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1
Rodger, S. A. "The chemistry of admixture interaction during cement hydration." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371554.
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Afshar, Ali Behrooz. "The early hydration of cement." Thesis, Heriot-Watt University, 1986. http://hdl.handle.net/10399/1059.
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This thesis details the development and use of an electrical response technique for monitoring the chemical and physical changes occurring within the cement paste during the initial 24 hours after gauging with water. Traditional empirical tests and the more sophisticated laboratory examinations such as X-ray diffraction, scanning and transmission electron microscopy are critically reviewed. The study involves the electrical measurements on realistic sample sizes and constituent proportions. A modified electricalmodel for the response of cement paste to an applied electrical field is proposed. An automated microcomputer data logging system has been developed to facilitate electrical measurements. It has been demonstrated that the electrical response measurements of cement paste can be related to the physio-chemical processes that take place during hydration. Extensive microstructural examination of fracture surfaces of cement pastes using Scanning Electron Microscopy revealed that regions of definite crystallization and the prediction as to the hydrate morphology can be linked to the electrical response. The technique could be offered as an additional tool for investigating the structure building processes and microstructure development within cement paste. The electrical response data can be used to monitor cement hydration and it is shown that assessment of the effect of varying chemical composition; age of cement; addition of admixtures and environmental conditions have a definite influence on hydration processes.
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Bien-Aime, Andre J. "Effect of Cement Chemistry and Properties on Activation Energy." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4439.
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The objective of this work is to examine the effect of cement chemistry and physical properties on activation energy. Research efforts indicated that time dependent concrete properties such as strength, heat evolution, and thermal cracking are predictable through the concept of activation energy. Equivalent age concept, which uses the activation energy is key to such predictions. Furthermore, research has shown that Portland cement concrete properties are affected by particles size distribution, Blaine fineness, mineralogy and chemical composition. In this study, four Portland cements were used to evaluate different methods of activation energy determination based on strength and heat of hydration of paste and mortar mixtures. Moreover, equivalency of activation energy determined through strength and heat of hydration is addressed. The findings indicate that activation energy determined through strength measurements cannot be used for heat of hydration prediction. Additionally, models were proposed that are capable of predicting the activation energy for heat of hydration and strength. The proposed models incorporated the effect of cement chemistry, mineralogy, and particle size distribution in predicting activation energy.
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Winbow, Howard David. "The chemistry and properties of magnesia-phosphate cement systems." Thesis, University of Sheffield, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249651.
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Zhang, Xiaozhong. "Some aspects of cement-aggregate interaction." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330017.
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Hökfors, Bodil. "Phase chemistry in process models for cement clinker and lime production." Doctoral thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-86004.
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The goal of the thesis is to evaluate if developed phase chemical process models for cement clinker and lime production processes are reliable to use as predictive tools in understanding the changes when introducing sustainability measures. The thesis describes the development of process simulation models in the application of sustainability measures as well as the evaluation of these models. The motivation for developing these types of models arises from the need to predict the chemical and the process changes in the production process, the impact on the product quality and the emissions from the flue gas. The main chemical reactions involving the major elements (calcium, silicon, aluminium and iron) are relatively well known. As for the minor elements, such as sodium and potassium metals, sulphur, chlorine, phosphorus and other trace elements, their influence on the main reactions and the formation of clinker minerals is not entirely known. When the concentrations of minor and trace elements increase due to the use of alternative materials and fuels, a model that can accurately predict their chemistry is invaluable. For example, the shift towards using less carbon intensive fuels and more biomass fuels often leads to an increased phosphorus concentration in the products. One way to commit to sustainable development methods in cement clinker and lime production is to use new combustion technologies, which increase the ability to capture carbon dioxide. Introducing oxy-fuel combustion achieves this, but at the same time, the overall process changes in many other ways. Some of these changes are evaluated by the models in this work. In this thesis, a combination of the software programs Aspen Plus™ and ChemApp™ constitutes the simulation model. Thermodynamic data from FACT are evaluated and adjusted to suit the chemistry of cement clinker and lime. The resulting model has been verified for one lime and two cement industrial processes. Simulated scenarios of co-combustion involving different fuels and different oxy-fuel combustion cases in both cement clinker and lime rotary kiln production are described as well as the influence of greater amounts of phosphorus on the cement clinker quality.
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Mitchell, Lyndon David. "Chemistry of Portland cement as affected by the addition of polyalkanoic acids." Thesis, Keele University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388947.
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Andac, Omer. "Calcium sulfoaluminate based cements." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602277.
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Knowledge of energy requirements, solid solutions and phase compatibilities of high temperature cement phases is essential to the economics and performance of cement clinkers. Both chemical engineering and chemical approaches have been used to determine phase compatibilities and solid solutions of calcium sulfoaluminate, C4A3 S, C3S and C2S as well as to develop a new type of cement based on calcium monosulfoaluminate, C4A3S, tricalcium silicate, C3S, and dicalcium silicate, C2S. Investigation of solid solutions, substitution mechanisms and phase compatibilities of C4A3S, C3S and C2S form the basis of this thesis, and the subject is addressed as follows: (i) Investigation of the structures, solid solutions, phase compatibilities, polymorphism and stabilisation of C4A3S (literature review, theoretical and experimental research). This research discloses the existence of a high temperature polymorph (a) of C4A3S. It can be stabilised to ambient temperature by Fe or Na-Si coupled substitution. Limits of Na, Fe, Si and P solubilities in the C4A3S structure were investigated. When limits of Na2O or NaF in C4A3S solid solutions (~3%) is exceeded, C4A3S becomes unstable as a result of Na2SO4 or Na2Ca(SO4)2 formation. C4A3S is compatible with C2S, with CaO, with C3A, with C12A7, with CA, with CA2, with Al2O3, with C2AS and with Ca3(PO4)2 at 1300 C. (ii) Investigation of the microstructure and microchemistry of commercial calcium sulfoaluminate cement (literature review, theoretical and experimental research). Because of extensive A1 and S substitution, a large Si deficiency can occur in C2S solid solutions. The open structured texture of calcium sulfoaluminate cement explains why it is easily ground. (iii) Investigation of A1 and sulfur substitution into C2S solid solutions (literature review, theoretical and experimental research). A1 and S substitute into C2S by several mechanisms, the most important of which are 2A1+S for 3Si and Ca+S for 2Ca+Si. (iv) Investigation of the NaF-CaO-SiO2 phase equilibria and its resultant effect on C3S formation (literature review, theoretical and experimental research). This investigation revealed that NaF not only acts as flux but mainly it has a mineralising effect on C3S formation and results in extensive solid solutions, NaxCa3.xSiO5.xFx. C3Sss, can be obtained as low as ~1000 C in the presence of NaF. In the course of this study, I phase, structurally similar to that of 9 C3S but consisting of 15 and 24 layer variants, has been characterised. (v) Investigation of the NaF-CaO-Al2O3-SiO2-SO3 system and its resultant effect on both C3S and C4A3S formation. Cement based on C3Sss and C4A3S can be made at ~1300 C if F and SO3 concentrations in the raw materials are controlled. SO3 in excess relative to that required for the formation of C4A3S should be added to inhibit C11A7.CaF2 and C3A formation. In the course of this study, large amount of Si deficiency in the C2S structure, such as that of belite in commercial calcium sulfoaluminate cement (as a result of 2A1+S for 3Si substitution), has been found.
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Worthington, J. C. "A study of the mechanism of chloride attack on concrete." Thesis, University of Hertfordshire, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234365.
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Wongariyakawee, Anchalee. "Novel layered double hydroxide chemistry for application in cement and other building materials." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:3670c777-c860-43a8-9cdc-5a7d2c87b71b.
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The investigation into the syntheses and the intercalations of LDHs is the focus of the work described in this thesis. An introduction to Layered Double Hydroxide (LDH) materials with an emphasis on the possible host lattices and to their applications is given in Chapter 1. The application of LDHs in cement including; history of cement, cement production process, and cement hydration is detailed. The synthesis of the Ga-doped Ca2Al(OH)6Cl•nH2O LDHs (Ca2GaxAl(1–x)-Cl; where 0 < x < 1) via the co-precipitation method is reported in Chapter 2. The effect of doping Ga3+ on a parameter of Ca2GaxAl(1–x)-Cl was determined by using Vegard’s law and the correlation between a parameter and x value was derived. The intercalation of organic anions including; sodium styrene sulfonate, sodium butene dicarboxylate, sodium fumarate and ammonium poly(styrene sulfonate), in Ca2Ga-Cl structure is described. The intercalation of lignosulfonate, naphthalene sulfonate and polycarboxylate into Ca2Al(OH)6NO3·6H2O (Ca2Al-NO3) is detailed in Chapter 3. The release behaviour for the LDHs and the kinetic modelling of the release are reported. The effects of these LDHs on cement hydration studied by using the in situ X-ray diffraction and the ultrasound shear-wave reflection are discussed. In Chapter 4, the synthesis of Ca2Al(OH)6NO3·nH2O via a non-ionic surfactant reverse microemulsion is reported. The effects of the amount and the solubility [Hydrophile-Lipophile Balance (HLB)] of non-ionic surfactant on the morphology and the size distribution of the LDHs are discussed. Two new nitrite intercalated Ca2Al-LDHs [Ca2Al(OH)6NO2·nH2O] synthesised via both the co-precipitation and the reverse micro-emulsion method are detailed in Chapter 5. The hydration of Portland cement samples with additive nitrate- and nitrite-intercalated Ca2Al-LDH made using co-precipitation is discussed. The synthesis of dispersed, uniform nanoplatelet [Ca2Al(OH)6DDS]•H2O LDHs is reported in Chapter 6. The effects of the amount of the surfactant on the morphology and size distribution of the LDHs are described. The experimental procedures and characterising techniques employed in this study are listed in Chapter 7. Additional data are provided in the Appendices.
