Dissertations / Theses on the topic 'Mercury intrusion porosimetry (MIP)'

Cette recherche vise à analyser et à identifier, par des essais, le comportement au fluage d'une argile de type kaolinite sous un état de contraintes triaxial. Une investigation fine de l’état microstructural, avant et après fluage, a par ailleurs été réalisée. Les résultats macroscopiques ont permis de constater que des phénomènes de dilatance et de contractante s’amplifient pendant le fluage. Les résultats montrent également que la position, sur le plan des contraintes (p'-q), du niveau de contrainte vis-à-vis des différents domaines volumétriques, contrôle le développement de la déformation au fluage et du taux de déformation. Les résultats de MEB ont montré que l'évolution microstructurale de l'argile, après le chargement mécanique, dépend fortement de l'histoire du chargement
The objective of this research is to analyze the creep behavior of a typical clay along triaxial tests, moreover, to analyze the microstructural mechanisms of creep. Analysis on the macroscopic results ascertained that both dilatancy and contractancy phenomena could occur during creep. The magnitude of the dilatancy/contractancy during creep was guided by the test conditions: stress level and the over consolidation ratio, which specifically governed the direction of the volumetric strain variations. The results of SEM indicated that the microstructural evolution of the clay after the mechanical loading depend on the stress history. Afterwards, the structural evolution in creep phase depends on the structural pattern developed in monotonic loading

El hormigón armado compuesto de cemento Portland fue inventado hace algo más de un siglo aproximadamente y se ha convertido en el material más utilizado en la construcción. La durabilidad de este hormigón es una de las consideraciones más importantes a ser tenidas en cuenta en el diseño de nuevas estructuras y en la evaluación estructural de las ya existentes. Cuando un hormigón sujeto a un ambientes o cargas que puede degradarlo, como puede ser su uso en puentes y ambientes marinos o si contiene grandes cantidades de alúmina o áridos reciclados, el conocimiento o predicción de su durabilidad es una aspecto crítico para su comportamiento en servicio. Los ensayos no destructivos se han mostrado como unos de los ensayos preceptivos con una importancia económica y social más relevante desde que se han aplicado para la auscultación de la durabilidad de las estructuras de hormigón pertenecientes a la ingeniería civil, donde estos materiales son ampliamente utilizados. En cualquier caso, el uso de las técnicas no destructivas en estos materiales no está suficientemente implementado, hecho este motivado por las características heterogéneas de su microestructura. De todos los métodos no destructivos aplicables para el hormigón, el uso de pulsos ultrasónicos es de gran interés para la caracterización de la microestructura y las propiedades de materiales heterogéneos. El objetivo del presente trabajo es obtener un procedimiento de evaluación del ciclo de vida del hormigón preparado y puesto en servicio para ambientes marinos. Además, será estudiado y analizado la incorporación de varias metodologías (destructivas y non destructivas) para caracterizar el proceso de degradación de morteros y hormigones expuestos a disolución de sulfato de sodio y a exposición en disolución de nitrato amónico. Con esta finalidad, una integración adecuada de diferentes técnicas será usada para la caracterización de propiedades y el seguimiento del proceso de degradación que afectan al hormigón. Como objetivos adicionales, destaca que fueron estudiadas las relaciones entre los parámetros destructivos y no destructivos, así como la relación entre los distintos parámetros no destructivos entre sí. Muchos de los estudios anteriores que han usado la inspección ultrasónica las cuáles fueron utilizadas para determinar la relación agua/cemento del mortero, de la pasta de cemento y del hormigón, o para monitorizar los cambios estructurales, para diferentes relaciones a/c, en el proceso de curado. En este trabajo de investigación fue analizado el efecto que tiene para diferentes relaciones a/c en los parámetros ultrasónicos durante el proceso de degradación. Para este objetivo, se utilizaron un Cemento Portland tipo II A L 42.5 (LPC), y otro sulforresistente tipo I 42.5R/SR (SRPC) que fueron usados en la fabricación de dos marcos de hormigón, los cuales fueron utilizados como hormigón en servicio (caso real). Para el estudio del efecto de la variación de a/c en los parámetros ultrasónicos durante la degradación se utilizaron muestras de mortero con deferentes relaciones agua cemento 0.525- 0.45- 0.375 and 0.30 a partir de LPC para obtener diferentes niveles de degradación. Para monitorizar el proceso de degradación se utilizó la inspección por pulso/eco (1 y 3.5 MHz) para la obtención del parámetro del área del perfil de atenuaciones (APA) el cual fue estimado por L Vergara et al., 2003 y usado por Fuente et al, 2004. Para seguir el proceso de curado de pasta de cemento y morteros, este parámetro ha demostrado una alta sensibilidad para caracterizar los cambios microestructurales de materiales derivados del cemento a lo largo de su curado. El método de transmisión se ha utilizado para la determinación de las velocidades de ondas longitudinales con la frecuencia de 1MHz y transversales con la frecuencia de 500 kHz. La velocidad ultrasónica también ha demostrado la capacidad para seguir los cambios microestructurales de un modo sencillo porque dicho parámetro está relacionado con la variación de las propiedades mecánicas, y bajo ciertas premisas, con la variación de la porosidad. El análisis con la imagen ultrasónica con 2 MHz fue también usada para la consecución de los mismos objetivos. Como métodos destructivos, los ensayos de resistencia a la compresión y flexión fueron los utilizados para determinar la pérdida de actividad resistente de morteros y hormigones, y la porosidad conectada al agua para analizar los cambios en la matriz porosa por el efecto de la difusión de elementos agresivos que penetran en el material provocando su degradación. La porosimetría de mercurio (MIP) fue usada para observar las variaciones del volumen y tamaño de poro y, por último, la microscopía electrónica de barrido (MEB) que fue utilizada para cuantificar y detectar los cambios en la microestructura por el ataque de elementos agresivos. Los resultados obtenidos muestran que, la degradación producida por exposición a sulfato de sodio, tiene dos etapas, en la primera etapa se forma la etringita que llena los poros pero que no produce microfisuración. En esta etapa se observó una variación en los parámetros obtenidos por ejemplo, incremento de la velocidad de la onda ultrasónica, de las resistencias a compresión y a la flexión o la disminución de la porosidad. Esta variación en los parámetros podría indicar una mejora en las prestaciones mecánicas del material objeto de la investigación, pero en realidad esto no es cierto porque los poros están llenos de etringita, provocando una expansión, que es la causa de la degradación en la segunda etapa. En dicha segunda etapa, se produce una microfisuración generalizada por la expansión de la etringita e incrementando su volumen dentro de los poros. Este hecho produjo un cambio en los parámetros medidos que contrastan con la evolución en la primera etapa, disminución de la velocidad de las ondas ultrasónicas, y de las resistencias mecánicas y consecuentemente un aumento de la porosidad. Por otro lado, la degradación por ataque de nitrato amonio tiene una única etapa debida al proceso de descalificación que comienza desde el principio del proceso de exposición y es lineal durante todo el periodo de exposición. Para ambos casos, la integración de las diversas técnicas se revela como satisfactoria para el seguimiento del proceso de degradación, encontrando buenas correlaciones entre los parámetros no destructivos y los parámetros destructivos de técnicas de análisis físico-químico.
