Publicações

One of the possible strategies to protect concrete from aggressive agents consists of applying impregnation products on its smface. This type of strategy is relatively often used in both new and existing structures. However, there are still several aspects conceming impregnation products whose understanding is still rather limited, inc1uding the influence of the concrete substrate on their performance. This paper presents an experimental study on the influence of the roughness and the moisture content of concrete substrates in the pelfOlmance of impregnation product~ used for superficial protection. For that purpose, two impregnations products based on epoxy resins were applied on concrete specimens with two different water/cement ratios (0.40 and 0.70). The concrete specimens were prepared according to different procedures, which created (i) three different smface roughnesses (no preparation, use of a 160 bar water jet and use of needle scalers) and (ii) three different moisture contents (3, 4.5 and 6 %). The perfOlmance of the protection systems was evaluated by means of the following tests suggested in EN 1504-2 standard: (i) product penetration depth; (ii) water absorption by immersion; (iii) abrasion resistance; (iv) impact resistance; and (v) bond strength. With the exception of the resistance to impact, the use of epoxy resins considerably improved the performance of the two types of concrete. Both surface roughness and moisture content proved to have a significant effect on the performance of the epoxy impregnations. However, such influence was different depending on the property at stake and the type of impregnation product.

Silicate-based impregnations are often used to protect concrete against aggressive external actions. However, the understanding of several aspects concerning this type of impregnations is still rather Iimited, incIuding the influence of the concrete substrate on their performance. This paper presents reslllts of an experimental study about O) the efficacy of silicate-based impregnations to protect concrete elements, and (ii) the inflllence of the concrete substrate's characteristics on the performance of such superficial protection. Concrete specimens with two different water/cement ratios (0.40 and 0.70) were produced and, prior to the application of the impregnation, were prepared following different procedllres that created O) three different surface roughnesses (no surface preparation, 160 bar water jet and needle scalers) and (ii) three different moisture contents (3.0%, 4.5% and 6.0%). The performance ofunprotected and protected concrete specimens was assessed by means of the following procedures, indicated in EN 1504-2 standard: O) product penetration depth; (ii) water absorption by immersion; (iii) abrasion resistance; Ov) impact resistance; and (v) bond strength. Results obtained show that the silicate-based impregnation was effective in improving the resistance to water penetration and abrasion resistance, but did not improve the resistance to impacto The surface roughness and the moisture content at the instant of the application of the surface protection proved to influence the performance of the impregnation product, however such influence was dependent on the property at stake.

The main goal of this work is to establish a correlation between the oxidation induction time (OIT) and the oxidation induction temperature (OIT*), which are frequently used to assess the thermo-oxidative stability of polyolefins, either as raw-materials or as finished products. Several tests have been performed at different temperatures (200, 210 and 220 C) using a set of polyethylene (PE) samples from different sources. The correlations found - based on a quadratic regression – make it possible to estimate the OIT value based on experimental data of OIT* and vice-versa. This method can be quite useful in cases when the PE is highly stabilized so that the OIT test at 200 C is expected to last for hours. Additionally, an Arrhenius plot has been developed to obtain the activation energy (Ea) associated with the beginning of the thermo-oxidation for each PE, which also allows us to determine OIT from calculated Ea. All estimated values, obtained by the developed regression models, using unknown specimens, have been confirmed by experimental testing. The regression models have also been checked by a residual analysis as a way to evaluate their reliability. The contribution of the uncertainties of measurement and calculation has also been evaluated, leading to increased reliability of the findings.

Apresentação das principais propriedades e descrição das formas de aplicação de materiais compósitos de matriz polimérica reforçados com fibras na reabilitação de estruturas

This article presents results of experimental investigations on the durability of glass-fibre-reinforced polymer (GFRP) pultruded profiles exposed to typical environments of civil engineering applications.

Neste artigo apresentam-se os resultados preliminares de um projeto de investigação em curso, cujo objectivo é analisar os efeitos de diferentes agentes de degradação ambiental (água, solução salgada, condensação em contínuo, nevoeiro salino, ciclos térmicos e radiação ultravioleta) nas propriedades físico-químicas e no desempenho de perfis putrudidos de polímeros reforçados com fibras de vidro (GFRP) constituídos por resina de poliéster e de viniléster.

