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1
Cheung, Yin Nee. "Investigation of concrete components with a pseudo-ductile layer /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20CHEUNGY.
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Gouru, Harinath. "Laboratory evaluation of asphalt-portland cement concrete composite." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12232009-020518/.
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Peled, Alva. "Cement Penetrability Characteristics in Textile Cement Systems." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244044138771-75495.
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Cement penetrability is a key factor in multifilament cement composites. However, the modes of action and the concepts vary because of brittle and ductile fibers. In the case of brittle fibers such as glass, high penetrability of cement products in between the bundle filaments can lead to brittle composite behavior, and therefore addition in ductility is required. In order to have efficient bundle action and high bonding, fillers can be introduced in between the glass filaments, keeping the telescopic mode of failure but at the same time improving the bond and stress transfer within the filaments of the bundle, even at late ages, resulting in a ductile and high strength composite. On the other hand, ductile fibers such as polypropylene (PP), which also developing low bonding with the cement matrix, result in ductile cement composite but with relatively low strength. Therefore, in this case good penetrability of the cement in between the filaments of the bundle is essential in order to maximize the reinforcing efficiency of the bundle by improving bond. The penetrability of the matrix into a fabric structure and especially in between the bundle filaments made up the fabric is a result of fiber- matrix compatibility, which depends on: level of opening and spaces between the filaments, bundle surface properties including wetting and chemical affinity to the cement matrix, matrix viscosity, processing of the composite, and the nature of the fabric junctions and the resulting tightening effects of the bundle, i.e., influenced by the fabric structure itself.
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Mohr, Benjamin J. "Durability of Pulp Fiber-Cement Composites." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7222.
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Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers.
Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure.
Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness losses) during wet/dry cycling. SCMs have been found to be effective in mitigating composite degradation through several processes, including a reduction in the calcium hydroxide content, stabilization of monosulfate by maintaining pore solution pH, and a decrease in ettringite reprecipitation accomplished by increased binding of aluminum in calcium aluminate phases and calcium in the calcium silicate hydrate (C-S-H) phase.
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El-Ashkar, Nabil H. "Wood pulp microfibers in cement-based composites : improving fiber distribution and characterizing composite behavior." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/21518.
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Xie, Ping. "Interface characterization and modelling of cement composite systems." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7672.
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A detailed review of cement paste-aggregate interface phenomena in concrete is presented as a precursor to identification of the specific problems addressed in the current interface investigation. The principal deficiencies with current interface investigations described in the literature are as follows: (i) a lack of effective and simple investigative methods to quantitatively characterize interfacial microstructure; (ii) no simple and effective method of interfacial modification. A systematic electrical conductivity theory for the interface characterization of cement composites is proposed in this study. Based on the proposed theory, a novel investigative tool, the electrical conductivity method, has been developed. The proposed theory indicates that the characteristics of interfacial microstructure and interfacial zone formation and development can be described uniquely by a parameter, referred to as the "$\theta$-parameter" or "interfacial excess conductance". The developed method was successfully applied to practical cement paste-aggregate systems. Several new findings pertaining to the nature of the aggregate-cement paste interface were obtained. Extensive experimentation indicates that the $\theta$-parameter is a powerful interfacial microstructural descriptor. It is also a useful parameter for characterizing chemical processes at interfaces in cement-aggregate systems. A hypothesis for interfacial microstructure formation is proposed in concert with observed features of the $\theta$-parameter. Electrical conductivity models of both the interfacial zone and the bulk paste are developed to formulate the hypothesis. The hypothesis stresses the significance of the water film on aggregates at mixing for the interfacial microstructure formation. A relationship between interfacial bond strength and interfacial microstructure is developed. It was deduced that reducing the thickness of the water film and using low w/c ratio are two possible methods of enhancing interfacial bond strength. A method of enhancing interfacial microstructure, i.e. coating aggregate surfaces with silica fume, was developed. The experiments indicated that the interfacial microstructure can be effectively densified by aggregate surface treatment. The consequence of interfacial densification is that compressive strength and sulphate resistance of mortar are increased; bending strength is however increased only at later hydration times. A new tool, an a.c. impedance spectroscopy technique, has been utilized recently to study hydrating cement systems. Its further application was however limited due to lack of a fundamental explanation of the a.c. impedance behavior of the hydrating cement systems. A theoretical model for a.c. impedance spectroscopy of hydrating cement systems was developed. A fundamental understanding of the a.c. impedance behavior of hydrating cement systems has been obtained through application of the proposed model, and the validity of the a.c. impedance technique in investigating hydrating cement systems has, therefore, been strongly enhanced. The established link between interface phenomena and ingress of sulphate ions into cement mortar prompted a re-examination of durability related to sulphate expansion. Sulphate expansion is an important research topic dealing with durability of concrete. The mechanism of sulphate expansion, however, remains controversial. A thermodynamic theory of sulphate expansion is proposed after a careful analysis of the physico-chemical processes concerning the sulphate expansion. The theory is validated by extensive experiments. It appears that most sulphate expansion phenomena in the previous work can be explained by the proposed theory.
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Treiber, Martin Paul. "Characterization of cement-based multiphase materials using ultrasonic wave attenuation." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26588.
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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jacobs, Laurence J.; Committee Member: Kim, Jin-Yeon; Committee Member: Qu, Jianmin. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Escalante-Garcia, Jose Ivan. "The effect of temperature on the hydration of portland cement and composite cement pastes." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242215.
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McMahon, P. H. "The mechanical properties of cement stabilized minestone." Thesis, University of Sunderland, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378952.
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Peng, Joe Zhou. "Modelling of the cellulose and cement mineral bond and the mechanism of aluminous compounds in retarding cement carbonation." Thesis, View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/26659.
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Analysis of calcium and oxygen atom arrays of known cement minerals and the structures of cellulose polymorphs were performed to see if it was possible to arrange a cellulose fibre on a cement mineral face such that the fibre is bonded by a repeating array of hydrogen or hydroxide coordination bonds for the full length of the attachment. Of the sixteen important cement minerals modelled, xonotlite, foshagite, tricalcium aluminate hydrate, chondronite and rosenhahnite could form such bonds to modified cellulose fibre. However, this was not the case for other cement minerals, especially tobermorite. Alumium hydroxide, when added to cement-quartz pastes and autoclaved at 180 degrees C, was found to improve the cement's ability to resist carbonation.
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Peng, Joe Zhou. "Modelling of the cellulose and cement mineral bond and the mechanism of aluminous compounds in retarding cement carbonation /." View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030714.164824/index.html.
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Kirca, Onder. "Temperature Effect On Calcium Aluminate Cement Based Composite Binders." Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607454/index.pdf.
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In calcium aluminate cement (CAC) systems the hydration process is different than portland cement (PC) systems. The hydration products of CAC are subjected to conversion depending on temperature, moisture, water-cement ratio, cement content, etc. Consequently, strength of CAC system can be seriously reduced. However, presence of other inorganic binders or additives may alter the hydration process and improve various properties of CAC based composites.
The objective of this study is to investigate the temperature effect on the behaviour of CAC based composite binders. Throughout this research, several combinations of CAC-PC, CAC-gypsum, CAC-lime, CAC-ground granulated blast furnace slag (CAC-GGBFS) were studied. These CAC based composite binders were subjected to seven different curing regimes and their strength developments were investigated up to 210 days. In addition, the mechanism of strength development was examined by XRD analyses performed at 28 and 210 days. Finally, some empirical relationships between strength-time-curing temperatures were formulated.
Experimental results revealed that the increase in ambient temperature resulted in an increase in the rate of conversion, thereby causing drastic strength reduction, particularly in pure CAC mix. It has been observed that inclusion of small amount of PC, lime, and gypsum in CAC did not induce conversion-free CAC binary systems, rather they resulted in faster conversion by enabling rapid formation of stable C3AH6 instead of metastable, high strength inducing CAH10 and C2AH8. On the other hand, in CAC-GGBFS mixes, the formation of stable straetlingite (C2ASH8) instead of calcium aluminate hydrates hindered the conversion reactions. Therefore, CAC-GGBFS mixes, where GGBFS ratio was over 40%, did not exhibit strength loss due to conversion reactions that occurred in pure CAC systems.
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Shahid, Muhammad Aslam. "Improved cement bound base design for flexible composite pavements." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362991.
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Collier, Nicholas Charles. "The encapsulation of iron hydroxide floc in composite cement." Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434632.
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Bailey, Stephen Peter. "Design, fabrication and characterisation of functional cement-composite micro-devices." Thesis, Birkbeck (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401238.
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Ferdiansyah, Teuku. "Design and characterization of a self-sensing cement-based composite." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30133.