Mahmoud, TI. (2013). Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27550
TESIS

Calcarenites are the most widely used natural stones in Sicily as building materials. The comprehension of the degradation style of these natural building stone is of great interest in order to preserve the ancient masonry, especially in the case of relevant Cultural Heritages. A large number of Sicilian monuments are included in UNESCO Heritage List as their special cultural or physical significance. Considering the cultural importance of these ones, smart solutions are required in the perspective of their conservation. In the framework of restoration actions, the complete knowledge of the internal structure of building stones is fundamental in order to estimate durability and prevent degradation processes. Salt growth is a significant cause of damage for natural stones. The effects of the salt weathering are, in addition to the properties of the salt itself and the climatic conditions, strongly related to the structural and textural features of materials. For this reason, an integrate study on petrographic, physical, mechanical and porosimetric proprieties changes due to salts crystallization could be useful to highlight correlation among textural, structural and engineering parameters. Moreover, one of the main problems in conservation field is the use of suitable consolidant and protective treatments able to preserve the masonry, being compatible with the stone substrate and not affecting its aesthetical proprieties. There are numerous tests able to verify the efficiency of consolidant or protective products, mainly devoted to verify their ability to not modify the appearance of stone and its physical proprieties, especially against water; however, particularly in the case of consolidant, one of the most important feature is related to its penetration depth, often difficult to evaluate by using the standard test routines. For aforementioned, this research work is devoted to apply a multi-methodological approach for characterizing and modeling pore structure modifications due to weathering processes in a coarse grained Sicilian calcarenite used as building and replace stones in Sicilian Cultural Heritages (Sabucina Stone), also through fractal models and innovative and non invasive methods. The obtained data on Sabucina stone have been employed for planning conservative treatments devoted to coarse grained calcarenite substrates. Therefore, innovative nanostructured and hybrid consolidant and protective products have been experimented and the results of efficiency tests along with the determination of surface and sub-surface changes due to the treatments are proposed. In conclusion, the applied theoretical and empirical approach has allowed to: highlight the potential of classical and innovative complementary methods in quantifying the structural changes in porous materials due to degradation processes and conservative treatments, explain how they help to facilitate the understanding of stone weathering and validate the use of geometrical models in describing complex pore systems.

L'étude de la microstructure des argiles remaniées et saturées est cruciale pour la compréhension de leur comportement mécanique et des mécanismes de déformations volumiques. Cette thèse vise à identifier en 3D les mécanismes locaux qui s'activent au niveau de la microstructure en lien avec le chargement mécanique des milieux argileux. D'abord le comportement mécanique du Kaolin K13 est étudié à l'échelle de l'éprouvette sur deux chemins de chargement : œdométrique et isotrope. Ensuite, un protocole d'observation a été mis en place pour l'acquisition des images tridimensionnelles en utilisant la microscopie électronique à balayage (MEB) couplée à la Sonde Ionique Focalisée (FIB). La reconstitution des images obtenues par FIB-MEB nous permet d'accéder à la géométrie 3D d'un sous volume de l'échantillon. La deuxième partie consiste à développer une approche d'analyse quantitative en 3D permettant d'identifier les propriétés de la microstructure sur les différents chemins de chargement étudiés. La morphologie des pores est étudiée en utilisant les paramètres : flatness, élongation et sphéricité. L'orientation des pores et des particules a été d'abord identifier sur des images 2D représentants des coupes dans l'échantillon et étendue au 3D sur l'ensemble du volume et ceci sur les deux chemins de chargement. Les résultats obtenus dans le cadre de ce travail de thèse ont permis de mettre en évidence l'apport des images 3D à la compréhension de la microstructure des argiles remaniées saturées
AbstractMicrostructure investigation is essential for a better understanding of the mechanical behaviour and volumetric deformation mechanisms of remolded and saturated clays. The goal of this thesis is to identify in 3D the local mechanisms which can be activated at the microstructural level in relation to the mechanical loading of clayey meida. The mechanical behaviour of Kaolin k13 is firstly studied at on two loading paths - oedometric and isotropic. Then, an observation protocol was established for the acquisition of three-dimensional images using Scanning Electron Microscopy (SEM) coupled with Focused Ion Beam (FIB). The reconstruction of the images obtained by FIB-SEM allows us to study the 3D geometry of a sub-volume of the sample. The second part consists of developing a quantitative analysis approach in 3D to identify the microstructure properties on different loading paths. The pore morphology is studied using parameters such as flatness, elongation, and sphericity. The orientation of the pores and particles was first identified on 2D images representing cross-sections in the sample and extended to 3D throughout the entire volume for both loading paths. The results obtained in this thesis highlight the contribution of 3D images for a better understanding of the microstructure of saturated remolded clays

Cette thèse présente un ensemble de résultats expérimentaux sur une argile remaniée non saturée proche de la saturation, dont le degré de saturation est généralement supérieur à 70%.Après une série d’essais de caractérisation physique et mécanique du matériau, plusieurs méthodes expérimentales ont été utilisées pour étudier le comportement et certaines pathologies du sol compacté telles que l’orniérage et le matelassage.Une étude systématique du comportement du sol compacté sur chemins de drainage-humidification dans différents états initiaux a été effectuée, complétée par des mesures de succion par papier filtre et psychromètre. Les essais de porosimétrie par intrusion de mercure ont apporté un éclairage sur la microstructure du sol.La thèse a également permis d’étudier les variations de pression interstitielle du sol compacté sur chemin triaxial non drainé en utilisant la technique de translation d’axes, où quelques améliorations et modifications du montage ont été proposées
