers namely naphthalene sulfonate formaldehyde condensate (SNF), lignosulphonate and polyacrylate grafted with polyether (PA) have been used throughout the work. The influence of the plasticizer type on the rheological properties of the cementitious pastes, their adsorption characteristics and their effects on heat of hydration of the pastes has been studied. Limestone has been used as a nonreactive model material for cement in some parts of the work.
All rheological measurements were performed with a parallel plate rheometer. Rather than describing the shear stress-shear rate flow curve with the usual Bingham model resulting in plastic viscosity and yield stress, the area under the curve (Pa/s) was used as a measure of “flow resistance”.
The effect of silica fume and limestone on the rheology of cementitious pastes
The rheological behaviour of cementitious pastes, with the cement being increasingly replaced by densified and untreated silica fume (SF) or limestone was studied. Three plasticizers were investigated namely two types of polyacrylate (PA1 and PA2) and SNF. PA2 proved to be the most efficient plasticizer of the three while PA1 and SNF provided comparable results.
The flow resistance was found to increase with increasing silica fume replacement when SNF and polyacryalte (PA1) were added as plasticizers which was explained by ionization of the silica fume surface and possible bridging with polyvalent cations like calcium. The flow resistance decreased, however, with increasing silica fume replacement when the second and more efficient type of polyacrylate (PA2) was utilized which was believed to occur since the cement pastes were better dispersed by PA2 than SNF and PA1. The silica fume particles could thus pack between the cement grains and displace water. An alternative explanation for reduced flow resistance with increasing silica fume replacement could be a ball-bearing effect of silica spheres.
There was found a trend of increasing gel strength with increasing silica fume replacement of cement even though the pastes seemed to be dispersed by PA2. Cement pastes with densified SF developed lower gel strengths than pastes with untreated SF. This phenomenon was attributed to more grain shaped agglomerates with lower outer surface in densified SF compared to dendritic agglomerated in untreated SF. Decreasing gel strength was found for pastes with increasing limestone filler replacement. Thus silica fume may be advantageous as stabilizing agent for self-compacting concrete preventing segregation upon standing due to a more rapid gel formation.
Effect of cement characteristics on flow resistance
Rheological experiments were performed on pastes prepared from 4 cements originating from the same clinker, but ground to different finenesses (Blaine). The results showed that the flow resistance increased exponentially with increasing Blaine number. No correlations between single cement characteristics such as Blaine, content of C3A, cubic C3A (cC3A) and C3S with the flow resistance were however found when cements from different clinkers were used. This finding indicates that cement should not be treated as a univariable material. However, the combined cement characteristic (Blaine•{d•cC3A+[1-d]•C3S}) was found to correlate with flow resistance, where the factor d represents relative reactivity of C3A and C3S. The flow resistance was found to be either a linear or exponential function of the combined cement characteristic depending on plasticizer type and dosage. Correlations were found for a mix of pure cement and cement with fly ash, limestone filler (4%), as well as pastes with constant silica fume dosage when the minerals were determined by XRD.
Influence of cement and plasticizer type on the heat of hydration
The initial heat of hydration peak was measured for the 6 main cements with 0.32% SNF, lignosulphonate and PA2 by cement weight. Correlations were attempted between the maximum heat of hydration rates of the initial peaks with various cement characteristics. The maximum heat of hydration rate seemed to correlate with the product of the cement fineness and C3A content regardless of plasticizer type. The fly ash cement had to be left out of the correlation plots due to its low initial heat of hydration.
