Incorporação de cinzas de biomassa como substituto do cimento em argamassas

Hoje em dias, as questões ambientais referentes à produção de cimento e à durabilidade do betão são muito importantes. Assim, a utilização de sub-produtos ou resíduos tem sido efectuada com a perspectiva de minimizar os problemas associados ao betão. As propriedades das cinzas volantes de biomassa (CVB) permitem a sua utilização como material pozolânico e bons resultados foram obtidos com a utilização destas cinzas como material substituinte do cimento. Este trabalho apresenta a caracterização das CVB e o seu efeito nas propriedades de argamassas. As cinzas foram caracterizadas em termos químicos e físicos, sendo estudado 3 níveis de substituição (20, 40 e 60%m) do cimento. As propriedades frescas e endurecidas das argamassas foram estudadas. Os resultados mostraram que a trabalhabilidade diminui com o aumento do teor de cinzas e que argamassas com 20% de substituição do cimento apresentam os melhores resultados em termos de resistências mecânicas e absorção de água. Para além disso, a incorporação de CVB diminui a perda de alcalinidade das argamassas, sendo menor essa diminuição quanto maior for o teor de cinzas volantes de biomassa presente nas argamassas. Este estudo mostra que a utilização de CVB conduz a bons resultados nas propriedades das argamassas e que a sua utilização na produção de betão conduz a uma melhoria no desempenho ambiental sem comprometer a durabilidade e a qualidade do betão.Os autores querem agradencer à FCT (Fundação para a Ciência e Tecnologia – Portugal) e ao programa doutoral Eco-ConstructionandRehabilitation por ajudarem no suporte financeiro através da bolsa com a referência PD/BD/52661/2014 e do projecto com a referência UID/MULTI/00308/2013

Effect of using biomass fly ash on the concrete sustainability

Biomass fly ash has been studied has a partial cement material, since this material has a positive effect on concrete properties. Even though, some mixes with BFA presents a positive benefit, they need to be economically competitive and present a good environmental performance. So, the analyse and comparison of concrete that uses BFA as raw material substitution in terms of environmental impacts related to the production of conventional concrete. One of the best approaches to develop this type of study is to use the life cycle assessment (LCA) method. This method quantifies both the input flows, such as energy, water and materials, as well as the output flows, such as CO2 emission, solid wastes and liquid wastes. Based both on the abovementioned context and methodological approach, a quantification and comparison of potential environmental impacts resulting from the production of 1 m3 of concrete was made, using different types of binder and quantities of cement substitution

The Pombaline cage (“gaiola pombalina”): an European anti-seismic system based on enlightenment era of experimentation

On November 1st, 1755, the lower part of Lisbon, a city of medieval character, was badly destroyed by the action of a violent earthquake, followed by a tsunami and violent fires. At the time, the Marquis of Pombal, ruled Portugal, and took several measures to safeguard the inhabitants and rebuild the city. It was decided to rebuild the city on the same site, according to a new urban plan with orthogonal streets. The conception of the new urban mesh was an Enlightenment Era design. The buildings were endowed with a series of unique characteristics, including an anti-seismic wooden structure - the Pombaline cage. This solution sought to resist earthquakes, making the building structure less rigid, aiming at dissipating the seismic energy through the lower weight and elasticity of the wood, the flexibility of the connections between the elements and even the lightening of the massive elements. This way, the total ruin of the building was avoided, in the event of an earthquake, and an interior area was created that could remain intact, serving as a refuge for the inhabitants. This anti-seismic system had great importance and influence in the panorama of engineering history, considering it could be at the genesis of seismic engineering in Europe. The perception that 18th century engineers had of the system to resist earthquakes through flexibility, should be the object of in-depth study, as it could be adopted in the reinforcement of constructions against possible earthquakes, especially the oldest ones, avoiding the introduction of rigid reinforcements in buildings otherwise characterized by their ductility. The present study seeks to explore the performance of this system, and to better understand how the increase in seismic performance is processed through flexibility, instead of the increase of the buildings stiffness.info:eu-repo/semantics/acceptedVersio

