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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
451

Se värde i avskräde : Cirkulär ekonomi i byggbranschen / The value in waste : Circular economy in the construction industry

Axelstorm, Ramona, Stallgård, Sigrid January 2022 (has links)
Det finns förbättringspotential för att öka den cirkulära ekonomin i Sverige, som idag är 3,4 procent. Återbruk av byggmaterial i byggbranschen är en åtgärd, som genererar till en cirkulär förbättring. I uppsatsen belyses utmaningar och möjligheter associerade med återbruk av byggmaterial, som förekommer hos aktörer längs försörjningskedjan. En generell tanke som ofta förekommer är att återbrukat byggmaterial genererar till ökade kostnader, vilket det i uppsatsen påvisas åtskilda åsikter kring. Vidare studeras det som krävs för att lyckas implementera en cirkulär ekonomi i byggbranschen genom affärsmodeller och strategier. Genom att lyckas implementera en cirkulär ekonomi och utveckla expertis inom området, påvisar teori att även konkurrensfördelar kan frambringas. / There is potential for improvement to increase the circular economy in Sweden, which today is 3.4 percent. Reuse of building materials in the construction industry is one action, which generates a circular improvement. The study highlights challenges and opportunities associated with the reuse of building materials faced by different actors along the supply chain. A common understanding is that reused building materials generate increased costs, which the study demonstrates separate opinions about. Furthermore, the requirements to succeed in implementing a circular economy in the construction industry are studied together with business models and strategies for implementation. By succeeding in implementing a circular economy and developing expertise in the field, theory shows that competitive advantages can be generated.
452

Klimat- och kostnadseffektivakontorsbyggnader : En fallstudie av ett flervåningshus / Climate and cost-effective office buildings : A case study of a multi-storey building

Johansson, Anders, Åström, Karl January 2023 (has links)
Syftet med denna studie var att undersöka klimat- och kostnadseffektiva lösningar för att minska kontorsbyggnaders påverkan på miljön. Byggnader står för en betydande del av Sveriges klimatpåverkan och kostnader, det finns därav behov av att hitta sätt att reducera den påverkan. Teorin som låg till grund för studien var livscykelanalys och livscykelkostnad, som tar hänsyn till klimatpåverkan och kostnader genom hela byggnadens livscykel. Metoden som användes var litteraturstudie, där tidigare forskning och studier analyserades. Diskussion fördes även med sakkunniga personer inom ämnet för att identifiera lösningar för att minska klimatpåverkan och kostnader i byggnader. En hypotetisk fallstudiebyggnad skapades där klimat- och kostnadseffektiva åtgärder implementerades. Genom att titta på byggnadsdelarna stomme, klimatskal, isolering och dess inverkan på energianvändning i en kontorsbyggnad identifierades olika åtgärder som kunde minska klimatpåverkan och kostnader. Dessa inkluderar användning av återvunnet material och minskad energiförbrukning genom förbättrade isoleringsegenskaper. Ytterligare undersöktes val av material och teknik vilket anses hållbara och energieffektiva. Resultatet visar att byggnadsmaterialen har störst påverkan på klimat och kostnaden under Produkt- och Byggproduktionsskedet, medan energiförbrukningen har störst påverkan under skedet Driftenergi i Användningsskedet. De klimatåtgärder som framstår som mest framstående och optimala lösningar för vår fallstudiebyggnad inkluderar användningen av kostnadseffektiva solceller på taket (Åtgärd 7), isolering av ytterväggarna med PIR-isolering (Åtgärd 5), tilläggsisolering av ytterväggarna med EPS-isolering (Åtgärd 3) samt minskat materialspill på byggarbetsplatsen med 25%. Dessa lösningar visar sig inte bara ha en betydligt lägre klimatpåverkan, utan även en mer fördelaktig kostnadseffektivitet över hela livscykeln för fallstudiebyggnaden. / The purpose of this study was to investigate climate and cost-effective solutions to reduce the environmental impact of office buildings. Buildings account for a significant portion of Sweden's climate impact and costs, and there is a need to find ways to reduce this impact. The theoretical framework underlying the report was life cycle analysis and life cycle cost, which consider the climate impact and costs throughout the building's life cycle. The method used was a document study, where previous research and studies were analyzed. A hypothetical case study building was created, where climate- and cost-effective measures were implemented. By examining the building components such as the structure, envelope, insulation, and their impact on energy consumption in an office building, various measures were identified to reduce climate impact and costs. Additionally, the selection of sustainable and energy-efficient materials and technologies was investigated. The results show that building materials have the greatest impact on the environment and cost during the Production and Installation stages, while energy consumption has the greatest impact during the Operational energy use module in the Use stage. The climate measures that stand out as optimal solutions include the use of cost-effective solar panels on the roof (Measure 7), insulating the outer walls with PIR insulation (Measure 5), additional insulation of the outer walls with EPS insulation (Measure 3), and reducing material waste at the construction site by 25%. These solutions not only demonstrate significantly lower climate impact but also exhibit a more advantageous cost-effectiveness over the entire lifecycle.
453

