New insights on the fundamentals and modeling of the external sulfate attack in concrete structures

The external sulfate attack (ESA) is a complex degradation process typically compromising the durability of underground foundations, nuclear or industrial waste containments and tunnel linings exposed to sulfate solutions. The structures affected usually remain covered its entire service life, which compromises the detection of this phenomenon before severe material degradation has occurred. Once diagnosed, the large size and criticality of the typical structures affected greatly limit the efficiency of the remedial actions. Consequently, monitoring of the evolution of the structural behavior is often the only applicable measure. This scenario places the development of reliable tools to assist the design of sulfate-resisting concrete structures and assess the risk of ESA in existing properties as key challenges for structural durability. The present thesis aims to advance knowledge in this field by presenting important contributions in three different research lines: numerical modeling of the ESA, role of porosity during the attack and the relevance of reproducing field-like conditions on ESA assessments. Advances on the ESA numerical modelization led to the development of a chemo-transport-mechanical model and a simplified assessment methodology. The former simulates the effects of ionic transport, chemical reactions, degradation mechanisms and the mechanical response of the structure. The validations performed indicate that the model captures the importance of the location of the ettringite formed within the pore network and provides a fair quantification of the overall expansions. The simplified assessment methodology evaluates the risk of failure during the ESA based on the aggressiveness of the media, the reactivity and mechanical properties of the material and the geometric characteristics and service life of the element under attack, without resorting to complex iterative algorithms. Unlike current design guidelines, the application of this simplified procedure allows the definition of flexible and optimized precautionary measures for each application. The second research line involved an extensive experimental program that led to the formulation of a conceptual model to explain the role of porosity during the ESA. The results obtained indicate that high durability against the attack might be achieved by limiting the penetration of sulfates or increasing the capacity of the matrix to accommodate expansive products. Both approaches correspond to opposing pore characteristics of the matrix: the former is usually associated with low porosities while the latter requires matrices with high porosities. These results question the common perception that high porosities are always negative for ESA durability and open up the possibility to design sulfate-resisting materials by increasing the capacity of the matrix to accommodate expansive phases. The third research line evaluates the influence of early sulfate exposure and the effects of confinement on the ESA by two experimental programs. The first study suggests that the delayed exposition to sulfates commonly adopted in accelerated laboratory tests might lead to imprecise damage estimations for structures cast in situ. In these cases, it is recommended to expose the samples to sulfates shortly after casting. The second study suggests that assessing sulfate resistance on specimens in free-expanding conditions might not be representative of the behavior of real structures where the attack is developed in combination with confining conditions. Results indicate that compressive stresses generated by confinement interact with the normal development of the attack by limiting or delaying the appearance of micro-cracks and reducing the amount of ettringite crystals exerting expansive pressures.El ataque sulfático externo (ASE) es un proceso de degradación complejo que afecta principalmente la durabilidad de estructuras de cimentación, contenedores de residuos nucleares o industriales y revestimientos de túneles. Dichas estructuras suelen permanecer enterradas toda su vida útil, lo que compromete la detección del fenómeno antes de que se hayan desarrollado altos niveles de degradación. Una vez detectado, el tamaño e importancia estratégica de las estructuras afectadas limitan las opciones de reparación y su eficacia. Debido a ello, habitualmente la única acción posible consiste en la monitorización de la evolución del comportamiento estructural. Este escenario sitúa el desarrollo de herramientas para el diseño de estructuras resistentes a sulfatos y la evaluación del fenómeno en propiedades existentes como desafíos clave para la durabilidad de estructuras enterradas. Esta tesis doctoral aspira a profundizar el conocimiento en torno a esta temática mediante contribuciones relevantes en tres líneas de investigación: la modelización numérica del ASE, el rol de la porosidad durante el ataque y la relevancia de reproducir condiciones de campo en la evaluación del ASE. Avances en el campo de la modelización numérica han dado lugar a un modelo avanzado y una metodología de evaluación simplificada del ASE. El primero se basa en la simulación de procesos de transporte iónico, reacciones químicas, mecanismos de degradación y respuesta mecánica de la estructura. Las validaciones realizadas indican que el modelo refleja la importancia de la localización de la etringita dentro de la red porosa y proporciona estimaciones ajustadas de las expansiones generadas. La metodología de evaluación simplificada mide el riesgo de fallo estructural basándose en la agresividad del medio, la reactividad y propiedades mecánicas del material y las características geométricas y vida útil del elemento atacado, sin recurrir a algoritmos iterativos. A diferencia de las guías de diseño actuales, su aplicación permite la definición de medidas preventivas ajustadas a cada aplicación. La segunda línea de investigación ha dado lugar a un modelo conceptual que explica el rol de la porosidad durante el ASE. Los resultados obtenidos indican que se pueden alcanzar altas resistencias al ataque mediante la limitación de la penetración de sulfatos en la estructura o incrementando la capacidad de la matriz de acomodar fases expansivas. Los dos enfoques se corresponden a características porosas opuestas de la matriz. La primera se suele asociar a bajas porosidades mientras que la segunda se maximiza en porosidades altas. Los resultados obtenidos cuestionan la idea de que porosidades altas siempre son negativas para la durabilidad ante el ASE y abre la posibilidad de diseñar materiales resistentes a sulfatos incrementando la capacidad de acomodar fases expansivas. La tercera línea de investigación evalúa la influencia de la exposición temprana a sulfatos y los efectos del confinamiento en el ASE. Resultados referentes al primer estudio indican que una exposición tardía a los sulfatos como la empleada en la mayoría de ensayos acelerados puede conllevar a estimaciones incorrectas del daño generado en estructuras fabricadas in situ. El segundo estudio, referente a los efectos del confinamiento, sugiere que el uso de probetas en condiciones de expansión libre puede no ser adecuado para reproducir los efectos del ASE en estructuras donde el ataque se desarrolla en condiciones confinadas. Las tensiones de compresión generadas interactúan con el desarrollo normal del ataque limitando o retardando la aparición de micro-fisuras y reduciendo la cantidad de cristales de etringita creciendo en condiciones confinadas y por ende, ejerciendo presiones expansivas.Postprint (published version

