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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Etude du comportement des enrobés bitumineux aux températures de mise en œuvre / Study of the behaviour of asphalt concretes at mixing and implementation temperatures

Fabre des Essarts, Angélique 12 April 2016 (has links)
Depuis les années 2000, les grandes entreprises routières axent leurs recherches sur l’abaissement des températures de fabrication et de mise en œuvre des enrobés bitumineux à chaud (de 30 à 50°C). Le développement de ces nouveaux enrobés, dits tièdes, a fait apparaître sur les chantiers des problématiques de maniabilité qui n’existaient pas dans le cas des enrobés à chaud, notamment lors des mises en œuvre manuelles. Ce sujet de thèse, inscrit dans cette thématique des enrobés bitumineux tièdes, vise à étudier leur comportement aux températures de mise en œuvre et à développer une démarche de caractérisation et d’évaluation de leur maniabilité. Pour cela, le travail expérimental a été réalisé à différentes échelles du matériau (liant, mastic et enrobé), sur des matériaux réels (aux liants bitumineux) et modèles (aux huiles de silicone), en s’articulant autour de deux axes principaux : les propriétés de viscosité des liants et des mastics d’une part, puis les propriétés de maniabilité des enrobés évaluées par un outil depuis peu normalisé, à savoir le maniabilimètre. Après un état de l’art sur les enrobés bitumineux, notamment tièdes, leur mise en œuvre et méthodes de caractérisation, et les propriétés rhéologiques des liants et des mastics bitumineux, une présentation des différents matériaux utilisés est faite. Les études rhéologiques menées sur liant et sur mastic sont présentées dans une première partie, depuis la mise en place des protocoles de mesure en plan-plan jusqu’à l’analyse des différents comportements, en fonction de paramètres choisis tels que la température, le taux de cisaillement, le taux de fines ou la présence d’additif tiède. Outre la vérification du caractère newtonien des bitumes et la validation des matériaux modèles, cette partie met en évidence le comportement non newtonien des mastics aux taux de fines testés, ainsi que la présence d’un phénomène de sédimentation dans les mastics, particulièrement à haute température, qui amène à s’interroger sur la pertinence de l’étude à l’échelle mastic par rapport à celle sur liant. En deuxième partie, l’analyse de la maniabilité à l’échelle de l’enrobé est menée à l’aide du maniabilimètre (NF P 98 258-1) ; l’intérêt de maîtriser la compacité de l’échantillon pour une bonne pertinence de l’essai est démontré. Une analyse de différents paramètres, tant géométriques que produits, initialement sur enrobés modèles puis réels, a permis de mettre en évidence la capacité et les limites de cet outil à caractériser la maniabilité, en corrélation avec les études rhéologiques sur liant et mastics / Since the 2000s, road industries have focused their researches on lowering the mixing and implementation temperatures of Hot Mix Asphalt (HMA) (from 30 to 50°C). These new asphalt concretes, called Warm Mix Asphalt (WMA), created a workability issue that did not exist in the case of HMA, especially during manual implementation. This thesis aims to study the behavior of these WMA at implementation temperatures and to develop a method to characterize and evaluate their workability. For that, the experimental work was done at several scales of the material (the binder, the mastic and the mixture), some made with bituminous binders and some with silicone oils. Two properties were studied: on the one hand the viscosity of binders and mastics, and on the other hand the workability of mixtures measured by the workability device, newly standardized. After a state of the art on asphalt concretes, in particular WMA, on their implementation and characterization techniques, on the rheological properties of bituminous binders and mastics, the different materials used are presented along with their characterizations. The rheological studies conducted on binder and mastic are exposed in a first part, from the setup of measure procedures to the analysis of different behaviors with respect to the chosen parameters