Papers
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Mitigation of Internal Expansive Reaction: the Role of Tungsten Mine Sludge
The concrete degradation caused by internal expansive reaction (IER) is a problem that affects many structures in the world. These reactions, which include the alkali-silica reaction (ASR)and the internal sulphate reaction (ISR) related with delayed ettringite formation, are very dangerous, due the expansive behavior of products formed, that cause the cracking of concrete. So it is urgent to find preventive methods to avoid or mitigate the onset of these reactions in new structures. This work aims to show the applicability of sludge from a tungsten mine in the mitigation of the IER. To evaluate the effect of sludge in the mitigation of ASR and ISR, mortar and concrete mixes were produced with 30% (%in mass) of cement replacement. The results obtained so far allow stating that tungsten mine sludge as Portland cement replacement could be effective in the ASR and ISR mitigation.
Year: 2013
Number Pages:
468-473pp.
Author(s): Sousa, S.; Santos Silva, A.; Velosa, A.; Gameiro, A.; Rocha, F.
: Materials Science Forum
Editor: Trans Tech Publications
Volume:
Vols. 730-732.
Keywords: Concrete; Tungsten mine sludge; Mitigation; Delayed ettringite formation; Alkali-silica reaction
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Phase and Microstructural Characterization of Lime-MK Blended Mixes
Metakaolin (MK) is nowadays a well-known pozzolanic material used in cement-based materials. Its benefits are related to its great pozzolanic reactivity when compared with some others pozzolanic materials, like fly ash or ground-granulated blast furnace slag. When MK reacts with calcium hydroxide, cementitious products are formed. It is known that the main phases produced during its pozzolanic reaction at ambient temperature are calcium silicate hydrates (CSH), stratlingite (C2ASH8) and calcium aluminate hydrate (C4AH13). However, in literature there are several discrepancies regarding these phases stability, namely the transformation of stratlingite and C4AH13 into hydrogarnet (C3AH6) at long term. The consequences of that instability are a reduction in the porosity and a loss of microstructural strength that can induce a complete material degradation. The MK is a material with great potential in Portugal, since there is a large abundance of kaolinitic clays, however its development is not yet achieved. In order to answer this demand a research project was initiated with the aim of optimizing the production of MK in Portugal and enhancing the durability of aerial calcitic lime mortars, to be mainly used in conservation and restoration of historical buildings. With the objective of studying the compounds formed in lime/MK and their stability during time, we have prepared different lime/MK ratio pastes (molar ratios). These lime/MK pastes were stored at saturated conditions (RH > 95%) and 23 ± 2 ºC temperature being analysed at several ages by TGA-DTA, XRD and SEM-EDS. In this paper the results obtained are presented and discussed.
Year: 2013
Number Pages:
135-140pp.
Author(s): Gameiro, A.; Santos Silva, A.; Veiga, M. R.; Velosa, A.
: Materials Science Forum
Editor: Trans Tech Publications
Volume:
Vols. 730-732.
Keywords: Tga; Xrd; Sem; Lime; Pozzolan; Metakaolin
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Rheological properties and hydration behavior of portland cement mortars containing calcined red mud
Red mud (RM) is a solid waste derived from processing bauxite ore to produce alumina and is considered a hazardous waste due to its high pH. This paper describes the use of untreated mud and after calcination at distinct temperatures (450, 650, and 1000 °C) to attempt to improve its reactivity in cement mortars. In the formulations, portland cement was replaced with up to 30 wt% red mud, and the addition of the red mud changed the hydration process, setting time, and workability. The temperature of hydration increased as more RM was added, particularly when calcined in the interval of 450650 °C. In these conditions, the hydration process was accelerated, and the workability decreased. These findings indicate that the presence of red mud significantly altered important properties of portland cement.
Year: 2013
Number Pages:
557-566pp.
Author(s): Ribeiro, D. V.; Santos Silva, A.; Labrincha, J. A.; Morelli, M. R.
: Canadian Journal of Civil Engineering
Editor: NRC Research Press Journal
Volume:
Vol 40.
Keywords: Hydration; Rheological proerties; Mortar; Calcination; Red mud
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Studies of the Performance of Nanostructured and Other Compatible Consolidation Products for Historical Renders
This work is inserted in a wider project aiming at the conservation and durability of historical renders, through compatibles techniques and materials; in particular the restitution of cohesion of historical renders, turned friable by the loss of binder due to physical or chemical actions, is studied. Surface consolidation, directed to restore cohesion and stability, is based on the use of materials with aggregating properties. This operation is reached usually through the application of organic or mineral consolidants, but inorganic consolidants (such as calcium hydroxide or ethyl silicate) are preferred due to better compatibility and durability. Based on the results of previous studies, two mineral compatible products were selected: a commercial suspension of nanoparticles of calcium hydroxide in propanol (Nanorestore); a silicate product, consisting on a limewater dispersion of ethyl silicate. Consolidation products were than applied on different mortars samples previously prepared, in order to assess their efficacy by determining their physical, mechanical and microstructural properties before and after the consolidation treatment. Mechanical and physical analyses were performed, such as compression and flexural strenght and superficial hardness. Microstructural and chemical analyses of the consolidation product and of the consolidated samples are also reported.
Year: 2013
Number Pages:
942-947pp.
Author(s): Borsoi, G.; Tavares, M.; Veiga, M. R.; Santos Silva, A.
: Materials Science Forum
Editor: Trans Tech Publications
Volume:
Vols. 730-732.
Keywords: Ethyl silicate; Nanolime; Compatibility; Consolidation products; Historical renders
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Ureasilicate Hybrid Coatings for Corrosion Protection of Galvanized Steel in Cementitious Media
This study is focused on the electrochemical behavior and surface analysis of an eco-friendly organicinorganic hybrid (OIH) coating for hot dip galvanized steel (HDGS) in contact with cementitious media. This treatment is a proposed alternative to replace toxic Cr(VI)-based pre-treatments used to control reactions between the zinc and wet concrete. HDGS samples were coated with two different sets of OIH gels obtained by a sol-gel process using a dip-coating method. Five distinct OIH matrices were obtained by reaction of functionalized metal-alkoxide (3-isocyanatopropyltriethoxysilane) with five different molecular weight diamine-alkylethers. One set of HDGS samples was coated with each of the five pure OIH matrices and another was coated with similar matrices doped with Cr(III). The morphology of OIH coatings over HDGS surface was characterized by SEM/EDS. Similar films were prepared separately and the respective resistivity was measured by electrochemical impedance spectroscopy. Polarization resistance and macrocell current density were used to evaluate the corrosion protection properties of the HDGS coated samples in contact with cementitious media for a period of 74 days. Results showed that the produced coatings provide barrier properties that withstand the high pH of the electrolyte, protecting the HDGS when it first contacts cementitious media.
Year: 2013
Number Pages:
12.
Author(s): Figueira, R. B.; Silva, C. J. R.; Pereira, E. V.; Salta, M. M.
: Journal of the Electrochemical Society
Editor: Journal of the Electrochemical Society
Volume:
volume 160, issue 10, C467-C479.