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Birnin-Yauri, Umar Abubakar. "Chloride in cement : study of the system CaO-Al2O3-CaCl2-H2O." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602295.
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Tn this work, the system CaO-Al2O3-CaCl2-H2O is investigated at 20 2 C. The subsystem, CaO-CaCl2-H2O, is studied by hydrating mixtures of CaO and CaCl2 in various proportions. Four hydrates are found to exist in the system at 20 2 C, viz. : Ca(OH)2, 3CaO.CaCl2.15H2O, CaO.CaCl2.2H2O and CaCl2.6H2O. The hydrate CaO.CaCl2.2H2O is not stable at temperatures below 20 C : transforms to 3CaO.CaCl2.15H2O. Both CaO.CaCl2.2H2O and 3CaO.CaCl2.15H2O are stable in contact with aqueous solutions only at high chloride concentrations. 3CaO.CaCl2.15H2O could only be prepared by hydrating a (1:1) mixture of CaO and CaCl2 at water/solid ?1.0. A good method for synthesis of CaO.CaCl2.2H2O is found to be dissolving 3CaO.CaCl2 15H2O in a saturated aqueous CaCl2 solution. Both 3CaO.CaCl2.15H2O and CaO.CaCl2.2H2O are efflorescent. Friedel's salt, C3A.CaCl2.10H2O, was synthesised by hydrating an equimolar mixture of C3A and CaCl2 in a filtered saturated Ca(OH)2 solution at solution/solid ratio of 1.0. Friedel's salt was found to dissolve congruently in water. Its solubility product is calculated as 3.467 x 10-28. Chloride-ettringite was prepared by hydrating a stoichiometric mixture of CaO and CaCl2 at water/solid ratio of 1.0. However the compound was found to be unstable at 20 2 C : it transforms to Friedel's salt. The transformation also occurs when drying and when washing with alcohol or water. Formation of solid solution series in the system CaO-Al2O3-CaCl2-H2O is studied by hydrating mixtures of C3A, CaCl2 and CaO at CaCl2/C3A molar ratio ranging from zero to 1.0. A series of solid solutions of the general formula C3A.(1-x)CaCl2.xCa(OH)2 (10+8x)H2O formed with a miscibility gap about x = 0.75 whereby the solid 3CaO.Al2O3.0.25CaCl2.0.75Ca(OH)2.11.5H2O coexists with C4AH19. The cell dimensions of the solid solutions increases with decreasing chloride content.
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Koh, Carolyn Ann. "The control of aluminium complexation in catalytic, cement colloidal and biological systems." Thesis, Brunel University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290955.
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Williamson, D. J. "Spectroscopic and related studies of hydraulic calcium aluminates and associated cement phases." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373213.
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Wilson, William S. M. Massachusetts Institute of Technology. "Grinding of cement clinkers : linking multi-scale fracture properties to system chemistry, mineralogy and microstructure." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82861.
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Thesis (S.M.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 162-172).
Growing environmental concerns encourage the cement industry to improve its environmental performance, which in turn renews the interest in clinker grinding efficiency. Current knowledge on clinker grinding was built over the past decades, but contributions from fracture mechanics remained limited. This research aimed to contribute to this field by investigating industrial clinkers with innovative techniques such as multiscale microscratching and statistical electron-probe microanalysis (EPMA). Microstructure investigations were first performed with scanning electron microscopy (SEM), and three characteristic length scales were defined for clinkers: the nodules at the macroscale, the clinker matrix and porosity at the intermediate scale, and the clinker phases at the microscale. A statistical EPMA method was developed to allow simultaneous determination of the clinker bulk chemistry, the chemistry of the clinker phases, and their abundance. The microscratch test method was downscaled to measure the fracture properties at each characteristic scale of clinkers. Measurements on single silicate grains provided access to the intrinsic fracture toughness, which was three to four time lower than the macroscale fracture toughness. A combination of microstructure effects and toughening mechanisms (crack deflection, crack tip shielding by microcracks, crack trapping, and crack pinning) explained this behavior. Comparison of industrial clinkers showed that higher macroscale toughness (i.e., poor coarse grindability) was associated with oversized alite crystals, which was explained by the increase of microcracks toughening with larger grain size. In contrast, lower macroscale fracture toughness (i.e., better coarse grindability) was associated with either poorly burned clinkers showing excessive porosity or well burned clinkers having a good repartition of small silicates. However, difficulties in fine grinding were expected for the poorly burned clinkers because of the increased amounts of clustered belite. Overall, this thesis presents new experimental methods to investigate clinkers, as well as links between clinkers properties and grindability, both of which hold interest to the scientific community and the cement industry.
by William Wilson.
S.M.
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Oberlink, Anne Elizabeth. "NON-PORTLAND CEMENT ACTIVATION OF BLAST FURNACE SLAG." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/25.
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The purpose of this project was to produce a “greener” cement from granulated ground blast furnace slag (GGBS) using non-Portland cement activation. By eventually developing “greener” cement, the ultimate goal of this research project would be to reduce the amount of Portland cement used in concrete, therefore reducing the amount of carbon dioxide emitted into the atmosphere during cement production.
This research studies the behavior of mineral binders that do not contain Portland cement but instead comprise GGBS activated by calcium compounds or fluidized bed combustion (FBC) bottom ash. The information described in this paper was collected from experiments including calorimetry, which is a measure of the release of heat from a particular reaction, the determination of activation energy of cement hydration, mechanical strength determination, and pH measurement and identification of crystalline phases using X-ray diffraction (XRD).
The results indicated that it is possible to produce alkali-activated binders with incorporated slag, and bottom ash, which have mechanical properties similar to ordinary Portland cement (OPC). It was determined that the binder systems can incorporate up to 40% bottom ash without any major influence on binder quality. These are positive results in the search for “greener cement”.
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Palme, Jahi. "Investigation of the Addition of Basalt Fibres into Cement." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1361.
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Mechanical properties of concrete are most commonly determined using destructive tests including: compression, flexure, and fracture notch specimen tests. However, nondestructive tests exist for evaluating the properties of concrete such as ultrasonic pulse velocity and impact echo tests. One of major issues with concrete (which has cement as its prime ingredient) is that unlike steel it is quasi-brittle material. It tends to want to crack when tensile stresses develop. Fibres have been added to concrete for many years to reduce the amount of and size of cracks cause by temperature changes or shrinkage. In more recent years, significant research has been carried out into the effect of the addition of basalt fibres to cement has on its mechanical strength. As well, developing concrete that is more durable, flexible, stronger, and less permeable than traditional concrete has been explored. It has become important to test and verify improvements that are made to the cement by basalt fibres as well as testing the general strength of concrete to stand up to constant pressure at varied strengths.
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Jones, Morgan Liane. "A Novel Pervious Cement Reaction Barrier (PCRB) in Situ Arsenic Remediation System." TopSCHOLAR®, 2010. http://digitalcommons.wku.edu/theses/169.
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Radonjic, Mileva. "Application of surface analysis in a study of the mechanism of alkali-carbonate reaction in concrete." Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/17a20752-0cde-492a-ac12-5e82b7cfc844.
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Panaščikaitė, Erika. "Mangano ir chromo nustatymo inversiniais elektroanaliziniais metodais tyrimai." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120710_120417-24006.
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Pasiūlytas mangano nustatymo metodas geriamajame vandenyje inversinės voltamperometrijos metodu naudojant gyvsidabrio plėvelinį elektrodą. Manganui nustatyti vandens mėginio nereikia chemiškai apdoroti. Optimalios nustatymo sąlygos: kaupimo potencialas –1,75 V, kaupimo trukmė 5–30 s, anodinis tirpinimas atliekamas naudojant kvadratinės bangos voltamperometriją. Mangano aptikimo riba kaupiant jį 30 s yra apie 0,4 μg l–1, o santykiniai standartiniai nuokrypiai darbiniame koncentracijų intervale ne didesni kaip 0,10. Realios kalcio, magnio ir geležies jonų koncentracijos geriamojo vandens mėginiuose netrukdo nustatyti manganą. Metodo palyginimas su standartiniu fotometriniu metodu parodė, kad jie yra ekvivalentiški, tačiau elektrocheminis metodas gali būti taikomas labai mažoms mangano koncentracijoms nustatyti, be to, jam netrukdo geriamajame vandenyje esantys geležies jonai.