The narrow mausolea at Conchada cemetery as part of Portuguese and European architectural heritage

Over millennia, death was the origin of great funerary constructions that have come down to us. These constructions aimed at ensuring eternity and perpetuating memory. Funeral art thus appears not in the service of death, but in the service of memory. In the modern age, funerary constructions do not have the dimensions and grandeur they did in ancient times, but there are still constructions with relevant architectural interest, built to perpetuate the memory of important families. In Conchada Cemetery, located in Coimbra, Portugal, a vast and diverse funeral heritage exists. Possessing various architectural styles, almost all built with limestone from the region, the narrow mausoleums stand out from this heritage. This work presents a study carried out on the architecture and construction of two types of narrow mausoleums, existing in the Conchada Cemetery, both of the Neo-Gothic style: one with an entrance from the front, and another from the back. As it is not possible to present the photographs of the burial vaults, since it would represent an intrusive approach to the families, the authors have resorted to representing them through Indian ink and watercolor illustrations.info:eu-repo/semantics/publishedVersio

Estudo de betões eco-eficientes através da utilização de cinzas volantes de biomassa

A indústria do betão é, na actualidade, constantemente desafiada a minimizar o consumo de recursos naturais, matérias-primas e energia, assim como melhorar a performance ambiental dos materiais que produz. O cimento Portland é um dos materiais que contribui significativamente para a emissão de dióxido de carbono para atmosfera e, consequentemente, para o aquecimento global. Por outro lado, são utilizadas na sua produção grandes quantidades de matérias-primas e energia. Deste modo, é uma mais-valia a sua substituição nos materiais de construção, tais como o betão, por materiais que mantenham as mesmas propriedades mecânicas e de durabilidade, mas permitindo produzir um material mais sustentável. Um estudo experimental foi desenvolvido com o intuito de se avaliara influência de cinzas volantes de biomassa nas propriedades de betões com elevados teores de cinzas volantes. As cinzas volantes de biomassa foram usadas como reservatório de alcalinidade, para se tentar perceber se estas permitem minorar os problemas relacionados com este tipo de betões, nomeadamente o problema da carbonatação, e consequentemente da corrosão das infraestruturas metálicas. Foram estudadas propriedades frescas e endurecidas, tais como: espalhamento, resistências mecânicas e carbonatação. Os resultados mostram que a adição, ao conteúdo total do ligante, de apenas 0,5%m de cinzas volantes de biomassa, conduz a uma melhoria em termos de qualidade e durabilidade do betão, quando comparado comum betão com elevado teor de cinzas eum betão convencional (só com cimento como ligante). Deste modo, com a utilização de cinzas volantes de biomassa, é possível a produção de materiais de construção com baixo teor de cimento, com resistências mecânicas satisfatórias e duráveis, mas com uma melhoria significativa na performance ambiental destes materiais.Os autores querem agradecer à FCT (Fundação para a Ciência e Tecnologia – Portugal) e ao programa doutoral Eco-Construction and Rehabilitation por ajudarem no suporte financeiro através da bolsa com a referência PD/BD/52661/2014. Este trabalho foi também financiado pelo FEDER, através de fundos do programa “Competitivity Factors Operational Programme” - COMPETE e por fundos nacionais através do projecto POCI-01-0145-FEDER-007633 e pelo programa operacional regional CENTRO2020 no âmbito do projecto CENTRO-01-0145-FEDER-000006.info:eu-repo/semantics/publishedVersio

Hybrid effect and pseudo-ductile behaviour of unidirectional interlayer hybrid FRP composites for civil engineering applications