Keywords: Coatings; Corrosion; Organic-inorganic hybrid; Sol-gel; Galvanized steel
Acompanhamento da Marca de Qualidade Qualanod em 2012 - Empresa ALFA SUL
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Effect of inorganic content on the performance of anticorrosive hybrid sol-gel coated EN AW-6063 alloy
The organic-inorganic hybrid sol-gel films have been reported as an effective anti-corrosion and environmentally friendly alternative to Cr(VI) pre-treatment for aluminium alloys. The sol-gel process used to obtain these coatings allows the variation of the different synthesis parameters to achieve coatings with optimized properties. In this work, hybrid films with different Zr/Si ratios were synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide (TPOZ) precursors. Electrochemical Impedance Spectroscopy (EIS) was used to evaluate the corrosion behaviour of coated aluminium specimens in 0.5 M NaCl solution. The morphology and chemical structure of the hybrid coatings prepared were studied by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), Fourier Transformed Infrared Spectroscopy (FTIR) and Thermo Gravimetric Analysis (TGA). It was found that increasing Zr/Si ratio leads to a more cross linked inorganic network, resulting in higher initial coatings resistance, but may turn coatings more hydrophilic, prone to rapid degradation in water, due to a less connected organic network. Consequently, the best anticorrosive performance derives from the balance between the two opposite trends and it was achieved with Zr/Si molar ratio of 0.25.
Year: 2012
Number Pages:
745-750pp.
Author(s): Fontinha, I. R.; Salta, M. M.; Zheludkevich, M.; Ferreira, M. G. S.
: Materials Science Forum
Editor: Trans Tech Publications
Volume:
730-732.
Keywords: Aluminium; Corrosion; Sol-gel; Hybrid coating
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Estudo das reações álcalis-sílica associadas ao uso da lama vermelha em argamassas colantes e de revestimento
A incorporação de resíduos industriais em matrizes cimentícias, com o objetivo de inertização, é uma alternativa de reutilização que tem sido bastante estudada nos últimos anos. No presente trabalho, estudou-se a lama vermelha, resíduo sólido gerado no processo de beneficiamento de bauxita e que, devido a seu elevado pH, é considerado perigoso. Apesar do uso deste resíduo ter sido reportada em trabalhos anteriores, algumas patologias podem estar associadas à sua utilização, devido à elevada concentração de iões alcalinos (principalmente o sódio), favorecendo as reações álcalis-sílica (RAS) e às dificuldades de moldagem (reologia) devido à elevada finura deste resíduo. Apesar destes prováveis problemas provenientes do uso indiscriminado da lama vermelha como adição às argamassas e betões, ainda são poucas as pesquisas que os contemplam, sendo este o foco do presente trabalho. Foram verificadas as propriedades reológicas das argamassas, utilizando um reómetro e a avaliação da RAS, de acordo com as normas ASTM C 1260-07 e NBR 11582. Os resultados obtidos foram bastante satisfatórios quanto ao comportamento das argamassas frente à RAS, apesar da elevada concentração de álcalis na lama vermelha, com grande influência reológica.
Year: 2012
Number Pages:
9.
Author(s): Ribeiro, D. V.; Santos Silva, A.; Labrincha, J. A.; Morelli, M. R.
: Cerâmica
Editor: Associação Brasileira de Cerâmica
Volume:
VOL. 58, 345 - JAN/FEV/MAR 2012.
Keywords: Reologia; Durabilidade; Ras; Lama vermelha; Argamassas; Cimento
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Hydration products of limemetakaolin pastes at ambient temperature with ageing
Mortars constituted of lime mixtures with pozzolanic additions have been extensively used in the past for the construction of historic and traditional buildings. This paper presents the results of blended pastes of lime and metakaolin (MK), namely compounds formed and their stability over time. This research is part of an extensive study aiming at the formulation of lime based mortars for restoration purposes. It has been shown for several years that MK has been applied in inorganic binders due to its capacity to react vigorously with calcium hydroxide (CH). In the presence of water originating a series of major hydrated phases, namely tetra calcium aluminate hydrate (C4AH13), calcium silicates hydrates (CSH) and calcium aluminium silicate hydrates (stratlingite C2ASH8). Several blended pastes of lime and MK, with different substitution rates of lime by MK (wt%) were prepared and cured at a temperature of 20 ?C and relative humidity RH > 95%. The phase composition of the formed hydrated phases was determined by X-ray diffraction (XRD) and simultaneous thermal analysis (TGDTA). The obtained results showed that lime/MK pastes compositions displayed different reaction kinetics during curing time, being the pozzolanic products content directly proportional to the substitution rate of lime by MK. Also, a relationship between the increase stratlingite content and the MK substitution rate of lime by MK was found.
Year: 2012
Number Pages:
36-41pp.
Author(s): Gameiro, A.; Santos Silva, A.; Veiga, M. R.; Velosa, A.
: Thermochimica Acta
Editor: Elsevier
Volume:
535.
Keywords: Pozzolanic reactions; Hydrated phase; Metakaolin; Lime; Xrd; Tgdta
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Lime-matakaolin hydration products: a microscopy analysis
Metakaolin (MK) is nowadays a well-known pozzolanic material being used in cement-based materials, like mortars and concretes. The reaction of MK with calcium hydroxide yields cementitious products, being calcium silicate hydrate (CSH), stratlingite (C2ASH8) and tetra calcium aluminium hydrate (C4AH13) the main phases formed at ambient temperature. The transformation of stratlingite and C4AH13 into hydrogarnet at long term is an important issue that may result in an increase in the porosity and a loss of compressive strength that can induce a complete material degradation. With the objective of studying the compounds formed in lime/MK pastes and their stability during time, blended pastes were prepared with several substitution rates (in weight) of lime by MK, and maintained at RH>95% and 23 ± 2 ºC. XRD and TGA-DTA were used to follow the kinetics of the lime/MK hydration as well the reaction products. Microscopic tests (SEM-EDS) results are performed and compared with the thermal and mineralogical data. The results obtained show that the quantity of the hydration products formed changes with the lime replacement, being the aluminum and calcium silicates more abundant in the higher MK content pastes, and C4AH13, C4ACH11 and C2ASH8 the major phases formed up to 90 days of curing.
Year: 2012
Number Pages:
145-148pp.
Author(s): Gameiro, A.; Santos Silva, A.; Veiga, M. R.; Velosa, A.
: Materiali in Tehnologije/Materials and Technology
Editor: Institut za kovinske materiale in tehnologije Ljubljana
Volume:
2.
Keywords: Metakaolin; Lime; Tga-dta; Xrd; Microscopy
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Comunicação
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Inhibition of ASR and DEF: evaluation of the microstructure of concrete mixes with pozzolanic additions
The use of pozzolanic mineral additions is a known method to inhibit the expansive chemical reactions in concrete, like the alkali-silica reaction (ASR) or the delayed ettringite formation (DEF). The ASR is a chemical reaction that occurs between certain types of minerals present in aggregates and alkali and hydroxyl ions present in the interstitial solution of cement paste in concrete. This reaction involve the dissolution of amorphous or poorly crystallized forms of silica, in alkaline medium, with the formation of an alkaline hygroscopic gel that absorbs water and expands, creating internal stresses in the concrete with cracking. The DEF is a pathology related with the formation of expansive ettringite due to an excessive heating of the concrete during the cure that induces swelling, cracking and decrease of the mechanical properties of the hardened concrete. This paper presents the results of SEM/EDS analysis of concrete mixes with different pozzolanic materials, like metakaolin, biomass fly ash, natural pozzolan and mine sludge from a tungsten mine. The microstructural evaluation is discussed and correlated with the expansion data of each concrete mix.
