Tesis sobre el tema "Cement composites"
Siga este enlace para ver otros tipos de publicaciones sobre el tema: Cement composites.
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 50 mejores tesis para su investigación sobre el tema "Cement composites".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore tesis sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
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.
Texto completo
2
Guodong, Xu. "Fibre-cement hybrid composites". Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/844012/.
Texto completoResumen
The theoretical stress-strain behaviour of individual fibre reinforced cement composites is reviewed. Based on the multiple cracking concept of the existing theory, analytical expressions are developed to describe the tensile stress-strain behaviour of a fibre-cement hybrid composite consisting of three components, i.e. two reinforcing fibres with different moduli, strengths and strains to failure and a common cement binder. The model predicts that the tensile stress-strain curve of the hybrid composites consists of five stages, instead of three stages of the existing models for individual fibre cements, and relates the tensile behaviour of each stage to the component properties of the components and the test system parameters. A description is given of the physical and mechanical properties of four types of reinforcing fibres used in the study. These were fibrillated polypropylene film, alkali-resistant glass, polyvinyl alcohol fibres and carbon fibres. A small number of direct tensile tests on continuous glass, carbon and polyvinyl alcohol were performed. The tensile stress-strain behaviour of four types of fibre-cement hybrid composites was studied with particular emphasis on that of the glass- polypropylene hybrids for which the flexural load-deflection behaviour was also examined. It is shown that the fibre-cement hybrid composites yield superior engineering properties over their parent composites and the improvements are sensitive to volume fractions of each of the two fibres. The measured tensile stress-strain curves of the hybrids were compared with the theoretical predictions and satisfactory agreement in general is obtained. Implications from the present work for the design of fibre-cement hybrid composites are assessed.
3
Cheung, Kwok Fai. "Applications of pseudo-ductile engineered cementitious composites for construction industry /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20CHEUNGK.
Texto completoResumen
Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 314-315). Also available in electronic version. Access restricted to campus users.
4
Mohr, Benjamin J. "Durability of Pulp Fiber-Cement Composites". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7222.
Texto completoResumen
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.
5
Kakemi, Manabu. "Hybrid continuous fibre cement composites". Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/606/.
Texto completo
6
Karade, Sukhdeo Rao. "An investigation of cork-cement composites". Thesis, Bucks New University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273892.
Texto completo
7
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.
Texto completo
8
Zhang, Jie. "Microstructure study of cementitious materials using resistivity measurement /". View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20ZHANG.
Texto completo
9
McNulty, Thomas A. "The durability of cement bound minestone". Thesis, Aston University, 1985. http://publications.aston.ac.uk/14289/.
Texto completoResumen
The demand for road making materials continues to pressurise the supply of traditional good quality aggregates. Over the years, therefore, consideration has been given to alternative materials including industrial wastes. This thesis is concerned with potential use of Minestone, the by-product of coal mining, for the lower structural layers of pavement construction. Because of their clay like nature, Minestones do not merit consideration for such applications in an unbound state and, therefore, some form of stabilisation is necessary. Previous research has demonstrated that certain cement bound minestones, containing between 5 and 10 per cent cement, satisfy current Department of Transport requirements for use in pavement construction and, furthermore, they are not frost susceptible. However, doubts concerning the durability of cement bound minestones still remain. The thesis includes a review of both the cement and lime stabilisation techniques and also traces the origin and development of the methods used to assess the quality and durability of stabilised materials. An experimental study is described in which cement bound minestone specimens were subjected to a programme of tests which examined compressive strength, resistance to immersion, and resistance to freezing and thawing. The results of the tests were related to the properties of the raw materials. It was discovered that the response to cement stabilisation was governed mainly by the source of the minestone and, to a lesser degree, the cement content. It was also found that resistance in the durability tests was generally improved when the initial moisture content was raised above the optimum value. The result suggest that current methods for assessing cement stabilised materials are not appropriate to cement bound minestones. Alternative methods and criteria, based on volume change and retained strength following immersion and freeze-thaw tests, have been proposed. It is believed that these methods and criteria should also apply to other cement bound materials.
10
Boulfiza, Mohamed. "Constitutive modeling of fiber reinforced cement composites". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0004/NQ27111.pdf.
Texto completo
11
Brooks, Randall E. "Performance of lightweight fiber reinforced cement composites /". Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136091361&sid=7&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Texto completo
12
Shang, Qinjiang. "Shear Behaviour of Engineered Cement-based Composites". Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1201.
Texto completo
13
Ding, Zhu. "Research of magnesium phosphosilicate cement /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20DING.