such as temperature, shear rate, filler content. This part highlights not only the Newtonian nature of binders but also the non-Newtonian behavior of mastics and the sedimentation phenomenon they endured at high temperatures which leads to investigate the legitimacy of the study at the mastic scale. In a second part, the workability of the mixtures is measured with the workability device (NF P 98 258-1), showing the importance of controlling the void content of the sample to guaranty a relevant test. An analysis of several parameters highlighted the ability and the limits of this device to characterize workability, with regard to the rheological studies on binders and mastics
2

Characterisation and Modelling of Asphalt Mastic and Their Effect on Workability

Hesami, Ebrahim January 2014 (has links)
<p>QC 20140902</p>
3

Performance-based characterisation of Bitumen and Mastic using the DSR

Rochlani, Mrinali Rajkumar 10 May 2021 (has links)
This dissertation presents the results of research undertaken for the characterization of bitumen and mastic which are constituents of Hot Mix Asphalt (HMA). The results of a large number of Dynamic Shear Rheometer (DSR) tests performed in the Laboratory of the Institute for Pavement Engineering at the TU Dresden form the background material for this work. The major objectives of this PhD research work were to gain a fundamental understanding about the mechanical behaviour of bitumen and mastic. The DSR tests undertaken included frequency sweeps for rheological behaviour, single stress creep recovery test (SSCR) for permanent deformation behaviour, Dresden cryogenic test (DDCT) for low temperature performance and fatigue testing with column cylindrical specimen. Selected tests were carried out on bitumen and mastic also to investigate the sensitivity of the materials to ageing. The frequency sweep data was also modelled using an appropriate rheological model to derive rheological data over a large frequency and temperature range. Based on the tests conducted, particular chosen parameters calculated were synthesized into a performance diagram which was developed within the framework of the dissertation. This was the main outcome of the PhD research work, which allows for optimum bitumen and mastic selection and ranking in terms of overall performance and specific desired criteria. Since this dissertation is a cumulative dissertation, it has been divided into three distinct parts. The first part forms a framework of the research undertaken and justifies the need and use of the dissertation in the future, along with explaining the test procedures in detail and resulting performance diagram developed using the data of three bitumen of the same penetration grade. The main part involves the published research – four journal papers and one chapter published in conference proceedings. The first paper uses the method developed to study one base bitumen and corresponding mastics with Limestone, Dolomite, Rhyolite and Granodiorite fillers. Other than understanding how fillers influence different mechanical properties, a main finding was that the specific surface area of the filler was the most sensitive parameter affecting the mechanical response of the mastics. Also, it was observed that the mastic prepared with Granodiorite filler showed the best fatigue and rutting resistance for this particular bitumen. Hence, the procedure could help identifying optimum filler-bitumen relations in advance. The second paper was about crumb rubber modified bitumen. This involved the study of four materials – one base bitumen and two different types of crumb rubber added different proportions. The results indicated an improvement in all performance-related properties by crumb rubber addition in bitumen and further allowing the ranking of materials. The third paper studied the feasibility of recycling a waste Ceramic powder as a filler alternative and it was found to have more superior performance than the commonly used Limestone filler. The fourth paper considers how addition of one filler, Limestone, to three differently-sourced bitumen of the same grade affects the properties of mastics. This study further emphasises the need to study mastics and