Influence of casting condition on the anisotropy of the fracture properties of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC)

Identification of the tensile constitutive behaviour of Fibre Reinforced Concrete (FRC) represents an important aspect of the design of structural elements using this material. Although an important step has been made with the introduction of guidance for the design with regular FRC in the recently published fib Model Code 2010, a better understanding of the behaviour of this material is still necessary, mainly for that with self-compacting properties. This work presents an experimental investigation employing Steel Fibre Self-Compacting Concrete (SFRSCC) to cast thin structural elements. A new test method is proposed for assessing the post-cracking behaviour and the results obtained with the proposed test method are compared with the ones resulted from the standard three-point bending tests (3PBT). Specimens extracted from a sandwich panel consisting of SFRSCC layers are also tested. The mechanical properties of SFRSCC are correlated to the fibre distribution by analysing the results obtained with the different tests. Finally, the stress-crack width constitutive law proposed by the fib Model Code 2010 is analysed in light of the experimental results.This work is part of the research project QREN number 5387, LEGOUSE, involving the companies Mota-Engil, CiviTest, the ISISE/University of Minho and PIEP. The first author would like to thank the FCT for the financial support through the PhD Grant SFRH/BD/64415/2009. The authors would like to express their sincere gratitude and appreciation to Ibermetais, Secil and SIKA, for supplying, respectively, the fibres, the cement and the super-plasticizer, respectively

Desenvolvimento de painel sanduíche multifuncional para a reabilitação sustentável de edifícios porticados de betão armado: caracterização de componentes

Esta comunicação apresenta um trabalho de investigação dedicado ao desenvolvimento de um painel sanduíche compósito multifuncional concebido para a reabilitação estrutural e térmica de edifícios porticados de betão armado construídos em Portugal a partir da década de 1960 e até meados da década de 1980. Este painel é composto essencialmente por três componentes que visam assegurar a multifuncionalidade pretendida, nomeadamente: (i) finas camadas exteriores, de cariz estrutural, em microbetão reforçado com fibras de aço recicladas resultantes do processo de reciclagem de pneus (MBRFR); (ii) núcleo em poliestireno, para assegurar isolamento térmico contínuo ao painel; e (iii) conetores poliméricos reforçados com fibras de vidro (GFRP), para conferir uma adequada conexão entre as diferentes camadas. O presente artigo aborda primeiramente a caraterização mecânica efetuada ao MBRFR (comportamento em compressão e tração) e aos conetores GFRP (ensaios de tração direta), sendo ainda apresentados os testes efetuados para seleção do material de isolamento térmico a adotar na conceção do painel sanduíche em desenvolvimento. Estes testes abrangem a realização de ensaios de corte em elementos compósitos representativos do referido painel, nos quais se fez variar a tipologia de poliestireno adotada para a camada de isolamento, com o objetivo de avaliar a influência que esta camada pode ter nas condições de ligação dos constituintes do painel sanduíche. Os resultados obtidos permitiram tirar conclusões importantes acerca desta influência, revelando que o material e especialmente a superfície de acabamento podem contribuir de forma não-negligenciável para o comportamento estrutural da solução compósitaFundação para a Ciência e Tecnologia (FCT) o apoio financeiro concedido através da bolsa de doutoramento PD/BD/52657/2014, atribuída no âmbito do Programa Doutoral em Construção e Reabilitação Eco-eficientes (EcoCoRe). Agradece-se ainda à FCT o apoio financeiro prestado, nomeadamente no âmbito do projeto PTDC/ECM-EST/2635/2014, e toda a colaboração e apoio prestado pelas empresas Twincon, BVT-Rausch, PreConTech, Danosa/Eurofoam e IberFibra

Projeto SECCLASS: O desenvolvimento de um sistema de classificação da construção com componente de sustentabilidade adaptado ao BIM

O projeto SECClasS – Sustainability Enhanced Construction Classification System – financiado pelo EEA Grants – pretende facilitar a Economia Circular na Construção introduzindo um Sistema de Classificação de Informações sobre Construção otimizado para a Sustentabilidade. Este sistema será orientado para a metodologia BIM e servirá não só a componente de sustentabilidade, mas também os restantes usos BIM, como a gestão do processo BIM, extração de quantidades, compatibilização de especialidades ou planeamento de obra, e todas as fases do ciclo de vida. É objetivo do projeto que o sistema de classificação seja usado pelos profissionais do projeto, construção e responsáveis pela gestão e manutenção de edifícios e outras infraestruturas. Um sistema de classificação permite unificar a terminologia a todas as escalas, facilitando a comunicação, seleção de materiais e componentes, bem como uma avaliação precisa dos impactos dos edifícios ao longo do seu ciclo de vida, com o objetivo de melhorar o desempenho dos edifícios e redução dos resíduos através de ferramentas digitais de gestão e seleção informada dos elementos construtivos. Este trabalho apresenta os frutos do projeto até à data, que incluem a tradução do sistema Uniclass 2015, as primeiras implementações do sistema em pilotos e ambientes de produção, e o trabalho e resultados esperados até à sua conclusão no final de 2022.info:eu-repo/semantics/publishedVersio

Cation Association with Sodium Dodecyl Sulfate Micelles As Seen by Lanthanide Luminescence