Texto completo
14
Lota, Jasbir Singh. "The hydration of class G oilwell cement". Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/7438.
Texto completo
15
Li, Xiangyu. "Rheological aspects and thermal behaviors of extruded panels /". View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20LIX.
Texto completo
16
Peterson, Vanessa Kate. "Diffraction investigations of cement clinker and tricalcium silicate using Rietveld analysis /". Electronic version, 2003. http://adt.lib.uts.edu.au/public/adt-NTSM20040830.173127/index.html.
Texto completoResumen
Thesis (Ph. D.)--University of Technology, Sydney, 2003."Submited for the degree of Doctor of Philosophy, University of Technology, Sydney, Dept. of Chemistry, Materials and Forensic Sciences, August 2003" Bibliographic references: leaves 224-232.
17
Kenai, Said. "Properties of cement composites reinforced with geotextile meshes". Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235667.
Texto completo
18
Richardson, I. G. "The microstructure and composition of hardened cement pastes". Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302868.
Texto completo
19
Garvin, Stephen Leslie. "Monitoring the hydration characteristics of cement-based materials". Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/839.
Texto completo
20
Boshoff, William Peter. "Time-dependant behaviour of engineered cement-based composites". Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/341.
Texto completo
21
Tao, Xiaoya. "Pull-out behaviour of steel reinforced cement composites". Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343924.
Texto completo
22
Boroujeni, Nariman Mansouri. "Monetite Cement Composites for Orthopedic and Dental Applications". University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1341378401.
Texto completo
23
Boughanem, Souhad. "Aspects of the behaviour of engineered cement composites". Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/808936/.
Texto completoResumen
Engineered Cement Composite (ECC) materials have the potential to be used in civil engineering applications where a level of pseudo-ductility is required. Of particular interest is the possibility of eliminating the steel from reinforced cementitious structures ensuring that no long-term corrosion exists, which is especially relevant for hydraulic tunnels. Uncertainties remain, however, with regard to the mechanical performance, physical properties, durability and shrinkage of these materials, especially when they are used in thick sections for large scale engineering structures. The current work has studied ECCs in this light. The physical properties such as density, porosity and fibre dispersion and orientation are also of interest: this forms the classic materials engineering triangle of the links between material composition and manufacturing process, the microstructure and mechanical properties. A cementitious matrix, reinforced with polymeric fibres, has been manufactured using two different processes and fibre types. Specimens have been tested in tension and flexure, and multiple matrix cracking has been observed, which leads to a pseudo-ductile behaviour. Enhanced mechanical performance in tension is in line with a greater fibre alignment and higher levels of porosity do not necessarily lead to a loss of pseudo-ductility. Flexure testing shows a pseudo-ductile behaviour maintained for over three years. The fibre surface coating and the interfacial properties are relatively stable, which is in line with the maintaining of the pseudo-ductility. Theoretical models suggest that the results are in line with the ACK model, particularly for a fibre volume fraction which considers fibre orientation and fibre pull-out is likely to be responsible for the pseudo-ductile behaviour of the material. ECC materials tend to exhibit a high shrinkage on cure; this could result in cracking, which could compromise the longevity of structures. Methods for controlling shrinkage include the controlling of the environment and use of additives such as powder micro-silica.
24
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.
Texto completoResumen
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.
25
Tolloczko, J. J. A. "Time dependent properties of heat cycled slag cement concretes". Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376503.
Texto completo
26
Tsoi, Wa Yeung. "Constitutive model development for lightly cemented scrap rubber tire chips /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20TSOI.
Texto completo
27
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.
Texto completoResumen
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.
28
Ilyas, Muhammad. "Development of nano-graphene cementitious composites (NGCC)". Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/15828.