Chromo nustatymui cemente gali būti naudojamas katalitinės adsorbcinės voltamperometrijos metodas naudojant kabančio gyvsidabrio lašo elektrodą. Terpės sudėtis Cr(VI) nustatyti: 0,15 mol l-1 CH3COONa, 5 mmol l-1 dietilentriaminpentaacto rūgšties (DTPA), 0.7 mol l-1 NaNO3, pH = 6. Optimalios votamperometrijos sąlygos: kaupimo potencialas –0.9 V, kaupimo trukmė 5-10 s, kvadratinės bangos voltamperometrijos režimas. Cr(VI) aptikimo riba yra apie 0,05 µg l 1, santykinis standartinis nuokrypis neviršija 3%. Iš cemento mėginių chromas išekstrahuojamas vandeniu arba azoto rūgštimi. Bendras chromo kiekis... [toliau žr. visą tekstą]There was proposed method for the determination of manganese in drinking water by inverse voltammetry using a mercury film electrode. The determination of manganese in drinking water does not need chemical treatment of a sample. Optimal detection conditions: accumulation potential of -1.75 V, accumulation time 5-30 s, anodic dissolution is performed using square wave voltammetry. Manganese accumulation by the detection limit of 30 seconds is about 0.4 mg l-1, and the relative standard deviations of the working range of concentrations do not exceed 0.10. Actual calcium, magnesium and iron ion concentration in samples of drinking water does not influence the manganese determination. Method comparison with a standard photometric method showed that they are equivalent, but the electrochemical method can be applied in very small concentrations of the manganese, in addition, it does not influence the iron ions in the drinking water. Determination of chromium in cement can be performed by catalytic adsorption voltammetry method using a hanging mercury drop electrode. The medium composition for Cr (VI) determination: 0.15 mol L-1 CH3COONa, 5 mmol l-1 diethylenetriaminepentaacetic acid (DTPA), 0.7 mol l-1 NaNO3, pH = 6. Optimal voltammetry conditions: accumulation potential of -0.9 V, accumulation time 5-10 s, square wave voltammetry mode. Cr (VI) detection limit is about 0.05 mg l-1, the relative standard deviation does not exceed 3%. Chromium was extracted from the cement samples... [to full text]
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Panaščikaitė, Erika. "Determination of manganese and chromium by electroanalytical stripping methods research." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120710_120425-12220.
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There was proposed method for the determination of manganese in drinking water by inverse voltammetry using a mercury film electrode. The determination of manganese in drinking water does not need chemical treatment of a sample. Optimal detection conditions: accumulation potential of -1.75 V, accumulation time 5-30 s, anodic dissolution is performed using square wave voltammetry. Manganese accumulation by the detection limit of 30 seconds is about 0.4 mg l-1, and the relative standard deviations of the working range of concentrations do not exceed 0.10. Actual calcium, magnesium and iron ion concentration in samples of drinking water does not influence the manganese determination. Method comparison with a standard photometric method showed that they are equivalent, but the electrochemical method can be applied in very small concentrations of the manganese, in addition, it does not influence the iron ions in the drinking water.
Determination of chromium in cement can be performed by catalytic adsorption voltammetry method using a hanging mercury drop electrode. The medium composition for Cr (VI) determination: 0.15 mol L-1 CH3COONa, 5 mmol l-1 diethylenetriaminepentaacetic acid (DTPA), 0.7 mol l-1 NaNO3, pH = 6. Optimal voltammetry conditions: accumulation potential of -0.9 V, accumulation time 5-10 s, square wave voltammetry mode. Cr (VI) detection limit is about 0.05 mg l-1, the relative standard deviation does not exceed 3%. Chromium was extracted from the cement samples... [to full text]Pasiūlytas mangano nustatymo metodas geriamajame vandenyje inversinės voltamperometrijos metodu naudojant gyvsidabrio plėvelinį elektrodą. Manganui nustatyti vandens mėginio nereikia chemiškai apdoroti. Optimalios nustatymo sąlygos: kaupimo potencialas –1,75 V, kaupimo trukmė 5–30 s, anodinis tirpinimas atliekamas naudojant kvadratinės bangos voltamperometriją. Mangano aptikimo riba kaupiant jį 30 s yra apie 0,4 μg l–1, o santykiniai standartiniai nuokrypiai darbiniame koncentracijų intervale ne didesni kaip 0,10. Realios kalcio, magnio ir geležies jonų koncentracijos geriamojo vandens mėginiuose netrukdo nustatyti manganą. Metodo palyginimas su standartiniu fotometriniu metodu parodė, kad jie yra ekvivalentiški, tačiau elektrocheminis metodas gali būti taikomas labai mažoms mangano koncentracijoms nustatyti, be to, jam netrukdo geriamajame vandenyje esantys geležies jonai. Chromo nustatymui cemente gali būti naudojamas katalitinės adsorbcinės voltamperometrijos metodas naudojant kabančio gyvsidabrio lašo elektrodą. Terpės sudėtis Cr(VI) nustatyti: 0,15 mol l-1 CH3COONa, 5 mmol l-1 dietilentriaminpentaacto rūgšties (DTPA), 0.7 mol l-1 NaNO3, pH = 6. Optimalios votamperometrijos sąlygos: kaupimo potencialas –0.9 V, kaupimo trukmė 5-10 s, kvadratinės bangos voltamperometrijos režimas. Cr(VI) aptikimo riba yra apie 0,05 µg l 1, santykinis standartinis nuokrypis neviršija 3%. Iš cemento mėginių chromas išekstrahuojamas vandeniu arba azoto rūgštimi. Bendras chromo kiekis... [toliau žr. visą tekstą]
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Muntingh, Yolandi. "Durability and diffusive behaviour evaluation of geopolymeric material." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2882.
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Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006.The study presented in this thesis symbolises one of the first ever efforts to better understand and describe the durability of geopolymers used in large scale commercial applications. In terms of the construction industry, geopolymers can be seen as a value-added approach to substitute the Ordinary Portland Cement (OPC) monopoly. It is particularly the fly ash-based geopolymers that are the main attraction, due to their economic and environmental advantages, over and above the large quantities of this material that are commonly available. Despite the fact that geopolymers have been around for thousands of years, it is only now that the accumulation of research across the globe has pooled their knowledge to broadly define this material in terms of its physical and chemical composition. The development of geopolymers for construction applications remains quite new, therefore requiring insight into the durability that can be expected from these materials, consequently leading to this work. Concrete technology and -science is one of many techniques which can offer considerable insight into effective durability studies, in addition to acting as a reference for firm material comparisons. Thus, this work is based on a collection of concrete durability studies and recommendations which resulted from a broad range of investigations. Principally, this work aims to confirm the superiority of geopolymers in terms of corrosion resistance. Chloride induced corrosion has been identified as being the main cause for deterioration of OPC structures and subsequently the origin of very costly, and frequent, reconstructive requirements. Geopolymers now have the opportunity to be introduced into this monopoly due to its advanced, yet credible, chloride penetration resistance. This thesis reports the development of the experimental design, as well as the associated analyses to describe the diffusive properties exhibited by fly ash-based geopolymers. Ultimately, two independent methods showed that Chloride Diffusion Coefficients (CDC) for all of the geopolymeric formulations are significantly lower (typically 1.43 x 10-15 cm2/s) than for cement (typically 0.5 x 10-8 cm2/s) or any other concrete mixture. Furthermore, the work presented here will consider the diffusive behaviour of the geopolymer formulations in an acidic sulphate environment, presenting this material’s superior resistance not only to the sulphate ion, but more so to the acid attack. Probable geopolymer applications are now further expanded to industrial applications, due to its acid resistance along with reduced Sulphate Diffusion Coefficients (SDC). In addition, the development of a time-to-corrosion software-tool is discussed. This tool may prove to be a valuable instrument for future geopolymer durability research, as well as iv commercial users in which extended material comparisons can be made. It may even assist the formulation-tailoring process where the relevant CDC/SDC can be chosen for a specific life-expectancy, reaching far beyond the limited scope of recipes covered in this work. Finally, this thesis provides the stepping-stone in proving geopolymer durability superiority. The formulations which proved to show the best results in terms of durability and acid resistance are highlighted and valuable recommendations are made towards the selection of suitable starting materials for optimum material robustness. The findings of this work, however, can be fortified by future research and exposure.
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Clark, David D. "Water Quality, Aesthetic, and Corrosion Inhibitor Implications of Newly Installed Cement Mortar Lining Used to Rehabilitate Drinking Water Pipelines." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32337.
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For decades, cement mortar relining has been used successfully to extend the life of drinking water pipelines, although, few quantitative data exist on the short-term water quality impacts of this process. This study investigated mortar lining impacts on disinfectant by-product formation, alkalinity, metal leaching, pH and disinfectant consumption, and odor generation shortly after in-situ installation. The experimental design used a 30-day, coupon immersion procedure that simulated a relined 4-inch diameter pipe located in a low-flow system. Four water regimes were utilized; no disinfectant, chlorine (2 mg/L at pH 6 .5 and 8), and chloramines. Flavor Profile Analysis panels evaluated odors of samples and controls. Additionally, the affects of three different phosphate-based corrosion prevention additive regimes were evaluated. Cement mortar leachates impacted water quality significantly during the first week of exposure. Alkalinity, hardness and pH increased dramatically after initial exposure, rising to approximately 600 mg/L as CaCO3 alkalinity, 770 mg/L as CaCO3 hardness, and pH 12 in the first two days. Sharp declines in alkalinity and hardness did not occur until after day 9 when the cement mortar was substantially cured and release of calcium hydroxide lessened. Chlorinated water residual disinfectant decay rate was increased substantially during the initial 24 hours and remained elevated until day 9. After day 1, there was not a significant increase in the formation of regulated haloacetic acids or trihalomethanes. Significant levels of aluminum (< 700 ug/L) and chromium (< 75 ug/L) were released at various times during the test period but their concentrations did not exceed USEPA water quality standards. Cement odor intensity levels were significantly higher than controls, persisted for 14 days, and were of an intensity that would be readily noticeable to consumers. The polyphosphate-based corrosion preventative resulted in less severe water quality effects than other phosphate additives or water without added phosphate.Master of Science
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Langaro, Eloise Aparecida. "Cimento álcali ativado a partir da valorização da escória de alto forno a carvão vegetal." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/1891.