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La possibilité d'utiliser les propriétés électriques du béton pour en faire un capteur intelligent capable de détecter de façon autonome des modifications de propriétés mécaniques ou physiques est un sujet très actuel. Cependant jusqu'à ce jour la tendance est d'introduire dans la matrice cimentaire des additions qui vont augmenter la conductivité du béton. La plupart des recherches décrites dans la littérature utilisent des fibres conductrices, à base par exemple de carbone et d'acier, et elles ont démontré une amélioration significative de la conductivité du béton, qui a également amélioré la capacité d'auto-détection. Bien qu'une étude sur l'auto-détection du béton renforcé de fibres métalliques amorphes ait été réalisée au début de cette recherche, l'objectif principal de ce travail est d'étudier les propriétés d'auto-détection du béton sans addition. Cela a été effectué en suivant les modifications de sa résistance électrique en utilisant un pont de Wheatstone. L'avantage d'utiliser ce type de circuit pour mesurer la résistance est lié à sa capacité à détecter et à suivre des changements de résistance électrique du béton, même s'ils sont très faibles. Dans cette thèse, la variation de la chute de tension au pont de Wheatstone a été suivie sous une sollicitation monotone et cyclique. L'influence de la tension électrique, de la fréquence du courant d'alimentation du pont de Wheatstone, du taux et de la vitesse de chargement sur la sensibilité du capteur à différents niveaux de contrainte a été analysée. Il a été constaté que la variation du taux de chute de tension change significativement en fonction de la contrainte appliquée. Il a également été observé que la tension et la fréquence du courant d'alimentation affecte la sensibilité du système, mais que l'effet de la vitesse de chargement ou le taux de contrainte ne semble pas significatif. La comparaison de la sensibilité du capteur en utilisant deux configuration d'électrodes, soit fixées la surface du béton soit noyées dans le béton est également réalisée. La thèse teste également l'efficacité du pont de Wheatstone pour surveiller l'endommagement du béton sans addition. Des essais de traction par flexion sur des poutres entaillées avec contrôle de la propagation de la fissure ont été réalisés. Les résultats ont montré que la réponse du capteur est sensible à la propagation de la dite fissure et surtout à son ouverture. En outre les résultats obtenus sur trois éprouvettes ont démontré la reproductibilité de la réponse du capteur. L'effet de la position des électrodes par rapport à la localisation de l'endommagement sur la sensibilité du capteur a également été évalué. Les résultats ont été confrontés à des mesures de hauteur de fissure obtenues par vidéo-corrélation. La sensibilité du dispositif vis-à-vis de la température et du degré de saturation est décrite dans la dernière partie de cette thèse. Les résultats ont révélé que le capteur est également sensible à ces deux paramètresIt is well known that electrically conductive concrete has a great potential for sensing applications. However, to utilize the full spectrum of sensing applications of electrically conductive concrete composites, most of time, a conductive addition is necessary. Most previous researches using conductive fibers, e.g. in carbon and steel, as the primary conductive material demonstrated a significant improvement in the conductivity of concrete, which also improved the self-sensing ability. Although a study on self-sensing of amorphous metallic fiber-reinforced concrete was carried out at the beginning of this research, the main focus of the work presented was to study the self-sensing properties of plain concrete. This was done by monitoring its electrical resistance by means of a Wheatstone bridge circuit. The advantage of using this type of circuit to measure resistance lies in its great ability to track and detect changes in electrical resistance, even if they are very small. In this thesis, the variation of voltage drop (ΔV) at Wheatstone bridge circuit was monitored under monotonic and cyclic loading. The effects of the voltage input values, stress rate and the alternating current frequency on sensing behaviour at different levels of loading are reported. The variation of voltage drop rate was found to increase with stress rate in non-linear way. It is also found that the voltage input and the frequency affect the sensitivity of the system but the stress rate effect seems to be insignificant. The sensing characteristics of two electrode positions, i.e. attached at the concrete surface or embedded inside the concrete are also investigated. The thesis also examines the efficiency of the Wheatstone bridge to monitor the damage of plain concrete. Three bending tests were performed on notched beams for this study. The results showed that the electrical conductivity was sensitive to cracks. The relationship between ΔV and crack opening was established. The ΔV increased and decreased with crack opening and closing for all cyclic tests. In addition, the effect of electrode positions with respect to the localization of the damage on the sensitivity of the technique was also evaluated. The performance of the Wheatstone bridge circuit to monitor temperature and degree of saturation through electrical resistivity of plain concrete is also reported in the last part of this thesis. The electrical resistivity variation was investigated for four levels of temperature at different degrees of saturation and results showed that the designed tool is efficient to monitor the variation of these conditions
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Duris, Martin. "Micromechanics of fracture of inclined fibres in a cement-based composite." Thesis, University of the West of Scotland, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358553.
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Adendorff, Christo Johan. "The time-dependent cracking behaviour of strain hardening cement-based composite." Thesis, Stellenbosch: University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2847.
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Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: Strain Hardening Cement-based Composite (SHCC) is part of the High Performance Fibre Reinforced Cement-based Composite (HPFRCC) family and is a relative new concrete composite. This Fibre Reinforced Cement-based Composite (FRCC) contains randomly distributed short fibres and when subjected to a uni-axial tensile load multiple cracking occurs. The multiple cracking generates fine cracks which are normally smaller than 100 μm and achieve a strain capacity of more than 5 %. There are limited publications regarding the research of sustained tensile tests on SHCC and especially the cracking behaviour of SHCC under quasi-static uni-axial as well as sustained tensile loads. The cracking behaviour is described as the average crack width, number of cracks and descriptive statistical properties which could be used to represent the distribution of the multiple fine cracks under uni-axial tension. There are two types of tests that were under consideration to determine the cracking behaviour of SHCC. The first is quasi-static uniaxial tensile tests and the second is sustained tensile tests. The latter was dependant on the uni-axial tensile tests in terms of the sustained load applied. The sustained loads ranged from 40 % to 80 % of the ultimate tensile resistance recorded from the uni-axial tensile tests that correspond with a strain rate of 0.001 /s. Different strain rates were used for the uni-axial tensile tests to determine the effect on the cracking behaviour. The cracking behaviour was determined with the aid of a non-contact optical 3D digital deformation measuring device called ARAMIS. The content of this thesis gives a background study of the cracking behaviour and relevant research performed on SHCC under certain loads as well as some literature about the timedependant effects of a cement-based composite. The functioning of the device called ARAMIS is explained as well as the resulting effects of this device on the preparation of the test specimens. The experimental framework for the uni-axial and sustained tensile tests is discussed. Thereafter, the experimental results of the tests are depicted and discussed. The results shed some light on the basic material properties such as the average ultimate stress and average ultimate strain, Young’s modulus, etc. for the quasi-static tensile tests as well as shrinkage and creep of SHCC. The cracking behaviour such as the average crack width, number of cracks, the variance and skewness of the distribution of the crack widths in the test specimens for the quasi-static uni-axial and sustained tensile tests are depicted and discussed. The cracking behaviour when subjected to uni-axial tensile tests with different strain rates is significantly governed by the formation of new cracks and the average crack width remains small with increase in strain. There is no significant difference for the cracking behaviour found when subjected to different strain rates. However, when SHCC is subjected to a sustained load then the average crack width is dependant on the number of cracks that form over time as well as the load level. The formation of fewer and wider cracks was observed for specimens loaded at average 40 % of the ultimate tensile resistance stress, however at loading percentages of higher than 65 % more cracks developed which resulted in a smaller average crack width.
AFRIKAANSE OPSOMMING: Vervorming Verharding Sement gebaseerde samestelling “Strain Hardening Cement-based Composite” (SHCC) is deel van die familie van “High Performance Fibre Reinforced Cement-based Composite” (HPFRCC) en is ʼn relatiewe nuwe beton samestelling. Hierdie vesel versterkte sement gebaseerde beton bevat willekeurig verspreide kort vesels en veelvoudige klein krake vorm onder monotoniese trekkragte. Hierdie veelvoudige klein krake is minder as 100 μm wyd en lei tot ʼn vervorming van meer as 5 %. Daar is ʼn tekort aan navorsing oor die kruip van SHCC sowel as die kraak gedrag van hierdie sement gebaseerde samestelling onderhewig aan trek. Die kraak gedrag word beskryf as die gemiddelde kraakwydte, aantal krake en ʼn paar beskrywende statistiese parameters. Hierdie kraak gedrag parameters kan gebruik word om ʼn verdeling te kan weergee van die veelvoudige klein krake onder ʼn trek belasting. Twee tipes toetse was uitgevoer om die kraak gedrag te beskryf. Die eerste tipe toets was monotoniese trek toetse en die tweede tipe was kruip toetse. Die tweede toets was afhanklik van die monotoniese trek toetse in terme van die belasting wat gebruik was vir die kruip toetse. Die belasting was gevarieer vanaf 40 % tot 80 % van die breekbelasting wat bepaal is met die monotoniese trektoetse wat ooreenstem met ʼn vervorming tempo van 0.001 /s. Verskillende vervorming tempo’s vir die monotoniese trektoetse was uitgevoer om te bepaal wat die effek is op die kraak gedrag. Die kraak gedrag was bepaal met behulp van ʼn geen-kontak optiese 3D digitale deformasie meet instrument genoem ARAMIS. Die inhoud van die tesis bevat ʼn kort opsoming oor ʼn agtergrond studie van die kraak gedrag en relevante navorsing oor vesel versterkte sement gebaseerde beton, sowel as literatuur oor die tydafhanklike effekte van ʼn sement gebaseerde samestelling. Die beheer en gebruik van die meet instrument ARAMIS word verduidelik, sowel as die effek van hierdie masjien op die voorbereiding vir die eksperimente. Die eksperimentele uiteensetting vir die monotoniese en kruip toetse word beskryf. Daarvolgens is die resultate van die eksperimentele toetse getoon en verduidelik. Die resultate verduidelik die basiese materiaal eienskappe, byvoorbeeld die gemiddelde breekspanning met die ooreenkomstige breekvervorming, Young’s modulus en so voorts vir die monotoniese trektoetse, sowel as eienskappe met betrekking tot krimp en kruip van SHCC. Die kraak gedrag naamlik die gemiddelde kraakwydte, aantal krake per meter, variansie en die skuinsheid van die ontwikkelde krake met die toets proefstukke vir die monotoniese en kruip trek toetse word weergegee en verduidelik. Die kraak gedrag van SHCC wanneer getoets word met verskillende monotoniese trektoets tempo’s word beheer deur die ontwikkeling van nuwe krake en die gemiddelde kraakwydte is beduidend laag met toenemende vervorming. Daar is geen beduidende verskil in die kraak gedrag ten opsigte van die verskillende monotoniese trek tempo’s nie. In teendeel, wanneer SHCC belas word met ʼn konstante las oor tyd word die gemiddelde kraakwydte beheer deur die ontwikkeling van nuwe krake sowel as die belasting wat aangewend is. Onder ʼn belasting van so laag as 40 % van die breekbelasting vorm daar minder krake, maar met ʼn groter gemiddelde kraakwydte. Wanneer belas word met meer as 65 % van die breekbelasting vorm meer krake wat lei tot ʼn kleiner gemiddelde kraakwydte.
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Monteiro, André Oliveirinha. "Development of a multifunctional carbon black/cement composite for traffic monitoring." Doctoral thesis, Universidade de Aveiro, 2018. http://hdl.handle.net/10773/23030.