Texto completoResumen
Ordinary Portland cement (OPC) is the main constituent of concrete works as a principal binder for aggregates and intrinsically transmits the brittleness into concrete through the formation of hydration crystals in the cement microstructure. A number of nano cementitious composites were developed in recent years to offset the brittleness with newly discovered nanomaterials and the most prevalent among those is the graphene oxide (GO). The main objective of this PhD research work is to develop nano graphene cementitious composites (NGCC) using low cost, two dimensional (2D) graphene nanoplatelets (GNPs) and one dimensional (1D) graphited carbon nanofibres (GCNFs) with unique conical surface morphology. The GNPs were sourced synthesised in an environmental friendly way via plasma exfoliation whereas, GCNFs were manufactured through catalytic vapour grown method. The project further investigated the effect of these nanomaterials in regulating the distinctive microstructure of cement matrix leading to enhance its mechanical properties. Three different types of high-performance NGCC namely NGCC-Dot, NGCC-Fnt and NGCC-CNF, are developed by activating pristine GNPs (G-Dot), functionalised GNPs (G-Fnt) and graphited nanofibers (G-CNFs) into the cement matrix respectively. It is found through various characterization and experimental techniques that both GNPs and GCNFs regulated the cement microstructure and influenced the mechanical properties of NGCC uniquely. A remarkable increase in the flexural and the tensile strength of newly developed NGCC has been achieved and that could be attributed to the formation of distinctive microstructure regulated by catalytic activation of these nanomaterials. The shape (1D, 2D) and unique morphology of these nanomaterials played a vital role in the mechanism of crystal formation to regulate the cement microstructure. Based on the observations of test results and comprehensive characterization, the possible mechanisms of crystal formation and development of distinctive microstructure of NGCC has been established which has then proceeded to the development of a physical model for NGCC development.
29
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.
Texto completo
30
Buckley, Patrick Joseph. "Mechanical properties of polymethyl methacrylate cement and bone composites". Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394589.
Texto completo
31
Tasong, William Ajua. "Geotechnical controls on aggregate-cement paste interfacial zone in concrete". Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252048.
Texto completo
32
Zhou, Xiangming. "Rheological behaviors of the fresh SFRCC extrudate : experimental, theoretical and numerical investigations /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20ZHOU.
Texto completo
33
Palos, Artemio. "Mechanical Properties of Polymer Modified Mortar". Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc3173/.
Texto completoResumen
The mechanical properties of the polymer-modified mortar are markedly improved over conventional cement mortar. We utilized recycled ABS in powder form and a polymer latex emulsion, polymer percentage ranges from 0 to 25 percent by polymer/cement ratio were investigated. The mechanical properties investigated were compression strength and adhesion strength. Compression strength effects did not have an impact on adhesion strength. Adhesion strength was calculated with pullout testing apparatus designed by the author. Results indicate that recycled ABS had a lower adhesive strength than the acrylic latex emulsion and the base mortar, but did increase in adhesive strength when mixed with maleic-anhydride. The adhesive strength was investigated for a Fiber Reinforced Polymer (FRP) made of an "E" glass fiber that is a continuous strand roving oriented and pre-tensioned longitudinally in an isopthalic polyester matrix material. The FRP rebar was compared to standard steel rebars, and found that the standard steel corrugated rebar had a higher adhesive strength, due to mechanical interlocking. This was clarified by measurements using a smooth steel rebar. Characterization of the polymer-modified mortar was conducted by pore analysis and scanning electron microscopy. Scanning Electron Microscopy was implemented to view the polymer particles, the cement fibrils formed by the hydration, and to prove Ohama's theory of network structure.
34
Shen, Bin. "Experimental approaches for determining rheological properties of cement-based extrudates /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202003%20SHEN.
Texto completoResumen
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 120-125). Also available in electronic version. Access restricted to campus users.
35
Baroonian, A. "Theoretical and experimental investigation of fibre cement corrugated sheeting under load". Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/843515/.
Texto completoResumen
The experimental performance together with the theoretical predictions of strains and deflections of thin fibre cement corrugated sheets are principally reported in this thesis. Existing theories of tensile behaviour of fibre reinforced cement are reviewed. Asbestos cement and alternative fibre reinforced cement technologies associated with these sheeting materials are discussed. Asbestos cement and polypropylene network reinforced cement corrugated sheeting have been tested under a variety of loading regimes and support conditions. Asbestos-free commercial products have also been tested. Finite element analyses based on the LUSAS system have been used to predict the shape of the uncracked load- deflection curves and deflection and strain profiles of various corrugated sheets with different geometrical profiles. Wetting and drying tests on uncracked asbestos cement and polypropylene network reinforced cement sheets have been carried out and a prediction made using the Lusas program of the warping stresses caused by moisture gradients. A new approach has been developed to predict the load-deflection curves and deflection profiles of semi-cracked and severely cracked polypropylene network reinforced cement sheets under various loading regimes. In this approach, cyclic loading characteristics of the tensile specimens were used to estimate the elastic moduli of the cracked composite for various numbers of cracks at two different load levels. Generally, the theoretical predictions show good agreement with the experimental results for uncracked and cracked sheets and hence the mathematical models could, with confidence, be used to assess the performance of a range of corrugated sheeting with various loading configurations.
36
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.