The main goals of the present work have been the evaluation of the influence of several variables and testing parameters on the melt flow index (MFI) of thermoplastics and the determination of the uncertainty associated with measurements. To evaluate the influence of testing parameters on the measurement of MFI the design of experiments (DOE) approach has been used. The uncertainty has been calculated using a “bottom-up” approach given in the “Guide to the Expression of the Uncertainty of Measurement” (GUM). Since an analytical expression relating the output response (MFI) with input parameters does not exist, it has been necessary to build mathematical models, by adjusting the experimental observations of the response variable in accordance with each input parameter. Subsequently, the determination of the uncertainty associated with the measurement of MFI has been performed by applying the law of propagation of uncertainty to the values of uncertainty of the input parameters. Finally, the activation energy (Ea) of the melt flow at around 200ºC and the respective uncertainty have been also determined.

Com o objectivo de avaliar a influência do contacto com a água, no desempenho dos revestimentos intumescentes usados na protecção ao fogo de estruturas de aço, procedeu-se à sua exposição a diferentes condições de humidade. O efeito dessa exposição foi analisado por termogravimetria e por espectroscopia de infravermelho por transformada de Fourier. Para avaliar o impacto dessa exposição na capacidade de intumescência dos revestimentos, analisou-se o seu comportamento, submetendo-os a uma temperatura de 750ºC. Os resultados obtidos sugerem que, em ambientes de elevada humidade, os componentes responsáveis pelo processo de intumescência podem ser lixiviados, com consequências adversas na formação da camada de isolamento que protege a estrutura.

This work is part of a much larger research study that is being made to predict the long-term behaviour of several commercial CFRP laminate/adhesive systems used in the rehabilitation of concrete structures. In the whole project it is recognized that the durability of these solutions depends, not only on the durability of the composite materials but also on the performance of the systems used to bond them to the concrete. The present document provides details about the part of the investigation concerning the durability of CFRP laminates.

This communication presents preliminary results of a research project on the effects of different environmental agents on the physical, chemical, aesthetical and mechanical properties of glass fibre reinforced polymer pultruded (GFRP) profiles made of either polyester or vinylester resin. In order to study the potential degradation of the two types of profiles in typical environments of civil engineering applications, test specimens are being subjected to the following exposure conditions: (i) immersion in demineralised water, at 23 ºC, 40 ºC and 60 ºC; (ii) immersion in salt-water, at the same temperatures; (iii) continuous condensation at 40 ºC; (iv) salt fog chamber; (v) thermal cycles, from -5ºC to 40ºC; (vi) accelerated weathering fluorescent ultraviolet light apparatus. Additionally, test specimens were placed in the roof of LNEC thereby being subjected to a natural degradation in a controlled environment. At predefined time intervals, batches of test specimens placed in the above mentioned exposure environments are being removed for physic-chemical and mechanical characterization, in order to assess their behaviour. / Nesta comunicação são apresentados os resultados preliminares de um projecto de investigação em que estão a ser avaliados os efeitos da degradação ambiental nas características físico-químicas de perfis pultrudidos de plástico reforçado com fibra de vidro com dois tipos de matriz – uma de poliéster e outra de viniléster. Com o objectivo de estudar os eventuais efeitos de degradação nos dois tipos de perfis, quando expostos a condições típicas das aplicações em engenharia civil, foram efectuadas as seguintes exposições em provetes retirados dos perfis: (i) imersão em água desmineralizada, a 23 ºC, 40 ºC e 60 ºC; (ii) imersão numa solução salina, às mesmas temperaturas; (iii) condensação em contínuo a 40 ºC; (iv) câmara de nevoeiro salino; (v) ciclos térmicos, entre -5 ºC e 40 ºC; (vi) envelhecimento artificial acelerado com lâmpadas fluorescentes de radiação ultravioleta. Para além disso, foram expostos provetes no telhado do edifício principal do LNEC, onde ficaram sujeitos a envelhecimento natural. Em intervalos predefinidos, foram efectuados ensaios de caracterização físico-química e mecânica dos materiais, para monitorizar o seu desempenho ao longo do tempo.