predetermine the optimum filler-bitumen combinations that could avoid long-term maintenance costs. The fifth paper emphasises the need to move from current empirical testing to more specialised testing for bitumen by presenting different performance based results for three commonly used bitumen of penetration grade 50/70 that showed significant differences in the performance parameters. The third part of the dissertation is an additional section that includes the paper that was submitted to a journal and is currently in the second round of reviews under review. This paper studies fatigue behaviour of bitumen at different temperatures and frequencies using the Dissipated Energy (DE) approach. Fatigue functions were determined based on the relation between DE and the load cycle at failure. Based on these, a temperature was found to be a ‘frequency-free transition temperature’ for this bitumen as the failure lines at this temperature were overlapping at both frequencies tested. / Diese Dissertation präsentiert die Ergebnisse einer Forschungsarbeit zur Charakterisierung von Bitumen und Mastix, die als Bestandteil von Asphaltgemischen verwendet werden. Die Ergebnisse einer großen Anzahl von Dynamisches Scherrheometer (DSR) Versuche, die im Labor des Instituts für Stadtbauwesen und Straßenbau der TU Dresden durchgeführt wurden, bilden die Grundlage für diese Arbeit. Das Hauptziel dieser Dissertation bestanden darin, ein grundlegendes Verständnis über das mechanische Verhalten von Bitumen und Mastix zu gewinnen. Die durchgeführten DSR Versuche umfassten Frequenzsweeps für die Erfassung des rheologischen Verhaltens, Single Stress Creep Recovery Versuche (SSCR) für die Charakterisierung des permanenten Verformungsverhaltens, Dresden Cryogenic (DDCT) Versuche zur Erfassung des Verhaltes bei niedrigen Temperaturen und Ermüdungsversuche. Des Weiteren wurden ausgewählte Versuche am Bitumen und Mastix durchgeführt, um die Alterungsempfindlichkeit der Materialien zu untersuchen. Die Ergebnisse der Frequenzsweeps wurden ebenfalls mit einem geeigneten rheologischen Ansatz modelliert, um rheologische Charakteristiken über einen großen Frequenz- und Temperaturbereich abzuleiten. Schließlich wurde im Rahmen der Dissertation ein Performancediagramm für Bitumen und Mastix entwickelt. Auf der Grundlage der durchgeführten DSR-Versuche konnten Parameter für dieses Performancediagramm synthetisiert werden. Da es sich bei dieser Arbeit um eine kumulative Dissertation handelt, wurde erfolgte eine Aufgliederung in drei Teile. Der erste Teil der Arbeit umfasst eine Zusammenfassung der durchgeführten Forschungsarbeiten. Insbesondere werden die durchgeführten DSR Versuche detailliert erläutert und das entwickelte Performancediagramm am Beispiel von drei verschiedenen Bitumen 50/70 dargestellt. Der Hauptteil der Arbeit umfasst vier Veröffentlichungen in Fachzeitschriften sowie ein Konferenzbeitrag. Die erste Beitrag widmet sich der Untersuchung des Einflusses von verschiedenen Füllern (Kalkstein-, Dolomit-, Rhyolith- und Granodioritfüller) auf das Verhalten von Mastix unter Verwendung desselben Bitumens 50/70. Dabei hat sich gezeigt, dass die spezifische Oberfläche des Füllers der entscheidende Parameter ist, der das Verhalten von Mastix beeinflusst. Es wurde auch beobachtet, dass der mit Granodiorit-Füller hergestellte Mastix die beste Ermüdungs- und Spurrinnenbeständigkeit für dieses spezielle Bitumen zeigte. Daher könnte das in der Veröffentlichung vorgestellte Verfahren dazu beitragen, das optimale Verhältnis zwischen Füller und Bitumen im Voraus zu ermitteln. Die zweite Veröffentlichung befasst sich mit gummimodifiziertem Bitumen. Dabei wurden vier Materialien untersucht - ein Grundbitumen und zwei verschiedene Arten von Gummigranulaten mit unterschiedlichen Anteilen. Die Ergebnisse zeigten eine Verbesserung aller leistungsbezogenen Eigenschaften durch den Zusatz von Gummigranulat im Bitumen. Die dritte Veröffentlichung untersuchte die Eignung von Keramikmehl als Füller für Asphaltgemische. Dabei konnte festgestellt werden, dass dieser Keramikfüller zu besseren Eigenschaften des Mastix für das verwendete Bitumen im Vergleich zu einem Kalksteinfüller führt. Die vierte Veröffentlichung befasst