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Enquanto que na produção do cimento Portland é feita a extração de matérias-primas não renováveis e o lançamento de CO2 de forma excessiva; a fabricação dos cimentos álcali ativados não envolve a calcinação dos materiais e pode utilizar como matéria-prima subprodutos da indústria. Nesse contexto, os cimentos álcali ativados surgem como uma nova classe de materiais aglomerantes de bom desempenho e baixo impacto ambiental, os quais podem ser sintetizados unicamente com resíduos, como por exemplo, escórias de alto forno ativadas com diferentes produtos alcalinos, gerando materiais com características interessantes para aplicações na construção civil. Em função da composição química, as escórias de alto forno geradas em fornos a coque são empregadas como adição ao cimento Portland; entretanto, aquelas oriundas de fornos a carvão vegetal não encontram a mesma destinação pois normalmente não se adequam aos módulos de basicidade prescritos nas normas, implicando assim um passivo ambiental. Esta pesquisa tem por objetivo à obtenção de cimentos álcali ativados (CAT) visando a valorização da escória A (ácida). Também foi utilizada uma escória proveniente de alto forno a coque (B) como matéria-prima, a fim de comparar a composição química de ambas. Foram elaboradas composições iniciais de CAT com hidróxido de sódio (NaOH) como ativador, as quais foram submetidas a dois processos de cura (úmida e imersa) para testes iniciais. A cura imersa se mostrou menos propícia no uso da escória como ligante, uma vez que o contato com a água lixivia o material diminuindo sua superfície de contato, o que traz consequências no desenvolvimento mecânico e da microestrutura. Já em cura úmida, com 5% de NaOH como ativador, as argamassas de escória A obtiveram ótimo desempenho mecânico, atingindo valores próximos a 45MPa aos 28 dias; sendo que o desenvolvimento da fase de C-S-H e hidrotalcita pôde ser observada a partir dos difratogramas de raios-X e análises térmicas. A escória B desenvolveu menor resistência na presença do ativador, mas as mesmas fases foram observadas em ambas as composições; constatando-se então que a composição química da matéria-prima tem forte influência no desempenho dos CAT’s.While production of Portland cement is made the extraction of non-renewable raw materials and the release of CO2 excessively; the manufacture of alkali activated cement does not involve the calcination of materials and can be used as raw material byproducts of industry. In this context, the alkali activated cements emerge as a new class of binder materials of good performance and low environmental impact, which can be synthesized only with waste, such as slag in blast furnace activated with different alkalis generating materials with characteristics interesting for applications in construction. Depending on the chemical composition, blast furnace slag generated in coke ovens are used as addition to Portland cement; however, those from charcoal ovens are not the same destination as usually is inappropriate the basicity modules prescribed in the rules, thus implying an environmental liability. This research has the purpose to obtain activated alkali cements (CAT) aimed at the valorisation of the slag (acid). Also used was a blast furnace from coke (B) as raw material, in order to compare the chemical composition of both. CAT initial compositions with sodium hydroxide was prepared (NaOH) as an activator, which were subjected to two curing processes (wet and immersed) for initial testing. The immersed cure was less benign in the use of slag as a binder caused a lower compressive strenght, since the contact with the water solubilizing the material reducing its contact surface. In wet cure, with 5% NaOH as an activator, the slag mortars A obtained high mechanical performance, arriving values close to 45MPa at 28 days; the development of C-S-H and hydrotalcite phase was observed from the XRD patterns of X-rays and thermal analysis. Slag B developed less strenght in the presence of the activator, but the same phases were observed in both compositions. It was possible to verify that the chemical composition of raw material had strong influence on the performance of the CAT’s.
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Ryno, Barnard. "Mechanical properties of fly ash/slag based geopolymer concrete with the addition of macro fibres." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95866.
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Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: Geopolymer concrete is an alternative construction material that has comparable mechanical properties to that of ordinary Portland cement concrete, consisting of an aluminosilicate and an alkali solution. Fly ash based geopolymer concrete hardens through a process called geopolymerisation. This hardening process requires heat activation of temperatures above ambient. Thus, fly ash based geopolymer concrete will be an inadequate construction material for in-situ casting, as heat curing will be uneconomical. The study investigated fly ash/slag based geopolymer concrete. When slag is added to the matrix, curing at ambient temperatures is possible due to calcium silicate hydrates that form in conjunction with the geopolymeric gel. The main goal of the study is to obtain a better understanding of the mechanical properties of geopolymer concrete, cured at ambient temperatures. A significant number of mix variations were carried out to investigate the influence that the various parameters, present in the matrix, have on the compressive strength of fly ash/slag based geopolymer concrete. Promising results were found, as strengths as high as 72 MPa were obtained. The sodium hydroxide solution, the slag content and the amount of additional water in the matrix had the biggest influence on the compressive strength of the fly ash/slag based geopolymer concrete. The modulus of the elasticity of fly ash/slag based geopolymer concrete did not yield promising results as the majority of the specimens, regardless of the compressive strength, yielded a stiffness of less than 20 GPa. This is problematic from a structural point of view as this will result in large deflections of elements. The sodium hydroxide solution had the most significant influence on the elastic modulus of the geopolymer concrete. Steel and polypropylene fibres were added to a high- and low strength geopolymer concrete matrix to investigate the ductility improvement. The limit of proportionality mainly depended on the compressive strength of the geopolymer concrete, while the amount of fibres increased the energy absorption of the concrete. A similar strength OPC concrete mix was compared to the low strength geopolymer concrete and it was found that the OPC concrete specimen yielded slightly better flexural behaviour. Fibre pull-out tests were also conducted to investigate the fibre-matrix interface. From the knowledge gained during this study, it can be concluded that the use of fly ash/slag based geopolymer concrete, as an alternative binder material, is still some time away as there are many complications that need to be dealt with, especially the low modulus of elasticity. However, fly ash/slag based geopolymer concrete does have potential if these complications can be addressed.
AFRIKAANSE OPSOMMING: Geopolimeerbeton is ‘n alternatiewe konstruksiemateriaal wat vergelykbare meganiese eienskappe met beton waar OPC die binder is, en wat bestaan uit ‘n aluminosilikaat en ‘n alkaliese oplossing. Vliegas-gebaseerde geopolimeerbeton verhard tydens ‘n proses wat geopolimerisasie genoem word. Hierdie verhardingsproses benodig hitte-aktivering van temperature hoër as dié van die onmiddellike omgewing. Gevolglik sal vliegas-gebaseerde geopolimeerbeton ‘n ontoereikende konstruksiemateriaal vir in situ gietvorming wees, aangesien hitte-nabehandeling onekonomies sal wees. Die studie het vliegas/slagmentgebaseerde geopolimeerbeton ondersoek. Wanneer slagment by die bindmiddel gevoeg word, is nabehandeling by omliggende temperature moontlik as gevolg van kalsiumsilikaathidroksiede wat in verbinding met die geopolimeriese jel vorm. Die hoofdoel van die studie was om ‘n beter begrip te kry van die meganiese eienskappe van geopolimeerbeton, wat nabehandeling by omliggende temperature ontvang het. ‘n Aansienlike aantal meng variasies is uitgevoer om die invloed te ondersoek wat die verskeie parameters, aanwesig in die bindmiddel, op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton het. Belowende resultate is verkry en sterktes van tot so hoog as 72 MPa is opgelewer. Daar is gevind dat die sodiumhidroksiedoplossing, die slagmentinhoud en die hoeveelheid water in die bindmiddel die grootste invloed op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton gehad het. Die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton het nie belowende resultate opgelewer nie. Die meeste van die monsters, ongeag die druksterkte, het ‘n styfheid van minder as 20 GPa opgelewer. Vanuit ‘n strukturele oogpunt is dit problematies, omdat groot defleksies in elemente sal voorkom. Die sodiumhidroksiedoplossing het die grootste invloed op die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton gehad. Staal en polipropileenvesels is by ‘n hoë en lae sterke geopolimeer beton gevoeg om die buigbaarheid te ondersoek. Die die maksimum buigbaarheid het hoofsaaklik afgehang van die beton se druksterkte terwyl die hoeveelheid vesels die beton se energie-opname verhoog het. ‘n OPC beton mengsel van soortgelyke sterkte is vergelyk met die lae sterkte geopolimeerbeton en daar is gevind dat die OPC beton ietwat beter buigbaarheid opgelewer het. Veseluittrektoetse is uitgevoer om die veselbindmiddel se skeidingsvlak te ondersoek. Daar kan tot die gevolgtrekking gekom word dat, alhoewel belowende resultate verkry is, daar steeds sommige aspekte is wat ondersoek en verbeter moet word, in besonder die styfheid, voordat geopolimeerbeton as ‘n alternatiewe bindmiddel kan optree. Volgens die kennis opgedoen tydens hierdie studie, kan dit afgelei word dat die gebruik van vliegas/slagmentgebaseerde geopolimeerbeton, as 'n alternatiewe bindmiddel, nog 'n geruime tyd weg is, as gevolg van baie komplikasies wat gehandel moet word, veral die lae elastisiteitsmodulus. Tog het vliegas/slagmentgebaseerde geopolimeerbeton potensiaal as hierdie komplikasies verbeter kan word.
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Dubina, Elina [Verfasser], Johann Peter [Akademischer Betreuer] Plank, and Cordt [Akademischer Betreuer] Zollfrank. "The Phenomenon of Cement Ageing on Moist Air: Surface Chemistry, Mechanisms and Effects on Admixture Performance / Elina Dubina. Gutachter: Johann Peter Plank ; Cordt Zollfrank. Betreuer: Johann Peter Plank." München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1031280685/34.
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Javadi, Ali. "METHACRYLATED POLY(ETHYLENE GLYCOL)S AS PRECURSORS FOR SUPERPLASTICIZERS AND UV-CURABLE ELECTRICAL CONTACT STABILIZATION MATERIALS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1508331641641639.