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Doutoramento em Engenharia CivilAs sociedades modernas estão fundadas em sistemas infraestruturais como redes de abastecimento de água, electricidade, comunicação e transporte. Com o aumento da procura global pela eficiência, imposto pelo século XXI, o desempenho esperado das estruturas segue inevitavelmente a mesma tendência. Esta busca de performance tem levado às infraestruturas físicas e à tecnologia digital se fundirem no conceito de “infraestruturas inteligentes”, através de vastas redes de monitorização, aliadas a subsistemas de informação. A disciplina de gestão de tráfego é talvez aquela que mais tem beneficiado destes avanços, com a implementação dos chamados Sistemas Inteligentes de Transporte (ITS). Avanços recentes na área dos materiais têm permitido o desenvolvimento de materiais de construção “inteligentes”, capazes de desempenhar tarefas autónomas. Os compósitos cimentícios piezoresistivos são um exemplo. Estes podem ser utilizados como sistemas de monitorização, graças às suas propriedades intrínsecas de sensitividade a estímulos mecânicos. A presente dissertação visa fazer a ponte entre o conceito de materiais cimentícios multifuncionais e a disciplina de monitorização de tráfego. Deste modo, um compósito piezoresistivo foi desenvolvido para aplicação em pavimentos, com base na adição de partículas de negro de fumo (CB), com o objectivo de avaliar dados de tráfego em tempo real. Numa primeira abordagem experimental foi determinada uma composição cimentícia sensitiva, concluindo que a incorporação de 7% de CB (em relação à massa de cimento) oferecia a melhor resposta resistiva a estímulos de compressão. Numa segunda campanha experimental, composição, ergonomia dos sensores cimentícios, tipologia de ensaios e sistema de aquisição foram otimizados e adequados, de acordo com a finalidade de monitorização de tráfego. Ciclos de compressão estáticos e dinâmicos demonstraram fatores de sensitividade médios (GF) de 60 e uma excelente resposta linear, não afetada por variações de temperatura, ao contrário da sensitividade piezoresistiva que registou diminuições até 30%. Em resumo, os resultados desta dissertação demonstram que a incorporação de elementos de betão sensitivo com adição de CB à superfície de pavimentos pode vir a constituir uma alternativa às soluções tradicionais de monitorização de tráfego, dado as suas vantagens como: baixo custo, simplicidade de implementação, propriedades estruturais, durabilidade e sensitividade
Today’s society is founded on infrastructure systems such as water, electricity, communication and transport networks. The global efficiency demand of the 21st century is growing rapidly and the expected performance of infrastructures follows the same trend. This pursuit for efficiency has led digital technology and physical urban infrastructures to fuse into the concept of ‘smart infrastructures’, relying on large monitoring networks coupled to information subsystems. Traffic logistics has been one of the fields which has benefited the most of such advances, with the implementation of the so-called Intelligent Transportation Systems (ITS). Over the last years, advances in materials science have enabled the development of a wide range of “smart” construction materials capable of autonomous tasks. An example of these are the piezoresistive cementitious composites, some of which may be used as monitoring systems, thanks to their self-sensing properties. The present dissertation aims to bridge the concept of multifunctional cement-based materials to the traffic monitoring discipline. Here, a stress-sensitive cementitious composite, based on the addition of carbon black (CB) particles, was developed for application in pavement surfaces with a view to perform permanent real-time evaluation of traffic data. In a first experimental approach, a sensitive CB-based cementitious composition was determined and results concluded that mixtures containing 7% of CB by mass of cement offered the most favourable piezoresistive response. In a second experimental campaign, materials, specimens design and measurement setup were reviewed, towards traffic monitoring requirements. Quasi-static and dynamic compressive load cycles showed gauge factors (GF) as high as 60 and a response linearity inaffected by temperature variations, despite registered reductions in sensitivity up to 30%. Taken together, results demonstrated that embedding conductive CB-based concrete elements in pavement surfaces may become a prospective alternative to conventional traffic monitoring solutions given their numerous advantages, including: low-cost, simplicity of implementation, structural properties, durability and good sensitivity.
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Mostert, F. "Improving the Deviro panel : technical enhancements of a wood fibre-cement composite from paper mill de-inking sludge." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/49988.
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Thesis (MScFor)--Stellenbosch University, 2004.ENGLISH ABSTRACT: This research focuses on the utilisation of de-inking sludge from a tissue mill to produce a wood-fibre inorganic composite called the Deviro panel. The study is based on the SA provisional patent 95/9594 by Ysbrandy and Gerischer' and the further research conducted by Crafford'. The patented Deviro panel contains up to 70% de-inking sludge. Cement and a cement extender serve to fortify the composite. The panel's fibre content of 25-30% is significantly greater than encountered in commercial fibre inorganic composites which contain 8-12% fibre by weight. The physico-mechanical characteristics of the Deviro panel compare favourably with resin bonded wood-fibre composites, but less favourably compared to conventional wood and wood-fibre inorganic composites. These properties are strongly dependent on panel density. For instance flexural strength being directly proportional while dimensional stability and hygroscopicity being inversely proportional to density. After confirming the results from the preceding work by Crafford, further improvements were investigated through chemical and curing enhancements. For instance, an autoclaving treatment during the curing period showed an increase in flexural strength. Addition of water glass could be associated with bulking of the panel, which resulted in increased flexural strength and a slight reduction of density. Panel density could be significantly reduced by the addition of Perlite, while inhibiting the concomitant reduction in strength. In addition a pilot production process was developed to produce 1m2 panels, which exhibited similar curing characteristics as the smaller panel units.
AFRIKAANSE OPSOMMING: Hierdie navorsing handeloor die gebruik van ontinkingsslyk van 'n sneespapier meule om die Deviro paneel, 'n houtvesel anorganiese saamgestelde produk, te produseer. Die studie volg uit die SA voorlopige patent 95/9594 deur Ysbrandy en Gerischer en verdere narvorsing deur Crafford'. Die gepatenteerde Deviro paneel bevat tot 70% ontinkingsslyk. Sement en sement-byvoegmiddels dien om die saamgestelde produk te versterk. Die paneel bevat 25-30% vesel wat aansienlik meer is as ander kommersiële anorganiese saamgestelde produkte wat 'n vesel inhoud van 8-12% het. Die megamese eienskappe van die Deviro paneel is vergelykbaar met houtvesel saamgestelde produkte waar hars as kleefiniddel dien, maar vergelyk minder gunstig teenoor konvensionele hout en houtvesel anorganiese saamgestelde produkte. Die paneel se eienskappe is afhanklik van sy digtheid Buig sterkte is eweredig terwyl dimensionele stabiliteit en hygroskopisiteit omgekeerd eweredig aan die digtheid van die paneel is. Die voorafgaande werk van Crafford is eers gestaaf voordat veranderinge aan die chemiese samestelling en drogingsmetodes van die paneel nagevors is. Daar is byvoorbeeld bevind dat, deur die paneel te outoklaveer gedurende die set periode, dit lei tot 'n toename in buig sterkte. Die byvoeging van water glas kan swelling laat plaasvind wat 'n afname in buig sterkte en 'n afname in digtheid tot gevolg het. Digtheid kan ook aansienlik verlaag word deur die byvoeging van Perlite terwyl 'n dienooreenkomstige verlaging in buig sterkte tot 'n mate voorkom word. 'n Loods produksie proses is ook ontwikkel om 'n 1m2 paneel te vervaardig wat dieselfde eienskappe toon as die kleiner paneel.
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Hassan, S. M. Mahmudul. "Development of Novel High Strength Composite Calcium Phosphate Cement for Orthopedic Applications." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533212629435654.
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Qin, Lei. "Development and application of cement-based piezoelectric composite in concrete behavior monitoring /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20QIN.
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Peled, Alva, Zvi Cohen, Steffen Janetzko, and Thomas Gries. "Hybrid Fabrics as Cement Matrix Reinforcement." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77694.
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Hybrid systems with two or more fiber materials were used to combine the benefits of each fiber into a single composite product. Strength and toughness optimization of hybrid thin sheet composites has been studied extensively using combination of different fiber types with low and high modulus of elasticity. Hybrid reinforcement is more significant when the reinforcing structure is in fabric geometry. Fabric structure provides full control on the exact location of each yarn and its orientation in the composite during production, thus maximizes the reinforcing efficiency. A high-strength, high-modulus fiber primarily tends to increase the composite strength with nominal improvements in toughness. A low-modulus fiber expected to mainly improve toughness and ductility. Combination of two or more types of fiber can produce a composite that is both strong and tough as compared to a mono fiber composite. The purpose of the current work was to study hybrid warp knitted fabrics as reinforcement for cementbased composite, having AR (Alkali Resistance) glass and Polypropylene (PP) as the reinforcing yarns. The examined ratios between the two different yarns were 0:100, 25:75, 50:50, 75:25, 100:0 (glass: PP, by percentage). It was found that in the hybrid system, the fracture mechanism is a superposition of the mono systems, and the tensile behavior is a combination between the two materials.
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Nieuwoudt, Pieter Daniel. "Quantifying the cracking behaviour of strain hardening cement-based composites." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20076.
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Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Strain Hardening Cement Based Composite (SHCC) is a type of High Performance Fibre Reinforced Cement-based Composite (HPFRCC). SHCC contains randomly distributed short fibres which improve the ductility of the material and can resist the full tensile load at strains up to 5 %. When SHCC is subjected to tensile loading, fine multiple cracking occurs that portrays a pseudo strain hardening effect as a result. The multiple cracking is what sets SHCC aside from conventional Reinforced Concrete (RC). Conventional RC forms one large crack that results in durability problems. The multiple cracks of SHCC typically have an average crack width of less than 80 μm (Adendorff, 2009), resulting in an improved durability compared to conventional RC. The aim of this research project is to quantify the cracking behaviour of SHCC which can be used to quantify the durability of SHCC. The cracking behaviour is described using a statistical distribution model, which represents the crack widths distribution and a mathematical expression that describes the crack pattern. The cracking behaviour was determined by measuring the cracks during quasi-static uni-axial tensile tests. The cracking data was collected with the aid of a non-contact surface strain measuring system, namely the ARAMIS system. An investigation was performed on the crack measuring setup (ARAMIS) to define a crack definition that was used during the determination of the cracking behaviour of SHCC. Several different statistical distributions were considered to describe the distribution of the crack widths of SHCC. A mathematical expression named the Crack Proximity Index (CPI) which represents the distances of the cracks to each other was used to describe the crack pattern of SHCC. The Gamma distribution was found to best represent the crack widths of SHCC. It was observed that different crack patterns can be found at the same tensile strain and that the CPI would differ even though the same crack width distribution was found. A statistical distribution model was therefore found to describe the CPI distribution of SHCC at different tensile strains and it was established that the Log-normal distribution best describes the CPI distribution of SHCC. After the cracking behaviour of SHCC was determined for quasi-static tensile loading, an investigation was performed to compare it to the cracking behaviour under flexural loading. A difference in the crack widths, number of cracks and crack pattern was found between bending and tension. Therefore it was concluded that the cracking behaviour for SHCC is different under flexural loading than in tension.
