The diploma thesis deals with possibility of utilization raw materials from alternative sources for production of cement-bonded particleboards. In theoretical part the possibilities of modifying composition of cement-bonded slabs with emphasis on their matrix are discussed in detail. On basis of the findings and their evaluation, waste from the formatting of cement-bonded particleboards, micronized limestone, heat sink and high temperature fly ash were selected to the composition modification. The mentioned raw materials were analyzed and subsequently tested as substitutes for the matrix of cement-bonded particleboards in the experimental part. The properties of the proposed materials were tested even in the longer term, including the microstructure.

Design and manufacture of test elements for experimental testing laboratory. Testing of selected mechanical characteristics of test elements. Experimental analysis of test elements in the lab, creating a mathematical model in ATENA software and static calculation. Evaluation of experimental analysis and comparison with the values of numerical analysis. Graphic comparing the results of a final overall evaluation.

As all materials used for exterior construction, cement-bonded particleboards also subject to climatic effects, such as frost, chemicals (eg. sulphates) or UV rays. Degradation of theese effects is slightly increased by organic base. Increased susceptibility can be eliminated by a effective coating, which reduces direct contact with aggresive influences on the board and provides longer durability. Theoratical part of this thesis analyzes different types of negatice influences and their effect on durability. Practical part contains selection of specific types of coating and assessment of their mechanical and aesthetic properties including spectrophotometric analysis of color change for each degradation effect.

