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[ES] Durante la presente tesis doctoral se ha desarrollado un proceso de mejora parcial in-situ en superficie de un crudo extrapesado que ha permitido obtener un buen rendimiento a un crudo sintético que cumple con las especificaciones necesarias para ser transportado a través de un oleoducto, esto es, un crudo sintético con una gravedad API superior a 19, una viscosidad inferior a los 300 cSt y libre de asfaltenos. Además, se ha conseguido eliminar prácticamente el 99% en peso de los metales, níquel y vanadio, presentes en el crudo de partida, lo que facilita el posterior procesado de este crudo sintético en una refinería. Las reacciones necesarias para desarrollar este proceso se han llevado a cabo utilizado una unidad Micro-Downer (MDU). Dicha unidad consta de un reactor de lecho transportado descendente y permite obtener resultados a nivel de laboratorio similares a los que se obtendrían al procesar cualquier crudo en un reactor tipo FCC a escala industrial. Se han estudiado las condiciones de reacción (temperatura, tiempo de residencia y relación sólido a carga) más adecuadas para llevar a cabo el craqueo térmico de un crudo extrapesado en este tipo de reactores. Asimismo, se ha encontrado que entre varios materiales sólidos con diferentes propiedades ácidas y texturales, es con el caolín, una arcilla natural con un cierto grado de porosidad residual en su estructura cristalina, con el que se obtiene el mayor rendimiento a productos líquidos que cumplen los requisitos de densidad y viscosidad necesarios para poder ser transportados a través de un oleoducto. Estos resultados se han obtenido tras llevar a cabo la reacción en condiciones no severas (530ºC, 0,3 s de tiempo de residencia y una relación sólido a carga de 8 g g¿1), y que por tanto no requieren de un elevado gasto energético. En contrapartida, se ha detectado que con cada uno de los sólidos utilizados y en cualquiera de las condiciones de operación estudiadas, todos los crudos sintéticos recogidos son inestables con respecto a la floculación de los asfaltenos. Con el fin de subsanar esta limitación de la tesis doctoral, en el apartado siguiente se ha intentado eliminar la fracción de asfaltenos de los líquidos finales. Para ello se ha utilizado, ya sea como sustituto del caolín o como aditivo junto a él, un material sólido con actividad para el craqueo de fondo (BCA, del inglés Bottom Cracking Additive). De este modo se pretende eliminar esta fracción de asfaltenos mediante craqueo catalítico, dando lugar a la formación de otras fracciones más ligeras de crudo, y/o mediante reacciones de condensación dan- do lugar a la formación de coque. En este apartado ha quedado demostrado que la presencia de un cierto grado de acidez, aunque residual, en el sólido de intercambio de calor empleado para procesar un crudo extrapesado como el utilizado para realizar este estudio, conlleva un incremento en el rendimiento a coque cuya principal consecuencia es una importante bajada en el rendimiento a crudo sintético final sin que, en contrapartida, se consiga eliminar el problema de la presencia de asfaltenos en los líquidos finales. Tras comprobar que para obtener crudos sintéticos estables con respecto a la fioculación de los asfaltenos es necesario eliminar la fracción residuo, es decir, los hidrocarburos con puntos de ebullición superior a los 537ºC, el siguiente paso se ha centrado en encontrar una combinación de etapas con las que sea posible convertir, o reciclar hasta la extinción, esta fracción residuo. Con este fin se han ideado tres estrategias de procesos de mejora y se han llevado a cabo estimaciones teóricas que nos han permitido conocer la mejor estrategia de procesado para obtener el mayor rendimiento a crudo sintético estable. Finalmente, la validez de este nuevo procesos se ha estimado comparando estos resultados experimentales obtenidos a escala de laboratorio con los generados al procesar este mismo crudo extrapesado en una planta piloto de delayed coking. / [CA] Durant la present tesi doctoral s'ha desenvolupat un procés de millora parcial in-*situ en superfície d'un cru extrapesado que ha permès obtenir un bon rendiment a un cru sintètic que compleix amb les especificacions necessàries per a ser transportat a través d'un oleoducte, això és, un cru sintètic amb una gravetat API superior a 19, una viscositat inferior als 300 cSt i lliure de asfaltenos. A més, s'ha aconseguit eliminar pràcticament el 99% en pes dels metalls, níquel i vanadi, presents en el cru de partida, la qual cosa facilita el posterior processament d'aquest cru sintètic en una refineria. Les reaccions necessàries per a desenvolupar aquest procés s'han dut a terme utilitzat una unitat Micro-Downer (MDU). Aquesta unitat consta d'un reactor