AFRIKAANSE OPSOMMING: “Strain Hardening Cement-based Composite” (SHCC) is ‘n tipe “High Performance Fibre Reinforced Cement-based Composite” (HPFRCC). SHCC bevat kort vesels wat ewekansig verspreid is, wat die duktiliteit van die material verbeter en dit kan die maksimum trekkrag weerstaan tot en met ‘n vervorming van 5 %. Wanneer SHCC belas word met ‘n trekkrag, vorm verskeie fyn krake wat ‘n sogenaamde vervormingsverharding voorstel. Die verskeie krake onderskei SHCC van normale bewapende beton. Normale bewapende beton vorm een groot kraak met die gevolg dat duursaamheidsprobleme ontstaan. Die gemiddelde kraakwydte van SHCC is minder as 80 μm (Adendorff, 2009) en het dus ‘n beter duursaamheid as normale bewapende beton. Die doel van die navorsingsprojek is om die kraak gedrag van SHCC te kwantifiseer en wat dan gebruik kan word om die duursaamheid van SHCC te kwantifiseer. Die kraak gedrag is beskryf deur ‘n statistiese verspreiding model wat die kraak wydtes se verspreiding voorstel en ‘n wiskundige uitdrukking wat die kraak patroon beskryf. Die kraak gedrag was bepaal deur die krake te meet tydens die semi-statiese een-asige trek toetse. Die kraak data was met behulp van ‘n optiese vervormings toestel, naamlik die ARAMIS, versamel. ‘n Ondersoek is gedoen op die kraak meetings opstelling (ARAMIS), om ‘n kraak definisie te definieer wat gebruik is om die kraak gedrag te bepaal. Daar is gekyk na verskeie statistiese verdelings om die kraak wydtes van SHCC te beskryf. Die kraak patroon van SHCC is beskryf met ‘n wiskundige uitdrukking genoem die “Crack Proximity Index” (CPI) wat die krake se afstande van mekaar voorstel. Dit is bevind dat die Gamma verdeling die kraak wydtes van SHCC die beste beskryf. Daar is waargeneem dat verskillende kraak patrone by dieselfde vervorming verkry kan word en dat die CPI kan verskil al is die kraak wydte verdeling dieselfde. ‘n Statistiese verdelingsmodel is dus gevind om die CPI verdeling van SHCC te beskryf by verskillende vervormings, en daar is vasgestel dat die Log-normaal verdeling die CPI verdeling van SHCC die beste beskryf. Nadat die kraak gedrag van SHCC bepaal is vir semi-statiese trek-belasting, is ‘n ondersoek gedoen waar die trek-kraak gedrag vergelyk is met buig-kraak gedrag. ‘n Verskil in die kraak wydtes, aantal krake en kraak patroon is gevind tussen buiging en trek. Dus is die gevolgtrekking gemaak dat die kraak gedrag van SHCC verskillend is in buiging as in trek.
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Khorami, M. "Application of natural and synthetic fibres as a replacement for asbestos fibres in cement boards." Thesis, Coventry University, 2011. http://curve.coventry.ac.uk/open/items/33ff6ca1-107b-482b-b598-f7ab050d8d42/1.
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The use of asbestos fibres in construction products has been banned in European countries for about two decades due to its effect on human health. At present, many developing countries use asbestos cement board as one of the most important construction products for roofing, cladding and partition walls. The Hatschek process is the most commonly used method to produce asbestos Fibre Cement Board (FCB). There are two major problems for the asbestos FCB manufacturers in replacing their products with non-asbestos FCB. The first one is finding materials and fibres that are available and competitive in price compared to asbestos fibres, and the second is providing inexpensive machines and equipment to produce non-asbestos FCB. In this research, an effort has been made to solve these two major problems. After the initial laboratory investigations on several natural and synthetic fibres some of the fibres with potential use in FCB were chosen for the further investigations. A slurry vacuum dewatering process was then designed and made for the laboratory use. The performance of material selections and mix designs selected from the laboratory studies were subsequently verified with factory Hatschek process in a factory site trial. Many specimens with natural and synthetic fibres incorporating silica fume and limestone powder were made and tested in the laboratory. Silica fume and limestone powder were used for enhancing flexural strength and suppression of alkalinity to reduce breakdown of the cellulose fibres. The results of mechanical, physical and II durability tests were analysed. The microstructure of the fibres and composites was also studied by SEM (Scanning Electron Microscopy). At some stages, mix design optimization was carried out to gain the highest flexural strength. The most suitable mixes were chosen for the factory site trials. A number of full-scale non-asbestos trial boards were made successfully in an asbestos FCB factory and tested in accordance with the current national and international standards. The results indicated that the trial boards fulfilled the requirements of the relevant standards. Based on the outcome of this research, a combination of acrylic fibres and waste cardboard in a mix incorporating silica fume and limestone powder in addition to Portland cement can be used to replace asbestos fibres. Although broadly compatible with the asbestos cement production process, this formulation change will necessitate some changes to the existing production lines in asbestos cement factories to produce non-asbestos FCB.
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Soyluoglu, Serdar. "Effects Of Separate And Intergrinding On Some Properties Of Portland Composite Cements." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611365/index.pdf.
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In the production of cement, to increase the cement/clinker ratio and decrease CO2 emission, the most important alternative is to produce mineral admixture incorporated cements (CEM II-III-IV-V) instead of portland cement
(CEM I). These cements are usually produced by intergrinding the portland cement clinker and the mineral admixtures. However, the difference between grindabilities of the different components of such cements may cause significant effects on the particle size distribution and many other properties.
For this reason, separate grinding of additives and clinker may be thought as an alternative. In this study, the effects of intergrinding and separate grinding on the particle size distribution and consequently on the strength of portland
composite cements which contained natural pozzolan (trass), granulated blast furnace slag (GBFS) and limestone besides portland cement clinker were studied.
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Naoum, Steven James. "SIGNIFICANT PROPERTIES OF UNIVERSAL RESTORATIVE MATERIALS CONTAINING PRE-REACTED GLASS IONOMER PARTICLES." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9019.
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ABSTRACT Carious lesions located at the margins of resin composite restorations and on unrestored proximal tooth surfaces in contact with resin composite restorations is an undesirable occurrence that can necessitate restorative intervention. Significantly however, several in vivo and in vitro studies have shown that should a composite restoration have fluoride releasing capability, the incidence of caries associated with resin composite restorations at these locations has the potential to be reduced. Further, it has been speculated that the inclusion of Pre-reacted glass ionomer (PRG) particles within resin composites can facilitate resin composite fluoride releasing capability. The aim of the present study therefore was to evaluate selected significant properties of resin composites containing Pre-reacted glass ionomer particles so to assess whether the inclusion of PRG particles within resin composites has the potential to improve the longevity of direct resin composite restorations and adjacent unrestored tooth surfaces through reducing the occurrence of caries induced restorative intervention. For reasons of relevance and propriety constraints this investigation centred on assessment of the most recently developed resin composite containing Pre-reacted glass ionomer particles (PRG) indicated for ‘universal’ restorative use; Beautifil II (Shofu Inc, Kyoto, Japan). Resin composites containing PRG particles have been given the classification Giomer. Properties of Beautifil II that were examined in this study include fluoride release, fluoride recharge, mechanical stability with ageing and the level of polymerisation contraction. The performance of Beautifil II in relation to these properties was compared to fluoride releasing composites, glass ionomers and ‘low polymerisation shrinkage’ composites as appropriate. The effect of repeated fluoride recharge on the stability of the adhesion between dentine and a bonding system incorporating PRG particles was also examined. In addition, the willingness of dental students and dental practitioners to employ resin composites containing Pre-reacted glass ionomer particles was assessed through a questionnaire and a material handling exercise. In the present study the ‘universal’ composite Beautifil II, containing Pre-reacted glass ionomer particles demonstrated: • Ability to sustain fluoride release over long term ageing (18 months). The concentration of fluoride release exhibited by Beautifil II was significantly (p<0.05) greater than the fluoride release from fluoride containing composites Gradia Direct X and Tetric EvoCeram, but was less than the release from the glass ionomer Fuji IX Extra. • Capacity to be recharged following application of topical fluoride. Importantly, this fluoride recharge capability was observed to continue after repeated fluoride applications and despite long term ageing (18 months). The fluoride recharge capability exhibited by Beautifil II was significantly (p<0.05) greater than the recharge capability of fluoride containing composites Gradia Direct X and Tetric EvoCeram but was less than that exhibited by the glass ionomer Fuji IX Extra. • Ability when exposed to daily five minute topical fluoride application to re-release fluoride at levels comparable to the fluoride released by glass ionomers after four weeks ageing; the ‘plateau’ fluoride release of glass ionomers. Notably it is the long term ‘plateau’ fluoride release from glass ionomers rather than the high ‘initial burst’ of released fluoride which is claimed to be responsible for any caries inhibitive action associated with the fluoride released from glass ionomers. • Maintenance of stability of mechanical properties (elastic modulus and hardness) despite long term (18 month) ageing, fluoride release and fluoride recharge at values comparable to conventional composites and significantly (p<0.05) exceeding those of glass ionomers. Additionally, the stability of giomer-dentine bond strengths was maintained over a four month period and despite repeated fluoride recharge to margins of Beautifil II-FL Bond II restorations; FL Bond II is an adhesive containing PRG particles. • A significantly greater (p<0.05) rate and volume of polymerisation contraction in comparison to newly developed ‘low shrinkage’ resin composites Kalore and Silorane. • A lower viscosity compared to conventional composites causing a reduction in clinician acceptance on the basis of handling. However, Australian dental practitioners indicated a clear interest in using composites containing PRG particles and are willing to accept a compromise in composite handling (78%) and aesthetic qualities (95%) if this is a necessary result of PRG particle inclusion. The greater polymerisation shrinkage and lower viscosity of Beautifil II in comparison to the other assessed composites can be attributed to the greater concentration of TEGDMA in giomers in comparison to TEGDMA levels within conventional and ‘low shrinkage’ composites. Consequently, within the scope and limitations of this study, the conclusions indicate that inclusion of Pre-reacted glass ionomer particles within resin composites has the potential to facilitate resin composite fluoride release. Consequently inclusion of PRG filler particles within resin composites has the potential to improve composite restoration longevity and the longevity of contacting unrestored tooth surfaces through fluoride mediated caries inhibition. The findings from this study therefore suggests that composites containing PRG filler particles should be considered by practitioners when restoring aesthetically demanding cavities and cavities subject to occlusal loading in high caries risk patients; situations in which fluoride availability for restoration margins and contacting tooth surfaces is advantageous but where glass ionomer placement is contraindicated. In order to optimise the potential benefits provided through PRG particle inclusion within composite resin matrices, incremental composite placement, regular fluoride application to placed PRG containing restorations and the incorporation of PRG particles within resin matrices of lower polymerisation contraction is recommended. The present study suggests that long term clinical evaluation of current and future generations of giomer restorations is warranted to enable clinical confirmation of the findings of this study.