L’Agence nationale pour la gestion des déchets radioactifs (l’Andra) en France propose un nouveau type de voussoirs de tunnel pour les ouvrages très profonds. Pour éviter des segments de tunnel trop épais, ils proposent d’intégrer une couche de matériau granulaire sur l’extrados d’un voussoir moins épais. Cette approche prétend utiliser la grande compressilibité de la couche granulaire constituée de particules broyables et les transferts de charge interne au matériau granulaire pour réduire l’épaisseur du voussoir tout en gardant des performances mécaniques importantes. Un segment de tunnel avec une telle conception est appelé un VMC monobloc compressible (brevet en instance de l’Andra & CMC). Il s’agit d’un nouveau type de revêtement de tunnel particulièrement innovant.Cette thèse est consacrée à la création d’un modèle numérique capable de reproduire le comportement mécanique d’un couche granulaire très compressible à l’aide de la méthode aux éléments discrets (DEM) en 3D. Le milieu granulaire est constitué de particules d’argile cylindriques creuses appelées textitcoques. Chaque coque est un tube de 2 cm de long avec un diamètre de 2 cm. La faible épaisseur de la coque cylindrique la rend essentiellement constituée de vide entourée d’une fine couche d’argile. Dans le modèle, un cluster sécable (la coque) est généré à l’aide de clumps sphéro-polyédriques allon- gées . Ces clumps, appelés secteurs, sont associés entre eux en utilisant deux lois de contact adhésives. Si la combinaison des forces de contact normales et tangentielles satisfait un critère de charge spécifique, la coque se casse au niveau de l’interface entre les deux secteurs. L’outil DEM Rockable mis au point pour cette recherche peut fonctionner sur ces particules fragiles. Les propriétés mécaniques des coques, composé de 12 à 24 secteurs, sont ajustées à l’aide d’essais de compression radiale uniaxiale (verticale). Les expériences à l’échelle du grain sur les coques en argile cuite ont servi de référence. Nous avons déterminé la plage réelle de rupture et sa distribution statistique (Weibull). Les paramètres numériques et mécanique ainsi obtenus ont été validés avec succès dans le cas de la compression radiale d’une coque contrainte latéralement.Dans un premier temps, l’étude des assemblages de coques porte sur la caractérisation expérimen- tale des échantillons avec un controle sur les variables d’état initiales telles que la densité et l’orienta- tions des coques. La reconstruction 3D à partir de tomographies à rayons X d’échantillons de coques carottés dans l’extrados d’un voussoir nous a permis de caractériser l’anisotropie de l’orientation des particules. Il s’agit là d’une information précieuse pour la génération d’échantillons numériques ayant les caractéristiques initiales pertinentes. Deuxièmement, des simulations DEM de compressions oedo- métriques sur des échantillons de ⟨2 000⟩ coques sont réalisées. Une étude paramétrique permet de mettre en évidence le rôle des variables d’état initiales. Un ensemble bien choisi de variables initiales et des paramètres DEM correctement adaptés permettent d’obtenir des simulations prédictives pertinentes pour une comparaison avec les expériences de laboratoire. Une analyse micro-mécanique de l’effet de la proportion des grains cassés sur les contraintes locales exercées sur les coques (et les fragments) est effectuée. Il est observé que la rupture des coques entraîné une compressibilité élevée du matériau. Par conséquent, la réponse mécanique en déformation est considérée comme une conséquence directe de l’évolution de la rupture des particules. Pour finir, un modèle analytique de prédiction de la re- lation Contrainte↔Déformation est proposé dans le cas de la compression oedométrique. Ce modèle prédictif tient compte des variables internes du milieu granulaire comme la résistance mécanique en compression des coques. / The National Agency for Radioactive Waste Management (FR Andra) in France suggested a new way to design a tunnel lining, especially, beneficial in the case of very deep tunnels. To avoid very thick tunnel segments, they propose to integrate a layer of granular material on the extrados of the thinner lining. This approach takes the advantages of the compressible capacity of the crushable particles and the load transfer in the granular material. A tunnel segment with such design is called a Mono-block Compressible Arch-segment VMC (Andra’s & CMC’s pending patent) and is an innovative new type of tunnel linings.This PhD dissertation is dedicated to the creation of a numerical model capable of reproducing the mechanical behaviour of this compressible granular layer using 3D Discrete Element Method (DEM). The granular packing is made of the brittle hollow coarse-size cylindrical particles, called shells. Each shell is a 2 cm long tube with a diameter of 2 cm. Its small thickness makes the cylindrical shell mainly made of void surrounded by a thin layer of clay. In the model, a breakable cluster (shell) is generated using sphero-polyhedral elongated clumps. These clumps, called sectors, are glued together using two adhesive contact force laws. If the combination of the normal and tangential contact forces exceeds a suitable failure criterion, a de-clustering of the shell (breakage) occurs. The DEM tool Rockable devel- oped for this research can operate on such crushable particles. The mechanical properties of the shell model, composed of 12 to 24 sectors, are adjusted in the case of a uniaxial (vertical) radial compres- sion of shells. The preceding grain-scale experiments on the true shells made of baked clay serve as a reference. We determine the true range of the failure tensile load and its statistical Weibull distribu- tion. The user-specified parameters is then successfully validated in the case of radial compression of a horizontally constrained shell.Firstly, the macroscopic study of shell assemblies focuses on the experimental characterisation of the samples with a control of the initial state variables like a number density and a spatial arrangement of shells (shells orientations). 3D reconstruction from X-ray tomographies of the original coated shells samples extracted from the extrados of a tunnel segment help us to characterise the anisotropy of the shells orientation. This is a piece of valuable information to the generation the numerical samples of shells with relevant initial features. Secondly, a series of DEM oedometric tests on ⟨1 000 : 2 000⟩ shells is simulated. A parametric study successfully leads to the understanding of each internal state variable role. A well-chosen set of initial variables with properly adapted DEM parameters give the relevant predictive simulations for a final comparison with the experimental oedometer tests. Thanks to a discrete insight into the micromechanics, the evolutions of the breakage level, the orientation anisotropy and the local stresses exerted on the shells (and/or the fragments) are quantified during the compression. The breakage of the shells result in high compressibility of the material. Therefore, the mechanical response is seen as a consequence of the breakage evolution. Finally, an analytical model is suggested in order to predict the Stress↔Void ratio relationship knowing the initial state of the sample and the tensile strength of the constituents: the shells.