This thesis present an experimental study of an unsaturated clayey soil close to saturation, whose degree of saturation is generally above 70%.After characterizing the physical and mechanical properties of the material, several experimental methods were used to study the behaviour and some pathologies of the compacted soil, such as rutting and quilting.A systematic study of the behaviour of the compacted soil on drying-wetting paths starting from different initial states was carried out, completed by suction measurements using filter-paper and psychrometer. Mercury intrusion porosimetry tests gave an insight of the soil microstructure.The thesis also addressed the question of the pore pressure variations of the compacted soil on undrained triaxial path using the axis-translation technique, where some improvements and modifications of the testing device were proposed

L'objectif de cette recherche est d’analyser l’apparition et la propagation des fissures de dessiccation et de mieux comprendre la relation entre les comportements macroscopique et microscopique de cinq argiles, une kaolinite, une montmorillonite et trois mélanges de kaolinite et montmorillonite. A l'échelle macroscopique, la méthode est basée sur (1) la mesure de la teneur en eau, de l’indice des vides et du degré de saturation en fonction de la succion au cours du séchage, qui permet de préciser la relation entre le retrait et la désaturation et met en évidence les phases caractéristiques du comportement; (2) des mesures de teneur en eau et des déformations globales dans les tests de dessiccation libre afin d'étudier leur homogénéité ; (3) la détermination des déformations et des déplacements locaux pendant le séchage avec les logiciels VIC-2D et VIC-3D ; (4) une étude classique des paramètres des fissures ; (5) des essais de traction pour déterminer les propriétés des argiles impliquées dans la formation de fissures . A l'échelle microscopique, l'étude est basée sur une analyse approfondie de la microstructure en utilisant en particulier le microscope électronique à balayage, couplé à une méthode adaptée pour l'identification des orientations préférentielles des particules. Cette étude microscopique est complétée par l'analyse de porosimétrie au mercure, une méthode qui permet de quantifier l'espace poral et de caractériser l’indice des vides local. Outre les recherches sur les sols argileux, les effets de la décompression et de la succion sur la formation des fissures dans une roche argileuse ont été analysés également. La relation entre les changements macroscopiques, les changements dans la microstructure et de la porosité a été étudiées. Lors des essais de dessiccation libre, les déformations et les déplacements sont obtenus avec Vic-2D. Les zones de l’échantillon où les fissures apparaissent sont identifiées ainsi que l’évolution des déformations et des déplacements avant l’apparition des fissures. A la fin du séchage, les fissures forment une sorte de réseau, où des bifurcation peuvent être observées dans certains cas. Deux modes de fissuration sont détectés pendant les essais : le mode de traction et le mode de déchirement. Lorsqu’une fissure est causée par des tractions, la direction de propagation suit la direction perpendiculaire à l’extension maximale. S’il y a des distorsions à proximité de la fissure, alors sa direction change. Au début du séchage, les déplacements et les déformations sur le bord sont plus importants que dans les autres parties du modèle. Au voisinage des fissures, les déplacements et les déformations deviennent plus grands que dans les autres parties. Dans la plus grande partie du modèle, les déformations principales sont essentiellement longitudinales et transversales. Pour un matériau donné, la résistance à la traction augmente lorsque la teneur en eau diminue. Le tracé des résultats en fonction de l’indice de liquidité permet de mettre en évidence l’effet de la minéralogie sur la résistance à la traction. Au même indice de liquidité, la contrainte maximale de traction diminue lorsque le pourcentage de monmorillonite augmente. L’effet de la succion sur la résistance à la traction semble qualitativement similaire à ce qui est observé dans le cas de la résistance à la compression simple : on observe que la résistance à la traction est une fonction linéaire du logarithme de la succion. L’analyse au MEB de quatre suspensions soumises à plusieurs succions met en évidence l’isotropie globale de la microstructure, avec une orientation aléatoire des particules, tandis qu’une analyse plus fine révèle que la microstructure peut présenter localement une certaine anisotropie
The objective of this research is to analyze the appearance and propagation of cracks related to desiccation and to provide a better understanding of the relation between the macroscopic and microscopic behavior of five clays, a kaolinite, a montmorillonite and three mixtures of kaolinite and montmorillonite. At the macroscopic scale, the method is based on (1) measurements of water content, void ratio and degree of saturation versus suction during drying, which allows to specify the relationship between shrinkage and desaturation and highlights the characteristic phases of behavior; (2) measurements of water contents and global deformations in free desiccation tests in order to study their homogeneity; (3) the determination of the local deformations and displacements during drying using the softwares VIC-2D and VIC-3D; (4) a classical study of the parameters of cracks; (5) traction tests in order to identify the tensile properties of the clays involved in the formation of cracks. At the microscopic scale, the study is based on a thorough microstructure analysis using in particular scanning electron microscope, coupled to an adapted method for the identification of preferential orientations of particles. This microscopic study is complemented by mercury intrusion porosimetry analysis, a method which allows to quantify the poral space and to characterize the local void ratio. In addition to the research on clay soils, the effects of decompression and suction on the formation of cracks in a clay rock were analyzed too. The relationship between macroscopic changes and the changes in the microstructure and porosity was investigated. During free desiccation tests, two-dimensional strains and displacements maps are obtained with Vic-2D. The zones of the sample where cracks appear are