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Kligys, Modestas. "Production technology and properties of composite material made out of porous cement paste and crushed expanded polystyrene." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20091204_085542-55180.
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The composite material of different density, where porous cement paste serves as matrix and crushed waste expanded polystyrene packages serve as inclusions, was developed. The compositions of formative mixtures and technological parameters of production for this composite material were selected and its properties were investigated.Sukurta skirtingo tankio kompozitinė medžiaga, kurioje matrica yra poringoji cemento tešla, o intarpai - trupintos polistireninio putplasčio pakavimo taros atliekos. Parinktos minėtos kompozitinės medžiagos formavimo mišinių sudėtys, gamybos technologiniai parametrai ir ištirtos jos bandinių savybės.
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Servián, Victor Manuel Acosta. "Resistência adesiva dos cimentos resinosos convencionais e autoadesivos à dentina contaminada por saliva." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/25/25148/tde-02102012-090935/.
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Muitas das lesões dentárias necessitam de restaurações indiretas que requerem cimentos adesivos para a sua fixação à estrutura dentária. Em algumas situações não é possível realizar o isolamento absoluto do campo operatório, o que pode levar à contaminação com saliva da dentina previamente aos procedimentos adesivos. Assim é necessário saber o nível de comprometimento da adesão em função deste fato. O presente estudo teve como objetivo analisar o tratamento da dentina contaminada com saliva na resistência adesiva dos cimentos resinosos convencional e autoadesivo através de testes de cisalhamento. Foram utilizados 50 incisivos bovinos que foram lixados até a exposição de dentina superficial e divididos em 6 grupos: Grupo ARC (controle): condicionamento ácido por 15s + sistema adesivo Scotchbond Multipurpose (3M/ESPE) + cimento RelyX ARC (3M/ESPE); Grupo ARClav: condicionamento ácido por 15s + contaminação com saliva + lavagem com água/ar 20 segundos + sistema adesivo + cimento RelyX ARC; Grupo ARCsec: condicionamento ácido por 15s + contaminação com saliva + secagem com papel absorvente + cimento autoadesivo RelyX ARC; Grupo ARCre: condicionamento ácido por 15s, contaminação + secagem jato de ar + recondicionamento por 15s + sistema adesivo Scotchbond Multipurpose + cimento RelyX ARC; Grupo U100 (controle): sem contaminação + cimento autoadesivo RelyX U100 (3M/ESPE); Grupo U100sec: contaminação + secagem jato de ar + cimento autoadesivo RelyX U100. Após a cimentação, os dentes foram armazenados em água destilada a 37ºC por 24 horas antes da realização do teste de cisalhamento. Os resultados obtidos foram submetidos à análise de variância a dois critérios e teste de Tukey com nível de significância de 5%. As médias gerais, dos grupos,expressas em MPa, foram G ARC: 9,02 ± 1,36 - G U100: 4,38 ± 0,74 - GARClav: 6,43 ± 0,98 GARCsec: 7,71 ± 1,14 GARCre: 5,68 ± 1,10 G U100sec: 3,87 ± 0,51. A análise dos resultados permitiu concluir que a adesão do cimento RelyX à dentina contaminada com saliva, lavada ou recondicionada com ácido fosfórico diminui significantemente quando comparada à adesão à dentina não contaminada ou àquela contaminada e apenas seca com papel absorvente. Já a contaminação com saliva não afetou significantemente a adesão do cimento RelyX U100 à dentina.Many dental injuries require indirect restorations fixed by adhesive cements. In some situations is not possible to isolate the operative field, which can lead to contamination by saliva of the dentin. The aim of this study was to analyze the treatment of dentin contaminated with saliva on shear bond strength of conventional and self-adhesive resin cements. Fifty bovine incisors were ground until exposure of dentin surface and divided into six groups: Group ARC (control) no contamination + acid etch for 15s + Scotchbond Multipurpose system (3M/ESPE) + cement Rely X ARC (3M/ESPE); Group U100 (control): no contamination + self-adhesive cement RelyX U100 (3M/ESPE), Group ARClav: acid etch for 15s + saliva contamination + rising with water / air + adhesive system RelyX ARC, Group ARCsec: acid etch + contamination with saliva + drying with absorbent paper cement RelyX ARC, Group ARCre: acid etched, contamination with saliva + drying with absorbent paper + reetched for 15s + adhesive system Scotchbond Multipurpose + cement RelyX ARC, Group U100sec: contamination + drying with absorbent paper + self-adhesive cement RelyX U100. After cementation, the teeth were stored in distilled water at 37° C for 24 hours prior to shear testing. The results were analyzed by One-way ANOVA and Tukey\'sTests with a significance level of 5% were: G ARC: 9.02 ± 1.36 G U100: 4.38 ± 0.74 G ARClav: 6.43 ± 0.98 G ARCsec: 7.71 ± 1.14 G ARCre: 5, 68 ± 1.10 G U100sec: 3.87 ± 0.51.The results showed that there was a significant difference in bond strength of RelyX ARC to dentin contaminated by saliva when it was rinsed or re-etched, but there was no difference when the contaminated dentin was just dried with absorbent paper. No statistical difference was found between the adhesion resistance of the RelyX U100 to dentin with or without saliva contamination.
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Sunnegårdh-Grönberg, Karin. "Calcium aluminate cement as dental restorative : Mechanical properties and clinical durability." Doctoral thesis, Umeå universitet, Tandhygienistprogrammet, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-270.
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In 1995, the Swedish government recommended the discontinuation of amalgam as restorative in paediatric dentistry. Because the mercury content in amalgam constitutes an environmental hazard, its use has declined. The use of resin composites is increasing, but the polymerisation shrinkage of the material is still undesirably high, and the handling of uncured resin can cause contact dermatitis. A new restorative material has recently been developed in Sweden as an alternative to amalgam and resin composite: a calcium aluminate cement (CAC). CAC has been marketed as a ceramic direct restorative for posterior restorations (class I, II) and for class V restorations. This thesis evaluates mechanical properties and clinical durability of the calcium aluminate cement when used for class II restorations. Hardness, in vitro wear, flexural strength, flexural modulus, and surface roughness were evaluated. A scanning electron replica method was used for evaluation of the interfacial adaptation to tooth structures in vivo. The durability was studied in a 2-year intra-individually clinical follow-up of class II restorations. Major results and conclusions from the studies are as follows: • The CAC was a relatively hard material, harder than resin-modified glass ionomer cement but within the range of resin composites. The CAC wore less than resin-modified glass ionomer cement but more than resin composite. • Flexural strength of CAC was in the same range as that of zinc phosphate cement and far below that of both resin composite and resin-modified glass ionomer cement. Flexural modulus of CAC was higher than both resin composite and resin-modified glass ionomer cement. The low flexural strength of CAC precludes its use in stress-bearing areas. • Surface roughness of CAC could be decreased by several polishing techniques. • For CAC restorations, interfacial adaptation was higher to dentin but lower to enamel compared with resin composite restorations. Fractures were found perpendicular to the boarders of all CAC restorations and may indicate expansion of the material. • After 2 years of clinical service, the class II CAC restorations showed an unacceptably high failure rate. Material fractures and tooth fractures were the main reasons for failure.
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Satioglu, Azize Ceren. "Analysis Of Mechanical Behavior Of High Performance Cement Based Composite Slabs Under Impact Loading." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610935/index.pdf.
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Studies on the behavior of steel fiber reinforced concrete (SFRC) and slurry infiltrated fibrous concrete (SIFCON) to impact loading have started in recent years. Using these relatively new materials, higher values of tensile and compressive strength can be obtained with greater fracture toughness and energy absorption capacity, and therefore they carry a considerable importance in the design of protective structures. In this thesis, computational analyses concerning impact loading effect on concrete, steel fiber reinforced concrete (SFRC) and slurry infiltrated fibrous concrete (SIFCON) are conducted by the aid of ANSYS AUTODYN 11.0.0 software. In the simulations, the importance of the concrete compressive and tensile strengths, and the fracture energy, together with the target and projectile erosion parameters, were investigated on the response of concrete target and projectile residual velocity. The obtained results of the simulation trials on concrete, SFRC and SIFCON have been compared with the experimental outcomes of three concrete, two SFRC and two SIFCON specimens in terms of deformed target crater radius, depth volume and striking projectile residual velocities.
The simulation analyses have shown that, compressive as well as tensile strengths of the concrete, SFRC and SIFCON specimens are of great importance on the crater volume while erosion parameters have a significant effect on the projectile residual velocity. Simulation outcomes possess a higher accuracy for concrete simulations when comparisons are made with available experimental results. This accuracy deteriorates for SFRC and SIFCON specimens. It was further concluded that related material tests of the specimens must be available in order to obtain higher accuracy.
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McCague, Colum. "Development of novel composite cement systems for the encapsulation of aluminium from nuclear wastes." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678940.
