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Downie, Brian. "Effect of moisture and temperature on the mechanical properties of concrete." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4240.
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Thesis (Ph. D.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains viii, 112 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 93-95).
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William, Gergis W. "Effect of temperature variations on premature cracking of dowel jointed concrete pavements." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3015.
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Thesis (Ph. D.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains viii, 139 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 123-139).
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廖智豪 and Chi-ho Timothy Liu. "Investigation of temperature distribution in highway bridges." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B31207364.
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Ding, S., S. Dong, Ashraf F. Ashour, and B. Han. "Development of sensing concrete: principles, properties and its applications." AIP publishing, 2019. http://hdl.handle.net/10454/17523.
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YesSensing concrete has the capability to sense its condition and environmental changes, including stress (or force), strain (or deformation), crack, damage, temperature and humidity through incorporating functional fillers. Sensing concrete has recently attracted major research interests, aiming to produce smart infrastructures with elegantly integrated health monitoring abilities. In addition to having highly improved mechanical properties, sensing concrete has multifunctional properties, such as improved ductility, durability, resistance to impact, and most importantly self-health monitoring due to its electrical conductivity capability, allowing damage detection without the need of an external grid of sensors. This tutorial will provide an overview of sensing concrete, with attentions to its principles, properties, and applications. It concludes with an outline of some future opportunities and challenges in the application of sensing concrete in construction industry.
National Science Foundation of China (51978127 and 51908103), the China Postdoctoral Science Fundation (2019M651116) and the Fundamental Research Funds for the Central Universities in China (DUT18GJ203).
National Science Foundation of China (NSFC) (Nos. 51978127 and 51908103), the China Postdoctoral Science Foundation (No. 2019M651116), and the Fundamental Research Funds for the Central Universities in China (No. DUT18GJ203).
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Rouhani, Siamak. "Temperature analyses of Concrete Frame Bridges with Finite Elements." Thesis, KTH, Bro- och stålbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145904.
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FE-modeling is a rapidly spreading method to analyze structures nowadays. With this theunderstanding of the outcome is of very high importance and potential inaccuracies areimportant to find so that faulty and over dimensioning of the structure does not occur whichleads to unnecessary costs. One of these inaccuracies is the unrealistic sectional forces that occurdue to thermal effects in the transversal direction for concrete frame bridges which leads to anexcessive amount much reinforcement in the structure than actually needed. This has beenstudied with several cases by using two approaches on how to apply the temperature in the framebridge, only in the superstructure and in the whole structure, but also by analyzing severalboundary conditions. By examining the results for the sectional forces and stresses one of thetemperature approaches could be disregarded because of the extreme values in the transitionbetween superstructure and support. But the other approach was much more useful because ofits better compliance with reality. With these results and by calculating the reinforcement neededfor the worst case, one model has been found to be the most favorable and can be used whenmodeling concrete frame bridges with acceptable outcome. The study resulted in a model whereone applies a varying temperature on the whole structure, with spring boundary conditions over asurface that represents the bottom slab.
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Benjamin, Sylvia Ella. "The effect of temperature on the pitting corrosion of Swedish Iron in OPC mortars." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290331.
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Rojas, Edyson. "Uniform Temperature Predictions and Temperature Gradient Effects on I-Girder and Box Girder Concrete Bridges." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/2193.
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In order to more accurately quantify the behavior and degradation of bridges throughout their service life, the Federal Highway Administration lunched the Long-Term Bridge Performance Program. As part of this program an I-girder, integral abutment bridge near Perry, Utah and a two span, box-girder bridge south of Sacramento, California were instrumented with foil strain gauges, velocity transducers, vibrating wire strain gauges, thermocouples, and tiltmeters.
In this research study, data from the thermocouples was used to calculate average bridge temperature and compare it to the recommended design criteria in accordance to the 2010 LRFD Bridge Design Specifications of the American Association of State Highway and Transportation Officials (AASHTO). The design maximum average bridge temperature defined in the 2010 LRFD Bridge Design Specifications was exceeded for both bridges. The accuracy of the 1991 Kuppa Method and the 1976 Black and Emerson Method to estimate the average bridge
temperature based on ambient temperature was studied and a new method that was found to be more accurate was proposed. Long-term predictions of average bridge temperature for both bridges were calculated. Temperature gradients were measured and compared to the 2010 AASHTO LRFD Bridge Design Specifications and the 1978 Priestley Method. Calculated flexural stresses as a function of maximum positive and negative temperature gradients were found to exceed the service limit state established in the 2010 AASHTO LRFD Bridge Design Specifications in the case of the California bridge.
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Goldsberry, Benjamin M. "Thermal effect curling of concrete pavements on U.S. 23 test road (DEL 23-17.28." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1176832475.
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McDonald, Hazel A. "Monitoring, interpreting and predicting temperature effects in concrete box girder bridges." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248559.
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Pati, Ardeep Ranjan. "Effects of Rebar Temperature and Water to Cement Ratio on Rebar-Concrete Bond Strength of Concrete Containing Fly Ash." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc28460/.
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This research presents the results on an experimental investigation to identify the effects of rebar temperature, fly ash and water to cement ratio on concrete porosity in continuously reinforced concrete pavements (CRCP). Samples were cast and analyzed using pullout tests. Water to cement ratio (w/c) and rebar temperature had a significant influence on the rebar-concrete bond strength. The 28-day shear strength measurements showed an increase in rebar-concrete bond strength as the water to cement ratio (w/c) was reduced from 0.50 to 0.40 for both fly ash containing and non fly ash control samples. There was a reduction in the peak pullout load as the rebar surface temperature increased from 77o F to 150o F for the cast samples. A heated rebar experiment was performed simulating a rebar exposed to hot summer days and the rebar cooling curves were plotted for the rebar temperatures of 180o F - 120o F. Fourier transform infrared spectroscopy was performed to show the moisture content of cement samples at the rebar-concrete interface. Mercury intrusion porosimetry test results on one batch of samples were used for pore size distribution analysis. An in-depth analysis of the morphological characteristics of the rebar-concrete interface and the observation of pores using the scanning electron microscope (SEM) was done.
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Kashyap, Anusha Venkitachalam. "Effects of water chemistry, temperature, gaseous cavitation & phosphate inhibitors on concrete corrosion." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35788.
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Concrete corrosion has serious societal and economic impacts and is an important concern in a utilityâ s overall corrosion control strategy. Though concrete based pipes and linings are only restricted to the distribution mains, they still make up a large percentage of the drinking water infrastructure at about 17% of its total length. An improved understanding of the corrosion mechanisms involved steps that can be taken to mitigate concrete corrosion are very important. This study examined the role of phosphate chemicals, water chemistry, temperature and gaseous cavitation on the degradation of cement-based pipes and linings. It also provides information for utilities to make informed decisions regarding the use, effectiveness, and application of phosphate corrosion inhibitors relative to concrete corrosion control.
Under low alkalinity and low pH conditions, considered to be highly aggressive in the literature, we noticed very substantial corrosion of concrete in laboratory experiments. At high pH and high alkalinity conditions, the buildup of scale (e.g., calcium carbonate) on the inside of the pipe is the major concern. The addition of phosphate inhibitors strongly influenced both concrete corrosion and scaling. At low alkalinity the addition of zinc orthophosphate or polyphosphate reduced corrosion of concrete. The addition of orthophosphate under low alkalinity conditions increased aluminum leaching and could push aluminum concentrations above the EPA SMCL threshold. At high alkalinity conditions the addition of orthophosphate is highly effective at reducing scaling, and aluminum leaching was not a concern.