N/A

The main purpose of this paper is to present the results of a study intended to assess the durability of stabilized PVC-U for outdoor applications, in form of calendered films and extruded plates. The samples were subject to different ageing conditions and their degradation state were evaluated, using techniques of molecular analysis, namely Fourier transformed infrared spectroscopy (FTIR), as well techniques for evaluation of macroscopic properties, as colorimetry and tensiles tests. The development of formulations, the ageing and the subsequent characterisation were done in LNEC. Therefore, after a brief introduction, this paper presents the experimental part of the study, as regards the composition of samples and the experimental methods of deterioration and characterisation. Subsequently, the results of the study, their interpretation and the final conclusions are also presented.

The main purpose of this paper is to present the results of a study intended to assess the durability of stabilized PVC-U for outdoor applications, in form of calendered films and extruded plates. The samples were subject to different ageing conditions and their degradation state were evaluated, using techniques of molecular analysis, namely Fourier transformed infrared spectroscopy (FTIR), as well techniques for evaluation of macroscopic properties, as colorimetry and tensiles tests. The development of formulations, the ageing and the subsequent characterisation were done in LNEC. Therefore, after a brief introduction, this paper presents the experimental part of the study, as regards the composition of samples and the experimental methods of deterioration and characterisation. Subsequently, the results of the study, their interpretation and the final conclusions are also presented.

The outdoor degradation of poly(vinyl chloride) (PVC) products is complex and not completely understood for most of the technical formulations. Furthermore, it is known that the behaviour of such materials is dependent of the photo-oxidation conditions, namely source of radiation, temperature, presence of water and humidity. In the present work, we have used X-ray photoelectron spectroscopy (XPS) to evaluate the influence of different photo-oxidation conditions on the surface degradation of stabilized PVC, low thickness calendered samples (~ 150 ?m). The main objective is the study of the influence of the weathering conditions on the degradation level of stabilized PVC products for outdoor applications trying to go deeper in the understanding of the mechanism of both the degradation and the stabilization of the surface under different environmental conditions, different polymer formulations and different processing methods (extrusion or calendering). Comparisons are made with previous results obtained using colourimetry and infrared spectroscopy. The role of PVC formulation and of radiation source and water were studied using artificial weathering. Results were compared with degradation induced by natural weathering in Lisbon.

The main purpose of this paper is to present the results obtained, during the years 2001 and 2002, from a study developed in LNEC. The object of this study was to assess the synergetic effect of three of the most significant deteriorating climatic agents (radiation, temperature and water) on the evolution of the properties of hard PVC stabilised with titanium dioxide, for outdoor applications. For the purpose, several samples were subject to natural and artificial weathering. Moreover, their physical and mechanical properties were characterised by techniques of analysis and assessment of the surface aspect (colour and brightness), of assessment of the molecular properties by infrared microscopy (MICROFTIR), as well as of determination of the tensile mechanical properties and assessment of the Charpy impact resistance. The paper was both orally presented and by poster at the panel meeting “Ageing, Irradiation, Stabilisation” of the Congress MoDeSt 2002. Therefore, this publication includes the text of the paper, the poster, as well as the slides from the oral communication. The development of the formulations, the ageing and the subsequent characterisation by colorimetry, brightness, Charpy impact and tension, were done in LNEC. The characterisation by infrared microscopy was performed in the Laboratoire de Photochimie Moleculaire et Macromoleculaire of the University Blaise-Pascal, Clermont-Ferrand, France.

The main purpose of this paper is to present the results obtained, during the year 2003, from a study developed in LNEC. The object of this study was to assess the synergetic effect of two deteriorating climatic agents (radiation and water) on the evolution of the properties of extruded plates made of hard PVC stabilised with titanium dioxide, for outdoor applications. For the purpose, several samples were subject to natural and artificial weathering, their deterioration condition having been characterised by means of techniques of analysis of colorimetry and infrared spectroscopy (FTIR). Initially, only the presentation of a poster titled “Artificial and Natural Weathering of Polyvinyl chloride for Outdoor Applications: the Influence of the Radiation and Water on the Evolution of the PVC Properties” was scheduled. Nevertheless, upon request from the secretariat of the Congress, the author also presented an oral paper on the same subject, but including experimental results obtained during the year 2004, which were not mentioned in the poster. Similarly, these results, which were obtained by means of surface analysis techniques by Scanning Electron Microscopy (SEM) and by X photoelectron spectroscopy (XPS), were not included in the paper submitted to the Congress. Therefore, this publication includes the text of the paper referring to the poster, which was initially predicted, as well as the slides of the oral communication presented. It also contains a few results obtained in 2004. The development of the formulations, as well as the ageing and the subsequent characterisation by colorimetry, by infrared spectroscopy and by scanning electron microscopy were performed in LNEC. The characterisation by X photoelectron spectroscopy was conducted at the Molecular Chemistry-Physics Centre of the Instituto Superior Técnico (Higher Technical Institute).