Die Arbeit führt Methoden zur Durchführung von Zugversuchen und bruchmechanischen Versu-chen ein und liefert mechanische Kennwerte für zwei kohlenstoffgebundene FFW im Bereich von RT bis 1500°C. Dafür standen ein grobkörniges MgO-C und ein feinkörniges Al2O3-C zur Ver-fügung. Die Werkstoffe zeigten bis 1200°C keine Duktilität und sprachen spröde. Die Schädigung erfolgte ausschließlich durch Risswachstum. Dieses fand beim MgO-C temperaturunabhängig auf Grund der rissbehafteten Mikrostruktur durch stabiles Risswachstum bereits vorhandener Risse statt. Es kam dabei zur Bildung von Rissnetzwerken sowie zu zahlreichen energiedissipierenden Prozessen. Beim Al2O3-C trat be RT instabiles Risswachstum auf. Bei hohen Temperaturen kam es durch thermisch aktivierte Prozesse zu duktilem Verhalten und stabilem Risswachstum. Beim grobkörnigen MgO-C wurden große Verformungen durch das starre Oxidgerüst verhindert. Zu-sätzlich zeigten die Werkstoffe auf Grund ihrer Mikrostruktur eine Zunahme der Festigkeit mit steigender Temperatur. Aus den Versuchen wurde ein Heißpressverfahren zur Herstellung von gradierten Werkstoffen abgeleitet.:1 Einleitung 2 Grundlagen 2.1 Feuerfestwerkstoffe 2.1.1 Einsatz und Beanspruchung von FFW 2.1.2 Einteilung von FFW 2.2 Kohlenstoffgebundene FFW 2.2.1 Kohlenstoff und seine Terminologie 2.2.2 Grundlegende Eigenschaften kohlenstoffgebundener FFW 2.2.3 Anwendungen kohlenstoffgebundener FFW 2.2.4 Aufbau und Mikrostruktur kohlenstoffgebundener FFW 2.2.5 Herstellungsparameter kohlenstoffgebundener FFW 2.2.6 Chemische Eigenschaften kohlenstoffgebundener FFW 2.3 Mechanische Eigenschaften kohlenstoffgebundener FFW 2.3.1 Mechanische Eigenschaften kohlenstoffgebundener FFW bei RT 2.3.2 Mechanische Eigenschaften kohlenstoffgebundener FFW bei HT 2.4 Grundlagen zur Werkstoffprüfung bei RT und hohen Temperaturen 2.4.1 Streuung und Einfluss der Probengröße 2.4.2 Belastungsrate 2.4.3 Zugversuche 2.4.4 Druckversuche 2.4.5 Biegeversuche 2.4.6 Bruchmechanische Untersuchungen 2.4.7 Temperaturwechselbeständigkeit 2.4.8 Kriechen 2.4.9 Spannungsrelaxation 2.4.10 Härtemessung 2.4.11 Hochtemperaturprüfung in Kaltkammerofen mit induktiver Heizung 2.4.12 Temperaturmessung mit Thermoelement, Pyrometrie, Thermographie 2.4.13 Bestimmung elastischer Konstanten mittels akustischer Methoden 2.4.14 Optische in situ Schadensbeschreibung mittels Mikroskopie und DIC 2.5 Heißpressverfahren 3 Experimentelles 3.1 Werkstoffe 3.1.1 Kohlenstoffgebundenes Magnesiumoxid (MgO-C) 3.1.2 Kohlenstoffgebundenes Aluminiumoxid (Al2O3-C) 3.1.3 Graphit (ISEM 8) 3.2 Mechanische Tests 3.2.1 Prüfmaschine für Druck- und Biegeversuche 3.2.2 Prüfmaschine für Zug-Druck-Versuche 3.2.3 Probengeometrien 3.2.4 Druckversuche 3.2.5 Biegeversuche 3.2.6 Bruchmechanische Versuche 3.2.7 Versuche mit Zugbeanspruchung 3.2.8 Versuchsabläufe der Hochtemperaturversuche 3.2.9 Temperaturmessung mittels Thermographie 3.3 Weitere Versuchsmethoden 3.3.1 Mikrostrukturuntersuchung mittels Mikroskopie und Röntgenbeugung 3.3.2 Porositäts- und Dichtemessung 3.3.3 Härtemessung 3.3.4 Dynamischer E-Modul 4 Methodische Erkenntnisse und Voruntersuchungen 4.1 Temperaturmessung und -verteilung 4.1.1 Temperaturmessung mittels Thermoelement und Pyrometer 4.1.2 Emissionskoeffizient und Probenbeschichtung 4.1.3 Temperaturverteilung 4.2 Dehnungsmessung 4.3 Zugversuche an Keramiken 4.3.1 Übertragung von Zugkräften 4.3.2 Axialität in Zugversuchen 4.4 Bruchmechanische Versuche 4.4.1 Kerbeinbringung 4.4.2 Überprüfung des optischen Messsystems 4.4.3 Bestimmung der Risslänge während des Versuchs 4.5 Überprüfung der Messmethodik mit dem Referenzwerkstoff Graphit ISEM-8 5 Ergebnisse 5.1 Mikrostrukturbeschreibung der untersuchten FFW 5.1.1 Mikrostruktur des MgO-C’s 5.1.2 Mikrostruktur des Al2O3-C’s 5.2 Mechanisches Verhalten bei RT 5.2.1 Mechanisches Verhalten von MgO-C bei RT 5.2.2 Mechanisches Verhalten von Al2O3-C bei RT 5.3 Mechanische Eigenschaften bei HT 5.3.1 Mechanisches Verhalten von MgO-C bei HT 5.3.2 Mechanisches Verhalten von Al2O3-C bei HT 5.4 Heißpressverfahren für kohlenstoffgebundene FFW 5.4.1 Beschreibung des Heißpressverfahrens 5.4.2 Physikalische Eigenschaften und Mikrostruktur des Presslings 5.4.3 Mechanische Eigenschaften des Presslings 6 Diskussion 7 Zusammenfassung und Ausblick Literatur Anhang