Optimised Mix designs for Self-Healing Concrete

Hermawan, Harry 23 January 2024 (has links)
[ES] El hormigón es considerado como uno de los principales materiales de construcción más ampliamente utilizado en obras de infraestructuras. Su consideración como material de gran durabilidad y su ventajosa relación calidad-precio en comparación con otros materiales le ha hecho indispensable en la era moderna. Sin embargo, las fisuras son prácticamente inevitables en las estructuras de hormigón armado y se consideran como uno de sus puntos débiles, ya que comprometen la durabilidad de las infraestructuras y pueden generar condiciones inseguras. Hay muchas técnicas de reparación para sellar y sanar las fisuras, pero suelen ser costosas y requieren tiempo de intervención. Por esta razón, en los últimos años, se han realizado muchas investigaciones buscando alternativas para resolver estos problemas desarrollando una nueva generación de hormigones que se han denominado hormigones auto sanables. Se ha demostrado que las tecnologías de auto sanado cierran eficazmente las fisuras parcial o totalmente en un sistema cementoso. Sin embargo, los estudios a nivel del hormigón son todavía bastante limitados y en la mayoría de los casos las dosificaciones de la mezcla no fueron optimizados para la introducción de agentes de autosanado. Del estudio amplio de la literatura se aprecia que la incorporación de agentes de autosanado no siempre conllevan efectos positivos en las propiedades del hormigón. En consecuencia, según el tipo de agente de sellado/sanado, será necesario optimizar la dosificación para garantizar que no reduce en alguna medida las prestaciones del hormigón colocado. Se analiza un amplio espectro de agentes de sanado/sellado: bacterias (BAC), adiciones cristalinas (CA), biomasas y agentes incorporados en micro o macro cápsulas. Previamente a su introducción en el hormigón se evaluó su compatibilidad con los materiales cementosos, como información básica para el diseño de las mezclas. La optimización del diseño de las mezclas de hormigón se llevó a cabo dependiendo del agente elegido y los objetivos de la investigación. Al utilizar CA, se encontró que aumentar su dosis y el contenido en cemento conducía a mejorar la eficiencia de curación (HE) y la de sellado (SE). La variación de la relación agua-cemento (a/c) no produjo una mejora notable de HE y SE. Se profundizó el conocimiento sobre las propiedades de adherencia entre las armaduras y la matriz de hormigón. La inclusión de agentes de sanado (BAC, CA, biomasas) conllevó la mejora de la adherencia con un crecimiento del 57% cuando se adiciona CA. Aunque la presencia de fisuras longitudinales redujo críticamente la adherencia, se logró una recuperación importante gracias a los efectos del auto sanado. Se encontraron efectos contrapuestos del uso de microcápsulas. Se confirma una reducción significativa de la resistencia mecánica y una mejora significativa del sellado. Los parámetros de diseño de mezcla se optimizaron para compensar la reducción de resistencia, con un programa experimental con diseño factorial completo. Por la estructura inerte, las macrocápsulas tiende a perturbar el empaquetamiento de los áridos. Para la optimización de la mezcla se desarrolló un modelo de empaquetamiento de partículas modificado para predecir la proporción de huecos de las mezclas de áridos y cápsulas. Con todo, el resultado de esta investigación puede servir como guía para comprender la contribución de los parámetros de diseño de mezclas que afectan las propiedades de auto sanado, que potencialmente ayudará a investigadores e ingenieros a formular mezclas de hormigón para aplicaciones de auto sanado. / [CA] El formigó és considerat un dels principals materials de construcció més àmpliament utilitzat en obres d'infraestructures. La seua consideració com a material de gran durabilitat i la seua relació qualitat-preu avantatjosa en comparació amb altres materials l'ha fet indispensable en l'era moderna. Tot i això, les fissures són pràcticament inevitables en les estructures de formigó armat i es consideren com un dels seus punts febles, ja que comprometen la durabilitat de les infraestructures i poden generar condicions insegures. Hi ha moltes tècniques de reparació per segellar i curar les fissures, però solen ser costoses i requereixen temps d'intervenció. Per aquesta raó, en els darrers anys, s'han realitzat moltes investigacions buscant alternatives per resoldre aquests problemes desenvolupant una nova generació de formigons que s'han anomenat formigons auto sanables. S'ha demostrat que les tecnologies de auto curat tanquen eficaçment les fissures parcialment o totalment en un sistema de ciment. Tot i això, els estudis a nivell del formigó són encara força limitats i en la majoria dels casos les dosificacions no van ser optimitzades per a la introducció d'agents d'auto curat. De l'estudi ampli de la literatura s'aprecia que la incorporació d'agents d'auto curat no sempre comporta efectes positius en les propietats del formigó. En conseqüència, segons el tipus d'agent de segellat/curat, cal optimitzar la dosificació per garantir que no redueix en alguna mesura les prestacions del formigó. S'analitza un ampli espectre d'agents de curat / segellament: bacteris (BAC), addicions cristal·lines (CA), biomassa