After the decade of 1950, and mainly in the last years, the interest of earth architecture reemer... more After the decade of 1950, and mainly in the last years, the interest of earth architecture reemerges concerning the actual environmental issues in the world. This way, new technologies appear to improve the durability of earth architecture. New processes were developed to make earth pressed blocks and monolithic walls with earth using machines for static or dynamic press, as well as extrusion processes to make blocks or plates and sprayed processes to apply earth mixtures directly in situ. In the last years studies of soil stabilization using natural or synthetic additives have been also performed by some researchers in order to evaluate the durability performance of earth as a construction material. These studies about soil stabilization methods show that, with the incorporation of appropriate stabilizing agents, it is possible to obtain earth architecture with greater durability against water actions. This increase of earth building durability could help to change the inappropriate and prejudiced perception still existing about the earth material. This paper presents also an experimental research work carried out by the author Rute Eires during her PhD thesis (Eires, 2012) with supervise of the other authors. One part of this research deals about techniques of protection against water action for earth construction and is presented here, as well as the main tests and results obtained on the experimental work. The motivation for this research was the lack of knowledge about methods to improve the durability of earth material and the necessity of more scientific research about soil stabilization specifically to get a better performance against water action. This way, the main objective was to achieve soil stabilization mixtures for building with compressed earth (rammed earth or compressed earth blocks, CEB) without additional coating, obtaining a good durability against water without compromise the aesthetic potential of the earth material.
During the 21 st century, within road infrastructure management there is a strong enforcement on ... more During the 21 st century, within road infrastructure management there is a strong enforcement on preserving assets and prevent roadway collapses. As a result, public agencies have to implement periodic inspections and asset condition assessments. As pavements and bridges also culverts management play a special role in roadway safety, because they prevent roadbed erosion. The scope of this investigation is the assessment and forecast of culverts performance regarding rating condition and network reliability forecast. In addition, it intends to analyze hazards influence in the culvert serviceability, modelling the hazards actions on the infrastructure. In this paper, is performed the literature review of studies done during the past decade comparing advantages and limitations. Five main subjects are identified in the development of a culvert management system, since the inventory and inspection framework, to forecasting models and risk assessment. Moreover, it will determine the correlation between subjects and will find gaps for improvement.
Reinforced concrete is usually subjected to carbonation attack. Although it is a slow development... more Reinforced concrete is usually subjected to carbonation attack. Although it is a slow development pathology, the consequences can be high, precisely in the places with greater human, residential or industrial occupation. To make matters worse, carbon dioxide concentration in the atmosphere has been increasing due to the impact of climate changes and also to the growth of number of large cities. One of the ways to increase the resistance to carbonation attack may be through the application of concrete coatings. In fact, many current constructions have a protective skin on the concrete, often ignored in the durability design project. For these reasons, this research has looked into the efficiency of the coatings when applied on concrete. Priority was given to traditional unpainted coatings, with cementitious base, hydrated lime or both. A coating based on fly ash and a thin coating of cement were also tested. All of them were applied in an ordinary Portland cement concrete. Accelerated carbonation tests were performed and the results were excellent. It was observed that the performance of the coated concretes was, on average, about 65% better when compared to the uncoated concrete
Hoje em dia, o sector da construção tenta encontrar soluções de utilização de alguns resíduos, co... more Hoje em dia, o sector da construção tenta encontrar soluções de utilização de alguns resíduos, com o intuito de minimizar os problemas relacionados com a produção do cimento e com a durabilidade do betão. Alguns estudos mostram que as cinzas volantes de biomassa (CVB) apresentam propriedades que permitem a sua utilização como material pozolânico. Contudo, existem ainda algumas limitações na sua utilização, nomeadamente as questões relacionadas com as barreiras comerciais. Este trabalho foca-se no efeito da sua utilização como material substituto do cimento na produção de argamassas, com três níveis de substituição do cimento (20, 40 e 60%m). Em cada nível de substituição foram estudadas propriedades frescas e endurecidas das argamassas produzidas, como por exemplo, espalhamento, resistências mecânicas e absorção de água. Os resultados mostraram que o espalhamento das argamassas diminuiu com o aumento da quantidade de cinzas adicionada. Argamassas com 20%m de substituição do cimento apresentaram os melhores valores em termos de resistência mecânicas e absorção de água. O uso de CVB parece ser promissor, tendo em conta que as argamassas com até 20% de substituição apresentaram bons resultados em termos de qualidade e durabilidade. Estes resultados indicam que o uso de CVB, na produção de outros materiais, por exemplo em betões, pode conduzir a bons resultados, contribuindo inclusive para uma melhoria na sustentabilidade desses materiais, tendo em conta que se substitui cimento por um resíduo, sem se comprometer a qualidade e a durabilidade dos mesmos
