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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.
401

Architektura ekofarem v České republice / Architecture of organic farms in Czech republic

Pohanková, Lucie January 2012 (has links)
New agricultural constructions in Czech Republic happen, in better case, privilege of civil engineer, in the worse case only privilege of the investor, in the past. While architects or enlightenment project architects with inventive and feeling for architecture, rarely interfered to their projection. In the practice, the preferred and implemented misconception, that it is a purely purpose-built buildings with economical advantageous solution type, when external design of the building and his effect in landscape plays just a minor role, meant a huge mistake, which disfeature face of a lot of villages. With the gradual development of organic and sustainable agriculture is obvious, that to the design of these buildings gets back the idea of invention and emotion of construction into the landscape. Essence of a dissertation is how to proceed with the draft of a new or completion of original organic farm in conditions of the Czech Republic and on which specific points to focus in the design. Objective of thesis is generalization of rules design new modern organic farm or new buildings on the existing organic farm, using the principles of organic architecture and architecture undemanding of energy, renewable source of energy and non-waste management and verification on the specific examples in the Czech Republic and neighboring Europa countries. Where else should apply the principles of organic architecture more than in the construction of organic farms. Moreover, organic farm offers a great number of functions and with related different operations with requirements for specific areas. This is an added bonus, diversity of construction and the possibility of building creativity in architectural solutions. It is then mainly limited functionality of the building, legislative, public health, fire and traffic regulations, with which any proposal must cope. Organic farms are a phenomenon, but also the future of sustainable agriculture in the Czech Republic, as well. Not only production side of organic farms, but also neglected building stock deserves the attention of experts. Only organic farm with the right comprehensive created building and energy concept on an ecological principle is becoming a well-functioning self-contained unit connected with the cycle of nature, the surrounding landscape and regional tradition.
402

Šetrné bydlení na venkově / Environment-Friendly Housing in Rural Areas

Čáslava, Petr January 2013 (has links)
While I spent 7 years of study, experience and dedication to this work, the building construction has passed evolution from construction boom to contemporary building crisis. Demand for cheap building construction, materials and family housing increased sharply. Energy prices are rising every year... It seems that we will all have to deal with our essential task today or in the near future . This task is mean to prevent the current rate of degradation and destruction of our planet's climate and our environment. In this point of view, it looks the question of energy-saving construction very topical. By entering the study was to examine the possibilities of environmental friendly housing in rural areas in terms of environmental issues. My hypothesis was if can I determine the suitable candidate for the construction of passive houses themselves by comparing their characteristic of pre-defined construction samples. My objective is to offer builders and designers overview of suitable building systems with the possibility to compare the various factors influencing the decision on the selection of a builder´s construction for a house. The thesis presents the comparison of seven structural systems as a basic element of architecture. In the implementation of energy-efficient house is an architectural form often conditioned by structure. For this reason it is necessary to offer this kind of overview with options and parameters of individual building systems, which can then be used by architect to design a house for the builder - free and easy realization of his own, let´s say DIY (do it yourself). For builders (mean investors) of DIY houses is economy and finance a crucial question, therefore, for this reason I will evaluate suitable building system which is relative performance vs. price in the end. It is necessary to take into account the architecture of the house and especially the space layout and design and the attitude with the context of the rural areas environment. My pupose was to prove that good architectural design can be used with of low-cost, energy-saving and environmental friendly house built in DIY way.
403

Certifieringens påverkan i byggbranschen / The impact of certification om the construction industry

Alsabti, Roni January 2019 (has links)
I detta examensarbete undersökes betydelsen av certifieringen för byggmaterial ute i byggbranschen. Studien har bedrivits på grund av bristen på information i hur certifieringen har påverkat byggbranschen. För att en producent skall kunna inneha certifiering för sin produkt krävs det att man genomgår en procedur som styrs av ett certifieringsorgan. Målet med att bli certifierade är en kvalitetsutveckling i material och producera mer hållbart och effektivt material. De som skapar direktiv och krav är EU och certifieringsorgan i Sverige som Nordcert erbjuder producenter denna certifiering vilket betyder att producentens produkt klarar EUs krav och innehar rätten att säljas inom EUs gränser. En kontakt med producenterna som upprätthölls var grund till denna studie. Kontakten skapade intervju med 19 producenter totalt och dessa intervjuer blev resultatet i denna studie. Frågeställningarna som besvarades lyder: · Har certifieringen bidragit till en effektivisering av material? · Har certifieringen bidragit till en kvalitetsutveckling i material? · Har certifieringen bidragit till förbättringar inom arbetsmiljön? · Finns det något samband mellan olika tidpunkter av certifieringen? Resultaten tyder till stor del att certifieringen har påverkat producenterna en hel del i och med vad den bidragit med. Det framstår att certifieringen följer ett samband i dess påverkan gentemot producenterna. Det framgår att certifiering är en lönsam process att genomgå för producenter då det gynnar dem i deras kvalitets-, arbetsmiljö- och effektivitetsutveckling. / In this thesis the impact of the certification for building materials in the construction industry is examined. The study has been conducted because of the lack of information on how the certification has made an impact on the construction industry. In order for a producer to be able to hold certification for his product, it is necessary to undergo a procedure that is controlled by a certification body. The goal of becoming certified is a quality development in materials and produce more sustainable and efficient materials. Those who create directives and requirements are EU and certification bodies in Sweden that Nordcert offers this certification to producers, which means that the producer's product meets the EU requirements and holds the right to be sold within the EU borders. A contact with the producers that was maintained was the basis for this study. The contact created interviews with 19 producers in total and these interviews were the result of this study. The questions that are answered read: • Has the certification contributed to improving the efficiency of materials? • Has the certification contributed to a quality development in materials? • Has the certification contributed to improvements in the work environment? • Is there any connection between different times lengths of the certification? The results largely indicate that the certification has affected the producers a great deal in terms of what it has contributed to. It appears that the certification follows a correlation with its impact on the producers. It is clear that a certification is a profitable process to go through for producers as it benefits them in their quality, efficiency and work enviromental develompent.
404