Filtrage et agrégation d'informations vitales relatives à des entités

Nowadays, knowledge bases such as Wikipedia and DBpedia are the main sources to access information on a wide variety of entities (an entity is a thing that can be distinctly identified such a person, an organization, a product, an event, etc.). However, the update of these sources with new information related to a given entity is done manually by contributors with a significant latency time particularly if that entity is not popular. A system that analyzes documents when published on the Web to filter important information about entities will probably accelerate the update of these knowledge bases. In this thesis, we are interested in filtering timely and relevant information, called vital information, concerning the entities. We aim at answering the following two issues: (1) How to detect if a document is vital (i.e., it provides timely relevant information) to an entity? and (2) How to extract vital information from these documents to build a temporal summary about the entity that can be seen as a reference for updating the corresponding knowledge base entry?Regarding the first issue, we proposed two methods. The first proposal is fully supervised. It is based on a vitality language model. The second proposal measures the freshness of temporal expressions in a document to decide its vitality. Concerning the second issue, we proposed a method that selects the sentences based on the presence of triggers words automatically retrieved from the knowledge already represented in the knowledge base (such as the description of similar entities).We carried out our experiments on the TREC Stream corpus 2013 and 2014 with 1.2 billion documents and different types of entities (persons, organizations, facilities and events). For vital documents filtering approaches, we conducted our experiments in the context of the task "knowledge Base Acceleration (KBA)" for the years 2013 and 2014. Our method based on leveraging the temporal expressions in the document obtained good results outperforming the best participant system in the task KBA 2013. In addition, we showed the importance of our generated temporal summaries to accelerate the update of knowledge bases.Aujourd'hui, les bases de connaissances telles que Wikipedia et DBpedia représentent les sources principales pour accéder aux informations disponibles sur une grande variété d'entités (une entité est une chose qui peut être distinctement identifiée par exemple une personne, une organisation, un produit, un événement, etc.). Cependant, la mise à jour de ces sources avec des informations nouvelles en rapport avec une entité donnée se fait manuellement par des contributeurs et avec un temps de latence important en particulier si cette entité n'est pas populaire. Concevoir un système qui analyse les documents dès leur publication sur le Web pour filtrer les informations importantes relatives à des entités pourra sans doute accélérer la mise à jour de ces bases de connaissances. Dans cette thèse, nous nous intéressons au filtrage d'informations pertinentes et nouvelles, appelées vitales, relatives à des entités. Ces travaux rentrent dans le cadre de la recherche d'information mais visent aussi à enrichir les techniques d'ingénierie de connaissances en aidant à la sélection des informations à traiter. Nous souhaitons répondre principalement aux deux problématiques suivantes: (1) Comment détecter si un document est vital (c.à.d qu'il apporte une information pertinente et nouvelle) par rapport à une entité donnée? et (2) Comment extraire les informations vitales à partir de ces documents qui serviront comme référence pour mettre à jour des bases de connaissances? Concernant la première problématique, nous avons proposé deux méthodes. La première proposition est totalement supervisée. Elle se base sur un modèle de langue de vitalité. La deuxième proposition mesure la fraîcheur des expressions temporelles contenues dans un document afin de décider de sa vitalité. En ce qui concerne la deuxième problématique relative à l'extraction d'informations vitales à partir des documents vitaux, nous avons proposé une méthode qui sélectionne les phrases comportant potentiellement ces informations vitales, en nous basant sur la présence de mots déclencheurs récupérés automatiquement à partir de la connaissance déjà représentée dans la base de connaissances (comme la description d'entités similaires).L'évaluation des approches proposées a été effectuée dans le cadre de la campagne d'évaluation internationale TREC sur une collection de 1.2 milliard de documents avec différents types d'entités (personnes, organisations, établissements et événements). Pour les approches de filtrage de documents vitaux, nous avons mené nos expérimentations dans le cadre de la tâche "Knwoledge Base Acceleration (KBA)" pour les années 2013 et 2014. L'exploitation des expressions temporelles dans le document a permis d'obtenir de bons résultats dépassant le meilleur système proposé dans la tâche KBA 2013. Pour évaluer les contributions concernant l'extraction des informations vitales relatives à des entités, nous nous sommes basés sur le cadre expérimental de la tâche "Temporal Summarization (TS)". Nous avons montré que notre approche permet de minimiser le temps de latence des mises à jour de bases de connaissances