Year: 2011
Number Pages:
15p.
Author(s): Santos Silva, A.; Soares, D.; Matos, L.; Divet, L.; Salta, M. M.
Editor: ZAG, Slovenian National Building and Civil Engineering Institute
Keywords: Pozzolanic additions; Microstructure; Scanning electron microscopy; Def; Asr
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Investigation of Alkali-Silica Reaction in Concretes with Biomass Fly Ash
The alkalisilica reaction (ASR) in concrete occurs by reaction of certain silica phases in the aggregates with alkalis and hydroxide ions in the pore solution of the hydrating cement to produce a hydrous alkali-silicate gel. This gel can swell by incorporating large amounts of water, causing severe and irreversible expansion and cracking of the concrete. The level of expansion and disruption in concrete containing reactive aggregate depends on the alkali content of the concrete and the reactivity of the aggregate. The levels of alkali that trigger the expansion depend, however, on the reactivity of the aggregates. Alkalis from Portland cement (OPC) are one of the major sources of these ions in concrete. The use of industrial by-products such as fly ash and slag has been found to be an effective preventive measure against ASR in concrete. This article presents the performance of biomass fly ash - an industrial by-product - in the mitigation/inhibition of ASR in concrete. Laboratory expansion tests were conducted to evaluate the performance of biomass fly ash, in replacement of OPC by 20% and 30% (w/w) in the experiments (ASTM C1260/ASTM C1567). The results revealed that biomass fly ash has a good potential in the expansion inhibition due to ASR.
Year: 2011
Number Pages:
7p.
Author(s): Rejini, R.; Soares, A. C.; Esteves, T.; Santos Silva, A.; Labrincha, J. A.; Ferreira, V.
Editor: Instituto de Ciencias de la Construcción Eduardo Torroja
Keywords: Industrial by-products.; Biomass fly ash; Alkali-silica reaction; Concrete
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Laboratory and microstructural tests on the detection and prediction of AAR
LNEC has been involved in research dealing with alkali-aggregate reactions for the past 20 years. In recent years, the research has been directed at identifying the magnitude of the problem in Portugal, identifying rock types which may be potentially reactive, determining the influence of supplementary cementing materials to counteract the expansion associated to AAR and the continuous improvement of the methodologies to prevent this deleterious reaction in new concrete constructions. International and national workshops and seminars on concrete durability, and particularly related to the concrete degradation by alkali-aggregate reactions, have been held to disseminate the information. One integral part of this research work has been the transfer of technology to the universities and concrete industry in the subjected area. This presentation is a perfect example of the cooperation between LNEC and the Portuguese Universities in this specific topic related with the laboratory and microstructural tests on the detection and prediction of AAR.
Year: 2011
Author(s): Santos Silva, A.; Fernandes, I.
Editor: LNEC
Keywords: Prognosis; Diagnosis; Microscopy; Tests; Alkali-silica reaction; Aar
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Metakaolin-lime hydration products and phase stability:
Metakaolin (MK) is nowadays a well-known pozzolanic material being used in cement-based materials, like mortars and concretes. The reaction of MK with calcium hydroxide yields cementitious products, being the main phases formed at ambient temperature the calcium silicate hydrate (CSH), stratlingite (C2ASH8) and tetra calcium aluminium hydrate (C4AH13). Several discrepancies are presented in literature regarding these phases stability, namely the transformation of stratlingite and C4AH13 into hydrogarnet at long term. The consequences of that instability are an increase in the porosity and a loss of compressive strength that can induce a complete material degradation. With the objective of studying the compounds formed in lime/MK pastes and their stability during time, blended pastes were prepared with 50%, 33%, 25%, 17%, 9%, 5% and 0% (wt.%) of MK. These lime/MK pastes were stored at 95% RH and 23 ± 2 ºC. After each predetermined curing time the hydration reaction was stopped subjecting the samples to acetone. TGA-DTA and XRD were used to follow the kinetics of the MK-lime reaction as well the reaction products formed. In this paper the results obtained by the application of microscopic methods, namely by SEM-EDS, are presented and compared with the thermal and mineralogical data.
Year: 2011
Number Pages:
10p.
Author(s): Gameiro, A.; Santos Silva, A.; Veiga, M. R.; Velosa, A.
Editor: ZAG, Slovenian National Building and Civil Engineering Institute
Keywords: Metakaolin; Lime; Tga-dta; Xrd; Microscopy
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Mineral Additions for the Inhibition of Delayed Ettringite Formation in Concrete: The Role of Limestone Filler
One of the most popular preventive measures to minimize the occurrence of chemical expansive reactions, namely the internal sulphate reaction (ISR), in hardened concrete is the use of mineral additions. This pathology is due to the formation of expansive ettringite (delayed ettringite formation - DEF) inside the material and is very difficult to deal with, because presently there is no efficient method to repair concrete structures affected by DEF. Hence, there is an urgent need to find preventive methods that may enable the inhibition of DEF in new constructions. Nowadays, its recommended the use of mineral additions to sustain this type of degradation. Moreover, their effect depends on the chemical and mineralogical composition and also the cement replacement. The research work presented in this paper deals with the influence of limestone filler, a type I mineral addition, in the inhibition of DEF (Santos Silva et al., 2010a, 2010b), and is part of an extensive study to elucidate the role that the mineral additions have in the mechanism of inhibition of DEF in concrete. For this purpose different concrete mixes were produced by using the same cement type (CEM I 42.5Ra with 3.11% SO3 and 6.4% C3A) and water/cement ratio (0.45), incorporating different amounts of mineral additions, like fly ash, metakaolin, blast-furnace slag, silica fume and limestone filler. The filler influence was followed by expansion and microstructure evaluation of concrete mix at several ages. These studies showed an interesting behaviour of limestone filler, which motivated new concrete formulations with different cement types (CEM I 42.5Rb and CEM I 52.5) that differ in SO3 and C3A contents, in order to investigate its influence in development of DEF. This research includes also a concrete composition with a cement type II (CEM II A-L 42.5R). The results obtained were compared and the conclusions were extracted. It was found that the concrete mixes with limestone filler showing higher expansions than the control composition. According to these results it seems that the limestone filler does not inhibit rather it promotes the expansion due to DEF. Thus, for concretes subjected to high temperatures in early ages, the limestone filler is not adequate to sustain DEF development rather it may even increase the expansion behaviour in concrete mixes. According to these findings, it was proposed that the ISR recommendations must prohibit this kind of mineral addition.
Year: 2011
Number Pages:
7.