i agents incorporats en micro o macro càpsules. Prèviament a la seua introducció al formigó es va avaluar la compatibilitat amb els conglomerants, com a informació bàsica per al disseny de mescles. L'optimització del disseny de les mescles de formigó es va dur a terme depenent de l'agent elegit i els objectius de la investigació. En utilitzar CA, es va trobar que augmentar-ne la dosi i el contingut en ciment conduïa a millorar l'eficiència de curació (HE) i la de segellat (SE). La variació de la relació aigua-ciment (a/c) no va produir una millora notable de HE i SE. S'aprofundí el coneixement sobre les propietats d'adherència entre les armadures i la matriu de formigó. La inclusió d'agents de curació (BAC, CA, biomassa) va comportar la millora de l'adherència amb un creixement del 57% quan s'hi afegeix CA. Tot i que la presència de fissures longitudinals va reduir críticament l'adherència, es va aconseguir una recuperació important gràcies als efectes del auto curat. S'han trobat efectes contraposats de l'ús de microcàpsules. Es confirma una reducció significativa de la resistència mecànica i una millora significativa del segellat. Els paràmetres de disseny de mescla es van optimitzar per compensar la reducció de resistència, amb un programa experimental amb disseny factorial complet. Per la seua estructura inert, les macrocàpsules tendeixen a pertorbar l'empaquetament dels àrids. Per optimitzar la mescles es va desenvolupar un model d'empaquetament de partícules modificat per predir la proporció de buits de les mescles d'àrids i càpsules. Amb tot, el resultat d'aquesta investigació pot servir com a guia per comprendre la contribució dels paràmetres de disseny de barreges que afecten les propietats de auto curat, que potencialment ajudarà investigadors i enginyers a formular barreges de formigó per a aplicacions de auto curat. / [EN] Concrete has been widely used as a major material for infrastructure works. The durable character and the advantageous price-quality ratio compared to other materials have made concrete indispensable in the modern era. However, cracks in concrete structures are inevitable and are known as one of the inherent weaknesses of concrete, thereby making a threat to the durability of infrastructure which can lead to unsafe conditions. There are many repair techniques to seal and heal the cracks, but these approaches are costly and time-consuming. Therefore, during past years, many researchers searched for alternatives to solve these problems by developing a new generation of concrete namely self-healing concrete. Self-healing technologies have proven to effectively close cracks partially or fully in the cementitious system. However, studies on the concrete level are still rather limited and in most cases, the mix designs were not optimized for the introduction of healing agents. Based on a comprehensive literature, it was revealed that not all healing/sealing agents induce positive effects to the concrete properties. Consequently, an optimization of the mix designs is necessary to guarantee that these agents do not negatively affect the concrete properties to some extent. In this PhD dissertation, a wide range of healing/sealing agents were utilized such as bacteria (BAC), crystalline admixture (CA), biomasses, micro- and macro-encapsulated agents. Prior to the introduction of these agents into the concrete, the compatibility between healing/sealing agents and cementitious materials was evaluated to serve as a basic input for designing the concrete mixtures. The optimizations of concrete mix designs were carried out depending on the choice of the agents and the research objectives. When using CA, it was found that increasing the CA dosage and cement content in the mix design improved the healing efficiency (HE) and sealing efficiency (SE). Varying the water-cement ratio (w/c) did not give a remarkable improvement of HE and SE. A deep insight in the bond properties between the steel reinforcement and the self-healing concrete matrix was achieved. The inclusion of healing agents (i.e., BAC, CA, biomasses) possessed a bond strength improvement with the highest enhancement of 57% attained by the CA addition. Although the presence of a longitudinal crack critically reduced the bond strength, a bond restoration was achieved due to self-healing effects. Dual effects of using microcapsules were found, confirming a significant reduction of mechanical strength and a significant sealing improvement. Therefore, the mix design parameters were optimized to compensate the strength reduction via full factorial designs. With respect to the inert structure, the incorporation of macrocapsules tended to disturb the packing of aggregates. Hence, a modified particle packing model was developed to predict the voids ratio of aggregate-capsules mixtures. All in all, the outcome of this PhD research can serve as a guidance to understand the contribution of mix design parameters affecting the self-healing concrete properties. This potentially helps researchers and engineers to formulate their concrete mixtures for self-healing application. / This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860006. / Hermawan, H. (2023). Optimised Mix designs for Self-Healing Concrete [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202610
454