The presence of high concentrations of magnesium and silicon could form magnesium aluminum oxyhydroxides and magnesium silicates which could act as a protective scale on the concrete surface. However, this precipitate forms only at pH values above 9.5. The effectiveness of this protective scale in reducing corrosion of concrete was not established unambiguously in this research. Temperature plays a key role in corrosion of concrete. Calcite solubility increases at lower temperatures however at higher temperatures corrosion of concrete increases, which implies that corrosion of concrete is not driven by calcite solubility. At higher alkalinities scaling of concrete is higher at lower temperatures. This indicates that calcite solubility controls scaling of concrete at higher alkalinities. Tests with gaseous cavitation indicate that corrosion of concrete does not increase in the presence of gaseous cavitation. Vaporous cavitation is more detrimental to concrete than gaseous cavitation.
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Mansour, Marwan. "Experimental tests on the effect of temperature on the short term behavior of FRC beams." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The effect of temperature under short term behavior on macro-synthetic polypropylene fibers reinforced concrete (MSFRC) was evaluated, to understand how this condition may affect the performance of this material. An experimental campaign of three-point bending, compressive tests and elastic modulus tests have been performed on prisms, cubes and cylinders cured at 6 temperatures, ranging from -30°C to +60°C. The results highlighted that, for the material tested, the increment of temperature causes a decrement of the peak and post-peak flexural strength. Further analysis have been done on the fibers number and failure type.
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Bardella, Paulo Sergio. "Avaliação das propriedades fisicas e mecanicas de concretos produzidos com os cimentos Portland de alta resistencia inicial e de alto-forno aditivados com silica ativa curados termicamente." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257816.
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Orientador: Gladis CamariniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-05T12:07:39Z (GMT). No. of bitstreams: 1 Bardella_PauloSergio_M.pdf: 1317917 bytes, checksum: 2bd53842fd42fd70b176488c91fedd8f (MD5) Previous issue date: 2005
Resumo: A durabilidade das estruturas de concreto depende da estrutura porosa e da impermeabilidade do concreto, uma vez que a entrada de água e de agentes deletérios iniciam os processos patológicos que diminuem a vida útil de uma estrutura de concreto. Dessa forma, o objetivo deste trabalho foi avaliar a resistência mecânica, permeabilidade, absorção e carbonatação natural de concretos submetidos a diferentes condições de cura. Os procedimentos de cura adotados são normalmente utilizadds em canteiros de obra e na produção de estruturas pré-moldadas de concreto: cura imersa até a idade de 7 dias, cura ambiente e cura térmica. A cura térmica foi realizada na temperatura de 60°C. Foram empregados concretos produzidos com cimento Portland de Alta Resistência Inicial (CP V ARI) e cimento Portland de Alto Forno (CP III) sem e com sílica ativa (em substituição ao cimento na proporção de 10% em massa) para cada um dos diferentes tipos de cura utilizados. Os resultados evidenciaram que o tipo de cura afeta o desempenho do concreto. A mudança do tipo de cura aplicada proporcionou variações nas propriedades mecânicas e na durabilidade dos concretos, principalmente no que diz respeito à sua estrutura porosa. Assim, um regime de cura adequado é essencial para garantir a resistência mecânica e a durabilidade dos concretos. A utilização de sílica ativa em substituição ao cimento melhorou o desempenho dos concretos, tanto para a resistência mecânica quanto para a durabilidade, independente do tipo de cura empregado
Abstract: The durability of concrete structures depends on porous structure and its impermeability. The entrance of water and deleterious agents begin the damage processes and reduce the life of the concretestructure. ln that way, the aim of this work was to evaluate the mechanical resistance, permeability, absorption and natural carbonation of concretes submitted to different curing procedures. The curing procedures adopted were usually used in civil construction and in the production of precast structures: moist curing until the age 6f 7 days, curing in air, and steam curing. The maximum temperature of steam curing was 60°C. All concretes were produced with High Early Strength Portland cement (CP V ARl) and Blastfurnace Portland cement (CP TIl) without and with silica fume (10% of replacement, by mass, of Portland cement) for each one of the different curing procedure used. The results showed that the curing procedure affects the concrete performance, providing variations in their mechanical properties and in their durability, mainly in porous structure. Therefore, the curing process used is essential to guarantee the mechanical resistance and the durability of the concretes. The use of silica fume improved the performance of the concretes, as for the mechanical resistance as for its durability, independent of the curing procedure used.
Mestrado
Edificações
Mestre em Engenharia Civil
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Østvik, Jan-Magnus. "Thermal aspects of corrosion of steel in concrete : effect of low temperature on the resistivity and the cathodic reaction rate." Doctoral thesis, Norwegian University of Science and Technology, Department of Structural Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1815.
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Andersson, Oskar, and Max Seppälä. "Verification of the response of a concrete arch dam subjected to seasonal temperature variations." Thesis, KTH, Betongbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169917.
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Many dams existing today were constructed around fifty years ago. Condition monitoring is essential for maintaining high safety and determining the current level of safety and stability for these dams. There is a need for new monitoring techniques and finite element coupled monitoring could be one of these techniques. A concrete arch dam located in Sweden is modelled and calibrated with respect to concrete temperature measurements. The temperature distribution is then defined as a prescribed strain in a structural mechanical model in which a parametric study is performed. The results from the parametric study are compared to measurements of the crest deformation and a combination of parameters is found giving the lowest difference between measurements and model results for the mid-section. The results show that the finite element model can be used to predict the behavior of the dam with acceptable deviation. The parametric study indicates that the reference temperature of the concrete has little effect on the amplitude of the deformation and that the governing factor is the coefficient of thermal expansion.Många av de dammar som finns idag byggdes för omkring femtio år sedan. Tillståndsövervakning är avgörande för att kunna bestämma nivån av säkerhet och stabilitet för dessa dammar. Det finns ett behov av ny övervakningsteknik och finita element-kopplad övervakning kan vara en av dessa tekniker. En betongvalvdamm modelleras och kalibreras med avseende på uppmätt betongtemperatur. Den beräknade temperaturfördelningen definieras sedan som en föreskriven töjning en strukturmekanisk modell i vilken en parametrisk studie utförs. Resultaten från parameterstudien jämförs med mätningar av kröndeformation och en kombination av parametrar identifieras som ger lägsta skillnad mellan mätningar och modellresultat för mittsektionen. Resultaten visar att modellen kan användas för att förutsäga dammens beteende med acceptabel avvikelse. Parameterstudien indikerar att referenstemperaturen för betongen har liten inverkan på amplituden för deformationen och att den styrande faktorn är längdutvidgningskoefficienten.
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DONG, XUHUA. "TRAFFIC FORCES AND TEMPERATURE EFFECTS ON SHEAR KEY CONNECTIONS FOR ADJACENT BOX GIRDER BRIDGE." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1016553463.
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El-Zaroug, Omer Ramadan. "Behavior of FRP reinforced and partially prestressed concrete members under the effects of temperature gradients." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/MQ47819.pdf.
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Nguyen, Nhan Hoa. "Dégradation du béton armé sous actions sévères : Etude du comportement résiduel de l’adhérence à l’aide de la technique d’émission acoustique." Thesis, Rennes, INSA, 2014. http://www.theses.fr/2014ISAR0019.