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Currently in the UK, composite blends of Portland cement (PC) and blastfurnace slag (up to 90%) are commonly used for the encapsulation of low and intermediate level wastes. The high volume replacement of PC is considered necessary in order to to reduce the high heat generation resulting from cement hydration in 500 litre waste packages. While suited to the majority of waste streams, the high pH environment in such systems (usually around 12.5 -13), will cause the corrosion of certain waste metals such as aluminium. Since aluminium is only passive between pH4 - 8.5, the use of an alternative low-pH cement system could serve to reduce/inhibit the corrosion. However, before such cements can be considered, two main research problems must be addressed, as follows: (1) quantitative evaluation of alternative cement systems based on their corrosion performance with aluminium; (2) high heat generation due to the rapid rate of hydration. The research in this thesis was thus divided into two strands, as follows: (1) The design and development of a novel, scientifically robust testing facility for the quantitative monitoring of aluminium corrosion in cement pastes; (2) the development of novel cement composites based on weakly alkaline calcium sulfoaluminate (CSA) cement for the encapsulation of aluminium from nuclear wastes. The output from this research is considered to be of interest to the UK nuclear industry.
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Thammajaruk, Putsadeeporn. "Influence of Ceramic Coating Pre-treatment Techniques on Bonding of Zirconia to Composite Cements." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19628.
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Zirconia is a ceramic widely used in dentistry as an indirect restorative material. In contrary to glass-ceramics, zirconia does not contain amorphous silica glass in its composition thus conventional bonding based on hydrofluoric acid etching followed by silane application is ineffective. The inability to etch and chemically treat the fitting surface of zirconia restoration is seen as a limiting factor for bonding composite cements to zirconia, particularly, in those clinical situations where achieving resistance and retention form of the abutments teeth is challenging. Objectives: The aims of this thesis were: (i) to update the current knowledge and to systematically review and evaluate which pre-treatments and type of cement provide the greatest bond strength between zirconia and composite cements and (ii) to evaluate and compare micro-tensile bond strength between composite cements and zirconia pre-treated with three ceramic coating techniques (DCMhotbond ceramic coating, nano-structured alumina coating, and lithium disilicate ceramic coating) versus conventional methods based on air abrasion, and (iii) to chemically characterise the nature of the bond. Results: The meta-analysis and systematic review appeared to indicate that ceramic coating techniques combined with methacryloyloxydecyl dihydrogenphosphate (MDP)-containing primers achieved the greatest long-term bond strength in aged condition. Testing of the micro-tensile bond strength showed that nano-structured alumina coating groups yielded comparable bond strength to air abrasion techniques, whereas DCMhotbond ceramic coating and lithium disilicate ceramic coating groups yielded lower bond strength than alumina air-abrasion techniques. Chemical bonds between primers and ceramic-coated or air-abraded zirconia were detected in all the protocols investigated. However, the nature of the bonds was different according to the material and protocol. Conclusions: Ceramic-coating techniques based on nano-structured alumina coating has the potential to be an alternative method to improve the bond strength between zirconia and composite cement. Other ceramic coating techniques were more sensitive to strength degradation following thermocycling and did not seem to be valid alternatives to air-abrasion protocols.
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Sunnegårdh-Grönberg, Karin. "Calcium aluminate cement as dental restorative : mechanical properties and clinical durability /." Umeå : Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-270.
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Aldahsh, Saleh. "Development of a new composite powder material of cement additive with polyamide 12 for selective laser sintering." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/10948/.
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Applications of rapid prototyping are expanding to new domains. This is particularly true of the selective laser sintering (SLS) process. In order for that process to be competitive and become a strong candidate for new applications, such as rapid manufacturing, the material used needs to be improved. The aim of the work presented in this thesis was to develop a new composite material made up of Polyamide 12 (a common SLS material) and cement, an inexpensive additive, for the purpose of improving the mechanical properties, as well as reducing the cost of the sintered components. An experimental study was conducted of the thermal properties of the cement-Polyamide 12 composite material with different proportions of cement and Polyamide 12. The purpose of the study was to determine optimal SLS parameters to produce good quality fabricated SLS specimens. The research also involved an experimental investigation of the mechanical properties (Young‟s modulus, tensile, flexural, compression and impact strengths, and density) as a function of the proportion of cement additive to Polyamide 12. Finally, a method of quickly and inexpensively producing test specimens by casting instead of using SLS was developed and experiments conducted to demonstrate the similarity in properties between cast and SLS specimens. II This research has shown that adding cement to Polyamide 12 yields a composite material that enables the production of sintered specimens with mechanical properties that are superior to those of pure Polyamide 12 specimens. As cement is much cheaper than Polyamide 12, the composite material is also obviously less expensive than pure Polyamide 12.
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Pham, Ngoc Phuong. "Rubberized cement-based composite as material for large surface applications : effect of the rubber-cementitious matrix bond." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30077.
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La capacité de déformation améliorée et la résistance à la fissuration par retrait rendent les composites cimentaire caoutchoutés adaptés aux applications de grande surface telles que les chaussées et les rechargements minces adhérents à base cimentaire. Cependant, le défaut d'adhérence entre les agrégats de caoutchouc et la matrice cimentaire, bien connu, demeure nuisible aux propriétés mécaniques et de transferts de ces matériaux. De plus, en raison de la faible rigidité des granulats caoutchouc, il est universellement accepté une réduction de certaines propriétés mécaniques des composites caoutchoutés à base de ciment. Néanmoins, leurs propriétés de transfert pourraient être compétitives avec le mortier à base de granulats naturels si la liaison à l'interface caoutchouc-ciment est améliorée. Afin d'améliorer l'interface, les granulats caoutchouc ont d'abord été revêtus d'un copolymère styrène-butadiène et après densification complète de ce copolymère à la surface des agrégats caoutchouc, ils ont été incorporés au mélange cimentaire. Dans un premier temps, une analyse microstructurale utilisant la microscopie électronique à balayage (MEB), la spectrométrie de rayons X à dispersion d'énergie (EDS) et la diffraction des rayons X (DRX) a permis de préciser que la pâte de ciment adhérait fermement aux granulats caoutchouc revêtus de copolymère. Dans un second temps, les propriétés mécaniques et de transfert de ce mortier ont ensuite été comparées à celles du mortier témoin (granulats naturels) et de deux autres mortiers caoutchoutés dans lesquels l'un d'entre eux a été ajouté un désentraineur d'air pour produire un mélange caoutchouté ayant la même teneur en air que le mortier témoin. Les résultats ont démontré une interface améliorée du caoutchouc-ciment fournissant une amélioration significative des propriétés de transfert telles que la perméabilité à l'air et l'absorption capillaire d'eau. Cependant, la diminution des propriétés mécaniques (résistance à la compression et module d'élasticité) demeure en raison de la faible rigidité des granulats caoutchouc. Quant à la résistance à la traction et la résistance résiduelle post-pic témoignent d'une énergie de rupture plus élevées dans le cas de granulats revêtus du copolymère, démontrant un effet de pontage amélioré rendu possible par la liaison entre les granulats caoutchouc et la matrice de ciment. Cet effet de pontage a également contribué à améliorer la résistance des composites caoutchoutés à la fissuration par retrait empêché Afin d'étayer les effets d'une interface caoutchouc-ciment améliorée, la durabilité des mortiers caoutchoutés dans des environnements agressifs a été étudiée. En ce qui concerne l'attaque à l'acide acétique, une faible profondeur dégradée et une réduction de la perte de masse et de résistance à la compression des mortiers caoutchoutés revêtus de copolymère ont été observés par rapport au mortier témoin. Le mortier caoutchouté enduit de copolymère se comporte également mieux en empêchant la diffusion du sulfate de sodium dans le composite. La dégradation des mortiers dans des environnements agressifs a également été évaluée sur la base d'une variable d'endommagement. Il en ressort que les matériaux caoutchoutés revêtus de copolymère étaient plus durables que les matériaux non traités exposés à des environnements agressifsProperties of improved strain capacity and high shrinkage cracking resistance make rubberized cement-based composites suitable for large surface applications such as cement-based pavements and thin bonded overlays. However, bond defect between rubber aggregates (RA) and cement matrix is well-known and detrimental to properties of rubberized cement-based materials. It is universally accepted a reduction in some mechanical properties of rubberized cement-based composites mainly due to low stiffness of RA. Nevertheless, their transfer properties could indeed be competitive with control mortar (without RA) if bond at rubber-cement matrix interface is improved. In order to enhance the interface, RA were firstly coated with styrene-butadiene copolymer and after complete densification of this copolymer on surface of RA, they were mixed with the pre-mixed cementitious mixture. Microstructural analysis using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDS), and X-Ray Diffraction (XRD) clarified that cement paste bonded firmly on copolymer-coated RA. Mechanical and transfer properties of this mortar were then compared to that of control mortar and two rubberized mortars in which one of them air-detraining admixture was added to produce rubberized mixture with the similar air content as the control mortar. Findings have demonstrated an enhanced rubber-cement matrix interface provided a significant improvement on transfer properties such as air permeability and water capillary absorption. However, a reduction in mechanical properties (compressive strength and modulus of elasticity) was still observed due to low stiffness of RA. Rubber coating appeared to limit the reduction in tensile strength and to result in a higher residual post-peak strength and fracture energy, demonstrating an improved material bridging effect made possible by the bond between RA and cement matrix. The bridging effect also contributed to improve resistance of rubberized composites to shrinkage cracking even under high restrained conditions. Based on above-mentioned characteristics, the study further investigated the durability of rubberized mortars under aggressive environments to observe the effects of RA incorporation and of an enhanced rubber-cement matrix interface. Regarding acetic acid attack, a low degraded depth and a reduction in loss of both mass and compressive strength of rubberized mortars, especially the one incorporating copolymer-coated RA, were observed compared to the ones of the control mortar. The coated rubberized mortar also behaves better in preventing sodium sulfate diffusion into the composite. The degradation of mortars under aggressive environments was also evaluated based on a damage variable, which was defined as a relative change in equivalent load-resisting area of mortar specimens between their original condition and at a given time when they were exposed to acid or sulfate solutions. From damage variable values, it can be concluded that coated rubberized mortar was more durable than the untreated one against aggressive environments. The durability of untreated and coated rubberized mortars under freeze-thaw cycles was also carried out and compared to that of control mortar. The rubberized cement- based composites were more resistant to freezing and thawing than the control one, especially in terms of dimensional expansion. The better performance can be attributed to high energy absorption of RA and to higher porosity, lower water capillary absorption and high strain capacity of rubberized mortars. Rubber coating, even reducing the permeability of rubberized cement-based composites, still remained high durability of their applications under frost environment
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Dolores, Gonzalo Mármol de los. "Low-alkalinity matrix composites based on magnesium oxide cement reinforced with cellulose fibres." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-17082017-113846/.