The second, third and fourth hydration peaks were measured on the cement pastes with 0-0.8% SNF, lignosulphonate and PA2 by weight of cement. Lignosulphonate was found to be the strongest retarder while SNF had the least effect on the setting time of the three plasticizers. No correlations could be found between the setting times and cement characteristics such as cement fineness, aluminate and alkali contents for un-plasticized pastes probably because the setting times might have been too close to each other to be able to obtain accurate values. Correlations between setting time and cement characteristics were however found for pastes with plasticizers. The setting times did not correlate with the cement fineness (Blaine) as a single parameter. The product of cement Blaine and C3A content, however, resulted in a correlation. Furthermore the setting time correlated with the cubic modification of C3A. It may seem that the setting times depend more on the cubic modification of C3A than the sum of orthorhombic and cubic aluminate. This finding indicates that the cubic aluminate modification is more reactive than the orthorhombic. The setting time decreased with increasing content of easily soluble K-ions in the cements probably due to the formation of syngenite, K2SO4·CaSO4·H2O, which removes some sulphate from solution that would otherwise retard C3A hydration. A similar correlation was not found between the setting time and the sodium equivalent.
Cement interactions with plasticizers
Three plasticizers were studied namely SNF, lignosulphonate and polyacrylate (PA2). PA2 was the most efficient plasticizer of the three tested even thought it was found to adsorb to a lesser extent on cement than SNF and lignosulphonate. SNF and lignosulphonate brought about comparable results.
PA2 was observed to induce flow gain within the 2 hours of rheological measurements which might be caused by the polymer expanding in the water phase and thus improve the dispersion of the paste. Furthermore the grafted side chains of the polymer are considered to be long enough to provide steric dispersion even thought the backbone might be embedded in the hydration products. Cement pastes with SNF and lignosulphonate exhibited flow loss as a function of time which indicates that the plasticizer molecules were consumed by the hydration products.
The concentrations of superplasticizer in the pore water were not found to change markedly in the time range 20-95 min after water addition, indicating that most of the plasticizer molecules were consumed (i.e. adsorbed or intercalated in surface hydration products) within the first 20 minutes after water addition.
The adsorption characteristics were found to depend on the plasticizer type. The adsorption curves of SNF and lignosulphonate reached a plateau at saturation characterizing high-affinity adsorption or increased continuously as a sign of low affinity adsorption. The adsorbed amounts of polyacrylate decreased, however, after saturation had been reached which might indicate that surplus molecules in the water phase compress the ionic double layer or that adsorbed molecules expand and hinder molecules in the water phase to attach at the surface (i.e. osmosis).
The plasticizer saturation dosages were found to depend on cement surface area (Blaine), amount of cubic C3A and easily soluble sulphates. The saturation dosage of lignosulphonate seemed to have a dependency on the amount of soluble alkali that was somewhat stronger than observed for pastes with SNF. This difference might be caused by lignosulphonate forming complexes with solvated ions in a higher degree than SNF. Moreover alkali sulphates are furthermore often added to commercial SNF based products as the one used in this work. The best correlation, overall, was found for the product of cubic C3A and Blaine which is logical since high surface and cubic aluminate contents accounts for high cement reactivity and since the plasticizers are known to coordinate with calcium sites. Correlations were also found between saturation dosage with the product of Naeqv and Blaine as well as the product of Naeqv and cubic C3A. The investigations seemed to indicate that the plasticizer saturation concentration increase with increasing alkali content. These findings, however, are rather unclear. According to literature an increased concentration of alkali sulphate in solution results in both an increased hydration rate (which would lead to a higher plasticizer intercalation) and a reduced plasticizer adsorption (due to SO42- - superplasticizer competition). The easily soluble sulphates might, of course, entail the opposing effects of Blaine and C3A in a way that smoothen the correlation plots of the plasticizer saturation dosage with the cement characteristics.
Effect of temperature on rheology and plasticizer adsorption
Flow resistance and adsorbed amounts of SNF, lignosulphonate and PA2 were measured at temperatures ranging from 11 to 40oC. Limestone was used as a nonreactive model material for cement. The adsorbed amounts of SNF and lignosulphonate on limestone were found to decrease after reaching a maximum which occurred at approximately 25oC. Decreased amounts of adsorbed plasticizer with increasing temperature might be explained by increased kinetic energy to the molecules or by an entropy effect. The adsorption of PA2 on limestone seemed to be independent of paste temperature in the range of 16-34oC which might be caused by low reduction of entropy at adsorption due to its short backbone and long, grafted side chains. The flow resistance of the limestone pastes generally increased with increasing temperature which may be caused by reduced amounts of adsorbed plasticizer and/or dehydration of the paste during the rheological measurements.