de llit transportat descendent i permet obtenir resultats a nivell de laboratori similars als que s'obtindrien en processar qualsevol cru en un reactor tipus FCC a escala industrial. S'han estudiat les condicions de reacció (temperatura, temps de residència i relació sòlid a càrrega) més adequades per a dur a terme el craqueig tèrmic d'un cru extrapesado en aquest tipus de reactors. Així mateix, s'ha trobat que entre diversos materials sòlids amb diferents propietats àcides i texturales, és amb el caolí, una argila natural amb un cert grau de porositat residual en la seua estructura cristal·lina, amb el qual s'obté el major rendiment a productes líquids que compleixen els requisits de densitat i viscositat necessaris per a poder ser transportats a través d'un oleoducte. Aquests resultats s'han obtingut després de dur a terme la reacció en condicions no severes (530 °C, 0,3 s de temps de residència i una relació sòlid a càrrega de 8 g g1), i que per tant no requereixen d'una elevada despesa energètica. En contrapartida, s'ha detectat que amb cadascun dels sòlids utilitzats i en qualsevol de les condicions d'operació estudiades, tots els crus sintètics arreplegats són inestables respecte a la floculació dels asfaltenos. Amb la finalitat d'esmenar aquesta limitació de la tesi doctoral, en l'apartat següent s'ha intentat eliminar la fracció de asfaltenos dels líquids finals. Per a això s'ha utilitzat, ja siga com a substitut del caolí o com a additiu al costat d'ell, un material sòlid amb activitat per al craqueig de fons (BCA, de l'anglès Bottom Cracking Additive). D'aquesta manera es pretén eliminar aquesta fracció de asfaltenos mitjançant craqueig catalític, donant lloc a la formació d'altres fraccions més lleugeres de cru, i/o mitjançant reaccions de condensació donen- do lloc a la formació de coc. En aquest apartat ha quedat demostrat que la presència d'un cert grau d'acidesa, encara que residual, en el sòlid d'intercanvi de calor emprada per a processar un cru extrapesado com l'utilitzat per a realitzar aquest estudi, comporta un increment en el rendiment a coc la principal conseqüència del qual és una important baixada en el rendiment a cru sintètic final sense que, en contrapartida, s'aconseguisca eliminar el problema de la presència de asfaltenos en els líquids finals. Després de comprovar que per a obtenir crus sintètics estables respecte a la fioculación dels asfaltenos és necessari eliminar la fracció residu, és a dir, els hidrocarburs amb punts d'ebullició superior als 537 °C, el següent pas s'ha centrat en trobar una combinació d'etapes amb les quals siga possible convertir, o reciclar fins a l'extinció, aquesta fracció residu. A aquest efecte s'han ideat tres estratègies de processos de millora i s'han dut a terme estimacions teòriques que ens han permès conèixer la millor estratègia de processament per a obtenir el major rendiment a cru sintètic estable. Finalment, la validesa d'aquest nou processos s'ha estimat comparant aquests resultats experimentals obtinguts a escala de laboratori amb els generats en processar aquest mateix cru extrapesado en una planta pilot de delayed coking. / [EN] During this doctoral thesis it has been developed an in-situ extra-heavy crude oil partial upgrading process that has allowed to obtain a good yield to a synthetic crude oil that meets the requirements of density and viscosity to be transported through a pipeline, that is, a synthetic crude with an API gravity grater than 19, a viscosity of less than 300 cSt and free of asphaltenes. Furthermore, practically all the metals, nickel and vanadium, have been removed from the starting extra-heavy crude oil, which greatly facilitates the further processing of this syncrude in a refinery. In order to develop this process a study has been conducted to determine the ideal reaction conditions (temperature, residence time and solid to oil ratio) to carry out the thermal cracking reaction of an extra-heavy crude oil in a downflow transported bed reactor. Moreover, it has been found that among several solid materials with different acidities and textural properties, it is the Kaolín, a natural clay with a small degree of porosity in its crystalline structure, which yields the largest amount of synthetic crude with the density and viscosity values required to be transported through an oil pipeline. These results have been obtained after performing the reaction under non-severe conditions (530ºC, 0.3 seconds and 8g g¿1) and therefore do not require a high energy expenditure. However, the liquids collected after each of the reactions carried out are unstable with respect to asphaltene flocculation, regardless of the solid heat exchanger or the reaction conditions used. To overcome this shortcoming, the next step has focused on eliminating asphaltenes