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Deschner, Florian [Verfasser], Jürgen [Akademischer Betreuer] Neubauer, Christian [Akademischer Betreuer] Kaps, and Frank [Akademischer Betreuer] Winnefeld. "Reaction of siliceous fly ash in blended Portland cement pastes and its effect on the chemistry of hydrate phases and pore solution / Florian Deschner. Gutachter: Jürgen Neubauer ; Christian Kaps ; Frank Winnefeld." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1054731675/34.
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Bilcati, Géssica Katalyne. "Produção de painéis de cimento Portland reforçados com fibra de curauá (Ananas erectifolius)." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1148.
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O presente trabalho trata do estudo referente ao desempenho da fibra vegetal amazônica curauá (Ananas erectifolius) aplicada no processo de produção dos painéis de cimento portland, analisando a compatibilidade, os tratamentos realizados nas fibras de curauá, visando à melhoria das propriedades físicas e mecânicas dos painéis. A metodologia deste trabalho foi desenvolvida a partir da produção dos painéis cimento portland reforçados com fibras de curauá, variando os teores e os tipos de tratamentos realizados nas fibras vegetais, sendo realizados ensaios de caracterização da fibra para posteriormente justificar o comportamento da mesma nos painéis. O resultado obtido no ensaio de inibição classificou a fibra de curauá sem tratamento como alta inibição, verifcando a necessidade de se fazer tratamentos para sua aplicação. Os tratamentos realizados nas fibras de curauá influenciaram positivamente, tanto na compatibilidade entre o cimento e a fibra de curauá como no grau de cristalinidade da fibra de curauá. Para a produção dos painéis os tratamentos realizados não tiveram influência nas propriedades mecânicas.The present work addresses the performance of the Amazon vegetal fiber curauá (Ananas erectifolius) as applied to the production process of portland cement panels, aimed at the improvement of the physical and mechanical properties of the panels. The methodology of this work was developed from the production of portland cement panels reinforced with curaua fibers, varyng of the amounts and the treatments applied to the vegetal fibers, being conducted tests for the fiber characterization to justify at a later stage the behavior of the latter in the panels. The results obtained from the inhibition test classified the curaua fiber without treatment as of high applied to the curaua fibers influenced positively both the compatibility between cement and the curaua fiber and the cristallinity degree of the curaua fiber. For the panels production the apllied treatments did not influence on mechanical properties.
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Silva, Renata Pinho da. "Determinação de HPA em ambiente ocupacional de indústria de cimento que co-processa resíduos." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-30072009-093248/.
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O co-processamento de resíduos em fornos de cimenteiras é uma alternativa de destinação de resíduos que consiste em substituir combustíveis ou matérias primas usados na fabricação do clínquer por diversos resíduos que apresentem poder calorífico e propriedades similares. Os resíduos são co-processados a temperaturas altas, porém podem ocorrer emissões de diversos poluentes devido a variedade de resíduos que podem ser co-processados. Entre esses poluentes estão os Hidrocarbonetos Policíclicos Aromáticos (HPA), que podem ser emitidos nas chaminés dos fornos das cimenteiras, ou também podem estar presentes no ambiente interno das mesmas. Considerando que os HPA são compostos orgânicos que apresentam potencial carcinogênico e/ou mutagênico, e assim oferecem risco à saúde humana, esse estudo tem o objetivo apresentar uma avaliação preliminar da presença e dos níveis de concentração de HPA em uma indústria de cimento que co-processa resíduos. As análises de HPA no ambiente ocupacional foram realizadas seguindo a metodologia proposta do NIOSH (National Institute for Occupational Safety and Health). Para isso utilizou-se como ferramenta analítica a técnica de cromatografia a líquido de alto desempenho (CLAE) com detecção por fluorescência, acompanhada da otimização e avaliação dos principais parâmetros analíticos do método, possibilitando assim a determinação dos 17 HPA prioritários pela NIOSH com confiabilidade analítica. Os resultados indicaram a presença de vários HPA no ambiente de trabalho estudado, porém numa concentração baixa (faixa de ng.m-3) e dentro da faixa de concentração encontrada em trabalhos em ambientes convencionais. Este estudo foi desenvolvido com a colaboração da FUNDACENTRO/MTE.The co-processing of residues in furnaces of cement industries is an alternative to dispose residues by substituting conventional combustibles and raw materials used for production of clinker by diverse organic residues of similar properties and calorific power. Co-processing is made at high temperatures, but emission of diverse pollutants may occur as a consequence of the large diversity of residues that are processed. Among these pollutants, Polycyclic Hydrocarbons (PAH) may be either emitted in the chimneys of the furnaces, or be present in the interior ambient of these industries. PAH pose risk to human health because they are organic compounds having potential carcinogenic and mutagenic activities. The present study aims to show the results of a preliminary evaluation of the presence and concentration levels of PAH in a cement industry co-processing residues. PAH analyses in the occupational environment were made according the methodology recommended by NIOSH (National Institute of Occupational Safety and Health). High performance chromatography (HPLC) with fluorescence detection was the analytical technique used for analyses. Optimization and evaluation of the major analytical parameters allowed the determination of the 17 PAH prioritized by NIOSH to be made with analytical confidence. Results showed the presence of several PAH in the studied environment, but at low concentrations (in the range of ng.m-3). These concentrations are of similar magnitude to the ones found in conventional environments. The present study was made in collaboration with FUNDACENTRO/MTE.
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Tyrer, Mark. "The Hydration chemistry of blended portland blastfurnace slag cements for radiactive waste encapsulation." Thesis, Aston University, 1991. http://publications.aston.ac.uk/14303/.
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Blended Portland-blastfumace slag cements provide a suitable matrix for the encapsulation of low and intermediate level waste due to their inherantly low connective porosity and provide a highly alkaline and strongly reduced chemical environment. The hydration mechanism of these materials is complex and involves several competing chemical reactions. This thesis investigates three main areas: 1) The developing chemical shrinkage of the system shows that the underlying kinetics are dominantly linear and estimates of the activation energy of the slag made by this method and by conduction calorimetry show it to be c.53 kJ/mol. 2) Examination of the soUd phase reveals that caldum hydroxide is initially precipitated and subsequently consumed during hydration. The absolute rate of slag hydration is investigated by chemical and thermal methods and an estimation of the average silicate chain length (3 silicate units) by NMR is presented. 3) The developing pore solution chemistry shows that the system becomes rapidly alkaline (pH 13 - 13.5) and subsequently strongly reduced. Ion chromatography shows the presence of reduced sulphur species which are associated with the onset of reducing conditions. In the above studies, close control of the hydration temperature was maintained and the operation of a temperature controlled pore fluid extration press is reported.
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Tyrer, Mark. "The hydration chemistry of blended Portland blastfurnace slag cements for radioactive waste encapsulation." Thesis, Aston University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315145.
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De, Silva Premalatha Samarawickrama. "Chemical and microstructural development of cements with metakaolin." Thesis, University of Aberdeen, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305005.
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Metakaolin (MK) is a nearly-anhydrous solid obtained by heating kaolin in the temperature range 450-800° C. Metakaolin shows pozzolanic properties and reacts with sodium, potassium and calcium hydroxides, with gypsum and with Portland cement or mixtures thereof. Since its reaction with calcium hydroxide yields mainly a product similar to C-S-H, obtained from Portland cement, MK can potentially be used as a major component in energy-saving binders, especially in tropical or subtropical countries where kaolin precursor is widely available. This project was aimed in achieving further progress on the use of metakaolin as a pozzolanic material. In doing so the hydration behaviour of metakaolin has been investigated. Calcium hydroxide was used as the main activator and, the effects of other secondary activators such as NaOH, Na2SO4, CaSO4 or a NaOH/CaSO4 combination have also been studied. The extent and kinetics of various reactions occurring during early hydration were investigated by calorimetry. The hydration behaviour of metakaolin cements has been found to manifest pronounced similarities to OPC hydration, especially in terms of heat evolution and set characteristics. The quantitative treatment of calorimetric data has unravelled an important feature of hydration process namely, the occurrence of both endothermic and exothermic reactions. This was mainly a feature of sulphate-containing systems, especially associated with the well known ettringite -+ monosul-phate transformation. The quantitative treatment of calorimetric data is found to be a tool in understanding mechanism of hydration reactions. The solid hydrates were characterized by XRD, DTA and aem techniques. The stability relations of the hydrates formed with respect to initial mix compositions are discussed in the temperature range 20-55°C. An attempt has been made to interpret the phase relations of CaO-Al2O3-SiO2-H2O system with regard to the products of metakaolin/Ca(OH)2 hydration. In lime rich formulations silicon-containing hydrogamet was found to be stable with C-S-H. When the amount of lime is less, metakaolin tends to form calcium aluminium silicate hydrate gels which are in equilibrium with C2ASHp. At higher temperatures (85°Q) die zeolite, gismondine, has been formed from the above gel. This finding is important as the formation of zeolites in cement mixtures has an ability to change the immobilization potential of cement. The continuous development of chemical environment -both solid and aqueous phases- of metakaolin/Ca(OH)2 system with secondary activators has also been examined. One of the important discoveries in the present study is the effect of mica-like impurities on the hydration of metakaolin. Solution phase studies disclose that muscovite, present as an impurity in kaolin, is activated during the calcination process. As a consequence, potassium is released to the pore solution with subsequent enhancement of the reactivity of the metakaolin, most notably with Ca(OH)2 and CaSO4. Thus the performance and activation of kaolins may depend partly on their alkali content. The effects of w/s ratio, curing temperature, initial MK/CH ratio and secondary activators on the mechanical properties of metakaolin cements have been examined. The consequence of solid phase volume changes associated with phase transformations on the compressive strength of metakaolin cements is also discussed. It has been found that the activators affect the hydration of metakaolin in a similar way as Portland or blended cements. The calcium hydroxide-CaSO4 combination was found to give the best strengths. The best binder phase for metakaolin cements is an aluminous C-S-H phase. Compressive strength development with time and temperature of MK cements is also found to be broadly similar to those of Portland cement systems.