Texto completo
37
Chanda, S. "The mechanical properties of a pulverised fuel ash blended cement paste". Thesis, University of Surrey, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370690.
Texto completo
38
Molapo, Katiso Tokoloho. "The behaviour of strain-hardening cement composites under biaxial compression". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5242.
Texto completoResumen
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Reinforced concrete is susceptible to cracking. This makes it less durable than it would be had it been crack-free. Ingress of harmful substances into reinforced concrete through cracks – which causes corrosion of steel – is not desirable. This can be mitigated by the use of fibre reinforced-concretes or mortars showing strain hardening properties accompanied by improved ductility and multiple cracking under tensile loading. Such materials are called Strainhardening cementitious composites (SHCC’s). At Stellenbosch University, work has been done in previous years on SHCC to determine its behaviour under various loading conditions. Some of the aspects of the material that have been studied are the behaviour under uni-axial tensile loading, uni-axial compression and shear. The behaviour of SHCC under biaxial stresses was investigated to enable the prediction of the material behaviour under complex stress conditions. Square plate specimens of nominal dimensions 100 x 100 x 20 mm were cast and subjected to biaxial compressive loading at stress path angles of 00, 150, 300 and 450; which were equivalent to vertical/horizontal stress ratios of 0/1, 0.27/1, 0.58/1 and 1/1 respectively, at ages 23 to 33 days. Comparisons were made between specimens tested using steel platens and those tested using Vesconite sheets. Those tested using Vesconite yielded lower failure stresses. Vesconite was used to reduce the retraining effect of the frictional force between the specimens and the steel platens. Poisson’s ratios were calculated for specimens tested using steel and those tested using Vesconite. The values for Vesconite were found to be higher than for steel. Additionally, the values for the uni-axial case were different from those obtained for other stress ratios. This could have been due to the assumption made that plane stress was realised and that Elastic moduli in tension and in compression was the same. The possibility of the existence of a triaxial stress state could render the calculated Poisson’s ratios incorrect. Shear slip type failure accompanied by wedging was observed. Vertical to near diagonal cracks were evident on the front faces of the specimens for the stress path angles of 00 to 450 respectively. The observed crack patterns showed closely spaced multiple micro-cracking on the narrow edges of specimens indicating Strain-hardening behaviour. The stress-strain curves also showed a slight indication of strain-hardening where tensile strains were measured.
AFRIKAANSE OPSOMMING: Gewapende beton is vatbaar vir krake. Dit maak dit minder duursaam as wanneer dit kraak-vry is. Instroming van skadelike stowwe in gewapende beton deur middel van krake - wat korrosie van staal veroorsaak - is nie wenslik nie. Dit kan verbeter word deur die gebruik van veselversterkte beton of mortel wat vervormingsverharding eienskappe toon, vergesel deur verbeterde rekbaarheid en veelvuldige krake onder trekspanning. Sulke materiaal word Strainhardening cementitious composites (SHCC's) genoem. Die Universiteit Stellenbosch, het in vorige jare werk gedoen om SHCC se gedrag te bepaal onder verskillende belastingstoestande. Sommige van die aspekte van die materiaal wat bestudeer is, is gedrag onder uni-aksiale trek, uni-aksiale druk en skuif. Die gedrag van SHCC onder biaksiale spannings is ondersoek om voorspelling van materiaalgedrag onder komplekse spanningstoestande moontlik te maak. Vierkantige plaat monsters van nominale dimensies 100 x 100 x 20 mm is gemaak en aan biaksiale drukkragte onderwerp, met spannningspad hoeke van 00, 150, 300 en 450; wat soortgelyk is aan die horisontale spanning verhoudings van 0/1, 0.27/1, 0.58/1 en 1/1 onderskeidelik, op ouderdomme 23-33 dae. Vergelykings is getref tussen monsters getoets met staal plate en diegene getoets word met Vesconite plate. Die proefstukke getoets met Vesconite het laer falingsspannings opgelewer. Vesconite is gebruik om die uitwerking van die wrywingskrag tussen die monsters en die staal plate te verminder. Poisson se verhouding is bereken vir die staal en Vesconite monsters afsonderlik. Daar is gevind dat die Vesconite waarde hoër was as die vir staal. Daarbenewens het die waardes vir die uni-aksiale geval, verskil van dié vir ander spanningsverhoudings. Dit kan wees as gevolg van die aanname van vlakspanning en dat die Elastiese moduli in druk en in trek dieselfde is. Die moontlikheid van die bestaan van 'n drie-dimensionele spanningstoestand, kan beteken dat die berekende Poisson’s verhoudings onakkuraat is. Skuif-glip tipe faling, vergesel deur vaswigting is waargeneem. Vertikale tot feitlik diagonale krake is duidelik sigbaar op die voorkant van die monsters vir spanningspadhoeke van 0-450 onderskeidelik. Die waargeneemde kraak patrone het nou gespasieerde, veelvuldige mikro-krake op die smal randte van die monsters, wat dui op vervormingsverharding. Die spanningsvervormings kurwes het ook effense aanduidings getoon van die vervormingsverharding waar trekvervorming gemeet is.