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De nos jours, le béton est le matériau de construction le plus utilisé dans le monde en raison de ses performances mécaniques, sa facilité de mise en oeuvre, son coût compétitif et sa « recyclabilité ». Toutefois, compte tenu de son caractère fragile en terme mécanique et de sa faible résistance à la traction, il est souvent renforcé par des armatures métalliques qui lui confèrent une bonne ténacité et une meilleure aptitude à supporter les efforts de traction. Ce composite béton-armature ne peut cependant assurer efficacement son rôle que si les deux composants sont étroitement liés l’un à l’autre. C’est donc dans la qualité de l’adhérence que réside l’efficacité du transfert des efforts entre les deux matériaux. Or, dès la mise en place des ouvrages en béton armé et pendant toute la durée de leur exploitation, différentes actions et agents agresseurs peuvent modifier la qualité de cette adhérence. Il peut s’agir de phénomènes naturels comme le gel/dégel et l’action du dioxyde de carbone atmosphérique, ou des sollicitations accidentelles comme l’incendie ou encore l’action de certains agents spécifiques comme les chlorures et les sulfates. Notre objectif dans cette thèse est de qualifier les modifications d’adhérence qui résultent de quatre types de sollicitations couramment rencontrées dans la vie des ouvrages en béton armé: l’effet des températures élevées, l’effet de la carbonatation, l’effet des cycles gel/dégel, l’effet de la corrosion. Nous évaluons la qualité de l’adhérence par la mesure de la résistance à l’arrachement et par l’analyse du comportement résiduel sous sollicitation mécanique. La technique d’émission acoustique est utilisée pour localiser en temps réel, l’endommagement du matériau sous sollicitation. Les applications de notre étude concernent non seulement les armatures et inserts classiques du béton armé mais aussi les nombreux dispositifs constructifs des structures mixtes acier – béton qui utilisent les liaisons par goujons pour relier les deux matériauxNowadays, concrete is the most used construction material in the world because of its mechanical performances, its ability to be molded or cast, its competitive cost and its recyclability. However, concrete has a low ductility and a relatively low tensile strength compared to other construction materials. Therefore, concrete is often reinforced by steel rebars to improve the ductility and tensile strength. Nevertheless, to make reinforced concrete being highly efficient material, the two components need to be correctly bonded each to other. The bond quality the efficiency of the force transfer between rebar and concrete surrounding ensures. In fact, since the casting of concrete and during the service life of reinforced concrete structure, various actions such corrosion action, freeze/thaw attack and chemical attack etc. may affect the bond quality. The objective of this PhD research work is to qualify the changes of adhesion property causing by four types of action which frequently takes place in the service life of reinforced concrete structures: the effect of high temperatures, the effect of carbonation, the effect of cycles freeze/thaw, the effect of corrosion. The concrete-rebar bond quality is evaluated by doing pull-out tests under static mechanical action and measuring the bond strength and analyzing residual behaviour. Moreover, the acoustic emission technique is used to locate the cracks and evaluate the cracking evolution in real time. The founding of this study can be also extended to apply to other concrete-steel structures like composite structures in which headed studs are used to connect steel profiles to concrete
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Menkulasi, Fatmir. "Development of a Composite Concrete Bridge System for Short-to-Medium-Span Bridges." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50413.
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The inverted T-beam bridge system provides an accelerated bridge construction alternative for short-to-medium-span bridges. The system consists of adjacent precast inverted T-beams finished with a cast-in-place concrete topping. The system offers enhanced performance against reflective cracking, and reduces the likelihood of cracking due to time dependent effects. The effects of transverse bending due to concentrated wheel loads are investigated with respect to reflective cracking. Transverse bending moment are quantified and compared to transverse moment capacities provided by a combination of various cross-sectional shapes and transverse connections. A design methodology for transverse bending is suggested. Tensile stresses created due to time dependent and temperature effects are quantified at the cross-sectional and structure level and strategies for how to alleviate these tensile stresses are proposed. Because differential shrinkage is believed to be one of the causes of deck cracking in composite bridges, a study on shrinkage and creep properties of seven deck mixes is presented with the goal of identifying a mix whose long terms properties reduce the likelihood of deck cracking. The effects of differential shrinkage at a cross-sectional level are numerically demonstrated for a variety of composite bridge systems and the resistance of the inverted T-beam system against time dependent effects is highlighted. End stresses in the end zones of such a uniquely shaped precast element are investigated analytically in the vertical and horizontal planes. Existing design methods are evaluated and strut-and-tie models, calibrated to match the results of 3-D finite element analyses, are proposed as alternatives to existing methods to aid designers in sizing reinforcing in the end zones. Composite action between the precast beam and the cast-in-place topping is examined via a full scale test and the necessity of extended stirrups is explored. It is concluded that because of the large contact surface between the precast and cast-in-place elements, cohesion alone appears to provide the necessary horizontal shear strength to ensure full composite action. Live load distribution factors are quantified analytically and by performing four live loads tests. It is concluded that AASHTO's method for cast-in-place slab span bridges can be conservatively used in design.Ph. D.
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Pickett, Ethan. "The Short and Long-Term Effects of Temperature and Strain on a Concrete Bulb-Tree Girder Bridge." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5811.
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The Utah Transportation Center (UTC) as well as the Mountain Plains Consortium, sponsored a study to investigate the long-term performance of a deck bulb tee girder bridge. The bridge in question is located in Nibley, Utah and was erected in early 2016. Temperature and prestress losses were analyzed from embedded instrumentation placed within two of the bridge girders before casting. These two girders contained a total of 50 thermocouples and 16 vibrating wire strain gauges. These instruments were placed at the mid-span and end of an exterior girder and the mid-span, quarter-span, and end of a center girder in order to effectively monitor the bridge response in one quarter of the bridge superstructure.
The monitoring performed with the thermocouples included the temperature of the girders during curing, weekly maximum and minimum temperatures compared to methods for predicting the average bridge temperature, maximum and minimum thermal gradients at each of the five selected cross sections compared to Code thermal gradients, and thermal camber by measured temperature compared to models to predict thermal gradients. The 16 strain gauges measured prestress losses at four girder cross-sections, which were compared to two predictive methods provided by AASHTO as well as a method by PCI. An additional comparison of the equations provided by AASHTO and a newly available equation used for determining the modulus of elasticity of concretes with a compressive strength of 6,000 – 12,000 psi was performed.
Additional exterior instrumentation were provided by Bridge Diagnostics Inc. (BDI) in order to monitor short-term changes within the bridge. A total of 8 strain gauges were attached to the exterior of the girders with 6 attached at the bottom face of 6 girders and 2 attached at the centroid of 2 girders. These sensors as well as the software and wireless data acquisition provided a method to measure the magnitude and frequency of the ranges of strain experienced by the Nibley Bridge.
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Miah, Md Jihad. "The effect of compressive loading and cement type on the fire spalling behaviour of concrete." Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3015/document.