sich hier mit der Frage, wie sich die Zugabe eines Füllers (Kalkstein-Füller) zu drei Bitumen unterschiedlicher Provenienz, jedoch derselben Sorte auf die Eigenschaften von Mastix auswirkt. Diese Studie unterstreicht weiter die Notwendigkeit, Mastix zu untersuchen um die optimalen Füller-Bitumen-Kombinationen zu bestimmen. Die fünfte Veröffentlichung betont die Notwendigkeit, von den derzeitigen empirischen Versuchen an Bitumen, wie z.B. Ring und Kugel Versuch zu performance-orientierten Versuchen für Bitumen überzugehen. Am Beispiel der Ergebnisse von DSR Versuchen an drei verschiedenen Bitumen 50/70 wird gezeigt, dass diese Bitumen sehr unterschiedliches mechanisches Verhalten aufweisen. Verdeutlicht wird dieser Sachverhalt in einem Performance-Diagramm, welches ausführlich in der Veröffentlichung diskutiert wird. Der dritte Teil der Dissertation beinhaltet eine Veröffentlichung, die bei Fachzeitschriften eingereicht wurde und sich derzeit im Review befindet. Zusätzlich wurde in dieser Arbeit das Ermüdungsverhalten von Bitumen bei verschiedenen Temperaturen und Frequenzen mit Hilfe des Dissipated Energy (DE)-Ansatzes untersucht. Die Versagenslinien wurden auf der Grundlage der Beziehung zwischen DE und der Lastwechselzahl beim Versagen entwickelt. Auf dieser Grundlage wurde eine Temperatur als 'frequenzfreie Übergangstemperatur' für dieses Bitumen ermittelt, da sich die Ermüdungsfunktionen bei dieser Temperatur bei beiden getesteten Frequenzen überlappen.
4

Aplikace metakaolinu v žárovzdorných materiálech / Application of metakaolin in refractory materials

Tvrdík, Lukáš January 2016 (has links)
Refractory materials are irreplaceable in all industrial fields where it is necessary to use high temperatures. This paper deals with the use of metakaolin in refractory materials that allows the operation of such facilities. In recent decades has the development made significant progress in quality parametres, which extended life period of refractory materials in their use and significantly decreased the specific consumption of refractory materials in various technologies. This phenomenon is also called "harakiri effect". At the same time a constant pressure to the lowest prices of products is on the refractory market. Metakaolin seems to be appropriate raw material, which may help to achieve interesting qualitative effects. It may affect many properties of the influence on the behavior of materials during processing, through physico-mechanical parameters and dipping to the economic efficiency of production.
5

Evaluation of the fatigue damage behavior of fine aggregate matrices prepared with modified asphalt binders / Avaliação do comportamento ao dano por fadiga de matrizes de agregado fino preparadas com ligantes asfálticos modificados

Ng, Andressa Ka Yan 24 August 2017 (has links)
The fatigue cracking process occurs by the repeated dynamic loading from the traffic of heavy vehicle. This phenomenon initiates as microcracks and develops under two circumstances: (i) after adhesive failure, when the crack occurs at the interface aggregate-mortar, and/or (ii) after cohesive failure, when the crack develops within the mortar. Based on such interpretation of the cracking phenomenon in asphalt concrete mixtures, researchers have been using the fine aggregate matrices (FAMs) to estimate the fatigue behavior of the asphalt concrete. Good agreement is observed between the properties of the FAM and asphalt concrete properties in studies related to moisture damage, fatigue cracking and permanent deformation. Regarding the fatigue resistance of the flexible pavements, it is important to investigate the effect of the use of modified binders and the binder aging on the fatigue properties of the asphalt concrete, once that the modified binder can enhance the fatigue behavior of the asphalt concrete, and the binder aging hardens the asphalt binder and turns it into a fragile material, with negative effects on the fatigue life of the asphalt concrete. Based on these evidences, this study has the objective of evaluating the effect of modified binders and aging level on the fatigue life of the FAMs, asphalt mastics and asphalt binders. The three scales are comprised of four asphalt