Främjande av återbruk av byggmaterial : En kvalitativ studie om branschens uppfattningar kring potentialen hos ekonomiska incitament / Återbruk av Byggmaterial : En Fallstudie om Ekonomiska Incitament, Hinder och Utmaningar

Afzali, Faizullah, Rashid, Renas January 2023 (has links)
Denna uppsats lyfter fram betydelsen av ekonomiska incitament för att stimulera återanvändning av byggmaterial i Sverige. Trots att byggindustrin ser fördelarna med återanvändning, visar studien att det saknas tillräckliga ekonomiska incitament för att göra det till en standardpraxis. Genom semistrukturerade intervjuer med representanter från byggindustrin och litteraturstudie, identifierade studien flera hinder som kvalitetsgaranti, byggregler, brist på kunskap och ekonomiska utmaningar. Studiens syfte var att undersöka vilka ekonomiska incitament som kunde främja användningen av återanvända byggmaterial och identifiera potentiella hinder för deras implementering. Resultaten tyder på att det för närvarande saknas direkta ekonomiska incitament som uppmuntrar byggföretag till att återanvända byggmaterial. Flera hinder har identifierats, bland annat utmaningar rörande kvalitetsgarantier, byggregler, brist på kunskap och ekonomiska svårigheter. Studien framhåller också att det krävs mer omfattande politiska och ekonomiska initiativ för att stimulera användningen av återanvända byggmaterial. Uppsatsen bidrar till den befintliga forskningen genom att ge rekommendationer till beslutsfattare och andra aktörer inom byggsektorn som är intresserade av att främja hållbarhet och miljövänliga metoder. Den föreslår att framtida forskning bör inriktas på att utforma och testa specifika ekonomiska incitament för att främja återanvändning av byggmaterial. Av studien framkommer det att byggföretag identifierar en mängd hinder och utmaningar vid återanvändning av byggmaterial. Det framkommer även att det finns en märkbar brist på ekonomiska incitament från staten för att främja användandet av återanvända byggmaterial i byggprojekt. Byggföretagen föreslog olika former av ekonomiska incitament som skulle kunna främja användningen av återanvända byggmaterial, inklusive bidrag, skattelättnader och digitala plattformar. Det fanns även en variation i politiska åsikter gällande idén om att införa ekonomiska incitament för att främja återanvändningen av byggmaterial, med en del som stödde idén och andra som motsatte sig den. / This paper highlights the importance of economic incentives in stimulating the reuse of building materials in Sweden. Although the construction industry recognizes the benefits of reuse, the study shows that there are insufficient economic incentives to make it a standard practice. Through semi-structured interviews with representatives from the construction industry and a literature review, the study identified several barriers such as quality assurance, building regulations, lack of knowledge, and economic challenges.The purpose of the study was to investigate what economic incentives could promote the use of reused building materials and identify potential barriers to their implementation.The findings suggest that there are currently no direct economic incentives that encourage construction companies to reuse building materials. Several obstacles have been identified, including challenges related to quality guarantees, building regulations, lack of knowledge, and economic difficulties. The study also emphasizes that more extensive political and economic initiatives are needed to stimulate the use of reused building materials. The paper contributes to the existing research by providing recommendations to policy makers and other actors in the construction sector who are interested in promoting sustainability and environmentally friendly methods. It suggests that future research should focus on designing and testing specific economic incentives to promote the reuse of building materials. In its conclusions, it emerges that construction companies identify a multitude of obstacles and challenges when reusing building materials. It also appears that there is a noticeable lack of economic incentives from the state to promote the use of reused building materials in construction projects. Construction companies suggested different forms of economic incentives that could promote the use of reused building materials, including grants, tax relief, and digital platforms. There was also a variation in political opinions regarding the idea of introducing economic incentives to promote the reuse of building materials, with some supporting the idea and others opposing it.
405

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.
406

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.
407

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.
408

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
409

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.
410

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.

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