Hampafiberns potential för en hållbar utveckling : En jämförande studie mellan hampafiberisolering och konventionella isoleringsmaterial ur ett livscykelperspektiv / The potential of hemp fibre insulation for a sustainable development : A comparative study between hemp fiber insulation and conventional insulation materials from a life cycle perspective

Svedin, Daniel, Wennberg, David January 2021 (has links)
Världens fokus på hållbar utveckling är större än någonsin tidigare, och konstruktionssektorn ansvarar för upp emot 25 till 40 procent av de globala koldioxid emissionerna. Ett av nyckelmaterialen för att öka en byggnads energieffektivitet är isoleringsmaterialen. Syftet med detta kandidatexamensarbete är att utvärdera GWP:n av hampafiberisolering jämfört med de två marknadsledande isoleringsmaterialen, mineralull och cellplast.  GWP:n av de tre isoleringsmaterialen beräknas efter att vardera isoleringsmaterial har blivit placerat i ett envåningshus med storleken 30 m2. Livscykelanalysen för byggnader används sedan som bakgrund för att beräkna GWP:n av de tre byggnaderna. De beräknade kategorierna för GWP:n av byggnaderna är: råmaterial, transport, produktion, konstruktion samt energianvändningen. Byggnaderna antas ha en inomhustemperatur på 20°C och har blivit konstruerade i Stockholm, Sverige.  Utan överraskning var hampafibern det isoleringsmaterial som hade lägst GWP i kategorierna; råmaterial, produktion och konstruktion. Däremot på grund av hampafiberns mindre optimala termiska konduktivitet jämfört med de andra isoleringsmaterialen var byggnaden med hampafiberisolering den minst energieffektiva.  Trots den lägre energieffektiviteten visade sig byggnaden med hampafiberisolering vara den med lägst GWP under en 30 årsperiod, förutsatt att förnyelsebara energikällor användes. Överraskande nog, var däremot källan från vart elektriciteten kom mycket viktig för att avgöra byggnadernas GWP. När den svenska elmixen från Boverkets klimatdatabas användes var skillnaden i GWP mellan de olika byggnaderna marginell. Användes istället förnyelsebara energikällor i form av vindkraft, var hampafiberisoleringen det mest fördelaktiga isoleringsmaterialet ur ett miljöperspektiv. / The world's focus on global warming has grown larger than ever before, and the construction sectorisresponsibleforupwardsof 25to40percentoftheglobalcarbonemissions.Oneof the key materials to increase the energy efficiency of buildings are insulation materials. The purpose of the thesis is to evaluate the global warming potential of insulation made out of hemp compared with the two leading insulation materials on the global market, Mineral wool insulation & EPS.  The global warming potential of the three insulation materials are calculated whilst each is placed in a 30 m2 one-story house. The life cycle assessment (LCA) of buildings is used as background to calculate the global warming potential of each of the three buildings. The calculated categories for the global warming potential are: raw materials, transportation, production, the construction phase, and energy usage in the building. The buildings are assumed to have an inside temperature of 20°C and have been constructed in Stockholm, Sweden.  To no surprise the hemp fibre insulation material had the lowest global warming potential out of the three materials during the raw material, production and construction phase. However due to the less optimal value of thermal conductivity for the hemp fiber insulation compared to the other materials, the energy efficiency in the building using hemp fibre insulation was comparatively the worst.  However, the building using hemp fibre insulation could be concluded as the one with the least global warming potential during a 30 year usage if the correct energy sources were used. Surprisingly enough it turned out that the source of electricity was vital for the global warming potential. When using the Swedish electricity mix found in Boverkets Climate database the difference between the buildings was marginal. If renewable sources in the form of wind power were used instead of the national mix for electricity the differences were more noticable and the building using hemp fiber as insulation was less impactful the lower the global warming potential of the energy source was per kWh.
455

Utmaningar med återbruk av byggmaterial i Malmö : Fallstudie av Snickeriet i Varvsstaden / Challenges with reuse of building materials in Malmö : A case study of Snickeriet in Malmö

Nordh, Stephanie, Olsen, Madicken January 2024 (has links)
​​I bygg- och fastighetsbranschen har hållbarhetsfrågor blivit alltmer framträdande på senare tid och aktörerna ställs inför högre krav. En övergång till en cirkulär ekonomi krävs för att hantera jordens resurser och minska branschens betydande klimatpåverkan. Studiens syfte är att undersöka utmaningarna med återbruk av byggmaterial i Malmö samt identifiera vad som krävs för att öka antalet intressenter att välja återbrukat byggmaterial i byggprocessen. En kvalitativ metod har använts och en fallstudie har genomförts för att granska den kommersiella fastigheten Snickeriet i Varvsstaden. Studien omfattar sju semistrukturerade intervjuer med relevanta aktörer, antingen direkt knutna till Snickeriet eller med djupgående kunskap inom det valda ämnet. Det teoretiska ramverket är organiserat i tre huvudteman: hållbarhet och cirkulär ekonomi, val av hållbara byggmaterial samt hinder för återbruk av byggmaterial. Empirin och analysen bygger på dessa tre huvudteman. Slutsatserna från studien identifierar betydande utmaningar för återbruk av byggmaterial och föreslår åtgärder för ökad acceptans och användning av återbruk i byggprocessen. Genom en fallstudie av Snickeriet i Varvsstaden samt intervjuer med relevanta aktörer identifieras komplexa hinder såsom tekniska, ekonomiska och logistiska svårigheter. Vidare krävs mer omfattande och detaljerade projekteringar samt integrering av återbruk av byggmaterial i de tidiga skedena av byggprocessen. För att öka användningen av återbruk krävs en koordinerad strategi för involverade aktörer inom byggsektorn och offentliga myndigheter. Anpassning av lagstiftning, förbättrad ansvarsfördelning och investeringar i infrastruktur för återbruk föreslås som viktiga åtgärder för att främja en cirkulär ekonomi inom byggsektorn. Slutligen betonas vikten av att öka medvetenheten och lyfta fram de övergripande fördelarna med återbruk för att stärka samhällets hållbarhet och för att få fler intressenter att välja återbrukat material framför nytt material. / In the construction and real estate industry, sustainability issues have become increasingly prominent in recent years and stakeholders are faced with higher demands. A transition to a circular economy is required to manage the earth's resources and reduce the industry's significant climate impact. The aim of the study is to examine the challenges with the reuse of building materials in Malmö and identify what is needed to increase the number of stakeholders choosing reused building materials in the construction process. A qualitative method has been used and a case study has been conducted to examine the commercial property Snickeriet in Varvsstaden. The study includes seven semi-structured interviews with relevant stakeholders, either directly related to Snickeriet or with in-depth knowledge within the chosen subject. The theoretical framework is organized into three main themes: sustainability and circular economy, selection of sustainable construction materials and barriers to the reuse of building materials. The empirical work and the analysis are based on these themes. The conclusions of the study identify significant challenges for the reuse of building materials and suggest measures for increased acceptance and use of reuse in the construction process. Through a case study of Snickeriet in Varvsstaden and interviews with relevant stakeholders, complex barriers such as technical, economic and logistical difficulties are identified. More comprehensive and detailed planning is required, as well as the integration of the reuse of building materials in the early stages of the construction process. To increase the use of reuse, a coordinated strategy is required for involved stakeholders in the construction sector and public authorities. Adaptation of legislation, improved distribution of responsibilities and investments in reuse infrastructure are proposed as key measures to promote a circular economy in the construction sector. Finally, the importance of increasing awareness and highlighting the overall benefits of reuse to strengthen society’s sustainability and to encourage more stakeholders to choose reused materials over new materials.
456