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La recherche présentée dans cette thèse vise à examiner le mécanisme d’écaillage des bétons exposés au feu et comprendre l’influence du chargement mécanique appliqué en compression durant le chauffage. Des cubes (200 x 200 x 200 mm3) et des dalles (800 x 800 x 100 mm3) de béton fabriqués avec des ciments CEM II et CEM III (B40-II et B40-III: fc28days ≈ 40 MPa) ont été exposés à un feu ISO 834-1 sous différents niveaux de chargement uniaxial (cubes) et biaxial (dalles). En outre, l'effet du chargement mécanique (pression de confinement et charge uniaxiale) sur la perméabilité résiduelle au gaz a été étudié. Afin de mieux analyser les résultats expérimentaux et comprendre les mécanismes à l’origine de l'écaillage, des calculs numériques ont été réalisés en utilisant un modèle thermo-mécanique du code aux éléments finis CAST3M. Les résultats expérimentaux ont clairement montré que les éprouvettes chargées (uniaxial et biaxial) présentent un risque d’écaillage plus important que les éprouvettes non chargées. L’écaillage augmente avec le niveau de contrainte appliquée. Une partie des essais mais pas tous, ont montré que le B40-II (3% de laitier) présente un écaillage plus important que celui du béton B40-III (43% de laitiers).À partir de cette étude sur deux bétons ordinaires, il peut être mis en évidence qu'un certain niveau de contrainte de compression externe (uniaxiale ou biaxiale) est nécessaire pour induire l'écaillage du béton ordinaire. Les pressions des pores se combine avec les contraintes thermiques dûes aux gradients thermiques. Les contraintes de compression appliquées empêchent la création de certaines fissures générées par l'incompatibilité des déformations thermiques de la pâte de ciment et des granulats et des gradients thermiques. Pour l'échantillon non chargé, la création de fissures augmente la perméabilité et empêche naturellement le développement des pressions de pores.Pendant un feu réel, les membres structurels en béton sont toujours chargés ou retenus. La présence d'un chargement compressif pendant le chauffage augmente considérablement le stress de compression (diminue le stress de traction) et la grandeur de la pression des pores, ce qui augmente le risque d'écaillage. Ensuite, le stress compressif appliqué est un facteur clé très important que la conception de la résistance au feu des structures en béton devrait prendre en compte lors de l'écaillage. Par conséquent, il est recommandé que les essais d'écaillage ne soient pas effectués uniquement sur des échantillons non chargésThe research presented in this thesis seeks to examine and understand the mechanism of fire spalling role played by the external compressive loading during heating. Concrete cube (200 x 200 x 200 mm3) and slab (800 x 800 x 100 mm3) specimens made with CEM II and CEM III cements (B40-II and B40-III: fc28days ≈ 40 MPa) were exposed to ISO 834-1 fire curve under different levels of external uniaxial (for cube) and biaxial (for slab) compressive stress. Additionally, the effect of external compressive loading (confining pressure and uniaxial load) on the residual gas permeability of concretes have been investigated. In order to better analyse the experimental results and to provide more insight into the mechanism behind the fire spalling behaviour of concrete, numerical computations were carried out by using the existing thermo-mechanical model implemented in a finite element code CAST3M. The experimental results have clearly shown that the loaded specimens (uniaxial and biaxial) are more prone to spalling than unloaded specimens, with increasing amounts of spalling for higher values of applied compressive stress. Part of the tests, but not all have shown that B40-II (3% of slag) exhibited higher spalling than the B40-III (43% of slag).From this study on two ordinary concretes, it highlights that a certain level of external compressive stress (uniaxial or biaxial) was necessary to induce spalling. A possibility is that the applied compressive stress prevents the creation of cracks naturally due to thermal mismatch between cement paste and aggregates and thermal gradients. For unloaded specimen, the creation of cracks increases the permeability and naturally prevents the pore pressure to exceed a value that favours spalling.During a real fire, concrete structural members are always loaded or restrained. The presence of compressive loading during heating significantly increases the compressive stress (decreases the tensile stress) and the magnitude of pore pressure, which increase the risk of fire spalling. Then, the applied compressive stress is a very important key factor that the fire resistance design of concrete structures should take into account when considering spalling. Hence, it is recommended that the fire spalling test should not be carried out only on unloaded specimens, especially for the ordinary concrete
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Ye, Dan. "Early-age concrete temperature and moisture relative to curing effectiveness and projected effects on selected aspects of slab behavior." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1472.
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Caple, Kacie Danielle. "A pilot study on the effects of temperature on the material properties of prestressed concrete and the use of thermogravimetric analysis in the assessment of heat-affected concrete." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202499264/.
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Acquaye, Lucy. "Effect of high curing temperatures on the strength, durability and potential of delayed ettringite formation in mass concrete structures." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013837.
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Galvan, Tanise Fuckner de Oliveira. "Condições de estresse e conforto térmico em fábrica de pré-moldado em Ponta Grossa - PR." Universidade Tecnológica Federal do Paraná, 2018. http://repositorio.utfpr.edu.br/jspui/handle/1/3106.
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O estresse térmico é um risco reconhecido a que os trabalhadores de várias indústrias estão expostos. De forma a verificar a condição de estresse e também conforto térmico na fábrica de pré-moldado em concreto, foi realizada uma pesquisa na qual as variáveis ambientais e pessoais foram obtidas através de medições e questionários. A avaliação preliminar do estresse térmico foi realizada pela escala HSSI, a qual indicou a não existência do mesmo nessa fábrica. Foi efetuada a avaliação do ambiente, através dos índices IBUTG e PHS, que ratificaram a não existência do estresse térmico. Como não houve a incidência do estresse térmico, o ambiente foi avaliado com relação ao conforto térmico, nas medições em que o índice PMV era aplicável, e foi calculado o índice PET. Através do cálculo do índice do PMV, verificou-se que em apenas uma medição o ambiente pode ser considerado confortável, nas demais o ambiente é considerado desconfortável termicamente. Os resultados do índice PET, demonstram que na maioria das medições também ficou caracterizada o desconforto térmico.Heat stress is a recognized risk that workers in various industries are exposed. In order to verify the stress condition and also thermal comfort in the precast concrete factory, a research was carried out in which the environmental and personal variables were obtained through measurements and questionnaires. The preliminary evaluation of the heat stress was performed by the HSSI scale, which indicated the absence of heat stress in this factory. To confirm this conclusion, the evaluation of the environment was carried out through the IBUTG and PHS indices, which confirmed the absence of heat stress. As there was no incidence of heat stress, the environment was evaluated with respect to thermal comfort, in the measurements in which the PMV index was applicable and the PET index was calculated. Through the calculation of the PMV index, it was verified that in only one measurement the environment can be considered comfortable, in the others the environment is considered to be thermally uncomfortable. Through the calculation of the PMV index, it was verified that in only one measurement the environment can be considered comfortable, in the others the environment is considered to be thermally uncomfortable. The results of the PET index show that thermal discomfort was also characterized in most of the measurements.
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Darestani, Mostafa Yousefi. "Response of concrete pavements under moving vehicular loads and environmental effects." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16662/.
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The need for modern transportation systems together with the high demand for sustainable pavements under applied loads have led to a great deal of research on concrete pavements worldwide. Development of finite element techniques enabled researchers to analyse the concrete pavement under a combination of axle group loadings and environmental effects. Consequently, mechanistic approaches for designing of concrete pavements were developed based on results of finite element analyses. However, unpredictable failure modes of concrete pavements associated with expensive maintenance and rehabilitation costs have led to the use of empiricalmechanistic approach in concrete pavement design. Despite progressive knowledge of concrete pavement behaviour under applied loads, concrete pavements still suffer from deterioration due to crack initiation and propagation, indicating the need for further research. Cracks can be related to fatigue of the concrete and/or erosion of materials in sub-layers. Although longitudinal, midedge and corner cracks are the most common damage modes in concrete pavements, Austroads method for concrete pavement design was developed based on traditional mid-edge bottom-up transverse cracking introduced by Packard and Tayabji (1985). Research presented in this thesis aims to address the most common fatigue related distresses in concrete pavements. It uses comprehensive finite element models and analyses to determine the structural behaviour of concrete pavements under vehicular loads and environmental effects. Results of this research are supported by laboratory tests and an experimental field test. Results of this research indicate that the induced tensile stresses within the concrete pavement are significantly affected by vehicle speed, differential temperature gradient and loss of moisture content. Subsequently, the interaction between the above mentioned factors and concrete damage modes are discussed. Typical dynamic amplifications of different axle groups are presented. A new fatigue test setup is also developed to take into consideration effects of pavement curvature on fatigue life of the concrete. Ultimately, results of the research presented in this thesis are employed to develop a new guide for designing concrete pavements with zero maintenance of fatigue damage.
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Dauti, Dorjan. "A combined experimental and numerical approach to spalling of high-performance concrete due to fire." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI062/document.