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A lower-alkalinity cement based on MgO and SiO2 blends is analysed to develop clinker-free Fibre Reinforced Cementitious Composites (FRCC) with cellulosic fibres in order to solve the durability problems of this type of fibres when used in FRCC with Portland cement. Hydration evolution from 7 to 28 days of different MgO-SiO2 formulations is assessed. The main hydration products are Mg(OH)2 and M-S-H gels for all the formulations studied regardless of age. Hardened pastes are obtained with pH values < 11 and good mechanical properties compared to conventional Portland cement. 60% MgO-40% SiO2 system is chosen as optimal for the development FRCC since is the most mechanical resistant and is less alkaline compared with 70% MgO-30% SiO2. FRCC based on magnesium oxide and silica (MgO-SiO2) cement with cellulose fibres are produced to study the durability of lignocellulosic fibres in a lower pH environment than the ordinary Portland cement (PC). Flexural performance and physical tests (apparent porosity, bulk density and water absorption) of samples at 28 days and after 200 accelerated ageing cycles (aac) are compared. Two types of vegetable fibres are utilised: eucalyptus and pine pulps. MgO-SiO2 cement preserves cellulosic fibres integrity after ageing, so composites made out of MgO-SiO2 exhibit significant higher performance after 200 cycles of accelerated ageing than Portland cement composites. High CO2 concentration environment is evaluated as a curing treatment in order to optimise MgO- SiO2 matrices in FRCC. Samples are cured under two different conditions: 1) steam water curing at 55°C and 2) a complementary high CO2 concentration (20% by volume). In carbonated samples, Mg(OH)2 content is clearly lowered while new crystals of hydromagnesite [Mg5 (CO3)4⋅(OH) 2⋅4H2O] are produced. After carbonation, M-S-H gel content is also reduced, suggesting that this phase is also carbonated. Carbonation affects positively to the composite mechanical strength and physical properties with no deleterious effects after ageing since it increases matrix rigidity. The addition of sepiolite in FRCC is studied as a possible additive constituent of the binding matrix. Small cement replacement (1 and 2% wt.) by sepiolite is introduced and studied in hardened cement pastes and, later, in FRCC systems. When used only in cement pastes, it improves Dynamic Modulus of Elasticity over time. Bending tests prove the outcome of this additive on the mechanical performance of the composite: it improves composite homogeneity. Ageing effects are reported after embedding sisal fibres in MgO-SiO2 and PC systems and submitting them to different ageing conditions. This comparative study of fibre degradation applied in different cementitious matrices reveals the real compatibility of lignocellulosic fibres and Mg-based cements. Sisal fibres, even after accelerated ageing, do neither suffer a significant reduction in cellulose content nor in cellulose crystallinity and crystallite size, when exposed to MgO-SiO2 cement. Fibre integrity is preserved and no deposition of cement phases is produced in MgO-SiO2 environment.Um cimento de baixa alcalinidade à base de blendas de MgO e SiO2 é analisado para o desenvolvimento de Compósitos Cimentícios Reforçados com Fibras (CCRF) celulósicas sem clínquer para resolver os problemas de durabilidade de este tipo de fibras quando são usadas em CCRF com cimento Portland. A evolução da hidratação, desde 7 aos 28 dias, das diferentes formulações é avaliada. Os principais produtos hidratados são o Mg(OH)2 e o gel M-S-H para todas as formulações independentemente da idade estudada. As pastas endurecidas apresentam valores de pH < 11 e bom desempenho mecânico comparado com o cimento Portland convencional. O sistema 60% MgO-40% SiO2 é escolhido como a formulação ótima para o desenvolvimento de CCRF já que é a mais resistente e menos alcalina comparada com 70% MgO-30% SiO2. CCRF com cimento à base de óxido de magnésio e sílica (MgO-SiO2) e fibras celulósicas são produzidos para a análise da durabilidade das fibras lignocelulósicas em ambientes com valores de pH mais baixos comparados com o cimento Portland (PC). O desempenho mecânico a flexão e os ensaios físicos (porosidade aparente, densidade aparente e absorção de água) são comparados aos 28 dias e após de 200 ciclos de envelhecimento acelerado. O cimento à base de MgO-SiO2 preserva a integridade das fibras após o envelhecimento. Os compósitos produzidos com este cimento exibem melhores propriedades após 200 ciclos de envelhecimento acelerado que os compósitos produzidos com cimento Portland. Ambientes com alta concentração de CO2 são avaliados como tratamento de cura para otimizar as matrizes MgO- SiO2 nos CCRF. As amostras são curadas sob 2 condições diferençadas: 1) cura com vapor de água a 55oC e 2) cura com alta concentração de CO2 (20% do volume). As amostras carbonatadas apresentam teores reduzidos de Mg(OH)2 enquanto é produzida uma nova fase cristalina: hidromagnesita [Mg5 (CO3)4⋅(OH) 2⋅4H2O]. Após a carbonatação, o conteúdo de gel M-S-H é reduzido também, indicando uma carbonatação desta fase. A carbonatação aumenta a rigidez da matriz o que influi positivamente no desempenho mecânico e as propriedades físicas dos compósitos sem efeitos prejudiciais ao longo prazo. A adição de sepiolita em CCRF é estudada como possível adição na composição da matriz aglomerante. Baixos teores (1 e 2% em massa) de cimento são substituídos por sepiolita para o estudo das pastas de cimento hidratado e, posteriormente, dos compósitos. O Módulo Elástico Dinâmico das pastas é incrementado com o tempo pela adição de sepiolita. Os ensaios a flexão demostram que a adição de sepiolita melhora a homogeneidade dos compósitos. Reportam-se os efeitos das fibras de sisal após da exposição a sistemas MgO-SiO2 e PC e submetidas a diferentes condições de envelhecimento. Este estudo comparativo da degradação das fibras expostas a diferentes matrizes cimentícias mostra a compatibilidade das fibras lignocelulósicas com os cimentos à base de Mg. As fibras de sisal, inclusive após o envelhecimento acelerado, não apresentam nem redução significativa no conteúdo de celulose nem na cristalinidade da celulose assim como do tamanho de cristalito, quando expostas a cimentos MgO-SiO2.
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Másilko, Jiří. "Zvyšování odolnosti MDF kompozitů proti působení vody." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216350.
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The subject of the diploma thesis is the study of moisture resistance of macrodefect-free (MDF) cements based on calcium-aluminate cement and polyvinylalcohol used as polymer. MDF cements are perspective materials providing unique properties relative to traditional cement pastes with great potential to incoming constructional utilization. But it is known that MDF cements exhibit sensitivity to water, with swelling and reduction of strength. Therefore the work is aimed in monitoring of an organic polymer effect on the moisture resistance of MDF materials and phase changes. Aluminate cement (SECAR 51) and polyvinylalcohol/acetate copolymer have been used for the MDF cement preparation. The moisture resistance of model MDF cement samples was investigated at two different curing conditions: in the moist atmosphere and immersed in water. The influence of composition and individual curing on the properties of model MDF cement samples was observed. The characterization of MDF samples was based especially on test of flexural strength, FT-IR, EDAX and optical microscopy analyses.
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Luo, Yan, and 羅琰. "Assessment of a glass polyalkenoate cement and a polyacid-modified resin composite for the restoration of posterior teeth." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31242121.
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Luo, Yan. "Assessment of a glass polyalkenoate cement and a polyacid-modified resin composite for the restoration of posterior teeth." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22242879.
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De, Caso y. Basalo Francisco Jose. "Sustainable Composite Systems for Infrastructure Rehabilitation." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/495.
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The development of composite materials by combining two or more constituents with improved mechanical properties, when compared to either of the constituents alone, has existed since biblical times when straw or horse hair was mixed with clay or mud to produce bricks. During the second half of the twentieth century, modern composites known as fiber reinforced polymers (FRP) - consisting of a reinforcing phase (fibers) embedded into a matrix (polymeric resin or binder) - were developed to meet the performance challenges of space exploration and air travel. With time, externally-bonded FRP applications for strengthening of reinforced concrete (RC) structures gained popularity within the construction industry. To date, the confinement of RC columns using FRP systems is a convenient and well established solution to strengthen, repair and retrofit structural concrete members. This technology has become mainstream due to its cost effectiveness, and relative ease and speed of application with respect to alternative rehabilitation techniques such as steel or concrete jackets. However, significant margins exist to advance externally-bonded composite rehabilitation technologies by addressing economic, technological, and environmental issues posed by the use of organic polymer matrices, some of which are addressed in this dissertation. Articulated in three studies, the dissertation investigates the development of a sustainable, reversible, and compatible fiber reinforced cement-based matrix (FRC) composite system for concrete confinement applications in combination with a novel test method aimed at characterizing composites under hydrostatic pressure. Study 1 develops and characterizes a FRC system from different fiber and inorganic matrix combinations, while evaluating the confinement effectiveness in comparison to a conventional FRP system. The feasibility of making the application reversible was investigated by introducing a bond breaker between the concrete substrate and the composite jacket in a series of confined cylinders. The prototype FRC system produced a substantial increase in strength and deformability with respect to unconfined cylinders. A superior deformability was attained without the use of a bond breaker. The predominant failure mode was loss of compatibility due to fiber-matrix separation, which points to the need of improving fiber impregnation to enable a more efficient use of the constituent materials. Additionally semi-empirical linear and nonlinear models for ultimate compressive strength and deformation in FRC-confined concrete are also investigated. Study 2 compares through a life cycle assessment (LCA) method two retrofitting strategies: a conventional organic-based, with the developed inorganic-based composite system presented in Study 1, applied to concrete cylinders by analyzing three life cycle impact indicators: i) Volatile Organic Compound (VOC) emissions, ii) embodied energy, and, iii) carbon foot print. Overall the cement-based composite provides an environmentally-benign alternative over polymer-based composite strengthening system. Results also provide quantitative information regarding the environmental and health impacts to aid with the decision-making process of design when selecting composite strengthening systems. Study 3 is divided into two parts, Part A presents the development of a novel "Investigation of Circumferential-strain Experimental" (ICE) methodology for characterization of circumferential (hoop) strain of composite laminates, while Part B uses the experimental data reported in Part A to explicitly evaluate the effect of FRP jacket curvature and laminate thickness on strain efficiency. Results showed that the proposed ICE methodology is simple, effective and reliable. Additionally, the ultimate circumferential strain values increased with increasing cylinder diameter, while being consistently lower when compared to similar flat coupon specimens under the same conditions. The ultimate FRP tensile strain was found to be a function of the radius of curvature and laminate thickness, for a given fiber ply density and number. The effect of these findings over current design guidelines for FRP confined concrete was also discussed.