Two types of cements were used to study adsorption and flow resistance with increasing temperature namely CEM I 42.5 RR and CEM I 52.5 R-LA. Amounts of plasticizer adsorbed and intercalated (consumed) by cement reached a plateau or even decreased with increasing temperature in the case of SNF and lignosulphonate. This finding might be caused by two opposing effects namely: increased number of adsorption sites due to increased hydration rate with increasing temperature and reduced adsorption due to increased kinetic energy and/or reduced entropy of the plasticizer. Amounts of PA2 consumed by cement increased linearly with increasing temperature as might be explained by the experiments with limestone where the adsorbed amounts of PA2 seemed to be independent of temperature. Increased consumption of plasticizer by the cements with rising temperature is thus probably governed by the increased number of adsorption cites due to increased hydration rate. The flow resistance of CEM I 52.5 R-LA cement increased exponentially with increasing temperature as a function of temperature most likely because of the increased hydration rate. The pastes of CEM I 42.5 RR cement were generally highly viscous and probably agglomerated. The flow resistance reached a plateau value with increasing temperature in this case.
Li, Yan, and 李彦. "Properties of mortars with binary and ternary blended cementitious materials." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48330097.
Повний текст джерелаpublished_or_final_version
Civil Engineering
Master
Master of Philosophy
Jha, Kaushal K. "An Energy Based Nanomechanical Properties Evaluation Method for Cementitious Materials." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/711.
Повний текст джерелаKarnati, Vijayasenareddy. "Flexural Response of Reinforced Concrete Beams Using Various Cementitious Materials." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470227287.
Повний текст джерелаHatzitheodorou, Alexandros. "In-situ strength development of concretes with supplementary cementitious materials." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441936.
Повний текст джерелаANGLANI, GIOVANNI. "Development and characterization of capsule-based self-healing cementitious materials." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2847154.
Повний текст джерелаMirzahosseini, Mohammadreza. "Glass cullet as a new supplementary cementitious material (SCM)." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/17565.
Повний текст джерелаDepartment of Civil Engineering
Kyle A. Riding
Finely ground glass has the potential for pozzolanic reactivity and can serve as a supplementary cementitious material (SCM). Glass reaction kinetics depends on both temperature and glass composition. Uniform composition, amorphous nature, and high silica content of glass make ground glass an ideal material for studying the effects of glass type and particle size on reactivity at different temperature. This study focuses on how three narrow size ranges of clear and green glass cullet, 63–75 [mu]m, 25–38 [mu]m, and smaller than 25 [mu]m, as well as combination of glass types and particle sizes affects the microstructure and performance properties of cementitious systems containing glass cullet as a SCM. Isothermal calorimetry, chemical shrinkage, thermogravimetric analysis (TGA), quantitative analysis of X-ray diffraction (XRD), and analysis of scanning electron microscope (SEM) images in backscattered (BS) mode were used to quantify the cement reaction kinetics and microstructure. Additionally, compressive strength and water sorptivity experiments were performed on mortar samples to correlate reactivity of cementitious materials containing glass to the performance of cementitious mixtures. A recently-developed modeling platform called “[mu]ic the model” was used to simulated pozzolanic reactivity of single type and fraction size and combined types and particle sizes of finely ground glass. Results showed that ground glass exhibits pozzolanic properties, especially when particles of clear and green glass below 25 [mu]m and their combination were used at elevated temperatures, reflecting that glass cullet is a temperature-sensitive SCM. Moreover, glass composition was seen to have a large impact on reactivity. In this study, green glass showed higher reactivity than clear glass. Results also revealed that the simultaneous effect of sizes and types of glass cullet (surface area) on the degree of hydration of glass particles can be accounted for through a linear addition, reflecting that the surface area would significantly affect glass cullet reactivity and that the effects of SCM material interaction on reaction kinetics were minimal. However, mechanical properties of cementitious systems containing combined glass types and sizes behaved differently, as they followed the weaker portion of the two particles. This behavior was attributed to the pores sizes, distruibution, and connectiity. Simulations of combined glass types and sizes showed that more work on microstructural models is needed to properly model the reactivity of mixed glass particle systems.
