Morteros realizados con materiales captadores de CO2 para su aplicación como sumideros urbanos de GEI

Desde mediados del siglo XX, el desarrollo de la economía, la industria y las nuevas tecnologías han transformado las condiciones de vida del ser humano. Se ha multiplicado exponencialmente la población mundial, el consumo energético, la producción de alimentos y la necesidad de bienes de consumo en general. Todo ello ha significado un incremento de la contaminación medioambiental, principalmente a través de la emisión de Gases de Efecto Invernadero (GEI). Este aumento de la contaminación se ha producido de forma acelerada y en poco tiempo, de tal forma que la sociedad parece abocada a sufrir las consecuencias del llamado Cambio Climático. Es, por tanto, urgente tomar medidas para mitigar estas consecuencias. El protocolo de Kyoto, las COP (Conferencias de las Partes de la Convención Marco de las Naciones Unidas sobre el Cambio Climático), el PECC (Programa Europeo sobre el Cambio Climático) o el Consejo Nacional del Clima en España son ejemplos de la puesta en marcha de planes para reducir los efectos nocivos de los GEI en los últimos años. En la industria del cemento y la fabricación de hormigones y morteros también se están investigando y desarrollando tecnologías para reducir las emisiones de CO2. Este gas, es emitido en la fabricación del cemento, y aunque se vuelve a fijar por los materiales base cemento en forma de CaCO3 en una reacción conocida como carbonatación, la cantidad fijada es mucho menor que la emitida. Por ello, este trabajo ha tenido como objetivo estudiar el uso de un aditivo para mortero monocapa con la capacidad de capturar CO2 durante su vida útil. La adición escogida es la hidrotalcita, un hidroxicarbonato de magnesio y aluminio que puede ser encontrado en la naturaleza en bajas proporciones o ser fabricado en laboratorio. Se trata de un hidróxido doble laminar que podría ser considerado como captador de CO2, especialmente si se calcina a 450 ºC - 500 ºC ya que tiene la particularidad de recuperar la estructura laminar original incorporando aniones carbonato (CO32-) en su interlámina. Durante la fabricación de hidrotalcita se adsorbe CO2, el cual es liberado en su calcinación, de tal manera que su coste de emisión es cero. La hidrotalcita calcinada presenta mejores propiedades de adsorción. La estructura porosa de la hidrotalcita calcinada es una combinación de microporosidad y mesoporosidad y alta superficie específica. Por otra parte, la hidrotalcita es compatible con materiales base cemento. Este trabajo realizado en este TFM está estructurado en dos partes diferenciadas. Una primera parte que constituye la caracterización de 2 muestras de hidrotalcita que se han estudiado en su forma calcinada y no calcinada y una segunda parte en la que se estudia un mortero monocapa con adición de una de las hidrotalcitas. El primer estudio ha proporcionado conocimiento sobre las características estructural y porosa de la hidrotalcita en su forma calcinada y no calcinada, realizando ensayos de difracción de rayos x, análisis termogravimétrico, isotermas de adsorción de nitrógeno, tamaño de partícula, microscopía de transmisión y barrido e isotermas de CO2 a varias temperaturas. Se han ajustado las isotermas de adsorción a los modelos de Freundlich, Langmuir, Dubinin-Raduskevich y Temkin. Los resultados mostraron una clara mayor adsorción física de CO2 en las muestras de hidrotalcita calcinadas, que está justificado por un aumento en el volumen de poros y de la superficie específica. De las dos familias de hidrotalcita, se ha escogido la de mayor adsorción (93,01 mg/g a 20 ºC) en el rango de temperaturas de 0-35ºC como aditivo añadido al mortero. Respecto al mortero se han analizado dos aspectos, el primero relativo al efecto de la incorporación de la hidrotalcita a los mismos y el segundo relativo a la captura de CO2. Los ensayos realizados al mortero han sido: consistencia, trabajabilidad, resistencia a flexión y compresión, humedad, densidad aparente y porosidad abierta. Los resultados han mostrado menor tiempo de trabajabilidad (35% menos) y un ligero empeoramiento de las resistencias con la adición de hidrotalcita, aunque se cumplen los límites indicados en el CTE para morteros monocapa. El estudio de captura de CO2 en las probetas de mortero se ha realizado utilizando las técnicas de difracción de rayos X y de análisis termogravimétrico. Los resultados mostraron un aumento del 7,5% de la captura de CO2 de las probetas a las que se ha adicionado un 2,44% de hidrotalcita con respecto a las probetas sin adición. Esto ha sido posible ya que, por unidad de masa, la hidrotalcita calcinada, como adición del mortero, capturó 4,95 veces más CO2 que lo capturado por el mortero por unidad de masa. En consecuencia, se puede concluir