identified as well as the evolution of strains and displacements before the appearance of cracks. At the end of desiccation, the cracks form a kind of network. Bifurcation of cracks can be observed in some cases. Two modes of cracks are detected during the tests: traction mode and tearing mode. When a crack is caused by traction, the propagation direction follows the direction perpendicular to maximum extension. If there are shear strains in the vicinity of the crack, then its direction changes. In the early time of desiccation, the displacements and strains on the boundaries are larger than those in the other parts of the model. In the vicinity of cracks, displacements and strains are relatively larger than those in the other parts. In most parts of the model, the principal strains are mainly longitudinal and transversal. For a given material, tensile strength increases when water content decreases. Plotting the results versus the liquidity index allows highlighting the effect of mineralogy on tensile strength. At the same liquidity index, the maximum tensile stress decreases when the montmorillonite content increases. The effect of suction on tensile strength seems qualitatively similar to what is observed in the case of unconfined compression strength with tensile strength being a linear function of the logarithm of suction. Analysis with SEM of four slurries submitted to several suctions highlights the global isotropy of the microfabric, with a random orientation of the particles, while a finer analysis reveals that the fabric may present locally some anisotropy

Natural and other aggregated or structured soils present peculiar mechanical behaviour which differs, in some parts, from the behaviour of soils reconstituted in laboratory. This difference can be explained by a specific structure which gathers the particles arrangement and bonding. However, numerous constitutive models were originally based on the behaviour of reconstituted soils. Therefore, classical models should be extended in order to reproduce more complex features of behaviour linked to the soil structure. This work provides a general framework to describe and predict the behaviour of aggregated and reconstituted soils. A multi-scale study was performed to understand the effect of the structure and its evolution upon loading. From an experimental point of view, a preliminary review of literature has been completed by an experimental program carried out on a silty soil in which different structures have been generated by various compaction conditions. At the macro-scale, conventional mechanical tests evidence the overconsolidation effect induced by structure and the important compressibility during its degradation. At the micro-scale, the fabric evolution during the destructuration process (induced by saturation and loading) has been mainly quantified by the evolution of the pore size distribution. This characterisation has been done by Mercury Intrusion Porosimetry. The samples compacted on the dry side of optimum exhibit a double porosity characterized by a bimodal pore size distribution, by opposition to the samples compacted on wet side of optimum that show a single class of pores. The deformation induced by mechanical loading is related to the closure of the biggest pores and the pore size distribution of aggregated soils tends towards unimodal shape upon the destructuration process. A constitutive critical state model (ACMEG) has been extended, based on experimental observations, in order to reproduce the behaviours of aggregated and reconstituted soils. In this purpose, a structure variable has been introduced in the yield function and its evolution has been integrated in the hardening law. Explicit and implicit methods of integration have been discussed and implemented to reproduce stress-strain responses on geomechanical tests (oedometric, isotropic and triaxial compression tests). Finally, the model has been validated by comparison of model predictions with the experimental results.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

A caracterização de rochas de reservatórios por microtomografia de raios X (MRX) consiste em uma técnica de análise digital para estudar tridimensionalmente microestruturas e formações geológicas. Para materiais geológicos porosos, a distinção do corpo mineral e dos vazios é facilmente realizada devido à diferença de atenuação dos raios X irradiados, fornecendo modelos tridimensionais de tamanho de grão, porosidade e estrutura de poros. Os métodos tradicionais de petrologia, como a microscopia óptica ou a microscopia eletrônica de varredura (MEV), apresentam menor significância estatística para a área analisada e são limitados à análise bidimensional; assim o MRX apresenta um avanço para as técnicas de caracterização por aquisição e análise digital de imagens. Paralelamente, são conhecidas outras técnicas experimentais para caracterização de porosidade de materiais geológicos por intrusão de fluidos ou envelopamento de partículas. Destas, destaca-se a porosimetria com intrusão de mercúrio que atua no intervalo de poros micro a nanométricos, e possibilita também a determinação da distribuição de tamanho de poros. Este trabalho tem por objetivo determinar a porosidade e densidade de análogos de rocha reservatório pela conjugação de procedimentos de MRX bi e tridimensionais, porosimetria por intrusão de mercúrio e picnometria com gás Hélio. As condições operacionais foram previamente avaliadas até se estabelecer parâmetros capazes de gerar resultados reprodutíveis e com elevada repetitividade. Os resultados demonstram que as melhores correlações foram estabelecidas entre os resultados da porosimetria com mercúrio e microtomografia tridimensional, considerando-se a mesma resolução de tamanho de poro. Apesar dos princípios serem distintos e das comparações serem entre medidas indiretas e análise de imagens digitais, ambas são medidas volumétricas. Na avaliação de continuidade de poros, a correlação entre as determinações bi e tridimensionais revela presença de heterogeneidades. As determinações de densidade por porosimetria com mercúrio e picnometria com gás hélio são congruentes, desde que a quantidade de poros fechados não seja significativa em relação à porosidade total. A microscopia de raios X contribui significativamente para análise digital de rochas reservatório com possibilidade de determinação de porosidade, distribuição de tamanho, morfologia e conectividade de poros. Com a proibição iminente do uso de mercúrio por restrições ambientais, a MRX se torna uma suplente possível para estudos de materiais com porosidades micrométricas, com limitações na detecção poros nanométricos.