O efeito erosivo da chuva dirigida (chuva carregada pelo vento), é considerado um dos principais ... more O efeito erosivo da chuva dirigida (chuva carregada pelo vento), é considerado um dos principais agentes de degradação nas fachadas de edificações, causando desde problemas estéticos a decomposição dos elementos que as compõem. Devido a atual tendência de uso de materiais de construção não convencionais, torna-se necessária a avaliação do desempenho destes quando em uso e, no caso de componentes para alvenarias externas, a resistência dos mesmos à ação de chuvas dirigidas. Os testes prescritos em normas internacionais são específicos para as condições climáticas do país ou região em que são adotados, havendo a necessidade de adaptações utilizando-se parâmetros coerentes com os dados meteorológicos da região para a qual o material se destina. Neste trabalho é apresentada uma proposta de equipamento de ensaio e descrita a metodologia para levantamento de dados e validação do teste por meio da correlação dos parâmetros adotados com os dados de caracterização de chuvas em Portugal. Foram avaliados diversos fatores, entre os quais o diâmetro da gota, velocidade, distância de aplicação e tempo de exposição. Tendo em vista que o potencial erosivo da chuva natural é medido em função da energia cinética, o teste e a metodologia proposta mostraram-se eficientes em simular a incidência de chuvas em vedações verticais externas, sendo possível, em duas horas de teste, acelerar o desgaste equivalente a 50 anos de exposição na região de maior índice pluviométrico de Portugal.
The concrete compressive strength is the most used mechanical property in the design of concrete ... more The concrete compressive strength is the most used mechanical property in the design of concrete structures. Therefore, the use of rational models to its prediction, to simulate the effects of its different constituents and its properties can play an important role in the achievement of the safety-economy required. Models to forecast the concrete compressive strength have already been presented before by some researchers. However, the comparison of different rational models and the application of models to predict the importance of the different constituents in the concrete behaviour have not yet been approached. Therefore, developing these models will be necessary namely to take into account the quality, i.e. the activity, of the most used mineral addition in concrete: fly ash. This study compared different Data Mining techniques to predict the compressive strength of fly ash concrete along time. The presented models are able to learn the complex relationships between several variables like the uniaxial compressive strength, the different concrete compounds and its mix design, the different properties of the fly ash used and the relative influence of its.
Progresso na ciência, bem como a sua aplicação, não é sempre linear. Há momentos em que ocorrem s... more Progresso na ciência, bem como a sua aplicação, não é sempre linear. Há momentos em que ocorrem saltos e têm uma in uência marcada no seu desenvolvimento e aplicação na vida prática. Assim aparenta ter sucedido com a introdução de Concreto Auto Adensável (CAA) nas últimas duas décadas do Séc. XX. A procura de atingir uma vida longa para o concreto, com a ajuda de adjuvantes e cientes, levou ao desenvolvimento do CAA. Designada também por Revolução Silenciosa, esta tecnologia apresenta melhorias signi cativas na redução do ruído e do tempo da construção, nas condições de trabalho com custo compatível com tecnologia convencional e, nalmente mas não menos importante, o desempenho global da obra. Apesar de já existirem algumas aplicações bem sucedidas de CAA, em grandes obras de construção civil, praticamente não se encontra nenhum livro exclusivamente dedicado à apresentação deste tema. O presente livro sintetiza um conjunto de informação técnica e cientí ca, dispersa na bibliogra a especializada sobre CAA. Este livro incorpora conhecimentos disponíveis na bibliogra a sobre o estado fresco, estado endurecido e ensaios exigidos para avaliação do auto adensamento do CAA. A apresentação de um caso prático de aplicação e estudo comprativo dos custos, em condições reais, com um concreto convencional equivalente, é uma mais valia deste documento. Este livro destina-se aos estudantes e pro ssionais de construção que pretendem atualizar os seus conhecimentos a m de poderem aplicar esta nova tecnologia quando as condições assim o exigirem. Espera-se ter dado uma contribuição modesta para colmatar uma lacuna na bibliogra a técnica nesta área, sentida por muitos. Acredita-se que o aumento do conhecimento técnico-cientí co conduzirá à aplicação mais frequente do CAA e, deste modo, poderá bene ciar a industria de construção. Cientes das limitações desta edição, prevê-se que as próximas edições, irão bene ciar amplamente dos comentários generosos dos leitores e, também, do aprendizado entretanto adquirido fruto das aplicações práticas futuras.