Author(s): Santos Silva, A.; Soares, D.; Matos, L.; Salta, M. M.; Gonçalves, A.; Ribeiro, A. C.; Pavoine, A.; Divet, L.
Editor: Instituto de Ciencias de la Construcción "Eduardo Torroja"
Keywords: Microstructure; Mineral additions; Limestone filler; Def; Isr
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Mitigation of Internal Expansive Reaction: the role of Tungsten Mine Sludge
The concrete degradation caused by internal expansive reaction (IER) is a problem that affects many structures in the world. These reactions, which include the alkali-silica reaction (ASR) and the internal sulphatic reaction (ISR) related with delayed ettringite formation, are very dangerous, due the expansive behavior of products formed, that cause the cracking of concrete. So it is urgent to find preventive methods to avoid or mitigate the onset of these reactions in new structures. This work aims to show the applicability of sludge from a tungsten mine in the mitigation of the IER. To evaluate the effect of sludge in the mitigation of ASR and ISR, mortar and concrete mixes were produced with 30% (%in mass) of cement replacement. The results obtained so far allow stating that tungsten mine sludge as Portland cement replacement could be effective in the ASR and ISR mitigation
Year: 2011
Number Pages:
6p.
Author(s): Sousa, S.; Santos Silva, A.; Velosa, A.; Gameiro, A.; Rocha, F.
Editor: Escola de Engenharia da Universidade do Minho
Keywords: Tungsten mine sludge; Mitigation; Delayed ettringite formation; Alkali-silica reaction
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Modeling the start of the expansion due to alkali silica reaction in concrete
Service life of a concrete affected by alkali-silica reactions (ASR) is the age at which expansion is no longer allowed for normal use of a structure; such expansion level depends on the application. Once the induction period ends, the expansion proceeds quickly. Thus, in the present study, the service life was approached by the induction time. Induction time is an abstract concept, its formulation depending on the model considered (additive, constant time in the diffusion model, or the abscissa of intersection of time axis by a tangent to the expansion curve at the inflexion point, in the nucleation and growth model). Mortar bars were made with Tagus river reactive aggregate according the ASTM C 1260 procedure (expansion of bars immersed in NaOH 1M) implemented at temperatures of 80, 70, 60, 50 and 37ºC, to model expansion at constant alkalinity, considering the aggregate reactivity and temperature as variables. The results show that the data has enough precision for a kinetic study. Two kinetic models were considered to fit the data, selecting one of which for further improvement, using the wide information basis on the ASR. The effects of the factors temperature, alkalinity and humidity assumed models referred to in literature, or obtained by regression both of kinetic parameters for each isothermal curve and their temperature coefficients of Arrhenius plots. The correlations obtained allow estimating the strain after the induction period, for any value of the mentioned factors, under laboratory conditions. The model estimates at ca 37ºC were compared with experimental data in the same setup and this temperature. The induction time prediction was satisfactory, but further expansion development pattern was different. The model was tentatively applied to a case reported in literature. Results match, but are affected by significant errors, some improvements being referred to improve accuracy.
Year: 2011
Number Pages:
17p.
Author(s): Gonzalez, L.; Santos Silva, A.; Soares, D.; Jalali, S.
Editor: lnec
Keywords: Service life; Prevision; Reaction start; Aar
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Natural consolidation of ancient historic buildings mortars submitted to humid and marine environment: a microscopic study
Ancient historical buildings are important features of the history, culture and development of a country and its people. This study presents the results of chemical, physical and microstructural characterization performed on mortars in order to assess their durability and good performance in a marine and humid environment, The mortars are collected in two historical monuments in Lisbon region, the Santa Marta Fortress (SM) in the coast line Lisboa-Cascais (XVII century), and the Defence Wall of Lisbon (M), constructed and reconstructed during many centuries, but with zones dated from the roman period to which the analysed samples belong. This edification, approximately 2 km long, was, during centuries, the only defence of the city and is scarcely visible nowadays due to several constructions and changes carried out along the time. The microstrutural characterization was done by optical and scanning electronic microscopy to identify the binder and aggregate types, reaction products and porosity. The microstructural observation reveals that all mortars have the pores normally fulfilled with reaction products, etringite in the SM mortars and calcium carbonate and phosphate in M mortars. Moreover, reaction rims are evident around some aggregates, suggesting the occurrence of pozzolanic reactions between aggregates and the calcitic binder that creates neoformation products, such as calcium-silico-aluminates, which seems be, besides the pores filling, the responsible for the resistance and cohesion of these ancient mortars submitted to aggressive humid environments.
Year: 2011
Number Pages:
15p.
Author(s): Borges, C.; Santos Silva, A.; Veiga, M. R.
Editor: ZAG, Slovenian National Building and Civil Engineering Institute
Keywords: Tga-dta; Xrd; Microscopy; Marine environment; Ancient lime mortars
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Petrographic characterization of granitic aggregates.
Granitic rocks are widely used as aggregates for concrete in Portugal. Although this type of rock is known in some countries to be non-potentially reactive to alkalis, there are reported cases of alkali-silica reaction related to granitic aggregates. As defined by the Portuguese specification LNEC E 461, the petrographic analysis is the first to be carried out when aggregates of unknown performance need to be characterized. The characterization is based on the determination of the percentage of reactive forms of silica in order to classify the aggregate as innocuous or as potentially reactive, according to classes similar to those defined in RILEM AAR-1. This assessment is followed by the mortar bar test (ASTM C 1260 or RILEM AAR-2) when the aggregate is classified in Class II or III. The local experience is that some of the granitic aggregates classified as innocuous by RILEM AAR-2 show a field performance different from that predicted by the tests. Therefore, a research project is being carried out in which systematic concrete prism tests (RILEM AAR-3 and RILEM AAR-4.1) are used to validate the results obtained by petrography and to establish which laboratory test(s) is(are) the most accurate for the assessment of the alkali reactivity of granites. In the present work, the first results of the research are presented, aiming to contribute to the reformulation of the national specification and to establish a possible correlation among the results from different methods.
Year: 2011
Number Pages:
9p.
Author(s): Ramos, V.; Fernandes, I.; Noronha, F.; Santos Silva, A.
Editor: ZAG, Slovenian National Building and Civil Engineering Institute
Keywords: Asr; Expansion tests; Petrographic characterization; Granitic aggregates
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Phase and microstructural characterization of lime-MK blended mixes
N/A
Year: 2011
Number Pages:
6p.
Author(s): Gameiro, A.; Santos Silva, A.; Veiga, M. R.; Velosa, A.
Editor: Escola de Engenharia da Universidade do Minho
Keywords: Sem; Lime; Pozzolan; Metakaolin
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Books
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Materiais de interesse histórico que constroem o património edificado: Correlações, usos, paisagens
Os artigos que compõem esta edição foram criteriosamente selecionados e aprimorados, seguindo igual metodologia de trabalho do número anterior, contribuindo para compor um dossier temático de elevado interesse e qualidade. No seu conjunto, os vários textos sublinham o papel dos materiais históricos na construção multidimensional do território humanizado, ligando os aspetos tangíveis e intangíveis, transportando saber e gosto, tradição e inovação. Estes artigos, bem como os do primeiro volume, são também uma fonte reflexão e de conhecimento sobre alguns dos materiais de construção mais empregues no Património abrindo, nalguns casos, novas perspetivas para futuras investigações nesta área do conhecimento.