Mayercsik, Nathan Paul. "Characterization of multiscale porosity in cement-based materials: effects of flaw morphology on material response across size and time scales." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/55308.
Повний текст джерелаJones, Christopher Andrew. "Hollow cylinder dynamic pressurization and radial flow through permeability tests for cementitous materials." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2924.
Повний текст джерелаRossetto, Hebert Luís. "Contribuições para a ciência e engenharia de materiais cimentícios: processamento, durabilidade e resistência mecânica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-19062009-214423/.
Повний текст джерелаThe materials engineering afforded the most paramount known advances on the mechanical performance of cementitious materials in the last decades, through either casting techniques or microstructure design. Therewith, it was demonstrated to be false the idea that low mechanical strengths should be inherent to cement-based materials, but, at the same time, the limited ingress of these new materials to fields of great demands relegated them to the condition of merely alternative. The fact that each ton of Portland cement does create another ton of gases related to global warming indicates that the former situation needs to be reviewed. That is why one of the main contributions of this work was to improve casting techniques to render massive production and excellent mechanical performance, in addition to durability, for the cementitious materials. The concept and the construction of a roll compaction equipment were the first step to the cost-effective production of cementitious plates with compressive strength in excess of 200MPa, in addition to a reproducibility inasmuch as that of a technical ceramic. In the same way, the extrusion, a technique able to largely produce components of complex geometries, was also well adapted to cement-based materials which, again, showed excellent reproducibility and bending strength of more than 20MPa. In both, pressing and extrusion techniques, the control of processing steps was enough to get cement-based products whose mechanical strength barely changes, even after exposure to deleterious environments. Hereby, we attribute the widest concept of durability to a material which depends on the mechanical strength throughout its service life. Anyway, we also developed an innovative method to improve the durability of these materials along this work: TEOS impregnation. TEOS is a molecular precursor of silica which reacts with calcium hydroxide to seal the cementitious pores wherefrom it penetrated. Quantitatively, the porosity of Portland cement-based products dropped down to values around 1% in volume, what is related to concomitant reduction of chlorine ion diffusion coefficient of an order of magnitude. In summary, the results that will be demonstrated in the following chapters are in resonance with the most rigorous rules for sustainability, precisely in a field where such an initiative is welcome to help encouraging its industrialization: the building construction. However, it seems that the biggest virtue of this work is not only the improvements for cementitious materials engineering, but also to apply the science for the understanding of the origin of their mechanical strength. According to our experimental evidences, the mechanical strength of these materials is ruled by water molecules which are confined in nanometric layers between the hydrating phases of Portland cement. These water nanolayers behave themselves as glassy phase and, in their turn, promote adhesion to the surfaces which confine them. To the best of our knowledge, this work is one of the most promising contributions to become possible the nanotechnology of these materials, through a subject up to that time unexplored: the adhesion by confined water. Hence, it is likely that the innovation about this subject could exceed the material itself, once life as we know owes its peculiarities to the intrigant properties of water and to their hydrogen bonding.
Mandaliev, Peter Nikolov. "Mechanisms of Nd(III) and Eu(III) uptake by cementitious materials /." [S.l.] : [s.n.], 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18095.