Reservoir rock characterization by X-ray microtomography (XRM) consists of a digital analysis to study microstructures and geological formations. The distinction of matrix and voids within the rock sample can be easily carried out due to the attenuation difference of irradiated X-rays, providing three-dimensional models of grain size, porosity and pore structure. Traditional petrology methods, such as optical microscopy or scanning electron microscopy (SEM) presents lower statistical significance for the characterized area and are limited to two-dimensional analysis; therefore, XRM presents an advance for characterization techniques by acquisition and digital image analysis. At the same time, experimental techniques are known for porosity characterization of geological materials by fluid intrusion or particle envelopment. It can be emphasized the mercury intrusion porosimetry acts in the range of micro and nanopores and also allows the analysis of pore size distribution. This study aims to determine porosity and density of reservoir rock analogous by the combination of two and three dimensional XRM procedures, mercury intrusion porosimetry and helium gas pycnometry. Operating parameters were prior evaluated to establish conditions for obtaining reproducible results with high repeatability. The results were assessed individually with subsequent correlations under the same resolution. The results demonstrate that the best correlations were established between mercury porosimetry and three-dimensional microtomography data, considering the same pore size resolution. Although the principles are completely different, and the comparisons refers to indirect measurements and digital image analysis, both considers volumetric measurements. In the evaluation of pore continuity, the correlation between two and three-dimensional determinations reveals the presence of heterogeneities. The density determinations by mercury intrusion porosimetry and pycnometry with helium gas are congruent, as long as the number of closed pores is not significant in relation to the total porosity. X-ray microscopy contributes significantly to reservoir rock digital analysis with the possibility of determining porosity, pore size distribution, morphology and pore connectivity. With the mercury use prohibition by environmental constraints, MRX becomes a possible substitute to characterize materials with micrometric porosities, with limitations in the detection of nanometric pores.

Background: Separation science is heavily reliant on materials to fulfill ever more complicated demands raised by other areas of science, notably the rapidly expanding molecular biosciences and environmental monitoring. The key to successful separations lies in a combination of physical properties and surface chemistry of stationary phases used in liquid chromatographic separation, and this thesis address both aspects of novel separation materials. Methods: The thesis accounts for several approaches taken during the course of my graduate studies, and the main approaches have been i) to test a wild-grown variety of published methods for surface treatment of fused silica capillaries, to ascertain firm attachment of polymeric monoliths to the wall of microcolumns prepared in silica conduits; ii) developing a novel porogen scheme for organic monoliths including polymeric porogens and macromonomers; iii) evaluating a mesoporous styrenic monolith for characterization of telomers intended for use in surface modification schemes and; iv) to critically assess the validity of a common shortcut used for estimating the porosity of monoliths prepared in microconduits; and finally v) employing plasma chemistry for activating and subsequently modifying the surface of rigid, monodisperse particles prepared from divinylbenzene. Results: The efforts accounted for above have resulted in i) better knowledge of the etching and functionalization parameters that determine attachment of organic monoliths prepared by radical polymerization to the surface of silica; ii) polar methacrylic monoliths with a designed macroporosity that approaches the desired "connected rod" macropore morphology; iii) estab¬lishing the usefulness of monoliths prepared via nitroxide mediated polymerization in gradient polymer elution chromatography; iv) proving that scanning electron microscopy images are of limited value for assessing the macroporous properties of organic monoliths, and that pore measurements on externally polymerized monolith cocktails do not represent the porous properties of the same cocktail polymerized in narrow confinements; and v) showing that plasma bromination can be used as an activation step for rigid divinylbenzene particles to act as grafting handles for epoxy-containing telomers, that can be attached in a sufficiently dense layer and converted into carboxylate cation exchange layer that allows protein separations in fully aqueous eluents.