Year: 2022
Number Pages:
218p..
Author(s): Veiga, M. R.; Santos Silva, A.; Menezes, M.
: Cadernos do Arquivo Municipal
Editor: Câmara Municipal de Lisboa
Volume:
Vol. II, Nº 17.
Keywords: Calçada Portuguesa; Ouro Preto, Brasil; Baixa Pombalina; Mansardas; Fábrica de cerâmica Lusitânia; Lisboa; Mármore; Raul Lino; Azulejo; Património; Materiais de construção
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On the origin of majolica azulejos production in Portugal. nº 2 - vol II.
Vários
Year: 2019
Number Pages:
97p.
Author(s): Pais, A.; Mimoso, J.; Rosmaninho, R.; Esteves, L.; Morais Pereira, S.; Antunes, M.; Cardoso, A.; Mirão, J.; Marques, A.; Ferreira, M.; Candeias, A.; Valona, R.; Morna, T.; Simões, J.
: Estudos em Cerâmica Vidrada Patrimonial
Editor: LNEC
Keywords: PT; Physical-chemical characterization; Azulejo; Manufacture; Glazed ceramics; Historic heritage
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Characterization of decorative Portuguese gypsum plasters from the 19th and 20th centuries: the case of the Bolsa Palace in Oporto
The use of gypsum plaster for the interior coating of walls and ceilings in the Portuguese architecture was particularly expressive in the period between the XVIII and the XX century. However, information about this important heritage is almost nonexistent, which is leading to a rapid loss of important patrimony. In this paper the results of the characterisation of five gypsum plaster samples from the second half of the XIX century belonging to the Arabian Room of the Bolsa Palace, located in Oporto, North of Portugal, are presented and discussed. XRD and TGA-DTA techniques were used to establish the mineralogical composition, and the relative proportions of the binders. Optical microscopy and FESEM-EDS observations were performed both in fractured and polished surfaces in order to determine the stratigraphy and the composition of individual layers. The results of this characterisation work showed that the plasters used were mainly composed of gypsum and hydrated lime in different proportions a feature that was correlated with the application techniques of the decorative elements analyzed - and allowed the determining of the restoration interventions they had already been submitted to. Some physical properties like the dynamic modulus of elasticity and capillary absorption were also determined, and a correlation between the results obtained was established with previous studies performed by the authors.
Year: 2012
Number Pages:
141-151pp.
Author(s): Freire, T.; Santos Silva, A.; Veiga, M. R.; Brito, J.
Editor: Springer
Volume:
Volume 7, RILEM Bookseries.
Keywords: Capillary absorption; Microscopy; Tga-dta; Xrd; Characterisation; Gypsum plasters
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Diagnosis, characterization and restoration of the internal renders of Santíssimo Sacramento church in Lisbon
The Santíssimo Sacramento Convent in the Alcântara quarter of Lisbon is one of the most important ecclesiastical structures of the Filipino Period (1580- 1640), showing an innovative architectural layout. An intervention aiming at the repair and restoration of the interior plasters of the Santíssimo Sacramento Church was performed in 2009 and 2010. To support the restoration plan, a physical, mechanical and chemical-mineralogical characterization of the internal plasters of the church was carried out. In this paper the main results are presented, such as various types of plasters, mortars, stuccos and pigments; and also the nature of the main anomalies were identified and characterized. The results obtained contributed to the identification of the main decorative programs characterized by the use of different materials and techniques. The mortars are in very good condition, being composed of aerial calcitic lime with quartzitic and basaltic aggregates. The stuccos are comprised by gypsum and non-hydraulic lime, while the decorative layers features lime with some precious pigments, such as ultramarine (lapislazzuli) and gold-foil gildings. The plaster conservation and restoration works were performed with compatible repair materials selected according to the physical-chemical characterization and on the evaluation of the conservation state.
Year: 2012
Number Pages:
175-194pp.
Author(s): Santos Silva, A.; Borsoi, G.; Veiga, M. R.; Fragata, A.; Tavares, M.; Llera, F.; Barreiros, B.; Teixeira, T.
Editor: Springer
Volume:
Volume 7, RILEM Bookseries.
Keywords: Pigments; Stuccos; Mortars; Plasters
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AS REACÇÕES EXPANSIVAS INTERNAS NO BETÃO. Prevenção dos riscos e gestão das estruturas afectadas
A degradação de estruturas de betão por reacções expansivas internas é uma patologia que, não sendo relativamente recente a nível internacional, tem vindo a manifestar-se duma forma crescente nos últimos anos em Portugal. Esta patologia tem afectado vários tipos de estruturas de betão, algumas de grande importância estratégica, nomeadamente grandes barragens e obras de arte (pontes e viadutos). A título de exemplo referem-se os casos do Viaduto Duarte Pacheco, e as Barragens de Alto-Ceira e Santa Luzia, alguns dos quais obrigaram a intervenções de elevado custo. Esta forma de degradação, que engloba a reacção álcalis-sílica (RAS) e a reacção sulfática interna (RSI), quando ocorre numa estrutura é particularmente nefasta porque está relacionada com a formação de compostos expansivos que provocam a fissuração do betão, contribuindo decisivamente para a diminuição da vida útil da estrutura, podendo em alguns casos obrigar à sua demolição. Associada a esta situação, acresce o facto de não se dispor actualmente dum método totalmente eficiente e económico de combater esta forma de degradação. Deste modo, para garantir os tempos de vida útil preconizados para as novas construções devemse adoptar medidas preventivas para evitar ou minimizar os efeitos da ocorrência deste tipo de reacções expansivas nas estruturas de betão. Em Portugal, medidas preventivas destas reacções expansivas internas estão contidas na Especificação LNEC E 461, citada na NP EN 206-1 Betão. Parte 1: Desempenho, especificação, produção e conformidade, a qual inclui a fixação de níveis de prevenção de acordo com a categoria de risco e exposição ambiental do elemento ou da estrutura de betão. Estas medidas passam por uma caracterização dos factores condicionantes destas reacções nos constituintes do betão e pela aplicação de medidas para a sua inibição. Neste particular, a utilização de adições minerais em substituição parcial do clínquer portland, é uma medida que além de diminuir o calor de hidratação, permite a redução da alcalinidade da solução intersticial do betão e contribui ainda para reduzir a quantidade de sulfatos no betão, evitando assim a formação de produtos expansivos. Actualmente é já conhecido que as adições minerais do tipo II, em substituição parcial do cimento no betão e em quantidade suficiente, podem mitigar os efeitos destas reacções. A acção destas adições minerais depende, no entanto, da sua composição e reactividade pozolânica.Apesar dos bons resultados já demonstrados por algumas adições, nomeadamente as cinzas volantes, o seu uso pode estar comprometido a curto/médio prazo, tendo em conta a cada vez maior preocupação, por parte da maioria dos Países, na utilização de renergias limpas. Esta tendência terá como consequência uma diminuiçãtt ou mesmo o esgotamento da produção de alguns subprodutos industriais. No caso dos produtos naturais, é previsível um agravamento das restrições ambientais associadas à sua exploração e tratamento. Foi neste contexto que se iniciou no LNEC, em colaboração com o Laboratoire Central des Ponts et Chaussées de Paris e as Universidades de Aveiro, Minho e Évora, um projecto de avaliação da utilização de novos materiais com características pozolânicas, capazes de responderem às necessidades da indústria do betão a curto/médio prazo. Este projecto, que contou com o apoio da Fundação para a Ciência e Tecnologia (Projecto PTDC/CTM/65243/2006 EXREACT Mitigação de reacções expansivas deletérias em estruturas de betão) visa ainda o aperfeiçoamento de metodologias de diagnóstico e prognóstico da ocorrência de reacções expansivas internas em estruturas de betão existentes. Os resultados do trabalho realizado no decorrer do projecto têm vindo a ser divulgados em artigos e comunicações em seminários nacionais e internacionais, mas também através duma página Web (http://www-ext.lnec.pt/EXREACT/index.html) e com a organização de reuniões como a do presente Workshop, que contou com o apoio do LNEC, da Comissão Organizadora do REABILITAR 2010 - Encontro Nacional de Conservação e Reabilitação de Estruturas e dos oradores convidados. Este Workshop visa apresentar os últimos desenvolvimentos sobre os aspectos da prevenção, modelação e reparação, proporcionando uma oportunidade para a compartilha de ideias e soluções para a gestão das estruturas afectadas por RAS e/ou RSI.