Modélisation des transferts couplés de chaleur, d'air et d'humidité dans les matériaux poreux de construction / Modeling of coupled heat, air and moisture in porous building materials

Abahri, Kamilia 11 December 2012 (has links)
Ces travaux de thèse visent à étudier les transferts couplés de chaleur, de masse et d’air au sein des matériaux poreux. Sur le volet de la modélisation, il s’agit de prédire le comportement hygrothermique de ces matériaux, à l’aide d’un modèle macroscopique, qui intègre à la fois l’effet du phénomène de thermodiffusion et celui de la pression totale de l’air s’exerçant sur les parois du bâtiment. Ce modèle, dont les paramètres d’entrée sont évalués expérimentalement, utilise des moteurs de transfert continus, d’où la possibilité de traiter des problèmes de transferts dans les matériaux multicouches. Il présente aussi l’avantage d’admettre, dans certaines configurations, des solutions analytiques d’où la possibilité d’entreprendre des comparaisons avec des solutions numériques. De plus, une justification formelle des équations de bilan de ce modèle a été abordée, moyennant l’utilisation d’une approche à changement d’échelle « micro-macro ». Il s’agit d’affiner la modélisation des transferts hydriques du comportement macroscopique, en utilisant des informations issues de la microstructure. Le passage de l’échelle microscopique à l’échelle macroscopique a été réalisé à l’aide de la méthode d’homogénéisation par prise de moyenne. Une des difficultés de l’utilisation de ce modèle réside dans l’identification des nombreux paramètres caractérisant les propriétés hygrothermiques des matériaux. Une partie du travail a été consacrée à l’évaluation des principales propriétés intrinsèques des matériaux moyennant l’élaboration de différents prototypes expérimentaux au laboratoire. Par ailleurs, une approche expérimentale dédiée à l’évaluation du processus de la thermodiffusion dans les matériaux poreux a été entreprise. Pour cela, une expérimentation relative à la détermination de l’effet du gradient de température et de la dynamique du processus d’échange d’eau à l’intérieur des parois a été mise en place au laboratoire. L’utilisation de la plateforme expérimentale MegaCup du Technical University of Denmark a permis de collecter des données relatives à la sensibilité de l’effet de la thermodiffusion sur les transferts couplés de chaleur, d’air et d’humidité. Une comparaison des résultats expérimentaux et numériques a ensuite été effectuée. Peu d’écarts ont été relevés. Aussi, une investigation expérimentale portant sur la contribution des infiltrations massiques sur les transferts hydriques dans les matériaux de construction a été réalisée. Moyennant le développement d’un banc d’essai, une caractérisation expérimentale du coefficient d’infiltration d’humidité a été entreprise. Ce dernier est utilisé comme paramètre d’entrée des modèles de simulation numérique. / The purpose of this thesis is to study coupled heat air and moisture transfer in porous building materials. Concerning the modeling part, the interest is to predict the hygrothermal behavior, with a macroscopic model, that incorporates simultaneously the effect of thermodiffusion phenomenon and that of total pressure on the building walls. The input parameters are evaluated experimentally using continuous driving potentials, where the ability to deal with problems of transfer in multilayer materials. In some configurations, it presents the advantage to undertake analytical solution that can be confronted with numerical solutions. Furthermore, a formal justification of balance equations of the developed model was addressed through the use of ascaling approach. Then, the modeling of macroscopic moisture transfer behavior, by implementing information from the microstructure can be refined. The transition of the microscopic to macroscopic scale was performed using the mean field homogenization. One of the difficulties with the use of this model lies in the identification of many parameters characterizing the hygrothermal properties of materials. Therefore, a part of the present work was devoted to the evaluation of the main properties of materials through the development of various experimental prototypes in the laboratory. More over, an experimental approach dedicated to the evaluation of the thermodiffusion process in porous materials has been undertaken. In this way, an experimentation concerning the determination of the temperature gradient and dynamics of water exchange process inside walls has been established. Furthermore, the use of the experimental platform MegaCup at theTechnical University of Denmark has collected data on the sensitivity of the thermodiffusion effect. Subsequently, a comparison of the experimental and the numerical results was performed. Few differences were observed. Otherwise, an experimental investigation on the contribution of the mass infiltration of water transfers in building materials was performed. A characterization of the moisture infiltration coefficient was performed through the development of the experimental test. This coefficient was used as an input parameter in the simulation models.
457

The impact of plant product harvesting on Derre Miombo woodlands, Mozambique / by Maria Cruz.