Restoration of buildings and monuments, Oct 1, 2010
The service life prediction of concrete rehabilitation works is nowadays more and more significan... more The service life prediction of concrete rehabilitation works is nowadays more and more significant. The rehabilitation techniques appeared as a need to solve problems posed by the degradation of concrete structures. Some years ago the rehabilitation techniques were not widespread developed and it was important to find effective and economic solutions for the problems. Now, there is more preoccupation with the service life of concrete rehabilitation techniques, like external strengthening with FRP, increase of concrete sections or reinforcement of cracked sections. The service life increase started with the quality of the concrete rehabilitation works. This includes the quality of the design, the products and the execution. Some standards are now available and establish specifications for concrete rehabilitation works. This work presents the main questions related with this subject. The use of polymers in concrete rehabilitation imposes a different analysis related with durability.
Anais da Mostra de Extensão, Inovação e Pesquisa, Jul 1, 2019
Considerando o potencial das tecnologias eletrônicas, é natural buscar meios onde a Engenharia Ci... more Considerando o potencial das tecnologias eletrônicas, é natural buscar meios onde a Engenharia Civil pode também se beneficiar. O Arduíno, plataforma open-source para desenvolvimento eletrônico, possui potencial na indústria da construção civil com baixo custo, facilidade de uso e boa confiabilidade, já em utilização por algumas empresas de construção. O monitoramento da evolução da resistividade elétrica em pastas e argamassas de concreto pode contribuir no controle de qualidade. Assim, o desenvolvimento de aparato com Arduino, para medir a evolução da resistividade elétrica do concreto fresco, representa avanço na aplicação de tecnologia em canteiro de obras, inclusive através da correlação entre o tempo de pega e a resistividade elétrica A pesquisa desenvolveu um aparato usando uma placa Arduino, sensor de corrente não invasivo, sensor de temperatura e umidade ambiente, e relógio para realizar leituras em tempos programados. As informações podem ser visualizadas em uma tela LCD assim como são salvas em um cartão MicroSD para posterior geração dos gráficos de correlação. O Arduino permite a integração de todos os componentes e programação pelos autores. As leituras são autônomas, cabendo ao operador a produção da argamassa, preenchimento do molde e ligação do aparato na rede elétrica comum, liberando-o para realização de outras tarefas. Ao final do ensaio, deve-se importar os dados do cartão para geração do gráfico evolutivo. Para validação do aparato foram feitos ensaios em composições de pastas de concreto, além de ensaios de Vicat para determinação dos tempos de pega. Os resultados comparativos entre os ensaios de resistividade e tempo de pega foram referenciados conforme as referências bibliográficas.
Phenolphthalein is the most common pH indicator used to measure the carbonation depth of cementit... more Phenolphthalein is the most common pH indicator used to measure the carbonation depth of cementitious materials. It is simple and quick to use, but according to some authors, is not an appropriate tool. Moreover, this substance is in the candidate list as a substance of very high concern by European Chemicals Agency. This article discusses the use of thymolphthalein rather than phenolphthalein. Accelerated carbonation tests were performed on cement mortars and high volume fly ash mortars. Once this kind of mixtures has low carbonation resistance additional alkalinity was provided by adding hydrated lime during its fresh mixture, and by curing the samples immersed in a calcium hydroxide solution. The results showed that the best indicator was the thymolphthalein, mainly for blends with lower carbonation depth. It was also checked that adding alkalinity can be useful for increasing the carbonation resistance.
University of Minho Mota-Engil machine to produce blocks with HiLoTec mold Materials and Tools Th... more University of Minho Mota-Engil machine to produce blocks with HiLoTec mold Materials and Tools These are the materials and tools that you will need in this phase: machine to produce the blocks, shovel, hoe, bucket, water, cement, sieve and plastic sheets to cover the blocks. University of Minho Mota-Engil hoe cement sieve plastic to cover the blocks water bucket 3. | 2 Manufacturing Blocks Objectives In this Chapter you will learn how to make the blocks for your house! University of Minho Mota-Engil Manufacturing Blocks 3 | 3. Corners Corners for division walls with reinforcements.
WSEAS transactions on environment and development, 2014
The choice between different materials and constructive systems can influence significantly the e... more The choice between different materials and constructive systems can influence significantly the environmental impact and economic cost of construction. In this context, four constructive systems used in South European were studied: one conventional -composed by hollow brick walls and steel reinforced post and beam concrete structure; and three non-conventional -light steel framing (LSF); wood frame (WF); and insulation concrete form (ICF). Using a case study based on a contemporary Portuguese typology of a single family dwelling, some environmental impact indicators, as well as the weight and the economic cost of these solutions were evaluated.