Year: 2010
Number Pages:
143.
Author(s): Santos Silva, A.; Gonçalves, A.; Divet, L.; Pavoine, A.; Germain, D.; Appleton, J.
Editor: LNEC
Keywords: Reparação; Modelação; Gestão; Prevenção; Def; Ras; Betão; Reacções expansivas
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Capítulo de Livro
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Analysis of the behavior of original air lime mortars used in structural brick masonry walls of ancient buildings
The growing interest in preserving the built heritage is a driving force towards the search for new rehabilitation solutions compatible with the original construction techniques of ancient buildings. For the design of an adequate reinforcement solution, it is necessary to know in detail the building to be rehabilitated, as well as its original constructive solutions and materials.This paper presents the results of an experimental campaign on samples of air lime-based laying and coating mortars, extracted from an old masonry building in the historic center of Lisbon, built in 1910, during the rehabilitation works. The different parameters analyzed allow for the composition characterization and evaluation of their mechanical, physical and chemical properties. Based on this characterization, the influence of these mortars on the overall behavior of load-bearing walls of buildings belonging to the typology under study is also evaluated.Considering the results obtained in the characterization tests for the mortars in study, it was verified that the binder used in both mortars was air lime. The values for compressive strength, modulus of elasticity and the curves obtained in the capillarity and drying tests, are also compatible with this type of mortars. It was determined that the mortars are similar in terms of physical and mechanical characteristics, to Portuguese mortars studied in current buildings of the same historical period. This type of information is crucial in a structural analysis and allows to identify materials compatible with the original ones that can be used in rehabilitation interventions.
Year: 2023
Number Pages:
15p..
Author(s): Candeias, P.; Ferreira, J.; Santos Silva, A.; Veiga, M. R.; Mera Marques, A.
: Conservation and Restoration of Historic Mortars and Masonry Structures
Editor: Springer
Keywords: Characterization tests; Air lime mortars; Structural brick masonry walls; Ancient buildings; Conservation and rehabilitation
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CDW as sources of CO2 absorption
Cementitious materials have a considerable global warming footprint. This is due mainly tothe cement incorporated. For a tonne of cement produced other 800 kg of CO2 [1] are releasedinto the atmosphere.According to the European Sustainable Development Goals, cement industry should becomecarbon neutral by 2050. To meet this goal, the European Cement Association (Cembureau)developed a Roadmap with specific guidelines by 2050 based on five approaches (5C). Thefirst four are focused on improvements in clinker production, cement formulation,construction processes and concrete formulations. The last 5C is re-carbonation of thecementitious materials.This research investigates the CO2 absorption capability of recycled aggregates (RA) fromconstruction and demolition wastes (CDW), when submitted to a forced carbonation. It isknown that CDW still have some potential to CO2 capture, which is a long-term and securecarbon storage. For that purpose, several CDW were collected from recycling plants, fromselective demolitions and from concrete plants.It was concluded that RA when submitted to forced carbonation absorb between 47 to 315 kgof CO2 per tonne of cement paste, which has a potential to meet the re-carbonation targetsestablished by the roadmaps to carbon neutrality.
Year: 2023
Number Pages:
243-257pp..
Author(s): Martins, I. M.; Santos Silva, A.; Veiga, M. R.; Infante Gomes, R.; Bastos, D.; Pederneiras, C.; Farinha, C.
: Proceedings of the V International Conference Progress of Recycling in the Built Environment
Editor: RILEM
Volume:
RILEM Proceedings PRO 137.
Keywords: Recycled aggregates; Forced carbonation; CO2 absorption; CDW
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Characterization of mortars and concretes from the Mirante da Quinta da Azeda, Setúbal (Portugal). A case study from the beginning of the 20th century
The Mirante da Quinta da Azeda, in Setúbal (Portugal), is a peculiar observation tower built in the early 20th century, and one of the first examples in which reinforced concrete was applied in Portugal. It has an unusual architectural configuration, displaying elements of great slenderness. In the scope of the CemRestore research project - Mortars for the conservation of early 20th century buildings: compatibility and sustainability, several mortar and concrete samples were collected from this structure and were characterized using a combination of mineralogical, microstructural, physical, and mechanical techniques, including XRD, petrography, SEM-EDS, open porosity, capillarity coefficient, compressive strength, and ultrasonic pulse testing. In this paper, the main characterization results are presented and discussed. The results show that all structural and decorative samples are made with Portland cement, while one rendering mortar is lime-based. The sand is mostly siliceous whereas pebbles and crushed limestone can be found as coarse aggregates in concrete samples. This characterization allows for broadening the scientific knowledge about the materials of that period used in Portugal, also enabling the establishment of the requirements to be met by mortars and concrete to be used in the repair of this distinct structure.
Year: 2023
Number Pages:
243-257pp..
Author(s): Velosa, A.; Veiga, M. R.; Santos Silva, A.; Lopes dos Santos, A. R.; Almeida, L.
: Conservation and Restoration of Historic Mortars and Masonry Structures
Editor: Springer
Keywords: Portugal; Characterization; Concrete; Mortar; 20th century
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Evaluation of the hygroscopic and CO2 capture capacities of earth and gypsum-based plasters
Earth mortars and gypsum mortars present ecological advantages compared to mortars made with other common binders. When applied as plasters, they are also referred as having advantages in improving comfort and indoor air quality. For earth plasters, this improvement is associated with the hygroscopic capacity of the clay minerals, which promotes high sorption and desorption capacity of water vapor. So, earth plasters can contribute to the regulation of the indoor relative humidity. Another important advantage of plasters could be their ability to capture carbon dioxide (CO2). In the present study, the sorption and desorption performance, and the capacity to capture CO2 by earth and gypsum plasters are evaluated. It is confirmed that the earth plaster has the greatest sorption and desorption capacity, but also higher CO2 capture capacity than gypsum plaster. This confirmation opens new perspectives for the use of functionalized plasters that guarantee greater control of air quality inside buildings.