binders (neat, AC+PPA, AC+SBS and AC+rubber) aged in short- and long-term. The fatigue properties of the three scales were evaluated by means of the viscoelastic continuum damage (VECD) concepts, once that this theory is able to predict the asphalt concrete behavior independent of loading mode (uniaxial or torsional), control mode (stress-control or strain-control), and amplitude loading applied to induce the damage. The overall results indicate that the addition of modified binder enhances the fatigue behavior and that extended aging is capable of compromise the fatigue performance. At the scales of the binder and the mastic, the AC+rubber presented the best fatigue performance, occupying the first position in the final rank order, and the AC+SBS presented the worst performance, occupying the last position. However, at the FAM scale, the FAMs prepared with the AC+SBS presented the best fatigue performance, occupying the first position in the final rank order, and the FAMs prepared with the neat binder presented the worst behavior, occupying the last position. The best correlation between the three scales regarding the short- and long-term aging was obtained between binder and mastics aged in the PAV with the FAMs aged in long-term for 30 days. / O processo de trincamento por fadiga ocorre devido ao carregamento dinâmico repetido do tráfego de veículos pesados. Este fenômeno tem o início por meio de microtrincas e se propaga por meio de duas condições: (i) após a ruptura adesiva, quando a trinca ocorre na interface entre agregado e mástique, e/ou (ii) após a ruptura coesiva, quando o processo de trincamento ocorre no mástique. Com base nesta interpretação para o trincamento por fadiga em mistura asfáltica, pesquisadores vêm usando matrizes de agregado fino (MAFs) para estimar o comportamento da mistura asfáltica completa quanto ao dano por fadiga. Boa correlação é observada entre as propriedades da MAF e da mistura asfáltica completa (MAC) em estudos relacionados ao dano por umidade, fadiga e deformação permanente. Com relação a resistência de pavimentos flexíveis, é importante avaliar o efeito do uso de ligantes asfálticos modificados e do envelhecimento do ligante nas propriedades da mistura asfáltica, uma vez que ligantes modificados podem melhorar o comportamento da mistura asfáltica quanto ao dano por fadiga, e o envelhecimento do ligante asfáltico pode enrijecer o material tornando-o mais frágil, reduzindo a vida de fadiga das misturas asfálticas. Levando em consideração as evidências apresentadas, este estudo tem por objetivo avaliar o efeito de ligantes asfálticos modificados e o nível de envelhecimento na vida de fadiga das MAFs, mástiques e ligantes asfálticos. Estas três escalas da mistura asfáltica completa foram compostas por quatro ligantes asfálticos (CAP 50/70, CAP+PPA, CAP+SBS e CAP+borracha) envelhecidos a curto e a longo prazo. As propriedades das três escalas quanto ao dano por fadiga foram avaliadas por meio dos conceitos da teoria do dano contínuo em meio viscoelástico (VECD), uma vez que esta teoria é capaz de prever o comportamento da mistura asfáltica independentemente do modo de carregamento (uniaxial ou torsional, tensão ou deformação controlada) e da amplitude do carregamento aplicado ao material para induzir o dano. De modo geral, os resultados indicaram que o uso de ligantes asfálticos modificados melhoram o comportamento das MAFs quanto ao dano por fadiga e o envelhecimento é capaz de comprometer o desempenho das MAFs quanto ao trincamento por fadiga. Na escala do ligante e do mástique asfáltico, o CAP+borracha apresentou o melhor desempenho à fadiga, ocupando o primeiro lugar no ordenamento final, e o CAP+SBS o pior desempenho, ocupando a última posição. Entretanto, na escala da MAF, as MAFs preparadas com CAP+SBS apresentaram o melhor desempenho à fadiga, ocupando o primeiro lugar no ordenamento final, e as MAFs preparadas com CAP 50/70 apresentaram o pior desempenho, ocupando o último lugar no ordenamento final. A melhor correlação entre as três escalas com relação ao envelhecimento a curto e a longo prazo, foi obtido entre os ligantes asfálticos e mástiques envelhecidos no PAV com as MAFs envelhecidas a longo prazo por 30 dias.