Tetrapods for coastal protection are frequently used in break waters for dissipation of wave ener... more Tetrapods for coastal protection are frequently used in break waters for dissipation of wave energy. During their service, these plain concrete elements usually exhibit degradation signs with frequent premature rupture of one or more of their legs when located in highly aggressive environments subjected to extreme wave action. These ruptures tend to decrease the efficiency of breakwaters as a whole, thus diminishing their capacity to absorb wave energy. The present paper aims to contribute to a better understanding of the stress levels that occur in this kind of mass concrete elements, taking into account imposed deformations (associated with heat of hydration) and applied loads. A thermo-mechanical numerical simulation tool (3D), based on the finite element method, is used for the assessment of heat of hydration induced stresses. After an initial discussion of the temperature development inside the tetrapod, the corresponding residual stresses are presented and discussed, and conclusions are withdrawn with regard to the available capacity of concrete to withstand further applied loads. Finally, the subsequent behaviour of the tetrapod is assessed and compared to alternative solutions with internal reinforcement of the tetrapod legs, such as reinforced concrete (using stainless steel), steel fibre reinforced concrete and reinforced concrete with FRP's.
Journal of Structural Engineering-asce, Aug 1, 2008
Over the last few decades, the astonishing developments of super plasticizers technology allowed ... more Over the last few decades, the astonishing developments of super plasticizers technology allowed great achievements on the conception of concrete mixes exhibiting self-compacting ability. Since the eighties, some methodologies have been proposed to achieve self-compacting requirements in fresh concrete mixes, based on the evaluation of the flowing properties of these mixes. There still persist, however, some doubts about the most appropriate strategy to define the optimum composition of a self-compacting concrete (SCC) mix, based on a required performance. The behavior of SCC as a structural material can be improved if adequate steel fiber reinforcement is added to SCC mix composition. In fact, the fiber reinforcement mechanisms can convert the brittle behavior of this cement based material into a pseudo-ductile behavior up to a crack width that is acceptable under the structural design point-of-view. Fiber addition, however, increases the complexity of the mix design process, due to the strong perturbation effect that steel fibers cause on fresh concrete flow. In the present work, a mix design method is proposed to develop cost effective and high performance Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC). The material properties of the developed SFRSCC are assessed as well as its potentiality as a structural material, carrying out punching and flexural tests on panel prototypes. A material nonlinear analysis is carried out, aiming to address the possibility of calibrating the constitutive model parameters by obtaining, with an inverse analysis, the fracture parameters using forcedeflection relationships recorded in simpler laboratory tests, like the three point notched beam bending test. The contribution of steel fibers for punching resistance is also, by this means, discussed.
A incorporação de resíduos e subprodutos industriais aos betões tem sido uma das alternativas enc... more A incorporação de resíduos e subprodutos industriais aos betões tem sido uma das alternativas encontradas para tentar reduzir o consumo mundial de cimento e, consequentemente, torná-lo um produto mais eco-eficiente. Neste sentido, e sabendo que um betão durável também promove a eco-eficiência do material, o trabalho em causa investiga a durabilidade de materiais cimentícios com incorporação de cinzas volantes (CV) face à ação combinada da penetração de cloretos e da carbonatação.
Abstract A proper evaluation as well as the considering of the second order effects on a steel st... more Abstract A proper evaluation as well as the considering of the second order effects on a steel structure-where the use of current slenderness elements caused by its geometric features-is an essential factor to take into account in the process of designing steel buildings assuring ...
Nowadays, the concrete production sector is challenged by attempts to minimize the usage of raw m... more Nowadays, the concrete production sector is challenged by attempts to minimize the usage of raw materials and energy consumption, as well as by environmental concerns. Therefore, it is necessary to choose better options, e.g. new technologies or materials with improved life-cycle performance. One solution for using resources in an efficient manner is to close the materials' loop through the recycling of materials that result either from the end-of-life of products or from being the by-product of an industrial process. It is well known that the production of Portland cement, one of the materials most used in the construction sector, has a significant contribution to the environmental impacts, mainly related with carbon dioxide emission. Therefore, the study and utilization of by-products or wastes usable as cement replacement in concrete can supply more sustainable options, provided that these types of concrete produced has same durability and equivalent quality properties as standard concrete. This work studied the environmental benefits of incorporating different percentages of two types of fly ashes that can be used in concrete as cement replacement. These ashes are waste products of power and heat production sectors using coal or biomass as fuels. The results showed that both ashes provide a benefit for the concrete production both in terms of environmental impact minimization and a better environmental performance through an increase in cement replacement. It is possible to verify that the incorporation of fly ashes is a sustainable option for cement substitution and a possible path to improve the environmental performance of the concrete industry.