que la adición de hidrotalcita al mortero cumple con el Código Técnico de la Edificación respecto a resistencias mecánicas del mortero y aumenta la capacidad de captura de CO2.Since the mid-twentieth century, the development of the economy, industry and new technologies have transformed the living conditions of the human being. The world population, energy consumption, food production and the need for consumer goods in general have multiplied exponentially. All this has meant an increase in environmental pollution, mainly through the emission of Greenhouse Gases (GHG). This increase in pollution has occurred rapidly and in a short time, so that society seems doomed to suffer the consequences of the so-called Climate Change. It is, therefore, urgent to take measures to mitigate these consequences. Kyoto Protocol, COP (Conferences of the Parties of the United Nations Framework Convention on Climate Change), PECC (European on Climate Change Programme) or the National Climate Council in Spain are examples of the plans to reduce the harmful effects of GHGs in recent years. In the cement industry and the manufacture of concrete and mortar are also researching and developing technologies to reduce CO2 emissions. This gas is emitted in the manufacture of cement and, although it is re-fixed by the cement-based materials in the form of CaCO3 in a reaction known as carbonation, the amount fixed is much lower than that emitted. Therefore, this work has aimed to study the use of an additive for monolayer mortar with the ability to capture CO2 during its useful life. The chosen addition is the hydrotalcite, a magnesium and aluminum hydroxycarbonate that can be found in nature in low proportions or be manufactured in laboratory. It is a double laminar hydroxide that could be considered as a CO2 collector, especially if it is calcined at 450 ºC - 500 ºC, since it has the peculiarity of recovering the original laminar structure incorporating carbonate anions (CO32-) in its interlayer. During the manufacture of hydrotalcite, CO2 adsorbed is released in its calcination, in such a way that its emission cost is zero. Calcined hydrotalcite has better adsorption properties. The porous structure of the calcined hydrotalcite is a combination of microporosity and mesoporosity and high specific surface area. On the other hand, hydrotalcite is compatible with cement-based materials. This work carried out in this TFM is structured in two different parts. A first part that constitutes the characterization of 2 samples of hydrotalcite that have been studied in its calcined and uncalcined form and a second part in which a monolayer mortar with addition of one of the hydrotalcites is studied. The first study has provided knowledge on the structural and porous characteristics of the hydrotalcite in its calcined and uncalcined form, performing x-ray diffraction tests, thermogravimetric analysis, nitrogen adsorption isotherms, particle size tests, transmission and scanning electron microscopy and CO2 isotherms at various temperatures. The adsorption isotherms have been adjusted to the Freundlich, Langmuir, Dubinin-Raduskevich and Temkin models. The results showed a clear greater physical adsorption of CO2 in the calcined hydrotalcite samples, which is justified by an increase in the volume of pores and the specific surface area. Of the two families of hydrotalcite, the one with the highest adsorption (93.01 mg / g at 20 ºC) was chosen in the temperature range of 0-35ºC as additive added to the mortar. Regarding the mortar, two aspects have been analyzed, the first concerning the effect of the incorporation of hydrotalcite on them and the second on the capture of CO2. The tests carried out on the mortar have been: consistency, workability, compressive and flexural strength, humidity, bulk density and open porosity. The results have shown less workability time (35% less) and a slight worsening of the strength with the addition of hydrotalcite, although the limits indicated in the CTE for monolayer mortars are met. The study of CO2 capture in the mortar prismatic specimens was carried out using X-ray diffraction and thermogravimetric analysis techniques. The results shown an increase of 7.5% of the capture of CO2 of the specimens to which a 2.44% hydrotalcite has been added with respect to the specimens without addition. This has been possible since, per unit mass, the calcined hydrotalcite, as an addition of the mortar, captured 4.95 times more CO2 than that captured by the mortar per unit mass. Consequently, it can be concluded that the addition of hydrotalcite to the mortar complies with the Technical Building Code regarding mechanical resistance of the mortar and increases the CO2 capture capacity.Universidad de Sevilla. Máster en Ingeniería de Caminos, Canales y Puerto