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Le béton est un matériau très utilisé dans l'industrie de construction. Une limite essentielle à un usage de ce matériau est sa dégradation par écaillage lorsqu’il est exposé au feu. Le phénomène d'écaillage consiste en une éjection du béton sous forme d'écailles à la surface du béton exposée à l'incendie. La section de béton s'en trouve progressivement réduite. De plus, ce phénomène expose les armatures et peut conduire à une rupture prématurée de structures telles que les tunnels, les gratte-ciels, les centrales nucléaires etc. De nombreuses recherches ont été consacrées à la mise au point de méthodes de prévention de l'écaillage et à la détermination des paramètres qui ont une influence sur ce phénomène. Cependant, la physique qui contrôle l'écaillage n'est pas encore entièrement comprise. L'objectif principal de la thèse est de fournir une meilleure compréhension des mécanismes impliqués dans l’écaillage du béton en utilisant une approche numérique-expérimentale, i.e., la tomographie neutronique couplée à la modélisation numérique avancée à une échelle adéquate.Dans ce travail, les premières mesures 3D de la teneur en eau du béton (grandeur locale indispensable au suivi du processus de déshydratation potentiellement responsable de l’écaillage) soumis à un chargement thermique sévère ont été réalisées à l'aide de tomographies neutroniques rapides. Le suivi de la déshydratation rapide du béton a été possible en réalisant un scan 3D toutes les minutes grâce à la source neutrons de l'Institut Laue Langevin (leader mondial), à Grenoble, France. Cette vitesse d'acquisition est dix fois plus rapide que toute autre étude tomographique rapportée dans la littérature. Un dispositif, adapté à l'imagerie neutronique et aux essais à haute température, a été développé pour réaliser de telles expériences. L'influence de la taille des agrégats sur la distribution de l'humidité au sein de l'échantillon est présentée. Les résultats quantitatifs sur l'accumulation d'humidité derrière le front de déshydratation, connue sous le nom de 'moisture-clog" et considérée comme un des facteurs principaux engendrant un excès de pression, sont également présentés et discutésEn parallèle, un modèle thermo-hydro-mécanique (THM) entièrement couplé a été mis en œuvre sur le logiciel élément fini Cast3M afin d'étudier et prédire le comportement du béton à haute température. Le code nouvellement implémenté est remarquablement plus rapide (20-30 fois) que le code existant sur lequel il est basé. Une approche mésoscopique a été adaptée au modèle pour prendre en compte l'hétérogénéité du béton. D'abord, le modèle est appliqué à des expériences de la littérature, qui étu-dient les paramètres standards tels que la température, la pression du gaz et la perte de masse. En-suite, des profils d'humidité 1D obtenus à partir d'expériences de radiographie neutronique sont utili-sés pour vérifier et améliorer le modèle en termes de lois de comportement critiques telles que les courbes de déshydratation et de rétention d'eau. Enfin, le modèle est utilisé pour prédire la distribution d'humidité 3D mesurée dans ce travail de doctorat par tomographie neutronique. Entre autres, des simulations THM mésoscopiques sont effectuées pour étudier l'influence d'un agrégat sur le front de séchageConcrete has been extensively used in the construction industry as a building material. A major drawback of this material is its instability at high temperature, expressed in the form of violent or non-violent detachment of layers or pieces of concrete from the surface of a structural element. This phenomenon, known as fire spalling, can lead to the failure of concrete structures such as tunnels, high rise buildings, nuclear power-plants, underground parkings etc. because the reinforcement steel is directly exposed to high temperature and the designed cross section of the concrete elements (e.g., columns, beams, slabs) is reduced. A lot of research has been dedicated on developing preventing methods for spalling and also on determining the parameters that have an influence on it. However, the physics behind this phenomenon is not yet fully understood.In this doctoral, the first 3D measurements of moisture content in heated concrete, which is believed to be one of the processes directly related to spalling, have been performed using in-situ neutron tomography. In order to follow the fast dehydration process of concrete, one 3D scan (containing 500 radiographs) per minute was captured thanks to the world leading flux at the Institute Laue Langevin (ILL) in Grenoble France. This acquisition speed, which is ten times faster than any other experiment reported in the literature, was sufficient to follow the dehydration process. A dedicated setup, adapted to neutron imaging and high temperature, has been developed for performing such kind of experiments. Concrete samples with different aggregate size have been tested. Quantitative analysis showing the effect of the aggregate size on the moisture distribution is presented. Results on the moisture accumulation behind the drying front, known as the moisture-clog, are also presented and discussed.In parallel, a numerically-efficient coupled thermo-hydro-mechanical (THM) model has been implemented in the finite element software Cast3M for understanding and predicting the complex behavior of concrete at high temperature in the context of spalling. The newly implemented code is remarkably faster (20-30 times) than an existing one, on which it is based. A mesoscopic approach has been adapted to the model for taking into account the heterogeneity of concrete. First the model is applied to experiments from literature monitoring standard parameters such as temperature, gas pressure and mass loss. Then, 1D moisture profiles obtained from neutron radiography experiments are used for verifying and improving the model in terms of some critical constitutive laws such as dehydration and water retention curves. Finally, the model is employed for predicting the 3D moisture distribution measured in this doctoral work via neutron tomography. Among others, mesoscopic THM simulations are performed for investigating the influence of an aggregate on the drying front
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TSIMBROVSKA, MARIANA. "Dégradation des bétons à hautes performances soumis à des températures élevées : évolution de la perméabilité en liaison avec la microstructure." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10030.
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Les betons a hautes performances (bhp), grace a leur durabilite et resistance mecanique elevees, sont de plus en plus utilises dans la construction. Cependant, sous certaines sollicitations thermiques (incendie, accident nucleaire) ces betons manifestent parfois un comportement fragile appele eclatement. Un des principaux parametres regissant l'eclatement est la permeabilite qui controle les transferts des fluides. Cette propriete est fonction de la microstructure du materiau, caracterisee par la porosite, la distribution des tailles de pores, la connectivite et la tortuosite du reseau poreux, la densite et l'ouverture des fissures. Ce travail a pour but d'etudier l'evolution de la permeabilite intrinseque des bhp degrades suite a un echauffement (jusqu'a 400c) et de correler cette evolution aux caracteristiques de microstructure. Une etude comparative avec les betons ordinaires est effectuee. La permeabilite intrinseque des betons est estimee a partir des mesures de la permeabilite aux gaz. Avant traitement thermique la permeabilite intrinseque des bhp est inferieure d'environ un ordre de grandeur a celle des betons ordinaires. Cependant sous l'effet de la temperature cette propriete augmente plus rapidement dans les bhp (2 ordres de grandeur) et apres traitement thermique a 400c les bhp sont plus permeables que les betons ordinaires. Le sous-espace poreux efficace vis-a-vis de la permeabilite est identifie comme celui constitue de pores de diametre superieur a 0,1m. L'evolution de ce sous-espace poreux avec la temperature et la microfissuration expliquent les variations de la permeabilite dans chaque type de materiau. Trois modeles reliant la permeabilite a la microstructure sont appliques et leurs previsions sont comparees aux resultats experimentaux. Cette comparaison est satisfaisante mais montre les limites des representations topographique et geometrique des reseaux poreux utilisees dans la modelisation des transferts de masse.
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Pan, Jing. "Effet de la température et de l'agitation sur les propriétés rhéologiques des bétons fluides à rhéologie adaptée." Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/7567.