After the decade of 1950, and mainly in the last years, the interest of earth architecture reemer... more After the decade of 1950, and mainly in the last years, the interest of earth architecture reemerges concerning the actual environmental issues in the world. This way, new technologies appear to improve the durability of earth architecture. New processes were developed to make earth pressed blocks and monolithic walls with earth using machines for static or dynamic press, as well as extrusion processes to make blocks or plates and sprayed processes to apply earth mixtures directly in situ. In the last years studies of soil stabilization using natural or synthetic additives have been also performed by some researchers in order to evaluate the durability performance of earth as a construction material. These studies about soil stabilization methods show that, with the incorporation of appropriate stabilizing agents, it is possible to obtain earth architecture with greater durability against water actions. This increase of earth building durability could help to change the inappropriate and prejudiced perception still existing about the earth material. This paper presents also an experimental research work carried out by the author Rute Eires during her PhD thesis (Eires, 2012) with supervise of the other authors. One part of this research deals about techniques of protection against water action for earth construction and is presented here, as well as the main tests and results obtained on the experimental work. The motivation for this research was the lack of knowledge about methods to improve the durability of earth material and the necessity of more scientific research about soil stabilization specifically to get a better performance against water action. This way, the main objective was to achieve soil stabilization mixtures for building with compressed earth (rammed earth or compressed earth blocks, CEB) without additional coating, obtaining a good durability against water without compromise the aesthetic potential of the earth material.
During the 21 st century, within road infrastructure management there is a strong enforcement on ... more During the 21 st century, within road infrastructure management there is a strong enforcement on preserving assets and prevent roadway collapses. As a result, public agencies have to implement periodic inspections and asset condition assessments. As pavements and bridges also culverts management play a special role in roadway safety, because they prevent roadbed erosion. The scope of this investigation is the assessment and forecast of culverts performance regarding rating condition and network reliability forecast. In addition, it intends to analyze hazards influence in the culvert serviceability, modelling the hazards actions on the infrastructure. In this paper, is performed the literature review of studies done during the past decade comparing advantages and limitations. Five main subjects are identified in the development of a culvert management system, since the inventory and inspection framework, to forecasting models and risk assessment. Moreover, it will determine the correlation between subjects and will find gaps for improvement.
Reinforced concrete is usually subjected to carbonation attack. Although it is a slow development... more Reinforced concrete is usually subjected to carbonation attack. Although it is a slow development pathology, the consequences can be high, precisely in the places with greater human, residential or industrial occupation. To make matters worse, carbon dioxide concentration in the atmosphere has been increasing due to the impact of climate changes and also to the growth of number of large cities. One of the ways to increase the resistance to carbonation attack may be through the application of concrete coatings. In fact, many current constructions have a protective skin on the concrete, often ignored in the durability design project. For these reasons, this research has looked into the efficiency of the coatings when applied on concrete. Priority was given to traditional unpainted coatings, with cementitious base, hydrated lime or both. A coating based on fly ash and a thin coating of cement were also tested. All of them were applied in an ordinary Portland cement concrete. Accelerated carbonation tests were performed and the results were excellent. It was observed that the performance of the coated concretes was, on average, about 65% better when compared to the uncoated concrete
Hoje em dia, o sector da construção tenta encontrar soluções de utilização de alguns resíduos, co... more Hoje em dia, o sector da construção tenta encontrar soluções de utilização de alguns resíduos, com o intuito de minimizar os problemas relacionados com a produção do cimento e com a durabilidade do betão. Alguns estudos mostram que as cinzas volantes de biomassa (CVB) apresentam propriedades que permitem a sua utilização como material pozolânico. Contudo, existem ainda algumas limitações na sua utilização, nomeadamente as questões relacionadas com as barreiras comerciais. Este trabalho foca-se no efeito da sua utilização como material substituto do cimento na produção de argamassas, com três níveis de substituição do cimento (20, 40 e 60%m). Em cada nível de substituição foram estudadas propriedades frescas e endurecidas das argamassas produzidas, como por exemplo, espalhamento, resistências mecânicas e absorção de água. Os resultados mostraram que o espalhamento das argamassas diminuiu com o aumento da quantidade de cinzas adicionada. Argamassas com 20%m de substituição do cimento apresentaram os melhores valores em termos de resistência mecânicas e absorção de água. O uso de CVB parece ser promissor, tendo em conta que as argamassas com até 20% de substituição apresentaram bons resultados em termos de qualidade e durabilidade. Estes resultados indicam que o uso de CVB, na produção de outros materiais, por exemplo em betões, pode conduzir a bons resultados, contribuindo inclusive para uma melhoria na sustentabilidade desses materiais, tendo em conta que se substitui cimento por um resíduo, sem se comprometer a qualidade e a durabilidade dos mesmos