Les réservoirs dits « tight gas » sont constitués de grès de faible perméabilité ayant des propriétés petro-physiques susceptibles de nuire à la productivité du gisement. Une importante zone de transition est observée in situ dans laquelle ni l’eau ni le gaz ne sont suffisamment mobiles pour permettre une extraction industrielle : c’est ce que l’on appellera le « permeability jail ». Cette étude vise principalement à caractériser l’influence du chargement mécanique (via l’utilisation de différentes pressions de confinement) et de la nature des roches (roches provenant de différents puits et prélevées à différentes profondeurs) sur les courbes de perméabilité relative au gaz et les caractéristiques poro-mécaniques de ces roches. La porosité accessible à l’eau mesurée est de 2 à 12%. La perméabilité intrinsèque au gaz a mis en évidence de fortes disparités sans lien avec la porosité des échantillons. Une grande sensibilité de la perméabilité relative au confinement a été observée dès l’application de pressions de confinement de 15 à 30 MPa. Deux familles d’échantillons ont ainsi été identifiées. Les échantillons les plus perméables (perméabilité compris entre 100 – 1000 μD), sont peu sensibles au confinement et leur perméabilité relative ne chute qu’à partir de saturations de l’ordre de 50%. Les échantillons les moins perméables apparaissent beaucoup plus sensibles à la fois au confinement et à la saturation.Des méthodes classiquement utilisées dans le domaine pétrolier reposant sur l’interprétation d’essais de porosimétrie par intrusion mercure, ont également été mise en œuvre pour évaluer les perméabilités relatives et les comparer aux mesures expérimentales
So-called tight gas reservoirs are constituted of low permeability sandstones, which petro-physical properties may interfere with proper gas recovery. They have a low absolute permeability (below 0.1 mD under ambient conditions), a porosity lower than 10%, and a strong sensitivity to in situ stresses as compared to conventional reservoirs. Moreover, an important transition zone is observed in situ, where partial water saturation is present, and which may extend over several hundred meters over the free water table. In such zone, where water saturation is on the order of 40-50%, neither gas nor water seems sufficiently mobile for industrial extraction: this is the permeability jail. Our aim is to assess their actual petro-physical properties, namely porosity, gas permeability under varying hydrostatic stress and water saturation level, in relation with sandstone microstructure. Accessible water porosity measured is between 2 to 12%. The intrinsic permeability to gas did not appeared related to the porosity of samples. A high sensitivity of gas permeability to confinement was observed. Two families of samples were identified. The more permeable samples (permeability between 100-1000 μD), are relatively insensitive to confinement and their relative permeability decrease for water saturation higher than 50%. Less permeable samples appear much more sensitive to mechanical loading and saturation.Methods classically used in oil and gas industry based on the interpretation of mercury intrusion porosimetry tests have also been used to evaluate relative permeability and compared with experimental measurements

Cette thèse concerne la caractérisation expérimentale d’un sable limoneux provenant du barrage de Livet – Gavet (38) dans le cadre du projet ANR TerreDurable avec plusieurs objectifs : 1- Caractériser au travers d’essais de laboratoire le comportement hydromécanique d’un sable fin limoneux (sol A1 dans la classification GTR) en fonction de son état de saturation. Lors de cette étude, un accent particulier est porté sur la caractérisation de ce comportement dans le domaine proche de la saturation. 2- Interpréter le comportement hydrique du matériau sur chemin de drainage – imbibition en relation avec l’analyse de sa microstructure. 3- Fournir d’un point de vue général une base de données et d’analyses exhaustive permettant le développement et la calibration de modèles de comportement des sols fins proches de la saturation, en particulier en considérant des chemins de chargement hydromécanique complexes. Pour l’ensemble de cette étude, le matériau est considéré sous deux états : soit à l’état de pâte (matériau normalement consolidé) préparée à une teneur en eau proche de la limite de liquidité, soit sous forme compactée (matériau sur-consolidé) à différentes énergies de compactage et différentes teneurs en eau initiales
This thesis concerns the experimental characterization of a silty sand from the Livet - Gavet dam (38) as part of the ANR TerreDurable project, for following objectives: 1- Through laboratory tests, characterize the hydro-mechanical behaviour of a fine silty sand (Type A1 in the GTR classification) according to its saturation state. In this study, particular emphasis is placed on the characterization of this behaviour in the near-saturated domain. 2- Interpret the water behaviour of material on the drainage - imbibition cycles, in relation to the analysis of its microstructure. 3- From a general point of view, provide a comprehensive database and analysis allowing the development and calibration of models of near-saturated fine soil's behaviour, in particular, by considering complex hydro-mechanical loading paths. For all tests in this study, the material is considered in two states: either in the state of paste (normally consolidated material) prepared at water content close to the limit of liquidity, or in compacted state (over consolidated material) at different compaction energies and different initial water contents

Soil organic matter loss is a widely recognized European soil threat and intensive and repeated tillage operations are known to negatively affect numerous soil properties and ecosystem services. In this view, the study on more sustainable agronomic managements is a pressing need for research community. Between sustainable techniques, conservation agriculture (CA) is nowadays a spread technique based on three main pivotal points: 1) minimum soil disturbance, 2) permanent soil covering and 3) crop diversification. CA is often associated with numerous soil functions such as increasing of soil biodiversity, organic matter stocks and aggregate stability and decreasing of runoff, erosion and P losses and dioxide carbon emissions. Despite the first estimates, CA practices are recently not recognized as a win-win solution for climate mitigation and agro-ecosystem improvement because the absence of tillage operations may impact the crop root growth through an increase in soil strength and bulk density, and reduce soil porosity and gas exchanges and lastly, the overall benefits of CA have been strictly related to soil type and climate. Within this viewpoint of not consistent results, more research is needed to understand and optimize the potential of sustainable agronomic practices. For these reasons, in this work, a field experiment was conducted including four farms on the low-lying plain of Veneto Region characterized by silty soils, in which conservation agriculture practices (no-tillage, cover crops and residues retention) were applied and compared to conventional tillage system. The first objective of the thesis was to evaluate the effects of CA practices on C cycle. The soil organic carbon (SOC) evolution in terms of both stock quantity and quality was monitored over a 3-yr transition period. The SOC stock was quantified through an equivalent soil mass approach up to 50 cm depth while the influence of each CA component was disentangled considering crop, cover crop and root biomasses, and tillage type as separate factors. The