6

Phenomena occurring during cyclic loading and fatigue tests on bituminous materials : Identification and quantification / Phénomènes apparaissant dans les matériaux bitumineux lors de chargements cycliques et d’essais de fatigue : Identification et quantification

Babadopulos, Lucas 15 September 2017 (has links)
La fatigue est un des principaux mécanismes de dégradation des chaussées. En laboratoire, la fatigue est simulée en utilisant des essais de chargement cyclique, généralement sans période de repos. L’évolution du module complexe (une propriété du matériau utilisée dans la caractérisation de la rigidité des matériaux viscoélastiques) est suivie de manière à caractériser l’endommagement. Son changement est généralement interprété comme étant dû au dommage, alors que d’autres phénomènes (se distinguant du dommage par leur réversibilité) apparaissent. Des effets transitoires, propres aux matériaux viscoélastiques, apparaissent lors des tout premiers cycles (2 ou 3) et produisent une erreur dans la détermination du module complexe. La non-linéarité (dépendance du module complexe avec le niveau de déformation) est caractérisée par une diminution réversible instantanée du module et une augmentation de l’angle de phase qui est observée avec l’augmentation de l’amplitude de déformation. De plus, pendant le chargement, de l’énergie mécanique est dissipée en raison du caractère visqueux du comportement du matériau. Cette énergie se transforme principalement en chaleur ce qui induit une augmentation de température. Cela produit une diminution de module liée à cet auto-échauffement. Quand le matériau revient à la température initiale, le module initial est alors retrouvé. La partie restante du changement de module peut être expliquée, d’une part par un autre phénomène réversible, appelé dans la littérature « thixotropie », et d’autre part par le dommage « réel », qui est irréversible. Cette thèse explore ces phénomènes dans les bitumes, mastics (bitume mélangé avec des particules fines, dont le diamètre est inférieur à 80μm) et enrobés bitumineux. Un chapitre (sur la nonlinearité) présente des essais de « balayage d’amplitude de déformation » avec augmentation ou/et diminution des amplitudes sont présentés. Un autre se concentre sur l’auto-échauffement. Il comprend une proposition de procédures de modélisation dont les résultats sont comparés avec des résultats des cycles initiaux d’essais de fatigue. Finalement, un chapitre est dédié à l’analyse du module complexe mesuré pendant le chargement et les phases de repos. Des essais de chargement et repos ont été réalisés sur bitume (où le phénomène de thixotropie est supposé avoir lieu) et mastic, de manière à déterminer l’effet de chacun des phénomènes identifiés sur l’évolution du module complexe des matériaux testés. Les résultats de l’étude sur la nonlinearité suggèrent que son effet vient principalement du comportement non linéaire du bitume, qui est déformé de manière très non-homogène dans les enrobés bitumineux. Il est démontré qu’un modèle de calcul thermomécanique simplifié de l’échauffement local, ne considérant aucune diffusion de chaleur, peut expliquer le changement initial de module complexe observé au cours des essais cycliques sur enrobés. Néanmoins, la modélisation de la diffusion de chaleur a démontré que cette diffusion est excessivement rapide. Cela indique que la distribution de l’augmentation de température nécessaire pour expliquer complètement le module complexe observé ne peut pas être atteinte. Un autre phénomène réversible, qui a des effets sur le module complexe similaires à ceux d’un changement de température, doit donc avoir lieu. Ce phénomène est considéré être de la thixotropie. Finalement, à partir des essais de chargement et repos, il est démontré qu’une partie majeure du changement de module complexe au cours des essais cycliques vient des processus réversibles. Le dommage se cumule de manière approximativement linéaire par rapport au nombre de cycles. Le phénomène de thixotropie semble partager la même direction sur l’espace complexe que la nonlinéarité. Cela indique que les deux phénomènes sont possiblement liés par la même origine microstructurelle. Des travaux supplémentaires sur le phénomène de thixotropie sont nécessaires. / Fatigue is a main pavement distress. In laboratory, fatigue is simulated using cyclic loading tests, usually without rest periods. Complex modulus (a material stiffness property used in viscoelastic materials characterisation) evolution is monitored, in order to characterise damage evolution. Its change is