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Résumé : Le climat local, le transport avec l’agitation entre l’endroit de bétonnage et le site de fabrication du béton influencent fortement les propriétés du béton frais et durci. Selon les particularités du béton autoplaçant (BAP), le maintien de l’homogénéité et l’ouvrabilité du BAP avant la mise en place est très important. Les propriétés des BAP sont généralement plus sensibles à la température et au transport par rapport à celles des bétons conventionnels. Une meilleure compréhension de l’effet de la température et de l’agitation sur la performance des BAP est nécessaire pour prévoir les conséquences du changement du climat (température) et de l’effet du transport (temps et vitesse d’agitation), puis pour donner des précautions à suivre afin de répondre à la demande des BAP pour un bon rapport performance-coût. De manière pragmatique, il s’avère nécessaire d’utiliser la méthode du mortier de béton équivalent (MBE) afin d’analyser rapidement les influences de la température et de l’agitation sur les propriétés rhéologiques, calorimétriques et mécaniques des BAP. Cinq températures (8, 15, 22, 29 et 36°C) et deux vitesses d’agitation (6 et 18 tr/min) ont été étudiées sur les MBE. Ensuite, quelques compositions spécifiques (type d’adjuvant et ajout cimentaire) ont choisies afin de vérifier avec des températures compasse entre 8 à 36°C et les agitations différentes (2 et 6 tr/min) sur les BAP destinés aux travaux de bâtiment (BAP-B) sans agent entraîneur d’air et sur des bétons semi-autoplaçant destinés aux travaux d’infrastructures (BSAP-I) avec agent entraîneur d’air. La fluidité initiale des MBE et BAP a été fixée en faisant varier la demande en SP, la température et l’agitation. Les résultats montrent qu’il y a un effet important de la température et de l’agitation sur l’efficacité des adjuvants, la fluidité, la teneur en air, les propriétés rhéologiques, calorimétriques et mécaniques des MBE et des BAP. Pour prévoir la performance de MBE à différentes températures, une équation mathématique est proposée pour déduire la demande en SP, la demande en AEA, le flux maximal et la résistance en compression à 1 jour en fonction des mêmes propriétés sur MBE à 22°C et de la température. Enfin, une corrélation linéaire a été trouvée entre les MBE et les BAP sur ces mêmes propriétés.Abstract : The local climate, the transport of agitated concrete after manufacturing but before being cast strongly influence the properties of the fresh and hard concrete. It’s important to keep the stability and workability of the self-consolidating concrete (SCC) because of its special characteristics. Compare to the normal concrete, the properties of SCC are generally more sensitive to the temperature and the transport. Therefore it’s necessary to understand the effects of the temperature and the agitation on the performance of the SCC in order to predict the consequences of climate change (temperature) and transport (time and speed of agitation), and then to give the better precautions with a good performance-cost report. In this study, the concrete mortar equivalent (CEM) method is used to quickly analyze the influences of the temperature and the agitation on the rheological, calorimetric and mechanical properties of the SCCs. Five temperatures (8, 15, 22, 29 and 36°C) and two agitation speed (6 and 18 tr/min) are varied in CEMs. And then, some compositions (type of adjuvant and supplementary cementing material) are chosen to be valued with the temperature (8-36°C) and the agitation (2 and 6 tr/min) in SCCs for the building without air-entraining admixture (AEA) and semi-flowable SCC for infrastructure with AEA. The initial slump flow of CEM and SCC is fixed, but the demand superplasticizer, the temperature and the agitation were varied. The results show that there are the effects of temperature and agitation on the effectiveness of admixture, the slump flow, the air content, the rheological, calorimetric and mechanical properties of CEM and SCC. A mathematical equation is proposed to predict the performance of SCC at different temperatures for the SP and AEA requirement, the maximum of heat flow and the compressive strength at one day by these same properties of SCC at 22°C and by the temperature. Finally, a good linear correlation is found between CEM and SCC for these properties.
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McCormick, Darryn. "High temperature concrete for nuclear reactors." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10980.
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Rozsypalová, Iva. "Stavebně technický průzkum objektu poškozeného požárem." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227489.
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Diploma thesis summarizes knowlegde related to the behavior of structures and material in the fire, focusing mainly on concrete and reinforced concrete structures. It deals with the design and implementation of diagnostic work of Building no. 103 in complex Svit Zlín affected by a large fire. There are presented evaluation of laboratory experiments of samples and static analysis.
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Recalde, Juan Jose. "Estimating Crack Growth in Temperature Damaged Concrete." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-11252009-111845/.
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Evaluation of the structural condition of deteriorated concrete infrastructure and evaluation of new sustainable cementitious materials require an understanding of how the material will respond to applied loads and environmental exposures. A fundamental understanding of how microstructural changes in these materials relate to changes in mechanical properties and changes in fluid penetrability is needed. The ability to provide rapid, inexpensive assessment of material characteristics and relevant engineering properties is valuable for decision making and asset management purposes. In this investigation, the effects of changes in dynamic elastic properties with water content and fluid penetrability properties before and after a 300 °C exposure were investigated as they relate to estimates of the crack density parameter, developed from the work by OâConnell and Budiansky (1974; 1977) on dry and saturated crack media. The experimental and analytical techniques described in this dissertation allow calculation of a value for the crack density parameter nondestructively from differences in wet and dry dynamic shear modulus of relatively thin disks. The techniques were used to compare a conventional concrete mixture and several mixtures with enhanced sustainability characteristics. The analysis provided quantitative assessment of changes with high temperature damage and autogenous healing, and provided estimates of increases in mean crack trace lengths. The three enhanced sustainable materials investigated were a very high fly ash mixture (mixture F), a magnesium phosphate cement based mortar (mixture M), and a magnesium phosphate cement based concrete (mixture G), and were compared to a conventional concrete mixture (mixture C). The results showed that water interaction, deterioration due to damage, and autogenous healing recovery were different for mixtures G and M than the concrete mixtures C and F based on portland cement. A strong correlation was found between log(API), Gd and crack density parameter. The findings imply that the test method and related analysis can be used to evaluate the validity of current standard test methods to new âgreenâ construction materials and therefore be a useful screening tool as well as providing important insight into microstructural changes in concrete under various exposures.
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Parham, Arash. "Temperature rise of mass concrete in Florida." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008823.
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Lee, Keun Kwang. "Evaluation of concrete behavior under high temperature." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3315814.
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Sarshar, Roozbeh. "Effect of elevated temperatures on the strength of different cement pastes and concretes." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/8602.
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Lagundzija, Sandra, and Marie Thiam. "Temperature reduction during concrete hydration in massive structures." Thesis, KTH, Betongbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210031.
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Concrete is one of the most used building materials in the world because of its good properties. However, cement which is one of the main components in concrete, produces a high amount of heat during the hydration process. The generated heat leads to temperature rise inside the structure. This temperature rise becomes an issue for massive concrete structures, such as hydropower plants and dams, since natural cooling is no longer sufficient. In combination with restrained boundary conditions, increasing temperatures result in tensile stresses causing thermal cracking of the structure. Reducing thermal cracking in a restrained massive concrete structure can be done by lowering or controlling the temperature rise. Several methods of cooling can be used to achieve this. These methods may be divided in pre-cooling and post-cooling methods. To pre-cool concrete the cement content can be reduced by replacing it with mineral additions such as limestone, fly ash, silica fume and ground granulated blast furnace slag. Another method is to increase the size of the aggregates or to pre-cool the aggregates. Ice can also be used to reduce the temperature at casting the concrete and reduce the amount of water that is needed in the mix. The main post-cooling method is cooling pipes, with cold water circulating in the pipes to cool the structure. This master thesis project focuses on comparing the possible methods to reduce the temperature in massive concrete structures. Simulations with the computer program HACON were performed to analyse the effect of these methods. The results from this study showed that cooling pipes gave the best reduction of the maximum temperature and the maximum temperature gradient by 42 % and 76 %, respectively. However, if cooling pipes were to be avoided, the best result of the studied mineral additions was with a replacement of 30 % fly ash resulting in almost the same reduction in maximum temperature but less than one third of the reduction in the gradient. The reduction obtained with fly ash was not as efficient as cooling pipes; therefore appropriate combinations of different pre-cooling methods were also studied. The results of the combination of fly ash, ice, and larger aggregates showed even better reduction of the maximum temperature reduction compared to cooling pipes. The results also showed that the obtained temperature reductions were almost independent from the thickness of the structure. This conclusion is however only valid for massive structures, where cases with 1.5 and 3.0 m were analysed. Further study may be on finding suitable combination of pre-cooling methods to avoid the use of cooling pipes, as well as analysing the cost for the different pre-cooling methods.Betong är ett av de mest använda byggmaterialen i världen, tack vare dess goda egenskaper. Cement, som är en av huvudkomponenterna i betong, genererar en stor värmeutveckling under hydratationen. Värmeutveckling som genereras leder till temperaturhöjningar i strukturen. Denna temperaturhöjning blir således ett problem för massiva betong- konstruktioner, såsom vattenkraftverk och dammar, på grund av att den naturliga avkylningen inte längre är tillräcklig för att avlägsna värmen. I kombination med yttre och inre tvång resulterar högre temperaturer i dragspänningar som orsakar sprickor i strukturen. Minskningen av sprickbildning i en fastgjuten massiv betongstruktur kan ske genom att minska eller reglera temperaturhöjningen. För att göra det kan flera kylmetoder användas. Dessa metoder kan delas in i förberedande kylning och efterkylning. Med förberedande kylning kan cementhalten i betong reduceras genom ersättning med mineraltillsatser såsom kalksten, flygaska, silikastoft eller markgranulerad masugnsslagg. En annan metod är att öka ballastens storlek eller att kyla ballasten. Is kan användas både för att minska temperaturen vid gjutning av betong och reducera mängden vatten som behövs i blandningen. Den vanligaste efterkylningsmetoden är användning av kylrör med cirkulerande kallt vatten för att kyla strukturen, dvs. utan att ändra mängden värme som produceras av cementhydratationen. Denna uppsats ämnar jämföra olika metoder för att reducera temperaturen i massiva betongkonstruktioner. Simuleringar har genomförts med datorprogrammet HACON i syfte att analysera inverkan av olika metoder. Resultaten från studien visade att kylrör gav den bästa minskningen av den maximala temperaturen och den maximala reduktionen av temperaturgradienten med 42 % respektive 76 %. Om kylrör ska undvikas erhålls det bästa resultatet vid användning av 30 % flygaska, vilket resulterade i en snarlik minskning i maximal temperatur med mindre än en tredjedel av reduktionen av gradienten. Då reduceringen med flygaska inte var lika effektiv som med kylrör har lämpliga kombinationer av olika förberedande kylmetoder studerats. Resultatet av kombinationen med flygaska, is och större ballast visade en ännu effektivare minskning av den maximala temperaturreduceringen jämfört med kylrör. Vidare visade resultaten även att de erhållna temperaturreduceringarna nästan var oberoende av konstruktionens tjocklek. Denna slutsats kan endast tillämpas för massiva konstruktioner, där fall med en 1.5 och 3.0 m tjock vägg analyserades. Fortsatta studier kan vara att hitta fler lämpliga kombinationer av förberedande kylmetoder för att undvika användning av kylrör, liksom att analysera kostnaden för de olika förberedande kylmetoderna.