In order to improve the purity of steel castings, the use of special reactive coatings on carbon-bonded ceramic foam filters was explored. Carbon nanotubes were dispersed in water by means of ultrasonic treatment, using xanthan gum to stabilize the nanotubes in suspension and control the rheological behavior. The coatings were applied by cold spraying and binding was achieved during heat treatment in reducing atmosphere, thanks to an artificial pitch added to the slurry. The coated filters were successfully immersed in molten steel for different times. The thickness of the first alumina layer generated at the interface was independent of the immersion time: concentration gradients through its thickness suggested that the formation of this structure is limited by diffusion. Investigation of the steel after solidification by means of ASPEX showed that the presence of the coating influenced the size as well as the chemical composition of the remaining inclusions. Nano-coated filters had the best filtration efficiency (up to 95% for alumina inclusions after 10 s), but longer tests resulted in worse performance. In addition, coatings based on calcium aluminates in combination with carbon showed an efficiency greater than 97% for steel samples taken directly from the melt.

Im Rahmen der vorliegenden Arbeit wurden neuartige keramik- und stahlreiche Verbundwerkstoffe, auf Basis von MgO-teilstabilisiertem Zirkoniumdioxid und hochlegiertem austenitischem TRIP Stahl entwickelt. Die keramikreiche Verbundwerkstoffe mit bis zu 30 Vol.% metallischer Partikelverstärkung wurden über die Schlickergusstechnologie bzw. die Druckschlickergusstechnologie hergestellt und können als thermo-mechanisch beanspruchte Bauteile zum Einsatz kommen. Es wurden weiterhin metallreiche Verbundwerkstoffe mit bis zu 10 Vol.% keramischer Partikelverstärkung erstmalig über die Papiertechnologie hergestellt. Dadurch ergeben sich vielfältige Möglichkeiten metallreiche Leichtbaustrukturen mit verbesserten Energieabsorptionsvermögen zu erzeugen. Im Mittelpunkt der vorliegenden Arbeit stand die Entwicklung der keramikreichen Schlicker, die Formgebungstechnologien, die Entwicklung geeigneter Entbinderungs- und Sinterregime sowie die Charakterisierung der Verbundwerkstoffe hinsichtlich ihrer Mikrostruktur sowie der mechanischen bzw. der thermo-mechanischen Eigenschaften.