generally interpreted as damage, whereas other phenomena (distinguishable from damage by their reversibility) occur. Transient effects, proper to viscoelastic materials, occur during the very initial cycles (2 or 3) and induce an error in the measurement of complex modulus. Nonlinearity (strain-dependence of the material’s mechanical behaviour) is characterised by an instantaneous reversible modulus decrease and phase angle increase observed when strain amplitude increases. Moreover, during loading, mechanical energy is dissipated due to the viscous aspect of material behaviour. This energy turns mainly into heat and produces a temperature increase. This produces a modulus decrease due to self-heating. When the material is allowed to cool back to its initial temperature, initial modulus is recovered. The remaining stiffness change can be explained partly by another reversible phenomenon, called in the literature “thixotropy”, and, then, by the “real” damage, which is irreversible. This thesis investigates these phenomena in bitumen, mastic (bitumen mixed with fine particles, whose diameter is smaller than 80μm) and bituminous mixtures. One chapter (on nonlinearity) presents increasing and/or decreasing strain amplitude sweep tests. Another one focuses on selfheating. It includes a proposition of modelling procedures whose results are compared with the initial cycles from fatigue tests. Finally, a chapter is dedicated to the analysis of the measured complex modulus during both loading and rest periods. Loading and rest periods tests were performed on bitumen (where the phenomenon of thixotropy is supposed to happen) and mastic in order to determine the effect of each of the identified phenomena on the complex modulus evolution of the tested materials. Results from the nonlinearity investigation suggest that its effect comes primarily from the nonlinear behaviour of the bitumen, which is very non-homogeneously strained in the bituminous mixtures. It was demonstrated that a simplified thermomechanical model for the calculation of local selfheating (non-uniform temperature increase distribution), considering no heat diffusion, could explain the initial complex modulus change observed during cyclic tests on bituminous mixtures. However, heat diffusion modelling demonstrated that this diffusion is excessively fast. This indicates that the temperature increase distribution necessary to completely explain the observed complex modulus decrease cannot be reached. Another reversible phenomenon, which has effects on complex modulus similar to the ones of a temperature change, needs to occur. That phenomenon is hypothesised as thixotropy. Finally, from the loading and rest periods tests, it was demonstrated that a major part of the complex modulus change during cyclic loading comes from the reversible processes. Damage was xivfound to cumulate in an approximately linear rate with respect to the number of cycles. The thixotropy phenomenon seems to share the same direction in complex space as the one of nonlinearity. This indicates that both phenomena are possibly linked by the same microstructural origin. Further research on the thixotropy phenomenon is needed.
7

Evaluation of the fatigue damage behavior of fine aggregate matrices prepared with modified asphalt binders / Avaliação do comportamento ao dano por fadiga de matrizes de agregado fino preparadas com ligantes asfálticos modificados

Andressa Ka Yan Ng 24 August 2017 (has links)
The fatigue cracking process occurs by the repeated dynamic loading from the traffic of heavy vehicle. This phenomenon initiates as microcracks and develops under two circumstances: (i) after adhesive failure, when the crack occurs at the interface aggregate-mortar, and/or (ii) after cohesive failure, when the crack develops within the mortar. Based on such interpretation of the cracking phenomenon in asphalt concrete mixtures, researchers have been using the fine aggregate matrices (FAMs) to estimate the fatigue behavior of the asphalt concrete. Good agreement is observed between the properties of the FAM and asphalt concrete properties in studies related to moisture damage, fatigue cracking and permanent deformation. Regarding the fatigue resistance of the flexible pavements, it is important to investigate the effect of the use of modified binders and the binder aging on the fatigue properties of the asphalt concrete, once that the modified binder can enhance the fatigue behavior of the asphalt concrete, and the binder aging hardens the asphalt binder and turns it into a fragile material, with