Cruz, Maria (Maria Regina Torres) 12 1900 (has links)
Thesis (MScFor)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: This study investigates how information on plant products can be used to incorporate local users into joint forest management planning by developing guidelines for sustainable collaborative management in Derre miombo woodland in the Zambézia Province in Mozambique. From the participatory appraisal, it was found that 46 woody miombo species were used in the five villages for at least 29 different purposes. Five of these species (Brachystegia boehmii, B. spiciformis, Pterocarpus angolensis, Terminalia sericea and Swartzia madagascariensis) were selected for analysis because of their multiple uses and the unknown impact of their harvesting on the future survival of those hardwood trees species. In order to determine the impact of human resource extraction on the forest and on the dynamics of tree canopy populations an inventory of woody plants was.carried out for two categories of forest land-use, namely selective harvesting and fallow land (approximately 15 years old). This was done for Golombe and Arame villages and for selective harvesting only for Mphoto village, on 23, I-ha random selected plots in the woodland adjacent to the three villages. The population structure of the five species T sericea, S. madagascariensis, P. angolensis, B. boehmii and B. spiciformis showed different trends in each of the three villages. Size class distribution of the first tree species gave evidence that the species were being harvested for building poles. This study has shown that, through plant species products, miombo contribute to the livelihoods of the local communities living in Derre woodlands. In this study it was found that usually more than one species were used for one product as well as most of the species being trees with multiple uses. This study has also provided some evidence that P. angolensis and S. madagascariensis can benefit from shifting cultivation and fire, which encourages coppice regeneration. More research is required to further validate this evidence. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die moontlikhede wat inligting oor spesifieke plantprodukte bied, in die betrekking van plaaslike gemeenskappe in die proses van gesamentlike bosbestuurs- en beplanningspraktyke. Verder word riglyne opgestel aangaande die volhoubaarheid van die gesamentlike bestuurs- en beplanningspraktyke in die Derre miombo bosveld, in die Zambézia Provinsie in Mozambique. Inligting verkry vanuit die deelnemende opname dui aan dat in die vyf nedersettings wat ondersoek is, 46 houtagtige miombo spesies vir ten minste 29 verskillende doeleindes aangewend word. Vyf van die spesies (Brachystegia boehmii, B. spiciformis, Pterocarpus angolensis, Terminalia sericea en Swartzia madagascariensis) is geselekteer vir gebruik in analises as gevolg van hul benutbaarheid deur plaaslike inwoners en die feit dat minimale inligting beskikbaar is oor die impak van gebruik van die harde hout spesies op hul volhoubare benutting en voortbestaan. 'n Opname van houtagtige spesies is uitgevoer in areas wat val in een van twee bosgrondgebruiks kategoriee nl. areas wat selektief geoes en benut word, en braaklande (ongeveer 15 jaar oud). Dit is gedoen om die impak wat verwydering van boshulpbronne deur mense op die boomkruin populasies het, vas te stel. Die opname strategie is gevolg in 23 ha persele, uitgelê in die gebiede wat die Golombe, Arame en Mphoto nedersettings omring - in die geval van laasgenoemde nedersetting is slegs die impak van selektiewe benutting ondersoek. Die populasie struktuur van die vyf studiespesies (T sericea, S. madagascariensis, P. angolensis, B. boehmii en B. spiciformis) het verkil vir elk van die drie nedersettings wat ondersoek is. Die verspreiding van grootte klasse vir die eerste spesie, het aangedui dat die spesie vir gebruik as konstruksie pale geoes word. Die miombo bosveld plantegroei-tipe dra by tot die lewensonderhoud van plaaslike gemeenskappe in die vorm van plant produkte, in die Derre omgewing. Daar is verder gevind dat meer as een spesie dikwels vir dieselfde doel aangewend kan word en die meeste van die spesies wat benut word is boomagtig met meer as een gebruik. In die studie is verder aanduidings gevind dat P. angolensis en S. madagascariensis kan baatvind by grondverbouings praktyke wat gereeld verskuif word en ook brande, omdat beide praktyke kreupelhout regenerasie stimuleer. Verdere navorsing word egter benodig om dié bevinding te ondersteun.
458

Wartime huts : the development, typology, and identification of temporary military buildings in Britain, 1914-1945

Draper, Karey Lee January 2018 (has links)
The use of temporary, prefabricated buildings in Britain during the twentieth century arose from wartime need to provide better, and perhaps more importantly, portable shelter for troops and equipment. This thesis provides the first comprehensive list of hut designs for the First and Second World Wars. The full lists and descriptions of each hut are given in the appendices. These lists, 20 types for the First World War and 52 from the Second World War, show the huge range and scope of the huts used and is the major contribution of this thesis. The concentration here is on generic types. Some huts were designed as one-offs and there is no possible way to catalogue these. This thesis has focused instead on those designs or industrially-produced types, which were meant to be produced en-masse as generic solutions to the problem: the sort of hut that might justifiably be given a name (such as a ‘Tarran’, a ‘Seco’, etc.). This thesis provides essential information enabling historians to be able to identify these types. It uses primary and secondary sources to trace the development of these huts and the effect that wartime shortages had on their design. Beginning with the earliest examples of temporary military building, it then focuses on the huts of the First and Second World Wars followed by a study of huts grouped in chapters by material. This research shows that the wartime period pushed industry to make giant leaps forward with construction methods and materials in just a few short years, where otherwise it may have taken decades. This thesis aims to provide the first overview of this process and to enable future researchers to identify and understand the development of these important wartime structures, many of which survive to this day.
459