from the synthetic crude. To do so, it has been employed, either alone or as an additive together with kaolin, a heat exchange solid with a certain grade of activity to performe the catalytic cracking of heavy molecules (BCA, Bottom Cracking Additive). This would allow asphaltenes removal by means of catalytic cracking reactions, giving rise to lighter hydrocarbons formation, and/or by means of condensation reactions, giving rise to coke formation. In this section it has been concluded that, due to the characteristics of the composition of the extraheavy crude oil used in the present study, the presence of any kind of acidity on the solid used as heat exchanger lead to a such increase in coke yield, with the concomitant reduction in the yield to syncrude, that made its used inadvisable. In addition, asphaltene flocculation continues to be observed within the reduced amount of liquids collected. So that, after assuming that in order to obtain stable liquids respect asphaltenes flocculation it is mandatory to get a syncrude free of residue fraction, hydrocarbon products with boiling points higher than 537ºC, in the next section has been analyzed the combination of different process steps to either thermally convert or recycle to extinction this heavy hydrocarbons fraction. Three different strategies of improvement processes have been schematized and the best one to produce the greatest amount of stable synthetic crude has been determined through theoretical calculations. Finally, this new partial upgrading process has been assessed by comparing these results obtained experimentally in the laboratory with the ones obtained after processing the same extraheavy crude oil in a Delayed Coking pilot plant. / Corresa Mateu, E. (2023). Aprovechamiento y mejora de crudos extrapesados [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/198857

This thesis examines the use of nonlinear ultrasound to evaluate sensitization, a precursor to stress corrosion cracking in austenitic stainless steel. Ultrasonic Rayleigh surface waves are generated on a specimen; as these waves pass through sensitized material, second harmonic generation (SHG) increases. In austenitic stainless steel with oven-induced sensitization, this increase is due only to the formation of chromium carbide precipitates, key products of the sensitization process. Weld-induced sensitization specimens demonstrate additional increases in SHG, likely caused by increased residual stress and dislocation density as a result of uneven heating. Experimental data are used to calculate the acoustic nonlinearity parameter, which provides a single value directly related to the quantity of micro- and nano-scale damage present within any given sample. Using this procedure, the effects of weld- and oven-induced sensitization are compared. Results demonstrate the feasibility of using nonlinear Rayleigh waves to detect and monitor stress corrosion susceptibility of welded material.

Master of Science / Department of Civil Engineering / Mustaque Hossain / Reclaimed Asphalt Pavement (RAP) is a useful alternative to virgin aggregates in hot-mix asphalt (HMA) as it reduces cost, conserves energy, and enables reuse of existing asphalt pavement. However, use of higher percentage of RAP sometimes leads to drier mixes that are often susceptible to early cracking. In this study, cracking resistance of Superpave mixtures with varying asphalt and RAP contents were investigated. HMA specimens were prepared based on Superpave mix design criteria for 12.5-mm (1/2-inch) nominal maximum aggregate size (NMAS). Specimens were compacted using the Superpave gyratory compactor. Static and repeated semi-circular bending (SCB) tests and Texas overlay tests (OT) (TEX-248-F) were performed in order to evaluate cracking resistance of Superpave mixtures containing three different asphalt contents (5.2%, 4.9%, and 4.6%) and three RAP percentages (20%, 30%, and 40%) from two distinct sources. Results from both crack tests showed that, with decreased asphalt content, cracking propensity increases. In general, higher percentage of RAP decreases cracking resistance. Statistical analysis of the results indicated a strong positive correlation between the asphalt film thickness and the number of load cycles before failure. Comparison of mean test results suggested that the Texas overlay test could do better evaluation of cracking resistance than the R-SCB test. This study was limited to mixtures with two sources of RAP. Because of such limitations and conflicting results from these RAP sources, a general conclusion regarding the minimum binder and maximum RAP contents without compromising cracking resistance could not be made. However, separate conclusions were drawn depending upon the characteristics of the RAP source.