Year: 2023
Number Pages:
207-215pp..
Author(s): Faria, P.; Gomes, I.; Santos Silva, A.; Santos, T.
: Conservation and Restoration of Historic Mortars and Masonry Structures
Editor: Springer
Keywords: Mortar; Indoor air quality; Hygroscopicity; Gypsum; Clayey earth; CO2 capture
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Os revestimentos e os acabamentos do Centro Histórico de Coimbra. Um contributo para o seu estudo
Coimbra apresenta um elevado valor arquitetónico demonstrado pelos 36 imóveis, conjuntos ou sítios (22 monumentos nacionais e 14 imóveis de interesse público) actualmente classificados (DGPC, 2015) sendo a maioria deles localizados no Centro Histórico de Coimbra (CHC) e zona alta da cidade. No âmbito do projecto POCI/HEC/60371/2004 Bases para o restauro dos revestimentos históricos do Centro Histórico de Coimbra, foi feito um levantamento das existências cromáticas existentes no CHC-Alta (zona de edifícios de habitação da Alta de Coimbra, Figura 3.1), a partir do qual se seleccionaram edifícios que ainda apresentavam vestígios de pinturas em várias camadas, o mais antigas possível.
Year: 2017
Number Pages:
49-74pp.
Author(s): Catarino, L.; Gil, F.; Duarte, T.; Veiga, M. R.; Santos Silva, A.
Editor: Almedina
Keywords: Cal calcítica; Cal dolomítica; Argamassas; Caracterização; Estratigrafia; Centro Histórico de Coimbra; Revestimentos
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Tese de Doutoramento
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Revestimentos nanoestruturados para protecção de liga de alumínio
Os revestimentos híbridos nanoestruturados apresentam um elevado potencial no âmbito da protecção anticorrosiva dos metais, prevendo-se que no futuro estes revestimentos possam, não só substituir os tratamentos à base de crómio usados na indústria do tratamento de superfícies metálicas para protecção anticorrosiva, como também evoluir para sistemas integrados multifuncionais que dispensem o pré-tratamento e sejam mais amigos do ambiente. O processo sol-gel usado para a obtenção destes revestimentos permite, através da combinação de diferentes precursores e da manipulação das condições de síntese desenhar e optimizar a estrutura química e a funcionalidade dos revestimentos nanoestruturados com o objectivo de obter as propriedades desejadas para uma determinada aplicação. O estudo apresentado no presente trabalho teve como objectivo principal a optimização de revestimentos híbridos nanoestruturados obtidos pelo processo sol-gel para a protecção anticorrosiva de uma liga de alumínio frequentemente utilizada na construção civil. Para alcançar este objectivo foram preparados diversos revestimentos híbridos nanoestruturados e aplicados na liga de alumínio EN AW-6063, cujo processo de síntese foi optimizado variando parâmetros como a composição, processo de cura e condições reaccionais sol-gel, visando a obtenção de revestimentos com propriedades anticorrosivas melhoradas. Posteriormente, foi feita uma avaliação do comportamento à corrosão dos revestimentos optimizados em diferentes condições corrosivas, individualmente e como parte integrante de um sistema de protecção anticorrosiva usualmente aplicado em ligas de alumínio para fins arquitecturais. No presente documento é apresentada uma revisão bibliográfica da aplicação deste tipo de revestimentos na protecção anticorrosiva, seguindo-se a descrição detalhada dos procedimentos experimentais do estudo, nomeadamente, os materiais e os procedimentos para obtenção e caracterização dos revestimentos estudados, a apresentação dos resultados obtidos no decurso do desenvolvimento experimental realizado, sua interpretação, discussão e as conclusões parciais mais relevantes. No final, resumem-se as principais conclusões obtidas no estudo e faz-se uma avaliação global da aplicabilidade dos revestimentos optimizados na protecção anticorrosiva de ligas de alumínio no âmbito da construção civil, e indicam-se necessidades de desenvolvimentos futuros.
Year: 2012
Number Pages:
256.
Author(s): Fontinha, I. R.
Keywords: Corrosão; Liga de alumínio; Sol-gel; Revestimentos híbrido nanoestruturados
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Passivação do aço inoxidável no betão
Nesta dissertação, estudou-se o comportamento electroquímico de cinco ligas austeníticas de aço inoxidável em meio alcalino, nomeadamente duas ligas de Fe-Cr-Ni (1.4301?SS0 e 1.4436?SS4) e três novas ligas de elevado teor em manganês Fe-Cr-Mn (SS1, SS2 e SS3). Os estudos incidiram na avaliação da resistência à corrosão das ligas, em soluções alcalinas e no betão, e na caracterização das propriedades dos filmes de passivação sob influências várias, designadamente, condições de estabilização (electrólito, tempo e potencial de formação do filme), composição e microestrutura das ligas, soldadura e estado da superfície do aço. O estudo da capacidade diferencial em função do potencial mostra o comportamento dos filmes de passivação como semicondutores tipo-n e tipo-p, respectivamente, para valores anódicos e catódicos relativamente aos potenciais de banda plana, possibilitando a determinação das suas propriedades electrónicas. Estas traduzem as principais diferenças dos dois grupos de ligas, sendo que as ligas de Fe-Cr-Mn mostram uma menor razão da densidade de aceitadores com a densidade total de portadores de carga, do que as ligas de Fe-Cr-Ni, e um nível de doadores profundo, cuja ionização depende do potencial aplicado. Todas as ligas revelaram uma elevada resistência à corrosão nos diferentes meios, sendo a sua estabilidade especialmente dependente do acabamento superficial do aço e da existência de condições que promovam a corrosão intersticial. A soldadura das ligas induziu a formação de picadas instáveis, cuja repassivação foi desfavorecida em duas das ligas de Fe-Cr-Mn (SS1 e SS3). A presença de fissuras no betão demonstrou a despassivação das ligas e a susceptibilidade à corrosão sob tensão da liga SS1 no betão. As propriedades dos filmes de passivação, nomeadamente as densidades dos portadores de carga, que podem ser correlacionadas com a composição e a microestrutura das ligas, justificam as diferenças no comportamento electroquímico das ligas de Fe-Cr-Ni e de Fe-Cr-Mn. Para além das diferenças promovidas pelos teores de níquel e de manganês e pela ferrite, a maior resistência à corrosão das ligas SS2 e SS4, respectivamente, quando comparadas com as restantes ligas de Fe-Cr-Ni (SS0) e Fe-Cr-Mn (SS1 e SS3), é devida à presença do molibdénio e seus eventuais efeitos sinergéticos com o crómio e azoto.
Year: 2009
Author(s): Correia, M. J.