39
Thompson, Ian. "Use of steel fibres to reinforce cement bound roadbase". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366364.
Texto completo
40
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/.
Texto completo
41
Swift, D. S. "Bond in cement based composites reinforced with bundles of fibres". Thesis, University of the West of Scotland, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380267.
Texto completo
42
ANJOS, MARCOS ALYSSANDRO SOARES DOS. "PULP REINFORCED CEMENT-BASED COMPOSITES: PHYSICAL, MECHANICAL AND MICROSTRUCTURES CHARACTERIZATION". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2753@1.
Texto completoResumen
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORAinda hoje, no Brasil, o fibrocimento à base de matriz cimentícia reforçados com amianto permanecem como o principal compósito fibroso utilizado em larga escala de produção, apesar da constatação dos seus malefícios, como doenças respiratórias e câncer, causados por esta fibra durante o processo de extração, fabricação e instalação. Nos EUA, União Européia e Canadá a produção de materiais reforçados com amianto foi proibida ou sofreu sérias restrições ao seu uso. No Brasil há uma promessa do governo federal de se iniciar a diminuição da extração do amianto a partir de 2005 até sua completa extinção. Frente a inadequação do uso do amianto para produção de materiais de construção sem riscos à saúde da sociedade, surge a necessidade de se encontrar um substituto com propriedades físicas e mecânicas adequadas que seja ecológico e de custo adequado. Neste trabalho é analisado o uso de polpas celulósicas de bambu, com dois estágios de tratamento diferentes, quais sejam polpas antes do processo de refino e após este processo, para reforço de matrizes cimentícias, utilizando o processo de produção Hatschek em escala laboratorial. As polpas celulósicas foram utilizadas nas porcentagens de 4, 6, 8, 10, 12, 14 e 16% em relação a massa do cimento, sendo utilizada a matriz plena como referência. Foi estudado ainda a substituição parcial do cimento por um resíduo de fábrica de tijolos na proporção de 20, 30 e 40% em relação a massa do cimento e o uso de dois tipos de equipamentos de produção diferentes. O objetivo deste trabalho é determinar a porcentagem ideal de reforço para os dois tipos de polpas utilizadas, discutindo as propriedades físicas, mecânicas e microestruturais de cada um destes compósitos.
Still today, in Brazil, the fibre cement to the base amianthus is the main fibrous composite to the base of main cement with wide production scale, despite verification of its damages, as breathing diseases and cancer, caused by this fiber during the extraction process, production and installation. In the USA, European Union and Canada the production of materials to the base of amianthus are prohibited or they suffered serious restrictions. In Brazil, the federal government wile begin to extinguish the amianthus extraction in 2005 due to the problems used for amianthus writer allow, it is necessary to get a new material with appropriate physical and mechanical properties, that is ecofriendly and of appropriate cost. In this work the use of pulps bamboo cellulose`s is analyzed, with two types of treatment, which are pulps before the process of I refine and after this process, for reinforcement of main cimentícias, using the production process Hatschek in scale laboratories. The pulps cellulose`s was used in the percentages of 4, 6, 8, 10, 12, 14 and 16% in relation to mass of the cement, being used the full head office as reference. In addition, it was substitution of the cement by a residue of the it manufactures of bricks in the proportion of 20, 30 and 40% in relation to mass of the cement and two types of equipment of different production. The aim of this work is to determine the ideal percentage of reinforcement for the two used types of pulps used, discussing the physical properties, mechanics and microstructure of each one of these composites.
43
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.
Texto completoResumen
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.
44
De, Klerk Marthinus David. "The durability of natural sisal fibre reinforced cement-based composites". Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96895.