Résumé : L’auto-cicatrisation des fissures des matériaux cimentaires présente un intérêt important pour améliorer leur durabilité (propriétés de transfert par exemple). L’impact du laitier de haut-fourneau sur ce phénomène a été peu étudié bien qu’il ait été observé sur des ouvrages du Génie Civil. Dans cette étude, la cinétique et l’amplitude de l’auto-cicatrisation ont été suivies par des essais non destructifs : la tomographie aux rayons X et la perméabilité à l’air, pour une fissuration créée à 7 jours et à 28 jours. Les résultats montrent que le laitier de haut-fourneau possède un potentiel d’auto-cicatrisation intéressant pouvant dépasser les résultats obtenus pour les formulations de référence sans laitier. Ce bon potentiel dépend des caractéristiques physico-chimiques des matériaux brutes et du potentiel d’hydratation de la formulation au cours du temps. De plus pour suivre l’auto-cicatrisation, un nouvel essai a été mis en place afin de fissurer les éprouvettes de mortier par retrait gêné et d’étudier l’auto-cicatrisation d’une fissure naturelle. Cet essai s’est avéré efficace sur la formulation de référence. Une caractérisation des produits de cicatrisation par MEB-EDS témoigne de la formation de nouveaux produits dans les fissures et de l’impact important des conditions de stockage sur le type de produits formés: des C-S-H pour un stockage sous eau et des carbonates de calcium pour un stockage en chambre humide (CO2 + eau). Les résultats de migration aux chlorures de nano-indentation montrent que ces produits de cicatrisation possèdent de bonnes propriétés de durabilité et des propriétés mécaniques à l’échelle microscopique intéressantes (pour le carbonate de calcium). Enfin, une modélisation du phénomène d’auto-cicatrisation est proposée au moyen du code de calcul de géochimie PHREEQC. L’étude a révélé le potentiel intéressant de PHREEQC pour modéliser l’auto-cicatrisation et en faire un outil de prédiction du phénomène. / Abstract : Self-healing of cementitious materials presents great interest to improve the durability of concrete structure (transfer properties for example). The impact of blast-furnace slag on this phenomenon is not yet clear even if the self-healing of concrete with blast-furnace slag was observed in building sites. To understand the blast-furnace slag influence, non-destructive methods were used to follow self-healing: X-ray tomography and gas permeability test. All specimens were cracked at 7 days and 28 days. The results show that the blast furnace slag has an interesting self-healing potential that can exceed the reference formulation results. This good potential depends on the physico-chemical characteristics of the raw materials and the hydration potential of the formulation over time. In addition to follow the self-healing, a new trial was set up to crack mortar specimens by restrained shrinkage and study the self-healing of a natural crack. In addition to follow the self-healing, a new trial was set up to crack mortar specimens by restrained shrinkage and study the self-healing of a natural crack. This test has proven effective over the reference formulation.The SEM with EDS analysis showed the formation of new products in the crack and the impact of storage conditions on these products : C-S-H for specimens stored in water and calcium carbonate for specimens stored in a damp chamber (CO2 + water). Migration chlorures and nano-indentation tests results showed that self-healing products had interesting durability properties and micro-mechanical properties (for calcium carbonate). Finally, self-healing modelling is proposed by means of geochemistry PHREEQC calculation code. The study revealed interesting potential PHREEQC to model self- healing phenomenon and make it a of predictive tool.

With the recent increase in Gold (Au) wire cost Copper (Cu) wire becomes an attractive way to manage overall package cost. On the other hand, Copper wire bonding introduces much higher mechanical impact to underlying BEoL structures and actives because of the higher stiffness and lower ductility of Copper compared to Gold. These trends are accompanied by the application of new porous or nano-particle filled materials like low-k and ultra low-k materials for Back-end of Line (BEoL) layers of advanced CMOS technologies. As a result, higher delamination and cracking risks in BEoL structures underneath bonded areas represent an increasing challenge for the thermo-mechanical reliability requirements. To overcome the related reliability issues the authors performed a two level nonlinear FEM-simulation approach. Initially nonlinear axi-symmetric modeling and simulation of the copper bonding process are coupled with a spatial simulation model of the whole BeoL and bond pad structure. Cracking and delamination risks are estimated by a surface based cohesive contact approach and the utilization of a crushing foam constitutive material model for ultra low-k materials.