Utilização de agregados de RCC e resíduo de polimento de placas cimentícias em artefatos de concreto / Use of CDW aggregates and cementitious slab polishing residue in concrete artifacts

Leviski, Anderson 20 December 2016 (has links)
A Construção Civil é um dos setores que mais consomem matérias-primas e também gera resíduos sólidos urbanos. É importante, que se consuma menos matérias-primas e que sejam aproveitados estes resíduos gerados. Uma das propostas para esta situação seria reciclar estes resíduos e transformá-los em agregados e filers, para então usá-los na produção de concretos. Ainda se encontram muitas barreiras para utilização destes agregados e filers em concretos, com e sem função estrutural e, dentre os principais motivos está a dificuldade de se alcançar resistências similares as dos concretos produzidos com matérias-primas naturais. Devido a este fato, foi proposto um estudo para analisar a influência do empacotamento de partículas nos agregados reciclados e ainda verificar a possibilidade de uso do filer de pó do polimento das placas de concreto para revestimento de piso. Inicialmente foram caracterizados dois lotes de agregados reciclados e apenas o de resíduo de concreto (ARC) foi considerado adequado para o estudo. Foram propostos três planejamentos experimentais compostos por mistura simplex com 4 fatores das misturas, contendo além dos agregados, filer e cimento Portland CP-V. Foram realizados estudos sobre as massas unitárias das amostras, para cada um dos planejamentos, considerando toda a faixa granulométrica, e também, amostras sem o material passante pela peneira com abertura de 0,150 mm. A quantidade de água foi determinada pelo consistômetro de Vebe, e a partir deste dado foi calculado o excesso de pasta. Após a obtenção dos corpos de prova, sob vibrocompactação, foi determinado o comportamento da resistência mecânica e da absorção de água. A análise dos resultados mostrou que o melhor empacotamento de partículas dos agregados ocorre na faixa de 42% a 58% de pedrisco. O filer utilizado em grandes quantidades, aumenta significativamente o consumo de água de amassamento e o de excesso de pasta, e por consequência, o aumento da absorção de água e perda de resistência do concreto seco. Entretanto, em quantidades menores que o volume de poros, a inclusão do filer é aceitável, pois não há afastamento das partículas. Conclui-se que, na faixa granulométrica estudada não houve alteração de resistência mecânica, sendo o fator preponderante a concentração de cimento. As resistências à compressão observadas mostram que estes agregados podem ser utilizados na fabricação de artefatos de concreto, como por exemplo, produção de blocos de vedação. / Civil Construction is one of the sectors that consumes the rawest materials and also generates municipal solid waste. It is important that less raw materials are consumed and that waste generated is used. One of the proposals for this situation would be to recycle these wastes and turn them into aggregates and filers and then use them in the production of concrete. There are still many barriers to the use of these aggregates and filers in concrete, with and without structural function, and among the main reasons is the difficulty of achieving similar resistance to concrete produced with natural raw materials. Due to this fact, a study was proposed to analyze the influence of the packing of particles in the recycled aggregates and to verify the possibility of using the filter of powder of the polishing of the concrete plates for floor covering. Initially, two batches of recycled aggregates were characterized and only that of concrete residue was considered adequate for the study. Three experimental schedules were proposed, composed of 4 factors of the mixtures, plus the aggregates, filer and Portland cement CP-V. Samples were analyzed for the sample masses, considering the entire grain size range, as well as samples without material passing through the sieve with a 0.150 mm opening. The amount of water was determined by the Vebe consist meter, and from this data, the excess paste was calculated. After the test specimens were obtained, under vibrarocompaction, the behavior of the mechanical resistance and the water absorption were determined. The analysis of the results showed that the best packaging of particles of the aggregates occurs in the range of 42% to 58% of hail. The filer used in large quantities significantly increases the consumption of kneading water and excess paste, and consequently, increased water absorption and loss of strength of dry concrete. However, in smaller amounts than the pore volume, the inclusion of the filer is acceptable, since there is no separation of the particles. It was concluded that in the granulometric range studied, there was no change in mechanical strength, being the preponderant factor the concentration of cement. The observed compressive strengths show that these aggregates can be used in the manufacture of concrete artifacts, such as the production of sealing blocks.
460

Medidas de concentração de radônio proveniente de argamassas de cimento portland, gesso e fosfogesso / Measurements of radon concentration from portland cement, gypsum and phosphogypsum mortars