Повний текст джерелаDíez, García Marta. "Synthesis by supercritical fluids methods of advanced additions for cementitious materials." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0573/document.
Повний текст джерелаCement is the most used material nowadays due to several reasons: its good mechanical properties to compression, its low cost, and its easy use. However, cement is fragile when submitted to high charges and it is susceptible to degradation by external agents. For this reason different additions are used modify the setting process or the final properties of the cement paste. Among them there are one type called “setting accelerators” that develop the cementitious matrix faster. There is one type of accelerating additions that act as seeds; these are nucleating points for the formation of C-S-H gel around them. The aim of this work is to develop a new synthesis route, based on supercritical water technology, of two calcium silicate hydrates nanoadditions. These products are xonotlite and tobermorite.The first approach to the synthesis was done under subcritical conditions. After that it was developed the supercritical continuous reactor in order to adapt it to the necessities of the synthesis of the nanoadditions. The syntheses were carried out at 400ºC and 22.5 MPa. Both xonotlite and tobermorite were obtained reducing drastically the reaction times from hours/weeks (under subcritical conditions) to just some seconds under supercritical conditions.The last point studied was the seeding effect of both particles into cement paste. In every case it was observed, an acceleration of the reaction and also an improvement of the strength trough mechanical test.As a conclusion this work presents a new ultrafast method to synthesize highly crystalline calcium silicate hydrates, and also proves the accelerating effect of these particles when they are used as seeds in cement pastes. This research proposes a new methodology for the synthesis of additions to cement
Wang, Ji-yong 1967. "Ultrasonic nondestructive evaluation and imaging of defects in reinforced cementitious materials." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/7964.
Повний текст джерелаIncludes bibliographical references (leaves 141-145).
Characterization of defect is one of the important objectives of nondestructive evaluation (NDE) for condition assessment of structures. Among many other NDE techniques, ultrasonic methods play a prominent role in the both quantitative and qualitative assessment of discontinuities in reinforced cementitious materials. Due to the heterogeneous nature of concrete, ultrasonic waves are highly scattered and attenuated, leading to the difficulty of concrete inspection using conventional ultrasonic techniques, including those that work well on relatively homogeneous materials such as metals. This thesis presents an advanced method for sizing and imaging of defects in reinforced cementitious materials. A two-dimensional, three-phase composite model of concrete is proposed to study the propagation and interaction behaviors of ultrasonic waves in concrete structures, and to gain a knowledge about wave diffraction with multiple cylindrical obstacles. The response of the modeled concrete structure to an incident ultrasonic pulse input signal (pulsed ultrasonic P-wave) is analytically investigated and simulated. A characteristic profile of the defect sizing as a function of focal depth is formulated via the synthetic focusing technique. A defect sizing parameter, called characteristic width, is obtained empirically to represent the defect sizing information for the concrete. Conventional 2-D ultrasonic B-scan imaging, for example, by migration, may introduce artifacts. In this thesis, the fundamental theory for synthetic aperture beam-forming through synthetic steering and focusing of array transducers is investigated. It is possible to achieve high spatial and temporal resolution ultrasonic image free of artifacts. A time-frequency signal processing and image reconstruction algorithm are also studied. The proposed defect sizing and imaging methodology is tested with numerically simulated ultrasonic waveform signals based on the mechanical properties of a custom-made concrete specimen. Experimental works confirm the feasibility of defect sizing and imaging of the method. With the knowledge about the concrete structures being tested this method may provide a useful tool for ultrasonic NDE application to reinforced cementitious materials.
by Ji-yong Wang.
Ph.D.
AHMAD, SAJJAD. "Innovative mix design of cementitious materials for enhancing strength and ductility." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2604771.
Повний текст джерелаKHUSHNOOD, RAO ARSALAN. "High Performance Self-Compacting Cementitious Materials Using Nano/Micro Carbonaceous Inerts." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2604995.