The interaction of trivalent lanthanides with sodium dodecyl sulfate micelles (SDS) in aqueous solution has been studied by a variety of experimental techniques. Potentiometric measurements with a sodium selective electrode, steady-state fluorescence spectra of Ce(III), emission lifetime measurements of Ce(III), Tb(III), and Eu(III), and electronic paramagnetic resonance spectra (EPR) of Gd(III) all show that the lanthanide ions bind to the micellar surface. From analysis of the Tb(III) lifetime measurements in water and D2O solutions, it is found that the lanthanide ions lose one hydration water on binding to SDS. However, the EPR measurements suggest that the lanthanide ions still have considerable freedom of movement. Energy transfer between Ce(III) and Tb(III) has been used to obtain further information on multiple lanthanide ion binding. From steady-state fluorescence measurements in aqueous solution in the absence of SDS no energy transfer is observed, although there is quenching of Tb(III) emission by Ce(III), which is found to follow good Stern-Volmer kinetics. In the presence of SDS micelles, very different behavior is observed and energy transfer occurs from excited Ce(III) to Tb(III). This is only possible when the two ions are on the same micelle. The energy transfer phenomena is highly dependent on micelle concentration and has been analyzed theoretically via a Monte Carlo simulation. This shows that the lanthanide ions bind close to the micelle surface, and are consistent with the loss of a water molecule. Also, assuming a Dexter-type model in which the energy transfer intensity is proportional to the inverse of the square root of the average distance between cerium and the closest terbium it is possible to reproduce qualitatively the experimental cerium(III)-sensitized Tb(III) luminescence intensity data

Zinc(II) phthalocyanines immobilized in mesoporous silica Al-MCM-41 and their applications in photocatalytic degradation of pesticides

In the present study the authors investigated a set of three new zinc(II) phthalocyanines (zinc(II) tetranitrophthalocyanine (ZnTNPc), zinc(II) tetra(phenyloxy)phthalocyanine (ZnTPhOPc) and the tetraiodide salt of zinc(II)tetra(N,N,N-trimethylaminoethyloxy) phthalocyaninate (ZnTTMAEOPcI)) immobilized into Al-MCM-41 prepared via ship-in-a-bottle methodology. The samples were fully characterized by diffuse reflectance-UV–vis spectroscopy (DRS-UV–vis), luminescence, thermogravimetric analysis (TG/DSC), N2 adsorption techniques and elemental analysis. A comparative study was made on the photocatalytic performance upon irradiation within the wavelength range 320–460 nm of these three systems in the degradation of pesticides fenamiphos and pentachlorophenol. ZnTNPc@Al-MCM-41 and ZnTTMAEOPcI@Al-MCM-41 were found to be the most active systems, with the best performance observed with the immobilized cationic phthalocyanine, ZnTTMAEOPcI@Al-MCM-41. This system showed high activity even after three photocatalytic cycles. LC–MS product characterization and mechanistic studies indicate that singlet oxygen (1O2), produced by excitation of these immobilized photosensitizers, is a key intermediate in the photocatalytic degradation of both pesticides

Zinc(II) phthalocyanines immobilized in mesoporous silica Al-MCM-41 and their applications in photocatalytic degradation of pesticides

International audienceIn the present study the authors investigated a set of three new zinc(II) phthalocyanines (zinc(II) tetranitrophthalocyanine (ZnTNPc), zinc(II) tetra(phenyloxy)phthalocyanine (ZnTPhOPc) and the tetraiodide salt of zinc(II)tetra(N,N,N-trimethylaminoethyloxy) phthalocyaninate (ZnTTMAEOPcI)) immobilized into Al-MCM-41 prepared via ship-in-a-bottle methodology. The samples were fully characterized by diffuse reflectance-UV-vis spectroscopy (DRS-UV-vis), luminescence, thermogravimetric analysis (TG/DSC), N2 adsorption techniques and elemental analysis. A comparative study was made on the photocatalytic performance upon irradiation within the wavelength range 320-460 nm of these three systems in the degradation of pesticides fenamiphos and pentachlorophenol. ZnTNPc@Al-MCM-41 and ZnTTMAEOPcI@Al-MCM-41 were found to be the most active systems, with the best performance observed with the immobilized cationic phthalocyanine, ZnTTMAEOPcI@Al-MCM-41. This system showed high activity even after three photocatalytic cycles. LC-MS product characterization and mechanistic studies indicate that singlet oxygen (1O2), produced by excitation of these immobilized photosensitizers, is a key intermediate in the photocatalytic degradation of both pesticides

Electron-Transfer Oxidation of Chlorophenols by Uranyl Ion Excited State in Aqueous Solution. Steady-State and Nanosecond Flash Photolysis Studies

The oxidation of chlorophenols by photoexcited uranyl ion was studied in aqueous solution at concentrations where the ground-state interactions were negligible. Nanosecond flash photolysis showed that a clean electron-transfer process from the chlorophenols to the excited uranyl ion is involved. This is suggested to lead to the formation of a U(V)/chlorophenoxyl radical pair complex. The efficiency of this charge-transfer process is unity for the three chlorophenols. However, low product yields suggest that in the absence of oxygen, back electron transfer, both within the radical pair and from separated uranium(V) to phenoxyl radicals, appears to be the major reaction pathway. In the presence of oxygen the quantum yields of disappearance of chlorophenol and of photoproduct formation increased. This leads to the conclusion that oxygen favors reaction with uranium(V) and/or the uranium(V)−phenoxyl radical pair, leading to the formation of the superoxide anion and its conjugate acid, HO2•, which then regenerate UO22+. Based on this, a catalytic cycle for chlorophenol photooxidation involving uranyl ion and molecular oxygen is proposed