Texto completoResumen
Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The building industry is responsible for a substantial contribution to pollution. The production of building materials, as well as the operation and maintenance of structures leads to large amounts of carbon-dioxide (CO2) being release in the atmosphere. The use of renewable resources and construction materials is just one of the ways in which the carbon footprint of the building industry can be reduced. Sisal fibre is one such renewable material. Sisal fibre is a natural fibre from the Agave Sisalana plant. The possibility of incorporating sisal fibre in a cement-based matrix to replace conventional steel and synthetic fibres has been brought to the attention of researchers. Sisal fibre has a high tensile strength in excess of polypropylene fibre and comparable to PVA fibre. Sisal fibre consists mainly of cellulose, hemi-cellulose and lignin. The disadvantage of incorporating sisal fibre in a cement-based matrix is the degradation of the composite. Sisal fibres tend to degrade in an alkaline environment due to changes in the morphology of the fibre. The pore water in a cement base matrix is highly alkaline which leads to the degradation of the fibres and reduced strength of the composite over time. Sisal fibre reinforced cement-based composites (SFRCC) were investigated to evaluate the durability of the composites. Two chemical treatments, alkaline treatment and acetylation, were performed on the fibre at different concentrations to improve the resistance of the fibre to alkaline attack. Alkaline treatment was performed by using sodium hydroxide (NaOH), while acetylation was performed by using acetic acid or acetic anhydride. Single fibre pull-out (SFP) tests were performed to evaluate the influence of chemical treatment on fibre strength, to study the fibre-matrix interaction and to determine a critical fibre length. A matrix consisting of ordinary Portland cement (OPC), sand and water were used for the SFP tests. This matrix, as well as alternative matrices containing fly ash (FA) and condensed silica fume (CSF) as supplementary cementitious material, were reinforced with 1% sisal fibre (by volume) cut to a length of 20 mm. The OPC matrix was reinforced with untreated- and treated fibre while the alternative matrices were reinforced with untreated fibre. Alternative matrices containing varying fibre volumes and lengths were also produced. Three-point bending- (indirect), direct tensile- and compression tests were performed on specimens at an age of 28 days to determine the strength of the matrix. The remainder of the specimens were subjected to ageing by extended curing in water at 24˚C and 70˚C respectively and by alternate cycles of wetting and drying, after which it was tested at an age of 90 days from production to evaluate the durability of the fibre. An increase in fibre volume led to a decrease in compressive strength and peak tensile strength. The optimum fibre length at a volume of 1% was 20 mm for which the highest compression strength was recorded. The combination of alkali treatment and acetylation was the most effective treatment condition, followed by alkali treatment at low concentrations of sodium hydroxide. At higher concentrations of sodium hydroxide, a significant reduction in strength was recorded. The addition of supplementary cementitious materials also proved to be effective in mitigating degradation, especially in the cases where CSF was used. FA proved to be less effective in reducing the alkalinity of the matrix. However, the use of FA as fine filler resulted in higher strengths. Specimens manufactured by extrusion did not have superior mechanical properties to cast specimens. The conclusion was made that the use of sisal fibre in a cement-based matrix is effective in providing ductile failure. Chemical treatment and the addition of supplementary cementitious materials did improve the durability of the specimens, although degradation still took place.
AFRIKAANSE OPSOMMING: Die boubedryf is verantwoordelik vir 'n aansienlike bydrae tot besoedeling. Die produksie van boumateriale, sowel as die bedryf en instandhouding van strukture lei tot groot hoeveelhede koolstof dioksied (CO2) wat in die atmosfeer vrygestel word. Die gebruik van hernubare hulpbronne en boumateriale is maar net een van die maniere waarop die koolstof voetspoor van die boubedryf verminder kan word. Sisal vesels is 'n voorbeeld van 'n hernubare materiaal. Sisal vesel is 'n natuurlike vesel afkomstig vanaf die Agave Sisalana plant. Die moontlikheid om sisal vesels in 'n sement gebasseerde matriks te gebruik om konvensionele staal en sintetiese vesels te vervang, is tot die aandag van navorsers gebring. Sisal vesel het 'n hoër treksterkte as polipropileen vesels en die treksterkte vergelyk goed met die van PVA vesels. Sisal vesel bestaan hoofsaaklik uit sellulose, hemi-sellulose en lignien. Die nadeel verbonde aan die gebruik van sisal vesels in 'n sement gebasseerde matriks is die degradasie van die komposiet. Sisal vesels is geneig om af te breek in 'n alkaliese omgewing as gevolg van veranderinge wat in die morfologie van die