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Darling, Maureen. "The design of novel glass-ionomer cements." Thesis, University of Greenwich, 1993. http://gala.gre.ac.uk/6142/.
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Pawluk, Katarzyna Malgorzata. "Release of antimicrobial compounds from glass-ionomer dental cements." Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/9813/.
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This thesis reports a study of the possibility of using conventional glass-ionomer cements (GICs) as matrices for release of antimicrobial compounds. Sodium fusidate, cetyl pyridinium chloride (CPC), benzalkonium chloride (BACH), triclosan and triclosan/zinc citrate at concentrations ranging from 1% to 5% by weight were added into Fuji IX and Chemflex cements. Disc-diffusion studies showed antimicrobial effect against Streptococcus mutans. Inhibition zones were proportional to the amount of added bactericide, CPC and BACH showed highest antibacterial activity. The release of the bactericides into water was studied for time intervals up to seven weeks. The amount of additive released varied from 0.61% to 5.00% of total bactericide added and samples containing more antimicrobial agent gave higher release into the surrounding water. The release was shown to be diffusion based for the first 2-4 weeks. Compressive strength and surface hardness of reformulated materials decreased in comparison with the control specimens. Addition of bactericides also decreased the amount of fluoride released. 27Al MAS-NMR showed that aluminium switches its coordination number from four, Al (IV), in the glass phase to six, Al (VI), in the cement matrix and addition of antimicrobial agents reduced the rate of this change. Incorporation of additives also prolonged the working time. By contrast, water loss properties were not affected by additives. The overall conclusion is that the presence of additives affects the setting and maturation reactions of GICs. These results can be interpreted as showing that the additives having an effect on the conformation of the poly (acrylic acid) (PAA) component in solution. Changes in the conformation of the PAA also influence the release of key ions from the glass (Al3+, Ca2+, F- and Na+). Alteration in the balance of these ions, especially Al3+, would result in slower cross-linking processes and lower cross-link density matrix. Additionally, adsorption properties of surfactants to GI aluminosilicate glass particles can also lead to reduction in the number of available active sites on the glass which can react with PAA. The reduction in available active sites on the glass will result in a lower bonding density and thus a weaker matrix. All above will leads to the observed changes in mechanical properties, working kinetics, F- release and kinetics of conversion of Al (IV) to Al (VI).
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Canham, Ian. "The control of alkali silica reaction using blended cements." Thesis, Aston University, 1987. http://publications.aston.ac.uk/9726/.
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It has been previously established that alkali silica reaction (ASR) in concrete may be controlled by blending Portland cement with suitable hydraulic or pozzolanic materials. The controlling mechanism has been attributed to the dilution of the cement's alkali content and reduced mobility of ions in concrete's pore solution. In this project an attempt has been made to identify the factors which influence the relative importance of each mechanism in the overall suppression of the reaction by the use of blended cements. The relationship between the pore solution alkalinity and ASR was explored by the use of expansive mortar bars submerged in alkaline solutions of varying concentration. This technique enabled the blended cement's control over expansion to be assessed at given `pore solution' alkali concentrations. It was established that the cement blend, the concentration and quantity of alkali present in the pore solution were the factors which determined the rate and extent of ASR. The release of alkalis into solution by Portland cements of various alkali content was studied by analysis of pore solution samples expressed from mature specimens. The specification for avoiding ASR by alkali limitation, both by alkali content of cement and the total quantity of alkali were considered. The effect on the pore solution alkalinity when a range of Portland cements were blended with various replacement materials was measured. It was found that the relationship between the type of replacement material, its alkali content and that of the cement were the factors which primarily determined the extent of the pore solution alkali dilution effect. It was confirmed that salts of alkali metals of the kinds found as common concrete contaminants were able to increase the pore solution hydroxyl ion concentration significantly. The increase was limited by the finite anion complexing ability of the cement.
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Mitani, Husam. "Variations volumétriques des matrices cimentaires aux très jeunes âges : approche expérimentale des aspects physiques et microstructuraux." Marne-la-vallée, ENPC, 2003. https://pastel.archives-ouvertes.fr/tel-00005721.
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Le retrait de la pâte de ciment est souvent à l'origine de nombreuses fissurations observées dans les structures en béton. Dans le cadre de cette étude nous nous sommes intéressés uniquement à l'étude du retrait endogène aux jeunes âges, ses effets sur la microstructure, les paramètres qui influencent sa cinétique, l'amplitude et l'origine de ce type de retrait. Le retrait endogène, conséquence de la contraction "Le Chatelier", est un phénomène bien connu de l'industrie cimentière. Dans les bétons confectionnés avec un rapport E/C de l'ordre de 0. 5, les effets de ce retrait sont inexistants. Le développement et l'utilisation de plus en plus fréquente des bétons à hautes et à très hautes performances posent de nouveaux problèmes sur l'apparition et la mesure du retrait endogène. Dans les premier et second chapitres, nous avons examiné la littérature concernant la structuration de la pâte de ciment à différentes étapes, les mécanismes d'hydratation, les différents types de retraits, les techniques de mesure associées et les facteurs qui influencent ce dernier. Dans le troisième chapitre, nous avons présenté une méthode que nous avons mise au point. Elle permet de mesurer les variations volumiques dès la fin du gâchage et sur une période de temps allant jusqu'à trois jours. Dans ce mémoire, nous présentons les résultats obtenus à partir d'une formulation de mortier à ultra hautes performances (UHP) et des résultats obtenus à partir de pâtes de ciment et de mortiers. Dans le quatrième chapitre, des analyses microstructurales, chimiques, minéralogiques, et physiques sont également présentées. Elles permettent de donner quelques indices sur l'origine du retrait endogène. Parallèlement nous avons présenté des résultats obtenus sur l'effet d'ajout de C3A dans un clinker, l'effet de la finesse Blaine et finalement les résultats de l'étude comparative entre différentes catégories de ciment.
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Wasson, Eleanor A. "The development of glass-poly(alkenoate) [glass-ionomer] cements for orthopaedic applications." Thesis, Brunel University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295811.
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Xie, Dong. "N-vinylpyrrolidone modified glass-ionomer resins for improved dental restoratives." The Ohio State University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/47196478.html.
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Boissonade, Jonathan James. "Direct contact measurement of the dielectric properties of glass ionomer cements for MEMs design." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6321/.
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This investigation was aimed at measuring the changes in dielectric properties of glass ionomer cements during their setting reaction in order to observe if there is a correlation between these properties and the cement curing. Commercial glass ionomer cements were prepared and their setting process was monitored over a 24 hour period using FT-IR and direct contact impedance measurement. An impedance bridge with a dielectric test assembly, based on previous work by Braden et al, was used to measure the dielectric properties of a number of different glass ionomer cements using a simple design. Using the dielectric properties of the glass ionomer cements, it could be possible to develop a micro-electro-mechanical sensor (MEMS) based on this design, which could be implanted into a dental restoration and interrogated remotely. During the curing of the cements examined, the dielectric data collected from the co-planar assembly showed a change in impedance over the course of the setting of the cement, which when compared to FT-IR spectra over the same period, showed a correlation between the dielectric properties and the chemical changes within the cement.
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Edwards, Christopher Lane. "Characterization via nuclear magnetic resonance of Portland cement and related materials." Thesis, 2007. http://hdl.handle.net/1911/20598.
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The physicochemical and engineering performance properties of several API class G and H ordinary Portland cements (OPCs) from various foreign and domestic sources have been investigated. The engineering performance properties are found to vary from sample to sample, and sources for this variation were sought out and identified. Magic angle spinning (MAS) 29Si nuclear magnetic resonance (NMR) experiments were marked by unusual relaxation behavior due to paramagnetism inherent in OPCs. A model system was created to mimic the paramagnetism of the cements and the system's relaxation behavior was analyzed. The iron in the calcium aluminoferrite (C4AF) provides the paramagnetism sufficient to substantially increase the relaxation rates of the 29Si in the tricalcium silicate (C3S) and dicalcium silicate (C2S) of cement. Several relaxation techniques were evaluated for analyzing cement relaxation, and saturation recovery was identified as the preferred technique. Correlations of data from the saturation recovery experiments with engineering performance properties, especially the strength development of cement pastes, were obtained facilely. An error analysis of the NMR and engineering performance testing techniques was conducted, which indicated that NMR measurements produced less error than the engineering performance tests. A best practice, modified from the saturation recovery experiment, is proposed for use in property correlations.
Additionally, 13C MAS NMR was used to characterize various fluorinated single-walled carbon nanotubes (F-SWNTs), which proved surprisingly effective in attenuating 13C-19F dipolar interactions and quantifying the extent of functionalization present at high degrees of reaction.
The mixed-metal nanocluster known as FeMoC was also characterized by MAS NMR. The impact of the paramagnetic Fe3+ in the Keplerate cage on the 31P nuclei in the caged Keggin ion of FeMoC was evident in the greatly reduced relaxation times measured.
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Bishop, Maximilienne. "Cement hydration inhibition and crosslinking in the guar-borate system." Thesis, 2001. http://hdl.handle.net/1911/17940.