Narloch, Danielle Cristine 14 September 2015 (has links)
CAPES / O cimento Portland é bastante empregado na construção civil e apresenta em sua composição o gesso natural. Para minimizar custos é possível substituir parte do gesso desta composição pelo fosfogesso. O fosfogesso é um resíduo gerado a partir da produção dos fertilizantes e é constituído, essencialmente, por cálcio dihidratado e algumas impurezas, como fluoretos, metais em geral e radionuclídeos. Atualmente, toneladas de fosfogesso são armazenadas à céu aberto próximo das indústrias de fertilizantes, causando a contaminação do meio ambiente. O elemento 226Ra, presente nesses materiais, ao passar pela série de decaimento radioativo, transforma-se em gás 222Rn. Esse gás, ao ser inalado pode decair dentro dos pulmões e neste caso, os seus produtos depositam-se nas paredes pulmonares ocasionando exposição à radiação, podendo ser um potencial causador de câncer pulmonar. Dessa forma, o objetivo desta pesquisa foi medir os níveis de concentração de 222Rn em corpos de prova de argamassa de cimento Portland, de gesso e de fosfogesso provenientes do Estado do Paraná, além de caracterizar o material e estimar a concentração de radônio em um ambiente de convívio humano hipotético construído com paredes destes materiais. Para as medidas de atividade do 222Rn foi utilizado o monitor AlphaGUARD (Saphymo GmbH). A análise qualitativa e quantitativa foi realizada por meio da espectrometria gama e da EDXRF com tubos de alvos de Au e Ag (AMPTEK), e com alvo de Mo (ARTAX) e os ensaios mecânicos com equipamento de raios X (Gilardoni) e com a prensa mecânica (EMIC). Os valores médios da atividade do radônio no ar obtidos pelo estudo dos materiais armazenados no recipiente foram de 854 ± 23 Bq/m3, 60,0 ± 7,2 Bq/m3 e 52,9 ± 5,4 Bq/m3 para argamassas de cimento Portland, de gesso e de fosfogesso, respectivamente. Estes resultados extrapolados para o ambiente hipotético de 36 m3 com paredes revestidas com os materiais foram de 3366 ± 91 Bq/m3, 237 ± 28 Bq/m3 e 208 ± 21 Bq/m3 para argamassas de cimento Portland, gesso e fosfogesso. Considerando o limite de 300 Bq/m3 estabelecido pela ICRP, observa-se que, para o revestimento de cimento Portland a exposição não é segura e requer alguns procedimentos de mitigação específicos. A partir da espectrometria gama foi calculado o valor do rádio equivalente (Raeq) para as argamassas de cimento Portland, gesso e fosfogesso que resultou em 78,2 ± 0,9 Bq/kg; 58,2 ± 0,9 Bq/kg e 68,2 ± 0,9 Bq/kg, respectivamente. Os valores do Raeq das amostras encontram-se inferiores ao limite máximo de 370 Bq/kg. Em relação a análise qualitativa e quantitativa das amostras por EDXRF, os resultados permitiram identificar e quantificar os elementos que compõe as amostras como o Ca, S, Fe, entre outros. / Portland cement being very common construction material has in its composition the natural gypsum. To decrease the costs of manufacturing, the cement industry is substituting the gypsum in its composition by small quantities of phosphogypsum, which is the residue generated by the production of fertilizers and consists essentially of calcium dihydrate and some impurities, such as fluoride, metals in general, and radionuclides. Currently, tons of phosphogypsum are stored in the open air near the fertilizer industries, causing contamination of the environment. The 226 Ra present in these materials, when undergoes radioactive decay, produces the 222Rn gas. This radioactive gas, when inhaled together with its decay products deposited in the lungs, produces the exposure to radiation and can be a potential cause of lung cancer. Thus, the objective of this study was to measure the concentration levels of 222Rn from cylindrical samples of Portland cement, gypsum and phosphogypsum mortar from the state of Paraná, as well as characterizer the material and estimate the radon concentration in an environment of hypothetical dwelling with walls covered by such materials. Experimental setup of 222Rn activity measurements was based on AlphaGUARD detector (Saphymo GmbH). The qualitative and quantitative analysis was performed by gamma spectrometry and EDXRF with Au and Ag targets tubes (AMPTEK), and Mo target (ARTAX) and mechanical testing with x- ray equipment (Gilardoni) and the mechanical press (EMIC). Obtained average values of radon activity from studied materials in the air of containers were of 854 ± 23 Bq/m3, 60,0 ± 7,2 Bq/m3 e 52,9 ± 5,4 Bq/m3 for Portland cement, gypsum and phosphogypsum mortar, respectively. These results extrapolated into the volume of hypothetical dwelling of 36 m3 with the walls covered by such materials were of 3366 ± 91 Bq/m3, 237 ± 28 Bq/m3 e 208 ± 21 Bq/m3for Portland cement, gypsum and phosphogypsum mortar, respectively. Considering the limit of 300 Bq/m3 established by the ICRP, it could be concluded that the use of Portland cement plaster in dwellings is not secure and requires some specific mitigation procedure. Using the results of gamma spectrometry there were calculated the values of radium equivalent activity concentrations (Raeq) for Portland cement, gypsum and phosphogypsum mortar, which were obtained equal to 78,2 ± 0,9 Bq/kg; 58,2 ± 0,9 Bq/kg e 68,2 ± 0,9 Bq/kg, respectively. All values of radium equivalent activity concentrations for studied samples are below the maximum level of 370 Bq/kg. The qualitative and quantitative analysis of EDXRF spectra obtained with studied mortar samples allowed to evaluate quantitate and the elements that constitute the material such as Ca, S, Fe, and others.

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