SOC quality was evaluated through humic carbon, its molecular weight distribution and microbial biomass analyses. The study showed that after short period, CA adoption did not increase C stock but rather its distribution within the soil profile while a positive effect was observed on humic carbon with the production of more polycondensed humic substances. The second objective regarded the evaluation of the soil gas exchange properties in the poorly structured silty soils of the low-lying plain. The effect of conservation agriculture practices on soil pore and gas transport characteristics was studied through the analyses of air permeability, gas diffusivity and air-filled porosity, and the derivation of soil structure indices on 144 undisturbed 100 cm3 soil cores. Gas transport measurements highlighted low transmission properties of the silty soils independently from agronomic management leading to critical value for both soil aeration and microbial aerobic activity. The third objective focused on the characterisation of the soil structure evolution after 5-yr of conservation agriculture management adoption. The soil pore network was quantified coupling mercury intrusion porosimetry and x-ray micro-tomography to study the total porosity and size distribution, from the macro- to the ultramicro- scale, and its architecture, on 96 undisturbed soil samples collected in the field experiment. Results suggested that silty soils of Veneto plain are micro-structured since much of the porosity is in the 0.0074-30 μm range and CA practices showed a positive influence on the ultramicroporosity range (0.1-5 μm) which are strictly linked to SOC stabilization. Concluding, silty soils of the Veneto region low-lying plain showed a slow reaction to conservation agriculture practices, as demonstrated by the poor effect on C sequestration, gas-transport characteristics and soil structure improvements. The limited amount of non-complexed organic carbon available for interaction with the soil fines prevented the formation of a more resilient soil structure leading to soil compaction that negated the exploitation of CA-related benefits. Despite such mechanisms, CA practices positively influenced C quality and ultramicroporosity range suggesting that a virtuous cycle between SOC and soil structure has been initiated. Longer transition period will be needed to reach a favourable equilibrium in the CA systems and more studies elucidating the mechanisms of structure improving conditions for silty soils, such as those examined in this study, are also required.
La perdita di sostanza organica è una delle minacce del suolo riconosciute a livello europeo e le ripetute lavorazioni del terreno sono state connesse con alcuni effetti negativi sulle proprietà del suolo e con i relativi servizi ecosistemici. Per questo, lo studio di pratiche agronomiche più sostenibili rappresenta una sfida per l’intera comunità scientifica. Tra le tecniche agronomiche sostenibili, l’agricoltura conservativa (AC) è una pratica ampiamente diffusa che è basata su tre principi cardine: 1) minimo disturbo del suolo, 2) copertura permanente del terreo e 3) diversificazione delle colture. AC è spesso associata a numerose funzioni del suolo quali l’aumento della biodiversità, dello stock di carbonio organico e della stabilità degli aggregati e la riduzione del runoff, dell’erosione, delle lisciviazioni di P e delle emissioni di anidride carbonica. Nonostante ciò, recentemente AC non è sempre considerata come una soluzione vincente per la mitigazione del clima e per il miglioramento dell’agroecosistema in quanto l’assenza delle lavorazioni del terreno possono influenzare negativamente lo sviluppo radicale mediante un aumento della densità e della resistenza del suolo e mediante una diminuzione della porosità e degli scambi gassosi. Per di più, i benefici delle pratiche conservative sono riconosciuti essere strettamente legati al tipo di clima e suolo. In quest’ottica di risultati contrastanti, maggiori studi sono necessari per studiare e ottimizzare le potenzialità di pratiche agronomiche più sostenibili. Per questi motivi, in questa tesi, è stata condotta una prova di campo comprendente quattro aziende agricole della bassa pianura Veneta caratterizzate da suoli limosi nei quali le pratiche conservative (non lavorazione, cover-crop e ritenzione dei residui) sono state adottate e confrontate con quelle tradizionali. Il primo obiettivo di questa tesi è stato quello di valutare gli effetti di AC sul ciclo del C. In particolare è stata valutata l’evoluzione del carbonio organico del suolo (COS) sia in termini quantitativi che qualitativi durante un periodo di transizione di tre anni. Lo stock di COS è stato quantificato mediante l’applicazione della massa equivalente fino a 50 cm di profondità mentre l’effetto delle diverse componenti del trattamento conservativo è stato studiato considerando le biomasse delle colture, delle cover-crop e degli apparati radicali e il tipo di lavorazione come fattori separati. La qualità del COS è stata invece caratterizzata analizzando il carbonio umico, le sue frazioni in peso e la biomassa microbica. Questo studio ha mostrato come dopo un breve periodo di applicazione di tali pratiche, lo stock di COS nel suolo non sia aumentato mostrando piuttosto una diversa ripartizione lungo il profilo. La qualità del carbonio organico ha invece beneficiato delle pratiche conservative con la produzione di sostanze umiche più policondensate. Il secondo obiettivo ha riguardato lo studio dell’influenza di AC sugli scambi gassosi del suolo mediante l’analisi della permeabilità all’aria, della diffusione, della air-filled porosity e mediante la derivazione di indici di struttura su 144 campioni indisturbati di suolo di 100 cm3. Le analisi hanno evidenziato le scarse proprietà di trasmissione dei suoli limosi indipendentemente dalla pratica agronomica adottata che hanno portato al raggiungimento di valori critici sia per l’aerazione del terreno che per le attività microbiche aerobiche. Il terzo obiettivo si è focalizzato sulla caratterizzazione dell’evoluzione della struttura del suolo dopo cinque anni dall’adozione delle pratiche di AC. La porosità del suolo è stata analizzata sia mediante l’utilizzo di microtomografie a raggi-x che di porosimetrie a intrusione di mercurio. La porosità totale, la distribuzione dei pori (dalla macro- alla micro-scala) e l’architettura dei pori sono state quantificate su 96 campioni indisturbati raccolti nelle quattro aziende sperimentali. I risultati hanno mostrato come i suoli limosi del Veneto siano “microstrutturati” in quanto la maggior parte della porosità ricade nel range 0.0074-30 μm e come le pratiche conservative abbiano positivamente influenzato la ultramicroporosità (0.1-5 μm) che è strettamente legata alla protezione della sostanza organica. Concludendo, come evidenziato dallo scarso effetto sul sequestro del C, sugli scambi gassosi e sulla struttura del terreno, i suoli limosi della bassa pianura Veneta hanno mostrato una lenta reazione alle pratiche conservative. Lo scarso contenuto di COS non complessato disponibile all’interazione con le particelle fini del terreno ha ostacolato la formazione di una struttura stabile portando al compattamento del suolo. Nonostante ciò, le pratiche conservative hanno però positivamente influenzato la qualità del C e la ultramicroporosità suggerendo che un ciclo virtuoso tra sostanza organica e struttura del suolo è stato inizializzato. Un periodo di transizione di più lunga durata sembra essere indispensabile per il raggiungimento di un nuovo equilibrio in sistemi conservativi e più studi sui meccanismi che regolano la struttura in suoli limosi risultano inoltre necessari.