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Williams, Andrew Robert. "Cracking Potential and Temperature Sensitivity of Metakaolin Concrete." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6603.
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Metakaolin is a pozzolanic material with the potential to reduce permeability and chloride ingress; however, quantification of the effects of metakaolin use on the cracking sensitivity of concrete mixtures is needed to ensure that these improvements in performance are not compromised. This study was conducted to investigate the early age cracking potential due to restraint stresses from incorporating metakaolin in concrete. Calorimetry testing showed that metakaolin was more sensitive to temperature than mixtures with only Portland cement. Results showed more shrinkage, less stress relaxation, and higher restraint stress from the inclusion of metakaolin, potentially increasing cracking sensitivity of mixtures.
1 This section was published in Construction and Building Materials[57]. Permission is included in Appendix A
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Liu, Chi-ho Timothy. "Investigation of temperature distribution in highway bridges /." [Hong Kong] : University of Hong Kong, 1985. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12321758.
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Lalan, Philippines. "Influence d'une température de 70°C sur la géochimie, la microstructure et la diffusion aux interfaces béton/argile : expérimentations en laboratoire, in situ et modélisation." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM047/document.
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Dans le concept actuel du stockage géologique des déchets radioactifs en France, les interfaces entre la roche encaissante, une argilite, et les matériaux cimentaires utilisés pour les bouchons de scellement et les corps des alvéoles de stockage pourraient subir une température de 70°C due à l’activité exothermique de déchets. Les évolutions minéralogiques, microstructurales et leurs conséquences sur les propriétés de transport à ces interfaces sont mal connues dans ces conditions de température.Deux dispositifs expérimentaux sont conçus. Le premier consiste à créer des interfaces pâte de ciment CEM I / argilite de Tournemire en cellules de diffusion. La chimie des solutions est suivie dans le temps et quatre échéances permettent d’étudier l’évolution temporelle des matériaux. Le second dispositif consiste à créer de telles interfaces in situ à 70°C dans le laboratoire souterrain de Tournemire. Ce dispositif, plus représentatif des conditions de stockage, est démantelé après un an d’interaction. Au préalable, le comportement de la pâte de ciment CEM I à l’issue d’une augmentation de température de 20 à 70°C est analysé. La modélisation en transport réactif (Hytec) est utilisée en support à la compréhension des évolutions physico-chimiques.La néoformation de tobermorite, de phillipsite (in situ uniquement), de C-A-S-H et de calcite formant un ruban à l’interface est avérée. Une cinétique de précipitation de la tobermorite a ainsi pu être évaluée. La pâte de ciment est décalcifiée et carbonatée. La porosité totale diminue dans la pâte de ciment, malgré une ouverture de la macroporosité par dissolution de portlandite. L’argilite semble être peu altérée. La température accélère la diffusion, tandis que les variations de porosité et le ruban ne changent pas significativement les propriétés de diffusion sur une annéeRadioactive wastes in future deep geological disposals will generate heat and locally increase temperature in the engineered barriers and host-rock. In the French design of disposal cells, temperature may reach 70°C in cementitious materials and at their contact with the clayey host-rock. The impact of temperature under such disposal conditions is still poorly known, especially regarding the geochemical and physical evolution at the interface between these two materials.Two experimental devices are designed. The first involves creating interfaces between OPC paste and argillite of Tournemire in diffusion cells. The evolution of solutions and materials are analysed over time. The second device involves creating OPC paste / argillite interfaces at 70°C under in situ conditions in the underground laboratory of Tournemire (France). This device, more representative of a deep disposal, is dismantled after one year. Prior to interface study, behaviour of the OPC paste after a temperature increase from 20 and 70°C was analysed and simulated. Reactive transport modelling supports the experimental results in order to better understand the physico-chemical evolutions at the interface.Neoformation of tobermorite (well-crystallised C-S-H), phillipsite (only in situ), C-A-S-H and calcite formed a layer at the interface. A kinetic of tobermorite precipitation is evaluated. Significant decalcification and carbonation were noticed in the cement paste. Total porosity decreases in the cement paste despite an opening of the macroporosity due to portlandite dissolution. Argillite seems to be weakly altered even if alkaline plume goes deeply through it. Porosity changes do not alter significantly diffusive properties at the studied time scale
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Qadir, Adnan. "Investigation Of Low Temperature Cracking In Asphalt Concrete Pavement." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612696/index.pdf.
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In this study, low temperature cracking of asphalt concrete is investigated based on a laboratory experimental program including the design variables of aggregate type, gradation, asphalt content, binder grading, binder modification, and the experimental variables of cooling rate, and specimen size. The design of experiment is proposed according to the fractional factorial design principles to reduce the required number of test specimens. Mix designs are performed according to the Superpave mix design guidelines using materials obtained from the Turkish General Directorate of High-ways. In the course of this study, a test setup for thermal stress restrained specimen test for asphalt concrete is developed and used successfully to test a number of as-phalt concrete beam specimens. The same setup is also used for measuring the glass transition temperatures to obtain various thermo-volumetric properties of mixtures. Statistical methods are used to identify the effect of experimental variables on frac-ture strength, fracture temperature and other dependent variables obtained from the testing program. Statistical models are also developed to predict the fracture strength, fracture temperature and other thermo-volumetric properties of mixtures. Results of analyses show that aggregate type, binder modification, and asphalt content significantly affect both the fracture strength and fracture temperature of asphalt concrete. While the glass transition temperature is affected by only aggregate type, coefficients of contraction before and after the glass transition temperature are not influenced by any of the experimental variables. The results of this study provide an important basis to prevent low temperature cracking in asphalt concrete pavements.
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Venturelli, John. "Seasonal temperature and stress distributions in concrete gravity dams." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56758.