The main purpose of this paper is to present the results of a study intended to assess the deterioration condition of extruded hard PVC plates, for outdoor applications. The plates were subject to different ageing conditions, using techniques of surface analysis, namely scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The development of formulations, the ageing and the subsequent characterisation by scanning electron microscopy were done in LNEC. The characterisation by X-ray photoelectron spectroscopy was done at the Centre for Molecular Chemistry-Physics of Instituto Superior Técnico (Higher Technical Institute of Lisbon). Therefore, after a brief introduction, this paper presents the experimental part of the study, as regards the composition of samples and the experimental methods of deterioration and characterisation. Subsequently, the results of the study, their interpretation and the final conclusions are also presented.

Procurou-se com a presente comunicação, apresentar uma metodologia de validação de um programa informático, desenvolvido no NMPC do LNEC especificamente para a calibração de um calorimetro diferencial de varrimento (DSC) e para calcular a incerteza associada à determinação da entalpia de fusão. Assim, após uma breve introdução, a presente comunicação expõe a formulação essencial que serviu de suporte ao desenvolvimento do programa informático referido, descreve os elementos que constituem o procedimento de validação do mesmo, apresenta o processo de estimativa da incerteza de medição e os resultados da análise efectuada.

O presente relatório (relatório 2) contém os resultados de um estudo desenvolvido no Núcleo de Materiais Orgânicos (NMO) inserido num projeto de Pós-Doutoramento com a duração de três anos e teve como objetivo a avaliação do melhoramento das propriedades fisicas e mecânicas de amostras de polietileno reciclado em misturas binárias com nanoargilas ligantes (nanoclays), para aplicação em tubagem na construção civil. Assim, após uma caracterização preliminar de reciclados de polietileno (relatório 1) e antes da análise do desempenho de tubagem incorporando material reciclado (relatório 3), realizou-se um estudo de otimização de formulações introduzindo materiais cerâmicos constituídos por silicatos e aluminatos (nanoargilas) com o objetivo de melhorar algumas propriedades térmicas e mecânicas da matéria-prima. Com diversas técnicas de análise, estando entre elas a calorimetria diferencial de varrimento, a análise mecânica-dinâmica e a termogravimetria, obtiveram-se resultados experimentais que foram analisados a nível estrutural.

O presente relatório, que é o último de uma série de 3, contém resultados de um estudo desenvolvido no Núcleo de Materiais Orgânicos (NMO) da instituição de acolhimento LNEC, inserido num projeto de Pós-Doutoramento, subsidiado pela FCT. O objetivo foi o de avaliar o desempenho e a degradação de tubos incorporando polietileno reciclado, proveniente da indústria portuguesa. Recorrendo à calorimetria diferencial de varrimento foram medidos o tempo e a temperatura de indução à oxidação de compostos granulados usados para o fabrico de tubos, bem como de amostras extraídas de tubos. Através de ensaios de resistência à pressão interior foram caracterizados tubos extrudidos laboratorialmente, utilizando amostras de PEADRepsol PE T1OONN e amostras recicladas, tal como suas misturas percentuais com masterbatch contendo nano argila e antioxidante.

Este relatório contém o conjunto de todas as normas EN e ISO referentes a sistemas de tubagem em material plástico, organizadas por aplicação, em vigor à data de Setembro de 2011.

Este relatório contém o conjunto de todas as normas EN e ISO referentes a sistemas de tubagem em material plástico, organizadas por aplicação, em vigor à data de Setembro de 2011.

N/A

No presente relatório apresentam-se os dados meteorológicos do ano de 2009, recolhidos na estação meteorológica existente no Núcleo de Materiais Orgânicos do Departamento de Materiais do LNEC, em Lisboa.