An experimental study on the tensile stress–strain curves of interlayer (layer-by-layer) unidirectional hybrid FRP composites was conducted aiming at evaluating the corresponding hybrid effect and pseudo-ductility of this innovative solution. Different combinations of the following dry unidirectional fabric materials, also varying the number of layers, were adopted in tests: high-modulus carbon, standard carbon, E-glass, and basalt. The composites were produced layer-by-layer by hand lay-up method, using an epoxy-based resin as matrix. The results have shown a strain increase at failure of both standard carbon and high-modulus carbon fibres with the volume decrease of these materials in hybrid combinations. It was also concluded that combining high-modulus carbon with E-glass, high-modulus carbon with basalt, or high-modulus carbon with standard carbon can lead to very good pseudo-ductile tensile behaviour. Finally, it should be highlighted that an existing analytical model in the literature was satisfactorily adopted to predict the tensile response of these hybrid composites.S&P Clever Reinforcement Ibérica Lda. PTDC/ECM-EST/1282/2014info:eu-repo/semantics/publishedVersio

Chloride Ingress Resistance, Microstructure and Mechanical Properties of Lightweight Mortars with Natural Cork and Expanded Clay Prepared Using Sustainable Blended Cements

The use of lightweight aggregates in construction materials is a good solution for increasing the contribution to sustainability of civil engineering works, such as maritime ones. In this regard, the possibility of using cork granulates and expanded clay is a current research topic. The combination of eco-friendly cements with lightweight aggregates could provide solutions for developing new building materials. In this work, it has been studied mortars prepared with sustainable cements and the lightweight aggregates of natural cork and expanded clay. These cements incorporated slag, limestone and fly ash. Reference mortars with only sand as aggregate were also made. The total porosity and pore size distributions were obtained. The non-steady-state chloride migration coefficient and compressive and flexural strengths were also determined. The tests were performed at 28 days and 1 year. The differences in the total porosity between the natural cork and expanded clay series were not high, depending on the binder. Natural cork mortars showed similar or slightly higher migration coefficients than the reference and expanded clay mortars at 1 year. This adequate chloride resistance and the low mechanical strengths observed for the natural cork mortars recommend the possible use of this new aggregate in non-structural cement-based materials for civil engineering works exposed to maritime environments.This work was partly funded by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020, and by the FEDER through the COMPETE2020 program, Portugal 2020, within the scope of project CENTRO-01-0247-FEDER-047067 (LIFE4STONE). José Marcos Ortega is indebted to the Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital de la Generalitat Valenciana (Spain), for a fellowship of the BEST/2020 program (reference BEST/2020/079)

3D finite element model for hybrid FRP-confined concrete in compression using modified CDPM

The main goal of the work herein presented is to propose an accurate three-dimensional finite element model to predict the compressive behaviour of hybrid FRP-confined concrete. This was achieved through the modification of the concrete damaged plasticity model (CDPM) available in ABAQUS software, since the original CDPM has shortcomings that make it unusable to predict the compressive behaviour of confined concrete. It was demonstrated that, by turning the yield function and the flow rule dependents on the confining pressure, it is possible to use the model referred to and obtain accurate results. An analytical model was used to obtain the input parameters needed to calibrate the CDPM. A specific user subroutine was developed to modify the original CDPM. Hybrid FRP properties were calibrated as well, using an appropriate analytical model. Plasticity was assumed in the hybrid combinations for which pseudo-ductile tensile responses occurred. The performance of the proposed CDPM was validated using both experimental results and analytical predictions. It was concluded that, by using the developed 3D finite element model for hybrid FRP-confined concrete in compression, a very good agreement between experimental, analytical and numerical compressive stress-strain and lateral strain-axial strain curves is reached.The authors wish to thank to FCT - Portuguese Foundation for Science and Technology and to the Doctoral Program Eco-Construction and Rehabilitation for supporting the PhD grant (PD/BD/52660/2014). Acknowledgements are extended to the following programs that partially supported the study herein presented: European Funds for Regional Development (FEDER) through the Operational Program for Competitiveness Factors (COMPETE), Operational Program for Competitiveness and Internationalization (POCI), and again FCT through both FRPLongDur POCI-01-0145-FEDER-016900 (FCT reference PTDC/ECM-EST/1282/2014) and POCI-01-0145-FEDER-007633 projects. Last but not least, the authors also acknowledge the support of both S&P Clever Reinforcement Ibérica Lda and Dalla Betta Group Company