negative effects on the fatigue life of the asphalt concrete. Based on these evidences, this study has the objective of evaluating the effect of modified binders and aging level on the fatigue life of the FAMs, asphalt mastics and asphalt binders. The three scales are comprised of four asphalt binders (neat, AC+PPA, AC+SBS and AC+rubber) aged in short- and long-term. The fatigue properties of the three scales were evaluated by means of the viscoelastic continuum damage (VECD) concepts, once that this theory is able to predict the asphalt concrete behavior independent of loading mode (uniaxial or torsional), control mode (stress-control or strain-control), and amplitude loading applied to induce the damage. The overall results indicate that the addition of modified binder enhances the fatigue behavior and that extended aging is capable of compromise the fatigue performance. At the scales of the binder and the mastic, the AC+rubber presented the best fatigue performance, occupying the first position in the final rank order, and the AC+SBS presented the worst performance, occupying the last position. However, at the FAM scale, the FAMs prepared with the AC+SBS presented the best fatigue performance, occupying the first position in the final rank order, and the FAMs prepared with the neat binder presented the worst behavior, occupying the last position. The best correlation between the three scales regarding the short- and long-term aging was obtained between binder and mastics aged in the PAV with the FAMs aged in long-term for 30 days. / O processo de trincamento por fadiga ocorre devido ao carregamento dinâmico repetido do tráfego de veículos pesados. Este fenômeno tem o início por meio de microtrincas e se propaga por meio de duas condições: (i) após a ruptura adesiva, quando a trinca ocorre na interface entre agregado e mástique, e/ou (ii) após a ruptura coesiva, quando o processo de trincamento ocorre no mástique. Com base nesta interpretação para o trincamento por fadiga em mistura asfáltica, pesquisadores vêm usando matrizes de agregado fino (MAFs) para estimar o comportamento da mistura asfáltica completa quanto ao dano por fadiga. Boa correlação é observada entre as propriedades da MAF e da mistura asfáltica completa (MAC) em estudos relacionados ao dano por umidade, fadiga e deformação permanente. Com relação a resistência de pavimentos flexíveis, é importante avaliar o efeito do uso de ligantes asfálticos modificados e do envelhecimento do ligante nas propriedades da mistura asfáltica, uma vez que ligantes modificados podem melhorar o comportamento da mistura asfáltica quanto ao dano por fadiga, e o envelhecimento do ligante asfáltico pode enrijecer o material tornando-o mais frágil, reduzindo a vida de fadiga das misturas asfálticas. Levando em consideração as evidências apresentadas, este estudo tem por objetivo avaliar o efeito de ligantes asfálticos modificados e o nível de envelhecimento na vida de fadiga das MAFs, mástiques e ligantes asfálticos. Estas três escalas da mistura asfáltica completa foram compostas por quatro ligantes asfálticos (CAP 50/70, CAP+PPA, CAP+SBS e CAP+borracha) envelhecidos a curto e a longo prazo. As propriedades das três escalas quanto ao dano por fadiga foram avaliadas por meio dos conceitos da teoria do dano contínuo em meio viscoelástico (VECD), uma vez que esta teoria é capaz de prever o comportamento da mistura asfáltica independentemente do modo de carregamento (uniaxial ou torsional, tensão ou deformação controlada) e da amplitude do carregamento aplicado ao material para induzir o dano. De modo geral, os resultados indicaram que o uso de ligantes asfálticos modificados melhoram o comportamento das MAFs quanto ao dano por fadiga e o envelhecimento é capaz de comprometer o desempenho das MAFs quanto ao trincamento por fadiga. Na escala do ligante e do mástique asfáltico, o CAP+borracha apresentou o melhor desempenho à fadiga, ocupando o primeiro lugar no ordenamento final, e o CAP+SBS o pior desempenho, ocupando a última posição. Entretanto, na escala da MAF, as MAFs preparadas com CAP+SBS apresentaram o melhor desempenho à fadiga, ocupando o primeiro lugar no ordenamento final, e as MAFs preparadas com CAP 50/70 apresentaram o pior desempenho, ocupando o último lugar no ordenamento final. A melhor correlação entre as três escalas com relação ao envelhecimento a curto e a longo prazo, foi obtido entre os ligantes asfálticos e mástiques envelhecidos no PAV com as MAFs envelhecidas a longo prazo por 30 dias.

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