No presente relatório descrevem-se os procedimentos adoptados pelo LNEC no âmbito dos estudos para concessão de um Documento de Aplicação (DA) a revestimentos por pintura para protecção de betão, em condições de exposição atmosférica no exterior e sem influência de tráfego ou de acções químicas severas. Indicam-se também as acções a desenvolver periodicamente para comprovar que continuam reunidas as condições para a concessão do DA.

Procedeu-se à avaliação da resistência à alteração de cor de tintas de várias cores, por observação visual e medição das coordenadas cromáticas e da diferença de cor ao longo do tempo de exposição em condições de envelhecimento natural e artificial, a fim de estabelecer requisitos mínimos para revestimentos por pintura coloridas para paredes exteriores de edifícios. Neste relatório descreve-se o plano experimental adoptado, o trabalho desenvolvido, os resultados obtidos e uma possível metodologia para avaliar a resistência à alteração de cor em tintas para paredes exteriores.

O presente relatório apresenta os resultados e as conclusões mais relevantes do estudo experimental que foi realizado com o objectivo da caracterização de betumes modificados com polímero com vista ao seu enquadramento na Norma Europeia EN 14023 - Bitumen and bituminous binder - Framework specification for polymer bitumens.

O presente relatório contém o trabalho final do estágio profissionalizante efectuado no Departamento de Materiais do Laboratório Nacional de Engenharia Civil pela aluna da Licenciatura em Química Tecnológica da Faculdade de Ciências da Universidade de Lisboa, Ana Luísa Seara Pires. O trabalho, intitulado “Caracterização por análise térmica de adesivos estruturais usados na Engenharia Civil”, teve como objectivo principal contribuir para o conhecimento dos efeitos das condições de cura na temperatura de transição vítrea em três adesivos epoxídicos utilizados na colagem de materiais compósitos reforçados com fibras a estruturas de betão, no âmbito da sua reabilitação.

Os resultados experimentais, obtidos através da medição de propriedades dos materiais e produtos, requerem tratamento específico e adequado, de forma a garantir a sua qualidade. É por isso muitas vezes necessário recorrer a métodos estatísticos para fazer a análise do tipo de distribuição dos resultados, proceder à deteção de valores suspeitos num conjunto de observações e à eventual rejeição de resultados anómalos. Este tipo de tratamento estatístico é principalmente adequado a ensaios de intercomparação, quer do foro metrológico (comparação de valores de padrões ou materiais de referência, mediante medição efetuada por operadores de diferentes laboratórios metrológicos, com incerteza variável), quer do âmbito dos laboratórios de ensaio. Os ensaios de Comparação Interlaboratorial realizados por laboratórios de ensaio, constituem uma ferramenta de garantia da Qualidade e são utilizados para a validação de métodos de ensaio (incerteza e robustez) e como um meio para a determinação das características de desempenho dos laboratórios, nomeadamente da reprodutibilidade e da repetibilidade. Nesta publicação faz-se uma descrição dos vários parâmetros que devem ser determinados em ensaios interlaboratoriais do tipo “Intercomparações com valor de consenso” e respetivos métodos de cálculo. A estatística aqui apresentada pode, numa boa parte dos casos, ser também aplicada à análise de resultados de medições experimentais correntes.

The main purpose of this Paper is to present a state of the art about weathering and polymer degradation. This review was presented during a training course promoted by the 5th European Weathering Symposium EWS (XXVIIth Colloquium of Danubian Countries on Natural and Artificial Ageing of Polymers), which was held in Lisbon on September 21 - 23, 2011, organised on behalf of CEEES (Confederation of European Environmental Engineering Societies) by the German Management Society for Environmental Engineering GUS (Gesellschaft für Umweltsimulation e.V.) and supported by SOPSAR (Sociedade Portuguesa de Simulação Ambiental e de Avaliação de Riscos), APIP (Associação Portuguesa da Indústria de Plásticos) and LNEC (Laboratório Nacional de Engenharia Civil). The main topics of this review are the weathering of polymers and composites, the determination, simulation and effects of relevant climatic quantities, innovative polymer additives, new test procedures and devices, instrumental methods of analysis to evaluate polymer degradation, recent developments in polymeric materials and composites designed for outdoor applications and methods for service-life prediction.

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A