Durabilidade de argamassas de base cimentícia reforçadas com fibras sintéticas

O presente artigo apresenta os resultados obtidos num programa experimental de caracterização de três argamassas de matriz cimentícia reforçadas com diferente tipo de fibras, nomeadamente, fibras de poliacrilonitrila (PAN), vidro (GF), polipropileno (PP) e de álcool polivinílico (PVA). A avaliação do desempenho das fibras como reforço efetivo de materiais de matriz cimentícia, foi realizada com ensaios de avaliação das propriedades reológicas, mecânicas (compressão e flexão) e de durabilidade (absorção de água por capilaridade e permeabilidade ao ar e à água). De modo a comparar e analisar os resultados obtidos, foram também realizados os mesmos ensaios com uma argamassa comercial de base cimentícia. Os ensaios são descritos e os principais resultados obtidos são apresentados e discutidos.Esta investigação foi realizada no âmbito do projeto InoTec - Material inovador de ultra elevada ductilidade para a reabilitação do património construído, promovido pela Empresa CiviTest e pela Universidade do Minho e financiado pelo COMPETE / QREN / FEDER (NORTE-07-0202 FEDER-023024). O primeiro autor agradece a bolsa de investigação atribuída ao abrigo deste projeto. Um especial agradecimento à empresa Owens Corning pelo fornecimento das fibras de vidro, à Exporplas pelas fibras de polipropileno, à Sika pelo superplastificante, à Secil pelo cimento, à CHRYSO pelo VMA e à S&P Clever Reinforcement Ibérica pelo fornecimento da argamassa comercial

Trypsin immobilisation on zeolites

This work compares different types of zeolites (NaA, NaX and NaY) as potential carriers for trypsin immobilisation. Silica was also used as a traditional carrier. Covalent attachment to the carriers was tested using glutaraldehyde. The efficiency of immobilisation and activity, operation and storage stability of free and immobilised enzyme on the three supports were studied. Optimum value of operation temperature was determined for trypsin immobilised on the best zeolite. Trypsin was most successfully immobilised on NaY by covalent attachment using glutaraldehyde. Though the best efficiencies were still obtained with silica, promising results were achieved with zeolite NaY. The ratio of immobilised protein achieved was very high, especially with silica, NaX and NaY. However there was a significant loss of enzyme activity with the immobilisation of trypsin. Optimal temperature obtained with immobilised enzyme was ca. 60 ºC, higher than the correspondent temperature for free enzyme (50 ºC).Fundação para a Ciência e a Tecnologia (FCT) - POCTI/2000/QUI/36452.European Social Fund (ESF)

A comparative analysis on the efficiency of different carriers for trypsin immobilization

CHISA 2008 - 18th International Congress of Chemical and Process Engineering (CD-ROM of Full Texts)info:eu-repo/semantics/publishedVersio

European grapevine moth and vitis vinifera l. phenology in the Douro Region: (A)synchrony and climate scenarios

The European grapevine moth (Lobesia botrana; Denis and Schiffermüller, 1775) is considered a key pest for grapevine (Vitis vinifera L.) in the Douro Region, Portugal. The phenology of both the grapevine and the pest has changed in the last decades due to the increase in temperature. Here, we assess the potential impact of climate change on the (a)synchrony of both species. The results show that the phenological stages (budburst, flowering and veraison) undergo an advancement throughout the region (at an ~1 km resolution) under a climate change scenario (Representative Concentration Pathways, RCP8.5) for the period 2051–2080, with respect to the historic period (1989–2015). For cv. Touriga Nacional and Touriga Franca, the budburst advances up to 14 days, whereas for flowering and veraison the advancements are up to 10 days (mainly at low elevations along the Douro River). For the phenology of Lobesia botrana, earliness was also verified in the three flights (consequently there may be more generations per year), covering the entire region. Furthermore, the third flight advances further compared to the others. For both varieties, the interaction between the third flight (beginning and peak) and the veraison date is the most relevant modification under the future climate change scenario (RCP8.5, 2051–2080). The aforementioned outcomes from the phenology models help to better understand the possible shifts of both trophic levels in the region under future climate, giving insights into their future interactions.This research was funded by the operation nº NORTE-06-3559-FSE-000067 and by the Clim4Vitis project “Climate change impact mitigation for European viticulture: knowledge transfer for an integrated approach”, funded by European Union’s Horizon 2020 Research and Innovation Programme, under grant agreement nº 810176. The authors also thank ADVID and its members, for providing meteorologicalnand phenological data and for collaborating in the data field collection namely the male catches in sex pheromone traps. The authors from CITAB were also supported by National Funds by FCT—Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020. Fátima Gonçalves is also grateful to the European Social Fund (ESF) through the Regional Operational Program North 2020, within the scope of the Program “Contratação de Recursos Humanos Altamente Qualificados”, Norte-06-3559-FSE-000188 and to the FCT for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020).info:eu-repo/semantics/publishedVersio