Comparative environmental life-cycle analysis of concretes using biomass and coal fly ashes as partial cement replacement material

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 type 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.The authors wish to thank to FCT (Fundação para a Ciência e Tecnologia – Portugal) and to the Doctoral Program Eco-Construction and Rehabilitation (EcoCoRe) for supporting the PhD scholarship (with the grant-number PD/BD/52661/2014)

Resposta à tração uniaxial de sistemas FRP híbridos

Hoje em dia, encontra-se amplamente reconhecido que o desempenho à compressão do betão, no que se refere tanto à sua resistência como à sua ductilidade, pode ser significativamente melhorado através do seu confinamento com sistemas compósitos de FRP. Esta solução tem particular interesse no reforço de pilares, sendo bastante eficaz no caso de pilares de secção circular, uma vez que a tensão de confinamento mobilizada é uniforme em toda a secção. No entanto, diversos autores têm reportado que a extensão de rotura dos sistemas de FRP utilizados no confinamento é bastante inferior à extensão última obtida nos correspondentes ensaios de tração de provetes planos. A redução de eficácia referida chega, por vezes, aos 50%, nos casos em que se recorre a fibras de maior módulo de elasticidade. No presente trabalho, recorreu-se a diferentes tipos de fibras, com valores distintos em termos de módulo de elasticidade, resistência, extensão última e custo, dando origem a um sistema híbrido (constituído por diferentes materiais de reforço na mesma matriz). A hibridização está associada à obtenção de um sistema FRP otimizado, em termos de resistência, extensão na rotura, módulo de elasticidade e custo, comparativamente a sistemas FRP tradicionais. Acredita-se que a hibridização pode ser muito vantajosa no caso particular do confinamento de betão, uma vez que permite uma utilização mais eficaz das fibras, em particular as de maior módulo, levando a que estas rompam mais tarde. As diversas combinações foram ensaiadas à tração, de acordo com a norma EN ISO 527-5. Os resultados obtidos permitiram constatar um efeito positivo nas combinações híbridas, traduzido num aumento entre 8 e 25%, em termos de extensão de rotura das fibras mais rígidas, num aumento entre 5 e 15 %, em termos de extensão última e numa redução do custo entre 28 e 62%, comparativamente aos sistemas FRP não híbridos de referência. Em contrapartida, registaram-se nas combinações híbridas perdas de resistência à tração entre 19 e 55% e de módulo de elasticidade entre 30 e 56%. Constatou-se que a redução de módulo de elasticidade é proporcional à diminuição de custo do produto final.Os autores agradecem às empresas S&P Clever Reinforcemente e Dalla Betta Group s.r.l o apoio prestado ao nível do fornecimento dos materiais destinados à campanha experimental. Este trabalho foi também apoiado por fundos nacionais através da FCT e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do Programa Operacional Fatores de Competitividade e internacionalização (POCI) e do Programa Regional de Lisboa no âmbito dos projetos FRPLongDur POCI-01-0145-FEDER-016900 (PTDC/ECM-EST/1282/2014). Os autores agradem ainda a disponibilidade e a colaboração do Laboratório de Estruturas da Universidade do Minho (LEST). O primeiro autor agradece à FCT – Fundação para a Ciência e a Tecnologia – o apoio concebido através da bolsa de doutoramento PD/BD/52660/2014, enquadrada no programa doutoral ‘Eco Construção e Reabilitação’ (EcoCoRe)