Austenitic stainless steels are frequently used for engineering applications in aggressive environments. Typical sources of component failures are associated with localized attack at grain boundaries, such as intergranular corrosion and stress corrosion cracking. To prevent premature failures, structural integrity assessments are carried out, with the aim of predicting the maximum likelihood of cracking that may develop. For accurate predictions it is of great importance to know the interaction of parameters involved in life-determining processes. This PhD thesis investigates the effect of microstructure and stress on intergranular stress corrosion cracking in Type 302 / Type 304 austenitic stainless steels. High-resolution X-ray tomography has been successfully applied to examine, for the first time in 3-dimensions, in-situ, the interaction between microstructure and crack propagation. The development and subsequent failure of crack bridging ligaments has been observed and correlated with regions of ductile tearing persistent on the fracture surface. These ductile regions were consistent with the morphology of low-energy, twin-type grain boundaries, and are believed to possess the capability of shielding the crack tip. Following this observation, a new grain bridging model has been developed, in order to quantify the effect of static stress and crack bridging on the maximum likely crack length. The model was compared and evaluated with in the literature available percolation-like models. Intergranular stress corrosion tests in tetrathionate solutions have been designed and carried out to validate the new model. The assessment comprised,(i) a thorough examination of the microstructure and analysis parameters employed,(ii) the determination of the degree of sensitisation with subsequent crack path investigations,(iii) the identification of a suitable test system with associated grain boundary susceptibility criteria,(iv) the application of Grain Boundary Engineering (GBE) for microstructure control,(v) statistical crack length assessments of calibrated IGSCC test specimens. The results of these tests showed that the new model successfully predicts the magnitude of stress and the effect of grain boundary engineering on the maximum crack lengths.

Since the introduction of Portland cement in the early nineteenth century the number of buildings constructed from concrete or using cement mortars and renders has grown exponentially, and cement is one of the most common building materials in use today. Consequently a significant proportion of the built heritage contains cementitious materials. The relative youth of these buildings means that less research has been undertaken to understand how and why they deteriorate than for traditional buildings, and that the development of appropriate conservation methods and techniques is less advanced. The primary aim of this research was to understand the causes and mechanisms of some of the types of deterioration commonly found in historic concrete and cement buildings and structures, with reference to the Second World War reinforced concrete and cement-rendered buildings at East Fortune airfield in East Lothian, Scotland. Additional aims were to investigate the efficacy of the building repairs and maintenance regimes undertaken to date, and to make recommendations for the future conservation of the buildings. East Fortune airfield contains a number of cement-rendered brick masonry buildings and a reinforced concrete air raid shelter. The initial visual survey identified several types of deterioration, from which the blistering and flaking of the render; the cracking and delamination of the render; and the spalling of the concrete in the air raid shelter were selected for further research. The research included time lapse photography, non-destructive testing, environmental monitoring and the physical, chemical and petrographic characterisation of the building materials. Hypotheses regarding the causes of deterioration were tested in the laboratory, for example with linear variable displacement transducer measurements, and modelled using crack propagation theories and models for water transport through porous media. It is demonstrated that the blistering and flaking of the render is caused by shale aggregate particles, which undergo sufficient expansion during freeze-thaw cycles to crack the surrounding render. This phenomenon is termed ‘pop-outs’ in the concrete literature. The more catastrophic cracking and delamination of the renders is also due to freeze-thaw cycling, which is shown to cause significant damage provided the moisture content of the render is above a certain threshold level. This type of deterioration has occurred at an accelerated rate for some of the modern render repairs, due to an inadequate understanding of the properties of the original and repair materials. In particular, the properties of the bricks are critical to the performance of the cement renders, and it is found that the sorptivity of historic bricks may vary considerably depending upon the orientation of the brick. Finally, the diagnosis for the air raid shelter is that the corrosion of the steel reinforcements is caused by high levels of chlorides present within the raw materials used to make the pre-cast concrete sections. The results of the investigations are used to suggest building conservation solutions for this particular site. Furthermore, since the deterioration mechanisms investigated are common for historic cement and concrete, the findings are relevant to many other sites. The over-arching methodology used to investigate the deterioration at the site and the methodologies developed to test particular hypotheses are also applicable for other investigations of historic building materials. There is much about this research that is innovative and new. The work on render cracking compares the results of dilation tests on cementitious and ceramic materials, which has not been done previously, and the pop-outs diagnosed in the work on render flaking have rarely, if ever, been reported for cement renders. The modelling work undertaken to quantify the stresses produced by the pop-outs and to explain the inclined crack formation patterns is entirely original. The use of petrography to diagnose causes of render failure is described in the literature, but this is one of very few case studies to be written up, and the work on the air raid shelter constitutes the only formal investigation of this type of Stanton shelter.