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The hydration of cement and its individual mineral phases in the presence of different inhibitors has been investigated. The behavior of an exemplary oligo-phosphate, nitriltris(methylene)phosphonic acid (H6ntmp), is compared to the behavior of more traditional retarders. The reaction between H6ntmp and calcium hydroxide, tricalcium silicate, tricalcium aluminate, and cement have revealed that the calcium phosphonate complex, [Ca(H 4ntmp)]infinity, plays a role in inhibition with phosphonates. NMR and XPS data suggest that the presence of uncoordinated P-O bonds in calcium phosphonates lends phosphonates the unique ability to simultaneously complex calcium ions while adhering to hydrating aluminate surfaces, promoting heterogeneous nucleation of calcium phosphonates at the surface of aluminate minerals and blocking normal hydration reactions. Reactions with tartaric acid also forms a calcium complex on top of the aluminate phases. In contrast, sucrose, appears to act directly on the silicate phases actually accelerates the reactions of the aluminate phases.
The reactions of borate ions with diols and monosaccharides have been used to model cross-linking in the guar-borate system. Specifically, the reactions of borate with alcohols were characterized by 11B NMR to determine which reactions are most favorable. It was found that the acidity of the hydroxyl groups plays an important role in the efficiency of cross-linking, and has a greater effect on the energy of the resulting borate-diol complexes than the conformation (i.e., cis versus trans) in reactions of borate with cyclohexanediols and monosaccharides. The role of Group 1 metal salts in the borate-diol reactions was also investigated by 11B NMR and by the synthesis of model compounds. It was found that the metal cations play an important role in stabilizing the borate-diol complexes in the solid state. In solution, it was found that cross-linking is enhanced by the presence of strongly coordinating cations, as opposed to more purely ionic cations, and cross-linking is decreased in the presence of non-coordinating ammonium cations.
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Al, Dehailan Laila 1981. "The effect of filler on the mechanical properties of a novel resin-based calcium phosphate cement." Thesis, 2010. http://hdl.handle.net/1805/2314.
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Indiana University-Purdue University Indianapolis (IUPUI)Several studies have found that resin-based amorphous calcium phosphate (ACP) composites can function well for applications that do not require high mechanical demand. Milled tricalcium phosphate (TCP), a new calcium-phosphate-releasing material, is crystalline in nature, suggesting it to be strong. In the present study, we investigated the use of a TCP-filled composite resin as a possible tooth restorative-material. An experimental TCP-based composite was prepared using monomer with a mixture of 34.3 percent by mass of EBPADMA, 34.2 percent by mass of HmDMA, and 30.5 percent by mass of HEMA. TCP fillers were added to the monomer mixture at different levels (30 percent, 40 percent, 50 percent, and 60 percent by weight). A universal testing machine (Sintech Renew 1121; Instron Engineering Corp., Canton, MA) was used to measure the compressive strength and modulus. FTIR was used to measure the degree of conversion. The depth of cure was determined according to the ISO standards for dental resin 4049 using the scrapping technique. Knoop hardness numbers were obtained by a microhardness tester (M-400; Leco Co., St. Joseph, MI). The viscosities of the experimental resin were determined in a viscometer (DV-II+ Viscometer; Brookfield, Middleboro, MA). The data were analyzed using a one-way analysis of variance (ANOVA). A 5-percent significance level was used for all the tests. Resin composites with 30-percent TCP filler showed the highest compressive strength and hardness values. Also, this group showed the lowest degree of conversion. Resin composites with 60-percent TCP filler showed the highest degree of conversion. However, this group showed the lowest compressive strength, depth of cure, and hardness. Resin composites with 50-percent filler showed the highest compressive modulus. Resin composites with 40-percent filler showed higher viscosity values than resin composites with 30-percent filler. In conclusion, increasing the filler level significantly reduced the compressive strength, hardness, and depth of cure, but increased the degree of conversion. Also, resin composites with the lowest filler level (30 percent) had the highest compressive strength, depth of cure, and hardness. From these results, it can be concluded that the experimental TCP-filled resin used in this study cannot be used as restorative material.
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AlJamhan, Abdullah Saleh 1982. "In-vitro wear and hardness of new conventional glass ionomer cement coated with nano-filled resin." Thesis, 2011. http://hdl.handle.net/1805/2703.
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Indiana University-Purdue University Indianapolis (IUPUI)Background: Since the introduction of glass ionomer cements (GICs) in the 1970s, many attempts have been made to improve them and expand their application in restorative dentistry. Recently, GC America introduced a new glass ionomer restorative system called EQUIA. The manufacturer claims that this material has improved wear resistance by coating the surface of high-strength GIC with a nano-filled resin coating. Objective: The objective of this study was to measure the wear resistance and hardness of EQUIA and to compare it to other current restorative materials. Materials and Methods: Four different materials were used in this study: EQUIA, Fuji IX GP Extra, Fuji II LC and Z-100. Six specimens of each material were made and then tested in a toothbrush abrasion machine for 20,400 cycles, after which the amount of volume loss was calculated. Eight specimens of each material were made and tested in a three-body Alabama wear testing machine under a load of 75 N for 400,000 cycles. Four surface profiles were obtained from each specimen and volume loss was calculated using computer software. Five specimens of each material were made and Knoop microhardness was determined by using the mean of the three values from the top surface of the specimen. Results of each test were collected and compared with the other materials using one-way analysis of variance (ANOVA) at a significance level of 0.05. Results: Wear-resistance results showed that EQUIA has wear-resistance values comparable to composite resin and higher values than those for the high-strength GIC. The results also showed that Fuji II LC had the highest wear among all tested materials. Microhardness results showed that EQUIA has significantly lower microhardness than Fuji IX GP Extra and Z-100. Conclusion: Based on the results of the present study, it can be concluded that coating the surface of glass ionomer restorations with a nano-filled resin coat results in increasing the wear resistance and decreasing the microhardness of the material. Within the limitations of this study, EQUIA has comparable wear resistance to composite resin.
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Al-Zain, Afnan Omar 1981. "The ion release behaviours and water sorption of novel resin-based calcium phosphate cement." Thesis, 2010. http://hdl.handle.net/1805/2313.
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Indiana University-Purdue University Indianapolis (IUPUI)Calcium phosphate-filled restorative materials were developed to provide calcium (Ca) and phosphate (PO4) ions, which have been proposed to enhance remineralization of demineralized tooth structure. Recently, tricalcium phosphate (TCP)-filled restorative materials were introduced as an alternative to amorphous calcium phosphate. The TCP filler has a more crystalline structure than ACP and is therefore potentially stronger. The aim of the present study was to examine TCP-filled restorative resins at different concentration levels at different time intervals to characterize the concentrations of Ca and PO4 ions released, and to measure the water sorption (WS) of these resins. An in vitro study was conducted by formulating resin composite using TCP as the filler mixed with EBPADMA, HmDMA, and HEMA as the resin matrix. One-hundred- sixty samples were prepared, 40 samples of each filler concentration (30 percent, 40 percent, 50 percent, and 60 percent) by weight. From each filler concentration, 5 samples of each of the 8 time points (time intervals of 4 h, 8 h, 12 h, 24 h, 3 d, 7 d, 14 d, and 21 d) were immersed in 100-ml deionized water. Calcium and PO4 ions were measured using atomic absorption spectroscopy and light spectroscopy, respectively. Water sorption (WS) was measured according to ISO 4049 specification and then the WS and the diffusion coefficient were calculated. The significance level was set at p = 0.001. The results indicated that Ca and PO4 ion release increased with increasing filler level at a rate faster than being linear. In addition, WS results were very high and failed to meet the ISO 4049 specification requirement. Diffusion coefficient results were also high. One-way ANOVA test for only 21-day data revealed that there is a statistically significant difference in filler level percent, and two-way ANOVA testing revealed that there is a statistically significant interaction between time and filler level percent on the Ca, PO4 released and WS. It can be concluded that the concentrations of Ca and PO4 released and WS were affected by composition of the monomers, filler level and type, dispersion, and the absence of coupling agent. Although this TCP-filled restorative material may release Ca and PO4, it cannot serve as a restorative material due to high WS values. Further study is needed to improve the material and evaluate its ability in promoting remineralization of the tooth structure in order for it to serve its purpose.
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Agyei, Nana Mensah. "The removal of phosphate ions from aqueous solution by fly ash, slag, ordinary Portland cement and related blends." Thesis, 2004. http://hdl.handle.net/2263/29682.
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Nadarajah, Parthiban. "Chemistry and Corrosion Mechanisms of Steels Embedded in High-density Slag Concrete for Storage of Used Nuclear Fuel." Thesis, 2011. http://hdl.handle.net/1807/31361.
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The chemistry and corrosion mechanisms associated with reduced sulfur compounds such as calcium sulfide, present in ground granulated blast-furnace slag (GGBFS), have been studied in high-density concrete, mortar and simulated pore-water environments. The high-density concrete and mortar samples were produced to replicate the high-density GGBFS concrete, in the dry storage containers (DSCs), used for radiation shielding from used nuclear fuel. Electrochemical measurements on embedded steel electrodes in high-density GGBFS concrete and mortar samples, showed that sulfide is capable of consuming oxygen to create a stable, reducing environment, though not in all cases, and the high-frequency electrolyte resistance increases with hydration time. Ion chromatography on simulated pore-water environments determined that thiosulfate is quite kinetically stable as a sulfide oxidation product and magnetite is capable of oxidizing sulfide. Microscopy has also been used to provide visual evidence of GGBFS hydration and elemental quantification of the hydrating microstructure in different environments.
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Alobaidi, Eassa Ali E. 1982. "Volumetric dimensional changes of luting cements." Thesis, 2014. http://hdl.handle.net/1805/6095.