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Rödel, Michaela [Verfasser], Jürgen [Gutachter] Groll, and Matthias [Gutachter] Lehmann. "Development of Dual Setting Cement Systems as Composite Biomaterials with Ductile Properties / Michaela Rödel ; Gutachter: Jürgen Groll, Matthias Lehmann." Würzburg : Universität Würzburg, 2019. http://d-nb.info/1189589281/34.
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Hussein, Oday. "Composite cement systems for encapsulation of barium sulphate scale from oil industry and application as high density support matrix." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4797/.
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Radioactive barium sulphate scales raise a serious concern in the oil and gas industries. They are often classified as low level radioactive waste, but there are no clear methodologies established world widely to deal with this well know issue. The present study investigates a potential use of composite cement systems based on Portland cement to encapsulate the barium sulphate scales, aiming to provide a feasible option for safe handling, storage and disposal. The investigation was conducted on three different aspects: basic formulation, wasteform development and potential use as a high density support matrix. The first part studied the basic formulation to clarify the impact of BaSO4 loading and water contents on the physical properties of the composite cementing system. Fine BaSO4 powders and excess water were found to influence the product phases whereas coarse BaSO4 particles showed larger impact on strength of the products. The second part investigated the effect of mineral admixtures to develop practical wasteform formulations. Fine BaSO4 powder, metakaolin and quartz were found to improve the workability of the pastes as well as the microstructure by eliminating highly porous interfacial transition zone, resulting in the higher compressive strength and reasonable leaching rates of elements. Addition of quartz was found to be most effective to minimise the degradation caused by the high temperature environment, by initiating the formation of stable tobermorite phase.
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Konradsson, Katarina. "Influence of a dental ceramic and a calcium aluminate cement on dental biofilm formation and gingival inflammatory response." Doctoral thesis, Umeå : Umeå University, Faculty of Medicine, Odontology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1069.
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Phung, Thi Thu Ha [Verfasser], Horst-Michael [Akademischer Betreuer] Ludwig, Jochen [Gutachter] Stark, and Wolfgang [Gutachter] Breit. "Metakaolin as an Additive in Composite Cement / Thu Ha Phung Thi ; Gutachter: Jochen Stark, Wolfgang Breit ; Betreuer: Horst-Michael Ludwig." Weimar : F. A. Finger-Institut für Baustoffkunde, 2012. http://d-nb.info/111580751X/34.
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Phung, Thi Thu Ha Verfasser], Horst-Michael [Akademischer Betreuer] [Ludwig, Jochen [Gutachter] Stark, and Wolfgang [Gutachter] Breit. "Metakaolin as an Additive in Composite Cement / Thu Ha Phung Thi ; Gutachter: Jochen Stark, Wolfgang Breit ; Betreuer: Horst-Michael Ludwig." Weimar : F. A. Finger-Institut für Baustoffkunde, 2012. http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20130705-19764.
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Banomyong, Danuchit. "Effects of glass-ionomer cement lining on sealing ability and postoperative tooth sensitivity after resin composite restoration of posterior teeth /." Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/3533.
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Song, Gao. "Matrix manipulation to study ECC behaviour." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/4647.
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Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005.192 leaves on CD format, preliminary i-xii pages and numbered pages 1-135. Includes bibliography, list of figures and tables.
ENGLISH ABSTRACT: As a fibre reinforced material, engineered cementitious composite (ECC) has tough, strain-hardening behaviour in tension despite containing low volumes of fibres. This property can be brought about by developments in fibre, matrix and interfacial properties. Poly Vinyl Alcohol (PVA) fibre has been developed in recent years for ECC, due to its high tensile strength and elasticity modulus. However, the strong interfacial bond between fibre surface and matrix is a challenge for its application. This study focuses on the tailoring of matrix and fibre/matrix interfacial properties by cement replacement with fly ash (FA) and Ground Granulated Corex Slagment (GGCS). In this study the direct tensile test, three point bending test, micro-scale analysis, such as X-Ray Fluorescence Spectrometry analysis (XRF), Scanning Electron Microscope (SEM), are employed to investigate the influence of cement replacement, aging, Water/Binder (W/B) ratio, workability on ECC behaviour. This study has successfully achieved the aim that cement replacement by FA and GGCS helps to improve the fibre/matrix interfacial properties and therefore enhances the ECC tensile behaviour. Specifically, a high volume FA-ECC has stable high tensile strain capacity at the age of 21 days. This enables a constant matrix design for the investigation of other matrix influences. The Slag-ECC has a higher tensile strength but lower tensile strain capacity. The combination of FA and GGCS, moderate tensile strength and strain capacity is achieved Both tensile tests and Micro-scale analyses infer that the high volume FA-ECC has an adhesive type fibre/matrix interfacial interaction, as opposed to the cohesive type of normal PVA fibre-ECC. The different tensile behaviour trend of steel fibre-ECC and PVA fibre-ECC with the FA content is presented and discussed in this research. The investigations of aging influence indicate that the high volume FA-ECC has a beneficial effect on the properties of the composite at an early stage. However, at a high age, it has some difficulty to undergo multiple cracking and then leads to the reduction of tensile strain capacity. The modified mix design is made with the combination of FA and GGCS, which successfully increases the interfacial bond and, thereby, improves the shear transfer to reach the matrix crack strength. Therefore, an improved high age tensile behaviour is achieved. The W/B and fresh state workability influence investigations show that the W/B can hardly affect the tensile strain at early age. However, the workability influences on composite tensile strain significantly, because of the influence on fibre dispersion. Other investigations with regard to the hybrid fibre influences, the comparison of bending behaviours between extruded plate and cast plate, the relation between bending MOR and tensile stress, and the relation between compression strength and tensile strength contribute to understand ECC behaviour.
AFRIKAANSE OPSOMMING: As ‘n veselversterkte materiaal, het ontwerpte sementbasis saamgestelde materiale, taai vervormingsverhardingseienskappe in trek, ten spyte van lae veselinhoud. Hierdie eienskap word bewerkstellig, deur ontwikkelings in vesel, matriks en tussenveselbindingseienskappe. Poli-Viniel Alkohol (PVA) vesels is ontwikkel vir ECC, as gevolg van die hoë trekkrag en hoë modulus van hierdie veseltipe. Die sterk binding tussen die PVA-veseloppervlak en die matriks is egter ‘n uitdaging vir sy toepassing. Hierdie studie fokus op die skep van gunstige matriks en vesel/matriks tussenvesel-bindingseienskappe deur sement te vervang met vlieg-as (FA) en slagment (GGCS).In hierdie navorsing is direkte trek-toetse, drie-punt-buigtoetse, mikro-skaal analise (soos die X-straal ‘Fluorescence Spectrometry’ analise (XRF) en Skanderende Elektron Mikroskoop (SEM))toegepas. Hierdie metodes is gebruik om die invloed van sementvervanging,veroudering, water/binder (W/B)-verhouding en werkbaarheid op die meganiese gedrag van ECC te ondersoek.Die resultate van hierdie navorsing toon dat sementvervanging deur FA en GGCS help om die vesel/matriks tussenveselbindingseienskappe te verbeter. Dus is die ECC-trekgedrag ook verbeter. Veral ‘n hoë volume FA-ECC het stabiele hoë trekvervormingskapasiteit op ‘n ouderdom van 21 dae. Dit bewerkstellig ‘n konstante matriksontwerp vir die navorsing van ander matriks invloede. Die Slag-ECC het ‘n hoër treksterkte, maar laer trekvervormingskapasiteit. Deur die kombinasie van FA en GGCS word hoë treksterkte, sowel as gematigde vervormbaarheid in trek verkry. Beide trektoetse en mikro-skaal analise dui aan dat die hoë volume FA-ECC ‘n adhesie-tipe vesel/matriks tussenvesel-bindingsinteraksie het, teenoor die ‘kohesie-tipe van normale PVA vesel-ECC. Die verskille in trekgedrag van staalvesel-ECC en PVA vesel-ECC ten opsigte van die FA-inhoud is ondersoek en word bespreek in die navorsing. Die navorsing toon verder dat die hoë volume FA-ECC goeie meganiese eienskappe het op ‘n vroeë ouderdom. Op hoër ouderdom word minder krake gevorm, wat ‘n verlaging in die trekvervormingskapasiteit tot gevolg het. Met die kombinasie van FA en GGCS, word die vesel-matriksverband verhoog, waardeur ‘n verbetering in die skuifoordrag tussen vesel en matriks plaasvind. Verbeterde hoë omeganiese gedrag word daardeur tot stand gebring. Navorsing ten opsigte van die invoed van die W/B en werkbaarheid dui daarop dat die W/B slegs geringe invloed het op die trekvormbaarheid, terwyl die werkbaarheid ‘n dominerende rol speel in hierdie verband.Verdere studies sluit in die invloed van verskillende vesels, die vergelyking van die buigingsgedrag van geëkstueerde plate en gegote plate, die verhouding tussen buigsterkte en treksterkte, en die verhouding tussen druksterkte en treksterkte dra by tot beter begrip van die gedrag van ECC.
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PINTO, KELLY N. C. "Reciclagem de residuos de materiais compositos de matriz polimerica: poliester insaturado reforcado com fibras de vidro." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11069.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Fukuda, Chisako. "Bone bonding ability and handling properties of a titania?polymethylmethacrylate (PMMA) composite bioactive bone cement modified with a unique PMMA powder." Kyoto University, 2012. http://hdl.handle.net/2433/157423.
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