vesel plaasvind. Die water in die porieë van 'n sement gebasseerde matriks is hoogs alkalies wat lei daartoe dat die vesel afgebreek word en die sterkte van die komposiet afneem oor tyd. Sisal vesel versterkte sement gebasseerde komposiete is ondersoek om die duursaamheid van die komposiete te evalueer. Twee chemiese behandelings, alkaliese behandeling en asetilering, is uitgevoer op die vesels teen verskillende konsentrasies om die weerstand van die vesels teen alkaliese aanslag te verbeter. Alkaliese behandeling was uitgevoer met natrium-hidroksied (NaOH) terwyl asetilering met asynsuur en asynsuurhidried uitgevoer is. Enkel vesel uittrek toetse is uitgevoer om die invloed van chemiese behandeling op veselsterkte te evalueer, om die vesel/matriks interaksie te bestudeer en om die kritiese vesellengte te bepaal. 'n Matriks wat uit gewone Portland sement (OPC), sand en water bestaan, is gebruik vir die enkel vesel uittrek toetse. Dieselfde matriks, sowel as alternatiewe matrikse wat vliegas (FA) en gekondenseerde silika dampe (CSF) as aanvullende sementagtige materiaal bevat, is versterk met 1% vesel (by volume) wat 20 mm lank gesny is. Die OPC matriks was versterk met onbehandelde- en behandelde vesels, terwyl die alternatiewe matrikse met onbehandelde vesels versterk is. Matrikse wat wisselende vesel volumes en lengtes bevat het is ook vervaardig. Drie-punt buigtoetse (indirek), direkte trek toetse en druktoetse is uitgevoer op proefstukke teen 'n ouderdom van 28 dae om die sterkte van die matriks te bepaal. Die oorblywende proefstukke is onderwerp aan veroudering deur verlengde nabehandeling in water teen 24˚C en 70˚C onderskeidelik en deur afwissilende siklusse van nat- en droogmaak waarna dit op 'n ouderdom van 90 dae vanaf vervaardiging getoets is om die duursaamheid van die matriks te evalueer. 'n Toename in vesel volume het tot 'n afname in druksterkte en piek treksterkte gelei. Die optimum vesel lengte teen 'n volume van 1% was 20 mm, waarvoor die hoogste druksterkte opgeteken is. Die kombinasie van alkaliese behandeling en asetilering was die mees effektiewe behandeling, gevolg deur alkaliese behandeling by lae konsentrasies natrium-hidroksied. Vir hoë konsentrasies natrium-hidroksied is 'n aansienlike afname in sterkte opgeteken. Die toevoeging van aanvullende sementagtige materiale was ook effektief om die degradadering van die vesels te verminder, veral in die gevalle waar CSF gebruik is. FA was minder effektief om die alkaliniteit van die matriks te verminder. Die gebruik van FA as fyn vuller het nietemin hoër sterkte tot gevolg gehad. Proefstukke wat deur ekstrusie vervaardig is, het nie beter meganiese eienskappe gehad as proefstukke wat gegiet is nie. Daar is tot die gevolgtrekking gekom dat sisal vesel in 'n sement gebasseerde matriks wel effektief is om 'n duktiele falingsmode te voorsien. Chemiese behandeling en die toevoeging van aanvullende sementagtige materiale het die duursaamheid van die proefstukke verbeter, alhoewel degradering steeds plaasgevind het.
45
Smith, McDonald William. "Cement compatible materials with potential application in the immobilisation of toxic wastes". Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387809.
Texto completoResumen
Cements and cement-based systems have excellent potential as immobilising matrices for toxic inorganic wastes. This potential is a result of the unique chemical and physical mechanisms which operate on particular waste species to prevent their release into ground waters. These mechanisms are reviewed in this thesis. Some wastes are suitable for direct cementing, such as waste streams form nuclear fuel reprocessing, where cement technology is applied. Other wastes are less well characterised and may be unsuitable for direct cementing. This often arises because waste species concentrations are higher than maximum permissable levels, but are still too dilute for economical cementing. In such cases, a preconcentration step prior to cementing is the favoured strategy. Arsenic and lead wastes present an additional challenge because they are expected to exist as soluble oxyanions under alkaline pore fluid conditions. Both arsenic and lead have also been shown to affect setting characteristics by interfering with normal cement hydration reactions. The materials studied in this thesis were chosen because of their known, or suspected, potential as anion exchangers. It may be possible to preconcentrate arsenic or lead in the anion exchanging solid before incorporation into cement. A further advantage of this method is that an additional barrier against re-release of the toxic species is created. The aim of this project was to determine the uptake capacity of different ion exchanging materials which are compatible with cement systems for hazardous oxyanion species. Three types of material were studied, hydrotalcite (a clay mineral), thaumastic (a phase which is isostructural to ettringite) and phosphate-modified zeolites (a new type of material derived from zeolites). The first two are known to occur in cements, the last is rather an unknown quantity, but many zeolites have been shown to be compatible with cement environments.