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Indiana University-Purdue University Indianapolis (IUPUI)The luting agent is a crucial factor in the outcome of cemented fixed restorations. A new water-based cement, Ceramir C&B (CM), approved to be marketed in the US, is composed of calcium aluminate and glass ionomer. CM is a luting agent indicated for permanent cementation of cast restorations, all-zirconia or all-alumina crowns, and prefabricated metal and cast dowel and cores. The manufacturer claims that the cement has demonstrated favorable biocompatibility properties when tested in vitro and in vivo and has proven to be bioactive. The objective of this study was to evaluate volumetric dimensional changes and the amount of Ca2+ released by the new luting agent. Twenty specimens of each material, namely calcium aluminate glass ionomer, resin-modified glass ionomer, and two resin luting agents, were fabricated and weighed. The 20 specimens for all materials were divided into four groups (five samples in each group) based on storage conditions: silicone oil at 22°C and 37°C and distilled water at 22°C and 37°C. Using the manufacturers’ instructions for each material, cylindrical specimens were prepared with dimensions of 7 +0.1 mm in diameter and 2 +0.1 mm in height. A 0.01-mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 minutes after mixing, and at the time intervals of 7 days, 14 days, 21 days, and 30 days, and after total dehydration of the specimen. Chemical analyses of the solutions were performed using atomic absorption spectroscopy to determine the Ca+2 ion concentration. Moreover, the pH values were measured to determine the OH–concentration in the solutions. The results showed that CM had the most expansion among the tested luting agents in distilled water at 22°C and 37°C, and significantly increased at higher temperature. In silicone oil, resin-modified glass ionomer shrank the most and also shrank more with the high temperature. The result of the ion concentration analysis indicated that Ca+2 and OHion release increased with increasing time and also significantly with temperature rise. In conclusion, calcium aluminate-glass ionomer exhibited the most significant dimensional change when stored in water storage. The solubility of the tested luting agents should be evaluated in the future because they were not evaluated in this study. Furthermore, to evaluate the clinical effect of the dimensional changes, the impact on the gap formation at tooth-crown margins should be determined in future work.
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Patel, Ashish G. 1981. "Microleakage in new resin-modified glass ionomer cements using new no-rinse conditioners : an in-vitro study." Thesis, 2012. http://hdl.handle.net/1805/2806.
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Indiana University-Purdue University Indianapolis (IUPUI)Since their introduction in 1970, glass ionomer cements have been used in a wide variety of clinical situations in dentistry. The main advantages of glass ionomer cements are chemical bonding, fluoride release and uptake, excellent seal against microleakage, and biocompatibility. The main objective of this study was to compare the microleakage of two new paste-paste glass ionomer systems to their traditional RMGIC counterparts when conditioning the dentin with newly developed no-rinse conditioners or polyacrylic acid. Materials and methods: Standardized cavity preparations were made, centered on the cementoenamel junction of the buccal surface, on 96 extracted human molars divided in 8 groups (n = 12). G1 Ketac Nano with Ketac Nano Primer, G2 Ketac Nano with Ketac Conditioner, G3 Photac Fil with Ketac Nano Primer, G4 Photac Fil with Ketac Cavity Conditioner, G5 Fuji Filling LC with GC Self Conditioner, G6 Fuji Filling LC with GC Cavity Conditioner, G7 Fuji II LC with GC Self Conditioner, G8 Fuji II LC with GC Cavity Conditioner. The cavities were treated with either a no-rinse or polyacrylic acid conditioner and restored with a paste-paste RMGIC or traditional RMGIC from the same manufacturer (n =12). The teeth were then sealed to within 2 mm of the restoration margins and thermocycled. The teeth were immersed in 2.0-percent methylene blue and stored at room temperature for 24 hours. Then, the teeth were be embedded in resin and sectioned longitudinally in a buccolingual direction making 1 section (1 mm thick) per tooth. The occlusal and gingival restoration margins of each specimen were examined with a stereomicroscope at X10 magnification to determine the degree of microleakage. Results: Mixed-model ANOVA was used to test the fixed effect of the eight groups and cervical vs. occlusal location within each tooth sample on microleakage, with sample as the random effect. Both main effects and the interaction are significant, p < 0001 for both group and location effects, and p = 0.0013 for the interaction of group and location. The cervical interface showed more microleakage in all groups except group 8 where microleakage was the same as at the occlusal margin. No significant difference was observed among groups for microleakage at the occlusal interface. There was significant difference among groups at the cervical interface with Fuji II LC using GC Cavity Conditioner performing best. For the occlusal interface Group 4 performed the best and Group 2 performed the worst, although the difference was not significant among the groups. For the cervical interface, Group 8 performed the best followed by Group 3, Group 4 and Group 6, although these four groups were not significantly different. For the cervical interface, group 2 performed the worst followed by group 1. Based on these results we can conclude that, overall, traditional RMGIC with polyacrylic acid conditioning performed better than the new paste-paste RMGIC systems utilizing the no-rinse conditioners.
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Posritong, Sumana 1974. "Effect of Hydrofluoric Acid Etching Followed by Unfilled Resin Application on the Biaxial Flexural Strength of a Glass-based Ceramic." Thesis, 2012. http://hdl.handle.net/1805/3180.
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Indiana University-Purdue University Indianapolis (IUPUI)Background: Numerous studies have reported the use of hydrofluoric (HF) acid as one of the most effective methods for the achievement of a durable bond between glass-based ceramics and resin cements. Nevertheless, there is little information available regarding the potential deleterious effect on the ceramic mechanical strength. Objectives: (1) to investigate the effect of HF acid etching regimens on the biaxial flexural strength of a low-fusing nanofluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar Vivadent), (2) to study the ability of an unfilled resin (UR) to restore the initial (i.e., before etching) mechanical strength, and (3) to evaluate the effect of HF acid etching on the ceramic surface morphology before and after UR treatment via scanning electron microscopy (SEM). Methods: One hundred and forty-four disc-shaped (15 ± 1 mm in diameter and 0.8 ± 0.1 mm in thickness) IPS e.max ZirPress specimens were allocated into 12 groups, as follows: G1-control (no etching), G2-30 s, G3-60 s, G4-90 s, G5-120 s, G6- 60 + 60 s. Meanwhile, groups (G7- G12) were treated in the same fashion as G1-G6, but followed by silane and UR applications. Surface morphology evaluation of non-etched and etched IPS e.max ZirPress (G1-G12) was carried out by scanning electron microscopy (SEM). The flexural strength was determined by biaxial testing as described in ISO 6872. Statistics were performed using two-way ANOVA and the Sidak multiple comparisons (α = 0.05). In addition, the Weibull statistics were estimated. Results: A significant effect of etching time (p=0.0290) on biaxial flexural strength was observed. Indeed, G4 led to a significantly (p=0.0392) higher flexural strength than G1. Correspondingly, G10 revealed a considerably higher flexural strength than G7 (p=0.0392). Furthermore, biaxial flexural strength was significantly higher for G7 – G12 than for G1 – G6 (p<0.0001). For G1 – G6, G4 showed the highest Weibull characteristic strength while the lowest Weibull characteristic strength was seen in G6. In G7 – G12, the highest Weibull characteristic strength was presented in G10 whereas G7 had the lowest. Finally, the SEM data revealed that the HF acid etching affected the surface of IPS e.max ZirPress by generating pores and irregularities and more importantly that the UR was able to penetrate into the ceramic microstructure. Conclusion: Within the limitations of this study, HF acid etching time did not show a damaging effect on the biaxial flexural strength of the IPS e.max ZirPress ceramic. Moreover, the ceramic biaxial flexural strength could be enhanced after UR treatment.
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Chotiwannaporn, Pavinee 1980. "Quantitative comparison of nanoleakage among five resin luting agents after aging." Thesis, 2012. http://hdl.handle.net/1805/2805.
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Indiana University-Purdue University Indianapolis (IUPUI)Potential problems of one-step adhesives have been identified, including water uptake and subsequent plasticization, water-and enzyme-induced nanoleakage, and the presence of voids due to phase-separation or osmosis. Clinically, adhesive failures due to marginal degradation present as retention loss, marginal discoloration, and secondary caries. However, the mechanisms of adhesive interface degradation of self-etching and self-bonding resin luting agents are not fully understood. The objective of the study was to investigate adhesive layer degradation by using a nanoleakage technique with five different resin luting agents. Materials and Methods: Five different resin luting systems, Variolink II, Panavia F2.0, RelyX Unicem, RelyX Unicem2, and Maxcem Elite were evaluated in this study. The 25 dentin specimens were randomly divided into five resin luting agent groups. Flat dentin surfaces were created mid-coronally and were luted with luting agents. Then, each tooth was sectioned occluso-gingivally. The first half of each tooth was used as a control group and the other half was used as the experimental group. The control group was immersed in artificial saliva at 37°C and SEM examination with chemical analysis was performed within 48 hours. In the tested group, all specimens were immersed in artificial saliva at 37°C for 10 days and thermocycled. For the SEM examination, the specimens were immersed in a 50-percent ammoniacal silver nitrate solution for 24 hours.22 SEM was used for observation of silver penetration of the specimens. Three scan lines were selected. For elemental analysis, natural apatite, olivine minerals, and pure silver metal were chosen as standards for Ca, Si and Ag. Data were analyzed using ANOVA with a 5-percent significance level. Results: At the bottom of the hybrid layer, there was no significant difference in silver uptake within the adhesive interface between luting agents (p > 0.05) and there was no significant change in silver uptake within the adhesive interface after thermocycling (aging) (p > 0.05). Conclusion: All resin luting agents exhibited nanoleakage after both 24-hour storage and 10-day storage with thermocycling.