O efeito erosivo da chuva dirigida (chuva carregada pelo vento), é considerado um dos principais ... more O efeito erosivo da chuva dirigida (chuva carregada pelo vento), é considerado um dos principais agentes de degradação nas fachadas de edificações, causando desde problemas estéticos a decomposição dos elementos que as compõem. Devido a atual tendência de uso de materiais de construção não convencionais, torna-se necessária a avaliação do desempenho destes quando em uso e, no caso de componentes para alvenarias externas, a resistência dos mesmos à ação de chuvas dirigidas. Os testes prescritos em normas internacionais são específicos para as condições climáticas do país ou região em que são adotados, havendo a necessidade de adaptações utilizando-se parâmetros coerentes com os dados meteorológicos da região para a qual o material se destina. Neste trabalho é apresentada uma proposta de equipamento de ensaio e descrita a metodologia para levantamento de dados e validação do teste por meio da correlação dos parâmetros adotados com os dados de caracterização de chuvas em Portugal. Foram avaliados diversos fatores, entre os quais o diâmetro da gota, velocidade, distância de aplicação e tempo de exposição. Tendo em vista que o potencial erosivo da chuva natural é medido em função da energia cinética, o teste e a metodologia proposta mostraram-se eficientes em simular a incidência de chuvas em vedações verticais externas, sendo possível, em duas horas de teste, acelerar o desgaste equivalente a 50 anos de exposição na região de maior índice pluviométrico de Portugal.
The concrete compressive strength is the most used mechanical property in the design of concrete ... more The concrete compressive strength is the most used mechanical property in the design of concrete structures. Therefore, the use of rational models to its prediction, to simulate the effects of its different constituents and its properties can play an important role in the achievement of the safety-economy required. Models to forecast the concrete compressive strength have already been presented before by some researchers. However, the comparison of different rational models and the application of models to predict the importance of the different constituents in the concrete behaviour have not yet been approached. Therefore, developing these models will be necessary namely to take into account the quality, i.e. the activity, of the most used mineral addition in concrete: fly ash. This study compared different Data Mining techniques to predict the compressive strength of fly ash concrete along time. The presented models are able to learn the complex relationships between several variables like the uniaxial compressive strength, the different concrete compounds and its mix design, the different properties of the fly ash used and the relative influence of its.
Progresso na ciência, bem como a sua aplicação, não é sempre linear. Há momentos em que ocorrem s... more Progresso na ciência, bem como a sua aplicação, não é sempre linear. Há momentos em que ocorrem saltos e têm uma in uência marcada no seu desenvolvimento e aplicação na vida prática. Assim aparenta ter sucedido com a introdução de Concreto Auto Adensável (CAA) nas últimas duas décadas do Séc. XX. A procura de atingir uma vida longa para o concreto, com a ajuda de adjuvantes e cientes, levou ao desenvolvimento do CAA. Designada também por Revolução Silenciosa, esta tecnologia apresenta melhorias signi cativas na redução do ruído e do tempo da construção, nas condições de trabalho com custo compatível com tecnologia convencional e, nalmente mas não menos importante, o desempenho global da obra. Apesar de já existirem algumas aplicações bem sucedidas de CAA, em grandes obras de construção civil, praticamente não se encontra nenhum livro exclusivamente dedicado à apresentação deste tema. O presente livro sintetiza um conjunto de informação técnica e cientí ca, dispersa na bibliogra a especializada sobre CAA. Este livro incorpora conhecimentos disponíveis na bibliogra a sobre o estado fresco, estado endurecido e ensaios exigidos para avaliação do auto adensamento do CAA. A apresentação de um caso prático de aplicação e estudo comprativo dos custos, em condições reais, com um concreto convencional equivalente, é uma mais valia deste documento. Este livro destina-se aos estudantes e pro ssionais de construção que pretendem atualizar os seus conhecimentos a m de poderem aplicar esta nova tecnologia quando as condições assim o exigirem. Espera-se ter dado uma contribuição modesta para colmatar uma lacuna na bibliogra a técnica nesta área, sentida por muitos. Acredita-se que o aumento do conhecimento técnico-cientí co conduzirá à aplicação mais frequente do CAA e, deste modo, poderá bene ciar a industria de construção. Cientes das limitações desta edição, prevê-se que as próximas edições, irão bene ciar amplamente dos comentários generosos dos leitores e, também, do aprendizado entretanto adquirido fruto das aplicações práticas futuras.