46
Chan, James. "The development of magnesium oxychloride cement as repairing materials /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20CHANJ.
Texto completo
47
Yilmaz, Veysel Turan. "Interactions between portland cement and sulphonated melamine formaldehyde superplasticizer and inorganic glass fibre". Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602281.
Texto completoResumen
In Part I of the thesis the effect oif sulphonated melamine formaldehyde (SMF) superplasticizer on the hydration, microstructure and internal chemistry of ordinary Portland cement, as well as on individual pure cement clinker components such as tricalcium aluminate (C3A) was investigated. Conduction calorimetry, thermal analysis, X-ray diffractometry, scanning electron microscopy and pore fluid extraction techniques were used. In order to determine SMF content of the cement pore fluids, it was necessary to develop a new analytical method for SMF. Because of high pH of cement pore fluids the conventional U.V. method was found to be inapplicable. Therefore a new method based on spectrofluorometry was developed; it can be used up to a. pH of about 10, and neutralization can be made using HN03 solution. The role of SMF during cement hydration was further assessed using the method. The results showed that C3A phase of Portland cement adsorbed large amounts of SMF superplasticizers from the aqueous phase of C3A-gypsum mixes in the first few minutes of hydration. In Part II of the thesis, chemical interactions between alkali-resistant (AR) glass fibres and cement matrices was studied. The effect of silica fume additions on the interactions were also investigated. The results of the present work suggest that there are a number of points to be clarified, concerning the use of superplasticizers and AR-glass fibres in cement. The future work to be carried out on superplasticizers may be divided into several groups such as alkali-silica reaction, corrosion of reinforcing steel and durability aspects. Superplasticizers are normally employed as sodium salts. It is evident that addition of superplasticizers into ordinary Portland cement increases the Na+ content of pore solution as well as its pH. Therefore, the rate of alkali-silica reaction may be enhanced due to the increasing pH of cement matrices. Superplasticizers are currently used for the placement of concrete in heavily steel-reinforced structures. The alkaline nature of concrete matrices provides excellent protection for steel reinforcement. However, carbonation of the concrete lowers the pH of the matrix. On the other hand, penetration of aggressive species such as Cl- ions from the sea or other sources accelerates the corrosion of steel reinforcement. There is as yet no detailed study on the chemical behaviour of superplasticizers in chloride- bearing concretes, especially, in relation to their effect on steel reinforcement corrosion kinetics. Superplasticizers greatly influence the morphology of cement hydration products, mainly calcium hydroxide. There is controversy as to whether calcium hydroxide crystals formed in cement paste make a positive or negative contribution to the strength development of cement pastes. In addition, the effect of the presence of thin calcium hydroxide crystals on the durability and long-term properties of cement pastes is not yet known. Zr02-containing commercial AR-glass fibres show poor durability characteristics in a Portland cement matrix, cured in a humid environment, although the deterioration of zirconia glass is much slower than that of ordinary glass. Attack on the fibres is attributed to both the high alkalinity of Portland cement matrices and the growth of hydration products, mainly calcium hydroxide. One solution to these problems seems to be to reduce both the alkalinity and the calcium hydroxide content of cement pastes. Pozzolanic materials such as silica fume, fly ash, slag etc. are very effective in reducing both the pH and the calcium hydroxide content of cement pastes. From the results presented in this thesis, the highly brittle nature of cement pastes with silica fume leads to a decrease in flexural strengths of AR-GFRC composites, although it improves the durability of composites to some extent. The use of other pozzolans, for example, fly ash and slag have not received much attention. Another possibility is the use of less alkaline cement matrices to decrease the chemical attack on AR-glass fibres. In addition to changing composition of cement matrices, the covering of the surface of original glass fibres by alkali- resistant organic or inorganic materials may protect the glass from chemical attack and slow down the corrosion process. Investigations on more alkali-resistant glass compositions may,- also result in the manufacturing of new types of glass fibres.
48
Joshua, Nilmini Sureka. "Novel phosphate bonding composites /". View thesis, 1997. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030828.115030/index.html.
Texto completo
49
Kim, Hong-Youl. "PMMA bone cement reinforced by plasma treated particles /". free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841158.
Texto completo
50
Sarandily, A. "High strength autoclaved cementitious matrices and steel fibre reinforced composites". Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374519.
Texto completo