Повний текст джерелаWiberg, Anders. "Strengthening of concrete beams using cementitious carbon fibre composites." Doctoral thesis, KTH, Civil and Architectural Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3582.
Повний текст джерелаThe research described in this thesis deals with the use ofcement-based carbon fibre reinforced composites forstrengthening of existing structural concrete.
There is a large world-wide need for simple and reliablemethods to repair and strengthen aging infrastructure andbuildings. The use of cementitious fi- bre composites offersseveral advantages over the existing methods. No other work onstrengthening of structural concrete with cementitiouscomposites reinforced with continuous high strength fibres wasidentified when the present work started in 1998. At presenttime, 2003, it still is a new technique and very littleresearch has been internationally reported. This work includesa literature survey describing the state of the art of thestrengthening of structural concrete with cement based fibrereinforced composites.
Due to the novelty of this technique no specially adaptedmaterials are available and ready for use in cementitiouscomposites. In order to make many small scale tests to optimizethe composite, a new test beam has been developed. Severalparameter studies have been done in this work to determine howdifferent parameters, for example fineness of grading of thecement, additives, and fibre configuration affect thecomposite.
Large scale tests of ordinary concrete beams strengthenedwith a cementitious fibre composite are reported. The compositeused was made of a polymer modified mortar and a unidirectionalsheet of continuous carbon fibres, applied by hand. Bothflexural strengthening and shear strengthening were tested. Arelatively new method for measuring strains with digitalcameras was used on the shear strengthenings with a goodresult. It is concluded that the large scale tests have proventhat this method works and has great potential for futureuse.
Design methods for strengthenings were studied andevaluated. It is concluded that design methods formulated forstrengthening of structural concrete with carbon fibrereinforced polymers can be adapted also to cementitiouscomposites by introducing an efficiency factor.
Tole, Ilda. "Mechanical activation of clay : a novel route to sustainable cementitious binders." Licentiate thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76362.
Повний текст джерелаUvegi, Hugo Jake. "Aqueous reactivity of glassy industrial byproducts in alternative cementitious systems." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129037.
Повний текст джерелаCataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 177-203).
Alkali-activated, geopolymeric, and other novel binders offer an opportunity to curb the carbon footprint associated with ordinary Portland cement (OPC). CO₂ emissions inherent to source-material processing (i.e., firing of limestone at 1450 °C) and annual OPC production volumes of 4.1 billion metric tons cause an estimated 5-11% of global annual greenhouse gas (GHG) emissions. Material substitution with lower-footprint resources is therefore necessary for GHG impact mitigation. Glassy silica-, alumina-, lime-, and/or alkali-rich industrial byproducts (IBs) exhibit the properties necessary to achieve emissions reductions while preserving final product attributes expected of cementitious binders. Research and industry have both focused primarily on metakaolin and IBs such as blast furnace slag and coal fly ash as supplementary and alternative cementitious precursors.
Given projected limitations in such IB supply, it is imperative that we efficiently expand the materials search to other useful precursor candidates. This thesis focuses on chemical characterization and kinetic reactivity analysis of lesser-studied glassy materials through a combined experimental-computational approach, resulting in (1) physicochemical drivers for material aqueous reactivity and (2) a framework for evaluating new materials. First, I describe laboratory experiments involving reaction of a siliceous mixed-feedstock Indian biomass ash in aqueous sodium hydroxide solutions with selectively present lime and alumina sources. These experiments respectively yield tobermoritic calcium silicate hydrate products (Ca/Si ~~ 0.6-1) and semi-crystalline zeolite / geopolymer products (Si/Al ~~ 1); shown compositional ratios are known to be relevant to final material properties.