Restoration of buildings and monuments, Oct 1, 2010
The service life prediction of concrete rehabilitation works is nowadays more and more significan... more The service life prediction of concrete rehabilitation works is nowadays more and more significant. The rehabilitation techniques appeared as a need to solve problems posed by the degradation of concrete structures. Some years ago the rehabilitation techniques were not widespread developed and it was important to find effective and economic solutions for the problems. Now, there is more preoccupation with the service life of concrete rehabilitation techniques, like external strengthening with FRP, increase of concrete sections or reinforcement of cracked sections. The service life increase started with the quality of the concrete rehabilitation works. This includes the quality of the design, the products and the execution. Some standards are now available and establish specifications for concrete rehabilitation works. This work presents the main questions related with this subject. The use of polymers in concrete rehabilitation imposes a different analysis related with durability.
Anais da Mostra de Extensão, Inovação e Pesquisa, Jul 1, 2019
Considerando o potencial das tecnologias eletrônicas, é natural buscar meios onde a Engenharia Ci... more Considerando o potencial das tecnologias eletrônicas, é natural buscar meios onde a Engenharia Civil pode também se beneficiar. O Arduíno, plataforma open-source para desenvolvimento eletrônico, possui potencial na indústria da construção civil com baixo custo, facilidade de uso e boa confiabilidade, já em utilização por algumas empresas de construção. O monitoramento da evolução da resistividade elétrica em pastas e argamassas de concreto pode contribuir no controle de qualidade. Assim, o desenvolvimento de aparato com Arduino, para medir a evolução da resistividade elétrica do concreto fresco, representa avanço na aplicação de tecnologia em canteiro de obras, inclusive através da correlação entre o tempo de pega e a resistividade elétrica A pesquisa desenvolveu um aparato usando uma placa Arduino, sensor de corrente não invasivo, sensor de temperatura e umidade ambiente, e relógio para realizar leituras em tempos programados. As informações podem ser visualizadas em uma tela LCD assim como são salvas em um cartão MicroSD para posterior geração dos gráficos de correlação. O Arduino permite a integração de todos os componentes e programação pelos autores. As leituras são autônomas, cabendo ao operador a produção da argamassa, preenchimento do molde e ligação do aparato na rede elétrica comum, liberando-o para realização de outras tarefas. Ao final do ensaio, deve-se importar os dados do cartão para geração do gráfico evolutivo. Para validação do aparato foram feitos ensaios em composições de pastas de concreto, além de ensaios de Vicat para determinação dos tempos de pega. Os resultados comparativos entre os ensaios de resistividade e tempo de pega foram referenciados conforme as referências bibliográficas.
Phenolphthalein is the most common pH indicator used to measure the carbonation depth of cementit... more Phenolphthalein is the most common pH indicator used to measure the carbonation depth of cementitious materials. It is simple and quick to use, but according to some authors, is not an appropriate tool. Moreover, this substance is in the candidate list as a substance of very high concern by European Chemicals Agency. This article discusses the use of thymolphthalein rather than phenolphthalein. Accelerated carbonation tests were performed on cement mortars and high volume fly ash mortars. Once this kind of mixtures has low carbonation resistance additional alkalinity was provided by adding hydrated lime during its fresh mixture, and by curing the samples immersed in a calcium hydroxide solution. The results showed that the best indicator was the thymolphthalein, mainly for blends with lower carbonation depth. It was also checked that adding alkalinity can be useful for increasing the carbonation resistance.
University of Minho Mota-Engil machine to produce blocks with HiLoTec mold Materials and Tools Th... more University of Minho Mota-Engil machine to produce blocks with HiLoTec mold Materials and Tools These are the materials and tools that you will need in this phase: machine to produce the blocks, shovel, hoe, bucket, water, cement, sieve and plastic sheets to cover the blocks. University of Minho Mota-Engil hoe cement sieve plastic to cover the blocks water bucket 3. | 2 Manufacturing Blocks Objectives In this Chapter you will learn how to make the blocks for your house! University of Minho Mota-Engil Manufacturing Blocks 3 | 3. Corners Corners for division walls with reinforcements.
WSEAS transactions on environment and development, 2014
The choice between different materials and constructive systems can influence significantly the e... more The choice between different materials and constructive systems can influence significantly the environmental impact and economic cost of construction. In this context, four constructive systems used in South European were studied: one conventional -composed by hollow brick walls and steel reinforced post and beam concrete structure; and three non-conventional -light steel framing (LSF); wood frame (WF); and insulation concrete form (ICF). Using a case study based on a contemporary Portuguese typology of a single family dwelling, some environmental impact indicators, as well as the weight and the economic cost of these solutions were evaluated.