Ternary Blends for Self-Compacting Mortars Production Composed by Electric Arc Furnace Dust and Other Industrial by-Products

This study is framed within the circular economy model through the valorisation of industrial by-products. This research shows the results of producing self-compacting mortars (SCMs) with electric arc furnace dust (EAFD) and other industrial by-products such as fly ash, conforming (FA) or not conforming (NcFA), from coal-fired power plants, or recovery filler (RF) from hot-mix asphalt plants. Three batches of SCMs, each with one industrial-by product (FA, NcFA, or RF), and three levels of EAFD ratio incorporation (0%, 10%, 20%), were tested. An extra batch with a greater amount of FA was manufactured. When the incorporation ratio of EAFD rose, the mechanical strength decreased, due to the presence of a calcium zinc hydroxide dihydrate phase; nevertheless, this decrease diminished over time. All SCM mixes, except the 40C 40FA 20 EAFD mix, were above 20 MPa at 28 days. All mixes named 70C and 40C reached 40 and 30 MPa, respectively, at 90 days. Mixes with EAFD showed less capillarity and no difference in water absorption by immersion with respect to mixes without EAFD after 91 days. The SCMs designed proved to be stable in terms of leaching of the heavy metals contained in EAFD, where all the hardened SCMs were classified as inert

A multi-purpose ontology-based approach for personalized content filtering and retrieval

Personalized multimedia access aims at enhancing the retrieval process by complementing explicit user requests with implicit user preferences. We propose and discuss the benefits of the introduction of ontologies for an enhanced representation of the relevant knowledge about the user, the context, and the domain of discourse, as a means to enable improvements in the retrieval process and the performance of adaptive capabilities. We develop our proposal by describing techniques in several areas that exemplify the explotation of the richness and power of formal and explicit semantics descriptions, and the improvements therein

A Multi-Purpose Ontology-Based Approach for Personalized Content Filtering and Retrieval

Abstract. Personalised multimedia access aims at enhancing the retrieval process by complementing explicit user requests with implicit user preferences. We propose and discuss the benefits of the introduction of ontologies for an enhanced representation of the relevant knowledge about the user, the context, and the domain of discourse, as a means to enable improvements in the retrieval process and the performance of adaptive capabilities. We develop our proposal by describing techniques in several areas that exemplify the exploitation of the richness and power of formal and explicit semantics descriptions, and the improvements therein. 1

Optimum Particle Size of Treated Calcites for CO₂ Capture in a Power Plant

This work has analyzed the influence of the particle size of a calcite from a quarry, whether original, calcined, or rehydrated, on the efficiency of CO2 capture of the gases emitted in a coal-fired power plant. Three different particle sizes 0.5 mm, 0.1 mm, and 0.045 mm have been studied. The calcination had a minimal effect on the particle size of the smaller samples A1045 and A1M1 (<30 μm). The N2 isotherms and the CO2 adsorption isotherms at 0 °C showed a very significant increase in the surface of the calcined and rehydrated samples (A15CH, A1045CH, and A1M1CH) with respect to the calcined or original samples. The results obtained showed that the capture of CO2 for the sample A1M1, with a smaller average particle size (<30 μm, is the most effective. For the sample A1M1 calcined and completely rehydrated (Ca(OH)2), the chemical adsorption of CO2 to form CaCO3 is practically total, under the experimental conditions used (550 °C and CO2 flow of 20 mL min−1). The weight increase was 34.11% and the adsorption capacity was 577.00 mg g−1. The experiment was repeated 10 times with the same sample A1M1 calcined and rehydrated. No appreciable loss of adsorption capacity was observed

Semantically enhanced information retrieval: an ontology-based approach

Currently, techniques for content description and query processing in Information Retrieval (IR) are based on keywords, and therefore provide limited capabilities to capture the conceptualizations associated with user needs and contents. Aiming to solve the limitations of keyword-based models, the idea of conceptual search, understood as searching by meanings rather than literal strings, has been the focus of a wide body of research in the IR field. More recently, it has been used as a prototypical scenario (or even envisioned as a potential “killer app”) in the Semantic Web (SW) vision, since its emergence in the late nineties. However, current approaches to semantic search developed in the SW area have not yet taken full advantage of the acquired knowledge, accumulated experience, and technological sophistication achieved through several decades of work in the IR field. Starting from this position, this work investigates the definition of an ontology-based IR model, oriented to the exploitation of domain Knowledge Bases to support semantic search capabilities in large document repositories, stressing on the one hand the use of fully-fledged ontologies in the semantic-based perspective, and on the other hand the consideration of unstructured content as the target search space. The major contribution of this work is an innovative, comprehensive semantic search model, which extends the classic IR model, addresses the challenges of the massive and heterogeneous Web environment, and integrates the benefits of both keyword and semantic-based search. Additional contributions include: an innovative rank fusion technique that minimizes the undesired effects of knowledge sparseness on the yet juvenile SW, and the creation of a large-scale evaluation benchmark, based on IR evaluation standards, which allows a rigorous comparison between IR and SW approaches. Conducted experiments show that our semantic search model obtained comparable and better performance results (in terms of MAP and P@10 values) than the best TREC automatic system

Improving the access, analysis and visibility of the information and the multilingual and multimedia net content for the Madrid Community

Presentación de las actividades del segundo programa de la red de investigación MAVIR de la Comunidad de Madrid.Presentation of the second program activities of the research net MAVIR of Madrid Region