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Seasonal thermal stresses have been found to contribute significantly to the long term degradation of strength and stiffness of concrete dams located in northern regions. Moreover, thermal stresses and strains must be evaluated to define the initial loading conditions for seismic safety analyses. In this study, finite element procedures to model the thermal response of concrete gravity dams are presented. Heat transfer and structural models of a typical dam-foundation-reservoir system are developed. The reservoir, foundation, and air temperature variations, as well as solar radiation, are evaluated from data collected from different sources. The rate of convergence of the numerical solution is examined, and a methodology to identify the critical temperature states and to compute the related stresses, considering creep, is presented.Extensive parametric analyses are then performed to determine the relative influence of (i) the geometrical, thermal, and mechanical properties of the dam, (ii) the reservoir, foundation and air temperature distributions, and (iii) the heat supply from solar radiation, on the stress-strain response of the system. Temperature states to define critical stress conditions for structural safety analysis are determined.
Significant thermal stresses occur in the vicinity of the exposed surfaces of the dam. The typical depth of frost penetration is about 6m. The parameters which affect the surface stresses most are the air temperature distribution and the height of the dam, while for the frost penetration they are the solar radiation, convection coefficient, and conduction coefficient.
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Shah, Vishal Sanjay. "Detection of microcracks in concrete cured at elevated temperature." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008824.
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Jonasson, Jan-Erik. "Modelling of temperature, moisture and stresses in young concrete." Doctoral thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 1994. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25735.
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The present study consists of three areas, namely modelling of- (1) temperature, (2) moisture state, and (3) stresses in young concrete. The derivation of models, examination of material data, and development of computer programs have progressed differently in these areas. The first area, modelling of temperatures, is the most comprehensive and complete, since it has been researched more extensively than the other areas. On the other hand, the way of modelling stresses in this study is purely theoretical and has not been tested against empirical data, but gives some guidelines for future applications. Finally, the modelling of moisture state is somewhere in between the other two areas. The results can be applied to different fields of concreting, such as estimation of form stripping times, estimation of necessary measures to be taken in winter concreting, study of drying shrinkage cracking, and study of stresses due to varying temperatures in early age concretes. The aim of this report is not to discuss applications, but to give the background and material data used in the models for calculating the temperature, moisture state, and stresses in young concrete. It is shown that temperature can be modelled to within an accuracy of 1 to 2°C which is acceptable for most applications. However, it is essential to have good knowledge of both material data and environmental conditions. For the study of moisture states, a consistent model for the description of desorption and absorption isotherms has been developed. The treatment of both desorption and absorption isotherms in the same theoretical framework makes it possible to introduce scanning curves between these limit curves for subsequent drying and wetting. The effects of alkali have been modelled as an alkali equilibrium isotherm estimated from the known amounts of sodium and potassium oxides in the cement. The alkali influenced curve can be combined with any description of the isotherms with respect to the physically bound water. The need for considering the effects of alkali for higher humidities has been shown in moisture calculations.Godkänd; 1994; 20070426 (ysko)
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Visagie, Madeleine. "The effect of microstructure on the properties of foamed concrete." Diss., Pretoria : [s.n.], 2000. http://upetd.up.ac.za/thesis/available/etd-01122007-171046/.
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Richardson, Michael. "The behaviour of reinforced concrete beams under cyclic temperature profiles." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/6791/.
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On a hot summer day, high levels of solar radiation are incident on concrete bridge decks, causing non-linear variations in temperature through the depths of the structures. The changes in temperature lead to axial expansion and curvature of decks. In addition, self-equilibrating stresses arise from the non-linearity of the temperature profiles. In continuous structures, where axial expansion and curvature may be restrained, secondary thermal stresses are induced also. Tests are described in which reinforced concrete beams were subjected to daily cycles of heating. Applied temperature profiles were similar to maximum positive profiles for the United Kingdom. It was found that a linear elastic analysis, based on the uncracked section, generally gave an adequate prediction of thermal strains of non-loaded and loaded single span beams during heating cycles. Changes in curvature, during heating, were substantially modified in the early stages of loading, due to the existence of creep curvatures. Two span beams were tested also, with special regard to changes in support reactions during heating. No evidence was found in any of the tests of increases in the extent of cracking as a result of heating. Daily heating cycles were imposed over several weeks and evidence was found of a steady increase in the coefficient of thermal expansion, attributed to drying. Changes in curvature resulting from non-uniform shrinkage were observed, these being greatest in non-heated beams. Creep curvatures were found to increase roughly in proportion to the time-averaged beam temperature. Creep results were compared with prediction methods, including an incremental rate of creep analysis. Additional tests are described in which variations in moisture content and in the coefficient of thermal expansion within members were identified, using a segmentation technique.
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Castillo, Carlos. "Effect of transient high temperature on high-strength concrete." Thesis, 1987. http://hdl.handle.net/1911/13275.
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The effect of transient high temperature in the uniaxial compressive strength of high strength concrete was investigated. The temperatures studied varied from 100$\sp\circ$ to 800$\sp\circ$C. The presence of loads in a structure was simulated by preloading the test specimens during the heating period.
Results showed that exposure to temperatures between 100$\sp\circ$ and 300$\sp\circ$C decreased the compressive strength of high strength concrete by 15 to 20 percent. For temperatures between 400$\sp\circ$ and 800$\sp\circ$C,the compressive strength of concrete decreased to thirty percent of that at room temperature. One third of the preloaded specimens failed explosively during the heating period. In the remaining specimens the presence of a preload had a beneficial effect and a smaller loss of strength was observed compared to unstressed specimens. Exposure to high temperature caused the modulus of elasticity to decrease in all specimens regardlessly of the preload condition and the strength of concrete.
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Chiu, Wei-Hsiang, and 邱韋翔. "Assessment of Temperature Effect on Curved Prestressed Concrete Viaduct." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/p4qx3n.
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碩士國立中興大學
土木工程學系所
106
This study is to discuss whether the curved prestressed concrete viaduct is safe, therefore we must first grasp a reasonable deformation range. Reasonable deformation factors include self-weight, moving loads, temperature effect, tendon loss and so on. Only after grasping the above elements can we judge whether the degree of deformation of on-site monitoring is safe and what causes the deformation. This study investigated the effects of temperature on three section models on the curved viaduct in Taiwan. The three models were established through Midas Civil and set the change amount of temperature of bridges structure in the models through the thermometer values in a year of the site and the “Temperature gradient curve for the design of concrete box girders in Taiwan” in the Highway Bridge Design Code. Finally, through the comparison and integration of the numerical simulation and the on-site monitoring results, the deformation of the three groups of bridge vibration units at the annual maximum temperature in Taiwan were summarized. From the results of numerical analysis, the maximum temperature-dependent relative subsidence of this curved viaduct in a year is about ± 2.5 centimeters, if the degree of deformation is greater than this range, there may be other factors. After integrating this result with other reasonable factors of deformation, a safe range of deformation can be obtained. If the monitoring value exceeds this range in the future, it is necessary to carry out inspections on the structural safety of the curved viaducts.
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Lue, Jing-Wen, and 陸景文. "Effect of Temperature on The Camber of Concrete Bridges." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/11102366259691134111.
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Chen, Pei-Yu, and 陳姵妤. "Effect of Climbing Plants in Reducing Temperature of Concrete Buildings." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/61138713111591083165.
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碩士國立臺灣大學
土木工程學研究所
98
Presently, green on roofs and on the plane is more popular method to make environment green. However, it is crowded in Taiwan urban area and the land resource is limited. Therefore, to carry out greening walls could increase the green view and also achieve the energy conservation to reduce effect of the carbon. The major purpose of this research is to discuss thermal effect of greening wall which focus on climbing plants in reducing temperature of concrete buildings. First, using thermal imagers examines some available greening wall cases in Taiwan. Using the result to do quantitative and qualitative analysis and compare the surface temperature differences of greening walls with that of bare walls. Second, ordinary performance concrete and light weight concrete are used for specimens to simulate the wall of a room. The surface temperature of concrete specimens with different leaf area density would be measured by thermal couples, and further, summarize the cooling effect, energy conservation and carbon reduction of climbing plants application on buildings.
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Kai, Shr Wen, and 施文凱. "A Study for Reinforced Concrete by FRP with Temperature Effect." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/84258299628486257198.
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