Les matériaux cimentaires ont été retenus afin de composer la barrière ouvragée du site français de stockage des déchets nucléaires en formation géologique profonde. Ce choix se justifie par les capacités physico-chimiques propres aux bétons : les hydrates de la matrice cimentaire (CSH) et le pH de sa solution interstitielle contribuent à la rétention des radionucléides ; d'autre part la compacité de ces matériaux limite le transport d'éléments. Il convient de s'assurer de la pérennité de cette structure pendant une durée au moins égale à celle de la vie des déchets (jusqu'à 100 000 ans). Sa durabilité a été éprouvée par l'évolution des propriétés de transfert en fonction de la décalcification de matériaux cimentaires, altération traduisant le vieillissement de l'ouvrage. Deux modes de dégradation ont ainsi été appliqués tenant compte des différentes interactions physico-chimiques induites par la formation hôte. Le premier, de type statique, a consisté en une décalcification accélérée par le nitrate d'ammonium. Il simule l'altération de la barrière ouvragée par les eaux souterraines. La cinétique de la dégradation a été estimée par le suivi du calcium lixivié et l'avancée du front de dissolution de l'hydroxyde de calcium. Pour évaluer l'impact de la décalcification, les échantillons ont été caractérisés à l'état sain puis dégradé, en terme de microstructure (porosité, distribution porosimétrique) et de propriétés de transfert (diffusivité, perméabilité au gaz et à l'eau). L'influence de la nature du liant (CEM I et CEM V/A) et des granulats (calcaires et siliceux) a été observée en répétant les essais sur différentes formulations de mortiers. A cette occasion, une importante réflexion sur la métrologie de cet essai a été menée. Le deuxième mode de dégradation, dynamique, a été réalisé par un perméamètre environnemental. Il recrée les sollicitations subies par l'ouvrage lors de sa phase de resaturation post-fermeture (pression hydraulique imposée par la couche géologique et exothermicité des déchets). Cet appareillage, basé sur le principe d'une cellule triaxiale, permet de fixer un gradient de pression entre 2 et 10 MPa et une température de 20 à 80°C. La variation de la perméabilité à l'eau en fonction de ces deux paramètres expérimentaux, découplés et couplés, a été mesurée et reliée aux modifications microstructurales des échantillons
Cementitious materials have been selected to compose engineering barrier system (EBS) of the french radioactive waste deep repository, because of concrete physico-chemical properties: the hydrates of the cementitious matrix and the pH of the pore solution contribute to radionuclides retention; furthermore the compactness of these materials limits elements transport. The confinement capacity of the system has to be assessed while a period at least equivalent to waste activity (up to 100. 000 years). His durability was sustained by the evolution of transfer properties in accordance with cementitious materials decalcification, alteration that expresses structure long-term behavior. Then, two degradation modes were carried out, taking into account the different physical and chemical interactions imposed by the host formation. The first mode, a static one, was an accelerated decalcification using nitrate ammonium solution. It replicates EBS alteration dues to underground water. Degradation kinetic was estimated by the amount of calcium leached and the measurement of the calcium hydroxide dissolution front. To evaluate the decalcification impact, samples were characterized before and after degradation in term of microstructure (porosity, pores size distribution) and of transfer properties (diffusivity, gas and water permeability). The influence of cement nature (ordinary Portland cement, blended cement) and aggregates type (lime or siliceous) was observed: experiments were repeated on different mortars mixes. On this occasion, an essential reflection on this test metrology was led. The second mode, a dynamical degradation, was performed with an environmental permeameter. It recreates the EBS solicitations ensured during the resaturation period, distinguished by the hydraulic pressure imposed by the geologic layer and the waste exothermicity. This apparatus, based on triaxial cell functioning, allows to applied on samples pressure drop between 2 and 10 MPa and temperature from 20 to 80°C. Water permeability evolution relating to experimental parameters, uncoupled or coupled, was relied to mortars microstructural modifications

碩士
中華技術學院
土木防災工程研究所
97
The cement based materials is a typical porous composite material. Pore structures of the cement based materials are very important influenced properties of ion transport behavior. The pore structure is composed of pore size, pore connective, and pore tortuosity.In this study,the pore structures will determined by mercury intrusion porosimetry (MIP).Test specimens will be manufactured with three different water-cement (w/c) ratios and five volume fraction of aggregate to investigate the pore structure.