Argamassa de ultra-elevada ductilidade para reabilitação: comportamento mecânico e durabilidade

Foi desenvolvida uma argamassa de ultra elevada ductilidade reforçada com fibras (FRCC) para uma nova técnica de reforço de estruturas existentes. São apresentados os estudos de caracterização do material, do ponto de vista mecânico (compressão e flexão), durabilidade (absorção de água por capilaridade, permeabilidade ao ar e à água, retração por secagem) e aderência ao suporte. É ainda apresentado um estudo da aplicação de diferentes tipos de conetores a empregar na técnica de reforço proposta, cujo desempenho foi determinado pela realização de ensaios de push-out.Fundação para a Ciência e a Tecnologia (FCT) FEDER - Programa Operacional do Nort

Durability of steel fiber reinforced self-compacting concrete

Publicado em "Proceedings of the 5th International Conference on The Concrete Future", ISBN 978-981-07-6067-0For conventional concrete without steel fibers, although still an aspect under discussion, there are some commonly used durability indicators. However, for steel fiber reinforced self-compacting concrete (SFRSCC) literature is sparse and the aspects of durability, particularly corrosion resistance, still deserve deeper research, mainly the corrosion of the fibers, since its influence on the appearance and on the serviceability limit states of a SFRSCC structure can be a concern. Therefore, in the ambit of an ongoing research project dealing with the development of SFRSCC sandwich panels, durability tests were executed to compare the performance of SFRSCC and self-compacting concrete (SCC) specimens. Nine different tests were performed, applied to SFRSCC and SCC in order to characterize their mechanical properties (elasticity modulus, compressive strength and flexural behaviour) and to evaluate its durability indicators normally used for plain concrete, namely: water absorption by immersion and by capillarity, permeability to air, electrical resistivity, chloride diffusion by migration under nonsteady state and carbonation. The results for the different concretes and curing times up to 28 days are presented and analyzed.(undefined

Processamento de imagem digital com MatLab : uma aplicação em ambiente industrial

Fundação para a Ciência e a Tecnologia (FCT

Influence of the concentration of locust bean gum on the gelling ability of whey peptic hydrolysates

The gelling ability of whey proteins can be changed by limited hydrolysis and by the presence of other components such as polysaccharides; depending on the environmental conditions it can either be improved or impaired. In this work the effect of LBG on the heat-set gelation of aqueous whey protein hydrolysates (10 % w/w) from pepsin was assessed at pH 7.0 by small deformation rheology. Whey protein concentrate (WPC) and hydrolysates with a degree of hydrolysis (DH) of 1.5, 2.5 and 4.9 % were used. Different LBG concentrations were tested: 0, 0.1, 0.3 and 0.55 % (w/w). The behaviour of gels from whey proteins or whey protein hydrolysates towards the presence of LBG was very similar. The evolution of the viscous and storage moduli followed the general behaviour reported for many biopolymer heat-set gelation processes including whey proteins gelation. The increase in the LBG concentration generally led to a decrease in the gel strength. However, for whey proteins a small amount of LBG (0.1 %) leads to a big enhancement in the gel strength probably due to an increase in the protein concentration of the protein enriched phase. Further increases in the LBG concentration led to a decrease in the gel strength. The gelation process is very sensible to environmental conditions and to processing and often leads to rather coarse data. The factorial planning used allowed validating conclusions using fewer experiments than those needed if no planning had been used, while still getting statistical significance out of the results. However, as many factors are involved, the modelling of the process was not straightforward

Spent-grains and zeolites as potential carriers for trypsin immobilisation

Trypsin is a widely used enzyme for protein hydrolysis and can be used to improve functional and nutritional properties of foods. The immobilization of enzymes on solid supports can offer several advantages over free enzymes including easy handling, recovery from the reaction medium, reuse and operation in continuous reactors. Traditional carriers include porous silica, porous glass and cellulose derivatives. Zeolites are porous alumino-silicates available in a wide range of particle size and porosity and can also be used as carriers. Spent grains are a brewing by-product with a high content in cellulose and can also be interesting as carriers for enzyme immobilization because, besides having the necessary conditions (as stability, rigidity, low mass transfer limitations, for instance), they are cheap and food grade. This work proposes the use of spent grains and zeolites as alternative carriers for trypsin immobilization and compares them with a traditional support (silica). Physical adsorption, ionic attachment and covalent attachment to the supports were tested. The efficiency of immobilization and activity, as well as the operation and storage stability of free and immobilized enzyme on the three supports were studied. Trypsin was most successfully immobilized on the supports by covalent attachment using glutaraldehyde. Though the best efficiencies were still obtained with silica, promising results were achieved with both spent grains and zeolite.Fundação para a Ciência e a Tecnologia (FCT) - project POCTI/2000/QUI/36452.European Social Fund (ESF)