Tetrapods for coastal protection are frequently used in break waters for dissipation of wave ener... more Tetrapods for coastal protection are frequently used in break waters for dissipation of wave energy. During their service, these plain concrete elements usually exhibit degradation signs with frequent premature rupture of one or more of their legs when located in highly aggressive environments subjected to extreme wave action. These ruptures tend to decrease the efficiency of breakwaters as a whole, thus diminishing their capacity to absorb wave energy. The present paper aims to contribute to a better understanding of the stress levels that occur in this kind of mass concrete elements, taking into account imposed deformations (associated with heat of hydration) and applied loads. A thermo-mechanical numerical simulation tool (3D), based on the finite element method, is used for the assessment of heat of hydration induced stresses. After an initial discussion of the temperature development inside the tetrapod, the corresponding residual stresses are presented and discussed, and conclusions are withdrawn with regard to the available capacity of concrete to withstand further applied loads. Finally, the subsequent behaviour of the tetrapod is assessed and compared to alternative solutions with internal reinforcement of the tetrapod legs, such as reinforced concrete (using stainless steel), steel fibre reinforced concrete and reinforced concrete with FRP's.
Journal of Structural Engineering-asce, Aug 1, 2008
Over the last few decades, the astonishing developments of super plasticizers technology allowed ... more Over the last few decades, the astonishing developments of super plasticizers technology allowed great achievements on the conception of concrete mixes exhibiting self-compacting ability. Since the eighties, some methodologies have been proposed to achieve self-compacting requirements in fresh concrete mixes, based on the evaluation of the flowing properties of these mixes. There still persist, however, some doubts about the most appropriate strategy to define the optimum composition of a self-compacting concrete (SCC) mix, based on a required performance. The behavior of SCC as a structural material can be improved if adequate steel fiber reinforcement is added to SCC mix composition. In fact, the fiber reinforcement mechanisms can convert the brittle behavior of this cement based material into a pseudo-ductile behavior up to a crack width that is acceptable under the structural design point-of-view. Fiber addition, however, increases the complexity of the mix design process, due to the strong perturbation effect that steel fibers cause on fresh concrete flow. In the present work, a mix design method is proposed to develop cost effective and high performance Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC). The material properties of the developed SFRSCC are assessed as well as its potentiality as a structural material, carrying out punching and flexural tests on panel prototypes. A material nonlinear analysis is carried out, aiming to address the possibility of calibrating the constitutive model parameters by obtaining, with an inverse analysis, the fracture parameters using forcedeflection relationships recorded in simpler laboratory tests, like the three point notched beam bending test. The contribution of steel fibers for punching resistance is also, by this means, discussed.
A incorporação de resíduos e subprodutos industriais aos betões tem sido uma das alternativas enc... more A incorporação de resíduos e subprodutos industriais aos betões tem sido uma das alternativas encontradas para tentar reduzir o consumo mundial de cimento e, consequentemente, torná-lo um produto mais eco-eficiente. Neste sentido, e sabendo que um betão durável também promove a eco-eficiência do material, o trabalho em causa investiga a durabilidade de materiais cimentícios com incorporação de cinzas volantes (CV) face à ação combinada da penetração de cloretos e da carbonatação.
Abstract A proper evaluation as well as the considering of the second order effects on a steel st... more Abstract A proper evaluation as well as the considering of the second order effects on a steel structure-where the use of current slenderness elements caused by its geometric features-is an essential factor to take into account in the process of designing steel buildings assuring ...
Nowadays, the concrete production sector is challenged by attempts to minimize the usage of raw m... more Nowadays, the concrete production sector is challenged by attempts to minimize the usage of raw materials and energy consumption, as well as by environmental concerns. Therefore, it is necessary to choose better options, e.g. new technologies or materials with improved life-cycle performance. One solution for using resources in an efficient manner is to close the materials' loop through the recycling of materials that result either from the end-of-life of products or from being the by-product of an industrial process. It is well known that the production of Portland cement, one of the materials most used in the construction sector, has a significant contribution to the environmental impacts, mainly related with carbon dioxide emission. Therefore, the study and utilization of by-products or wastes usable as cement replacement in concrete can supply more sustainable options, provided that these types of concrete produced has same durability and equivalent quality properties as standard concrete. This work studied the environmental benefits of incorporating different percentages of two types of fly ashes that can be used in concrete as cement replacement. These ashes are waste products of power and heat production sectors using coal or biomass as fuels. The results showed that both ashes provide a benefit for the concrete production both in terms of environmental impact minimization and a better environmental performance through an increase in cement replacement. It is possible to verify that the incorporation of fly ashes is a sustainable option for cement substitution and a possible path to improve the environmental performance of the concrete industry.
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Papers by Aires Camões