Through this work, I demonstrate a novel approach to calculating reaction product composition using spectroscopic solution analysis of dissolution / precipitation experiments. Subsequently, I describe computational efforts to mine literature-reported data for potential precursor materials. This results in a database of material compositional and physical property data represented by a SiO₂-Al₂O₃- CaO ternary diagram. Finally, I employ supervised and semi-supervised computational models, which confirm log-linear relationships between glass dissolution rates (i.e., log₁₀(rate)) and pH, inverse temperature (1/K), and glass connectivity (i.e. non-bridging oxygens per tetrahedron). While less interpretable, black-box models are observed to be more robust to the presence of additional features. Throughout the research program, reactivity is understood via material dissolution in aqueous solutions.
by Hugo Jake Uvegi.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
Zhang, Mo. "Geopolymer, Next Generation Sustainable Cementitious Material − Synthesis, Characterization and Modeling." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/455.
Повний текст джерелаHazelwood, Tobias. "Investigation of a novel self-healing cementitious composite material system." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/76766/.
Повний текст джерелаOlsson, Nilla. "Experimental studies of ion transport in cementitious materials under partially saturated conditions." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1014/document.
Повний текст джерелаMorency, Maxime. "Cracking sensitivity of cementitious repair materials: assessments and development of test methods." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30410/30410.pdf.
Повний текст джерелаThe premature deterioration of concrete repairs in service is a result of a variety of physico-chemical and electrochemical processes. Among the most serious causes of repair failures is cracking of the repair. Cracking may result in the reduction of an effective cross-sectional area of the repaired structure and increase the effective permeability of the concrete cover, thus promoting corrosion of the reinforcement and further deterioration. The main objective of this project was to contribute to the development and assessment of a reliable test method for evaluating the sensitivity to cracking of repair materials. A performance test was developed and used to establish correlations with existing indirect test methods (ring test, beam deflexion test, drying shrinkage test, etc.). The performance test method uses of a reference slab containing a cavity on the top surface to be filled with the repair material to be tested. The reference test slab, which offers a degree of restraint comparable to what is found in reality, allows simulating the behavior of the material in real concrete repair conditions. In order to better evaluate the test methods, experimental repairs have also been made on existing structures exposed to service conditions.
Jin, Fei. "Characterisation and performance of reactive MgO-based cements with supplementary cementitious materials." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708376.
Повний текст джерелаSalah, Uddin K. M. [Verfasser]. "Elucidation of chemical reaction pathways in cementitious materials / K. M. Salah Uddin." Kassel : kassel university press c/o Universität Kassel - Universitätsbibliothek, 2021. http://d-nb.info/1231394889/34.
Повний текст джерелаSiddiqui, Md Sarwar. "Effect of temperature and curing on the early hydration of cementitious materials." Thesis, Kansas State University, 2010. http://hdl.handle.net/2097/4322.
Повний текст джерелаDepartment of Civil Engineering
Kyle Riding
Concrete is the most widely used construction material. Concrete strength and durability develop from a series of exothermic reactions involving water called hydration. Long-term durability and performance of concrete is very much dependent on the early hydration behavior of cementitious materials. This study examined the effects of curing temperature and access to moisture on the early age reaction rate of cementitious materials, and methods for quantifying these effects. Apparent activation energy (Ea) relates the effects of temperature on the cement hydration reaction. There are various methods and calculation techniques for estimating Ea that result in greatly varying values. Cement paste and mortar are often used to calculate Ea and used later for concrete. Ea values were calculated using cement mortar and paste by isothermal calorimetry and showed excellent correlation. This validates the use of Ea based on cement paste in modeling concrete behavior. Ea values were also calculated by chemical shrinkage and it showed potential for use in calculating Ea. Cementitious materials need free water to be available for hydration to continue. Curing with either waxy curing compounds or ponded water are common practices. The thickness of distilled water, lime-saturated water, and cement pore water used as a curing method affects the rate of hydration. Water-cementitious material ratio (w/cm) and sample depth affect the performance of water curing, with low w/cm being the most significant. Partial replacement of sand by fine lightweight aggregate also improves the hydration of cementitious material much more than conventional water ponding. Curing compounds showed improvements in cement hydration compared to uncured samples.