In order to considerably improve the quality of steel products, efforts are being made to increase the cleanness of steel. It is known that the size, type and distribution of non-metallic inclusions (NMIs) in metals significantly influence their mechanical properties. Within the frame of the Collaborativ Research Centre 920 'Multifunc-tional filters for metal melt filtration – a contribution to zero defect materials.”, carbon-bonded alumina filters for steel melt filtration has been investigated. In the present thesis, the interactions between coated carbon-bonded alumina filters and a steel melt were investigated in more detail, with the porous coatings being based on alumina. The time-depended behaviour was evaluated by immersing coated filters for different dwell times. After the immersion tests, the microstructure of the filter surface and the NMIs remaining in the solidified steel were examined to comprehend the interactions. The here presented results imply that carbon of the carbon-bonded alumina sub-strate took part in the filter–steel interactions. The presence of dissolved carbon at the filter–steel melt interface is essential to promote alumina dissolution and pre-cipitation processes. Thereby, the melt was locally supersaturated with aluminium, which reacted with dissolved oxygen to form secondary corundum. During these interactions, a liquid oxide film was formed directly at the ceramic surface and provided nuclei for heterogeneous nucleation of secondary corundum. After immersion during cooling, a characteristic layer built-up formed at the filters surface. All alumina-based coated filters contributed to the filtration of especially alumina-based NMIs, and outperformed the uncoated carbon-bonded alumina filter. During the first experimental trials, it became obvious that the thermal shock resistance of the alumina coating has to be enhanced. For this purpose, a material combination was investigated which so far has not been used as a coating material to the author’s knowledge: alumina-zirconia-titania in the ration 95 : 2.5 : 2.5. This material is known for its excellent thermal shock resistance. Thereby, the influence of zirconia or titania doping of the coating were considered. The addition of titania enhanced wetting of this filter by the steel melt. As a result, alumina inclusions of the steel melt were modified: they were more in number, but distinctly smaller compared to trials without filter or the immersion of the other filter types. Especially, the decreased average area of the alumina inclusions is interesting because the particle size of NMIs strongly influences the fatigue life of a steel product. The deformability of a steel product, however, is determined by the amount of NMIs. Thus, the modification of alumina inclusions by adding titania to the filter coating might present a way to tailor these inclusions depending on the product’s application.

This diploma thesis is focused to use bonded base layers with different types of admixures for base layers of roads. The first, theoretical part of the work deals with summary of the available literature. Deals with basic and uncoventional type of admixures used for bonded base layers. The second, partical part of the work deals with comparsion of 5 bonded base layers with recycled asphalt with added artifical fibers, cellulose fibers or without admixures and one mixtures created only from First of all is described tesťs methods with design of mixtures and described materials. In the practical part of the work was tested compressive strength, transverse tensile strength and compressive strength after effects of frost. In the end of the work is comparsion all mixtures between themselves and determination effects admixtures on compressive strength and transverse tensile strength.

The dissertation thesis is focused on a design of new methodology that can be used for selection of optimal variant for the revitalization of light building facade system known as OD-001 “Boletice panel” when current construction solutions and materials are implemented. Thermographic measurement and engineering survey of selected buildings was carried out to determine the defects and insufficiencies that might accompanied these structures and their revitalization. Another point of my thesis was a possibility of revitalization by bonded facade. Mechanical resistance of bonded facade was verified throughout experimental testing and by mathematical calculation. The usability was confirmed on the basis of specific criteria that were stipulated in advance. The selected criteria are focused on areas which are important for investors. These are mainly financial cost, payback period but also the impact on the environment. Simulations and advanced methods of decision making were used.