Entity-Oriented Search

This open access book covers all facets of entity-oriented search—where “search” can be interpreted in the broadest sense of information access—from a unified point of view, and provides a coherent and comprehensive overview of the state of the art. It represents the first synthesis of research in this broad and rapidly developing area. Selected topics are discussed in-depth, the goal being to establish fundamental techniques and methods as a basis for future research and development. Additional topics are treated at a survey level only, containing numerous pointers to the relevant literature. A roadmap for future research, based on open issues and challenges identified along the way, rounds out the book. The book is divided into three main parts, sandwiched between introductory and concluding chapters. The first two chapters introduce readers to the basic concepts, provide an overview of entity-oriented search tasks, and present the various types and sources of data that will be used throughout the book. Part I deals with the core task of entity ranking: given a textual query, possibly enriched with additional elements or structural hints, return a ranked list of entities. This core task is examined in a number of different variants, using both structured and unstructured data collections, and numerous query formulations. In turn, Part II is devoted to the role of entities in bridging unstructured and structured data. Part III explores how entities can enable search engines to understand the concepts, meaning, and intent behind the query that the user enters into the search box, and how they can provide rich and focused responses (as opposed to merely a list of documents)—a process known as semantic search. The final chapter concludes the book by discussing the limitations of current approaches, and suggesting directions for future research. Researchers and graduate students are the primary target audience of this book. A general background in information retrieval is sufficient to follow the material, including an understanding of basic probability and statistics concepts as well as a basic knowledge of machine learning concepts and supervised learning algorithms

Risk Management for the Future

A large part of academic literature, business literature as well as practices in real life are resting on the assumption that uncertainty and risk does not exist. We all know that this is not true, yet, a whole variety of methods, tools and practices are not attuned to the fact that the future is uncertain and that risks are all around us. However, despite risk management entering the agenda some decades ago, it has introduced risks on its own as illustrated by the financial crisis. Here is a book that goes beyond risk management as it is today and tries to discuss what needs to be improved further. The book also offers some cases

Study on open science: The general state of the play in Open Science principles and practices at European life sciences institutes

Nowadays, open science is a hot topic on all levels and also is one of the priorities of the European Research Area. Components that are commonly associated with open science are open access, open data, open methodology, open source, open peer review, open science policies and citizen science. Open science may a great potential to connect and influence the practices of researchers, funding institutions and the public. In this paper, we evaluate the level of openness based on public surveys at four European life sciences institute

Empirical Modeling and Its Applications

Empirical modeling has been a useful approach for the analysis of different problems across numerous areas/fields of knowledge. As it is known, this type of modeling is particularly helpful when parametric models, due to various reasons, cannot be constructed. Based on different methodologies and approaches, empirical modeling allows the analyst to obtain an initial understanding of the relationships that exist among the different variables that belong to a particular system or process. In some cases, the results from empirical models can be used in order to make decisions about those variables, with the intent of resolving a given problem in the real-life applications. This book entitled Empirical Modeling and Its Applications consists of six (6) chapters