Keywords: Corrosão; Propriedades semicondutoras; Filme de passivação; Aço inoxidável
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Dissertação de Mestrado
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Caracterização de argamassas tradicionais e históricas de edifícios religiosos do Alentejo
O estudo da composição de argamassas antigas, que implica usualmente a utilização de técnicas de caracterização físico-química, mineralógica e microestrutural, desempenha um papel fundamental para a preservação do património cultural, permitindo obter um conhecimento bastante profundo sobre os seus constituintes e revelando detalhes importantes sobre as técnicas de construção, eventuais reparações e o estado de conservação e desempenho das mesmas. Neste trabalho foram analisadas argamassas provenientes de quatro edifícios religiosos da região do Alentejo, nomeadamente a Sé Catedral de Évora (Séc. XIII-XVII), a Igreja de Nossa Senhora da Assunção em Elvas (Séc. XVI), a Igreja Matriz de Mértola (Séc. XII) e o Conjunto Monumental de Amieira do Tejo (Séc. XIV-XVI). A metodologia de caracterização empregue recorreu a diversas técnicas, nomeadamente difracção de raios X (DRX), análise termogravimétrica (ATG), microscopia óptica (MO), microscopia electrónica de varrimento acoplada a espectroscopia de raios X por dispersão de energias (MEV-EDS), espectrofotometria de absorção atómica (EAA), potenciometria, gravimetria, sorção de água por capilaridade, resistência mecânica, porosimetria de mercúrio e a adsorção de azoto a 196 ºC. A aplicação da metodologia proposta permitiu determinar a composição e o estado de conservação das diversas argamassas, tendo-se constatado que nas argamassas da Sé Catedral de Évora e da antiga Sé de Elvas foram utilizados dois tipos de ligantes aéreos, cal calcítica e cal dolomítica, sendo o primeiro tipo o predominante. Nos casos de estudo da Igreja Matriz de Mértola e do Conjunto Monumental de Amieira do Tejo, as argamassas apresentam um ligante essencialmente calcítico. Verificou-se que os agregados utilizados são correlacionáveis com a litologia local de cada caso de estudo. As argamassas apresentam diferentes proporções de agregado, e nos casos de estudo da Sé Catedral de Évora, antiga Sé de Elvas e Igreja Matriz de Mértola foram utilizados fragmentos cerâmicos como aditivos.
Year: 2009
Author(s): Adriano, P.
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Estabilidade stabilidade de taludes em rochas silto-argilosas
Os fenómenos de instabilidade de taludes são frequentemente causa de acidentes humanos e materiais constituindo por esse motivo um problema geotécnico de maior importância. Os estudos dos movimentos de terra, são relativamente morosos e complexos, uma vez que é necessário ter em atenção muitos factores, quer relacionados com características internas ao maciço, ou seja, características geológicas e geotécnicas, quer com acções externas. Os estudos das instabilidades de taludes ou vertentes naturais, têm como objectivo avaliar avaliar a perigosidade associada à sua ocorrência, os correspondentes riscos e definir medidas de prevenção e de controlo dos movimentos de terra que possam ocorrer. As modificações geológicas e climáticas experimentadas ao longo do tempo geram uma modificação constante na geometria dos taludes devido à sua sucessiva adaptação a novas condições de equilíbrio. Geralmente, as áreas mais propícias à ocorrência deste tipo de movimentos, correspondem a zonas montanhosas, escarpadas e sujeitas a elevada precipitação ou a condições hidrogeológicas desfavoráveis. Deste modo, a presente dissertação tem por objectivo fazer uma abordagem da problemática associada à instabilidade de taludes em rochas silto-argilosas, dando uma panorâmica das técnicas de engenharia usadas para o controlo dessas situações e salientando-se algumas técnicas de biorremediação apropriadas para o controlo de movimentos superficiais. Os temas abordados são explicados com uma aplicação a um caso real de estudo em Portugal.
Year: 2008
Author(s): Matos, L.
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Relatório Científico
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Aplicação de titânio e suas ligas na construção - Estudo da corrosão galvânica do par aço inoxidável/titânio em meio alcalino
Neste relatório, após uma introdução em que se resumem as características do titânio e das suas ligas mais relevantes para a aplicação como material de construção e se apresentam aplicações destes materiais na construção civil, apresentam-se resultados de um trabalho experimental preliminar desenvolvido com o objectivo de estudar a corrosão galvânica de aço inoxidável quando associado a titânio, em meio alcalino, a várias temperaturas.
Year: 2007
Number Pages:
69pp.
Author(s): Pereira, E. V.; Ferreira, P.
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Projecto SCORBA - Desenvolvimento de um sensor de resistividade para monitorização da corrosão no betão armado
N/A
Year: 2007
Number Pages:
49pp.
Author(s): Pereira, E. V.; Santos, J.
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Outro
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Effect of inorganic content on the performance of anticorrosive hybrid sol-gel coated EN AW-6063 alloy
The organic-inorganic hybrid sol-gel films have been reported as an effective anti-corrosion and environmentally friendly alternative to Cr(VI) pre-treatment for aluminium alloys. These hybrid materials, constituted by nanostructured polymer networks, interconnecting organic and inorganic materials, are of interest because the synergic effect on the mechanical and chemical properties achieved. The organic components impart flexibility, density and functional compatibility with organic coatings, while inorganic components impart hardness, resistance to abrasion and improve adhesion to the metal substrate. The sol-gel process used to obtain these coatings, through a series of simultaneous hydrolysis and condensations reactions between alkoxide precursors, yields highly adherent, chemically inert films on metal substrates and allows the variation of the different synthesis parameters to achieve coatings with optimized properties. In this work, hybrid films were synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide (TPOZ) precursors, using different amounts of TPOZ (10%, 20%, 30%) and applied to EN AW-6063 alloy by dip-coating, aiming to achieve the best anticorrosive coating. The corrosion behaviour of aluminium specimens coated with these films was evaluated by Electrochemical Impedance Spectroscopy (EIS) in 0.5 M NaCl solution for 63 days. The results obtained revealed that the hybrid films provided effective corrosion protection, exhibiting good barrier properties, however, it was found that 30% of TPOZ led to a marked decrease in the barrier properties with time. The hybrid films prepared were also characterized by Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), Infrared Spectroscopy and Thermogravimetric Analysis (TGA-DTG) in order to relate their morphology and chemical structure with the corrosion behaviour.
Year: 2011
Author(s): Fontinha, I. R.; Salta, M. M.; Zheludkevich, M.; Ferreira, M. G. S.
Editor: Materais 2011 - SPM
Keywords: Aluminium; Corrosion; Sol-gel; Hybrid coating
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Characterization of the concrete alkali reactivity of granitoid and dolomitic aggregates
The general designation of internal expansive reactions includes the alkali-silica reaction (ASR) and the internal sulfate attack by delayed ettringite formation (DEF). These reactions are characterized by the formation of expansive compounds in hardened concrete and consequent cracking of the structure. In Portugal, the number of structures, mainly dams and bridges, affected by ASR is very significant and in some cases require considerable investment in rehabilitation interventions. Moreover, previous research has shown that the use of some aggregates, initially regarded as inert, can cause problems, proving the need for further insight on the role of aggregates and prevent the occurrence of ASR in constructions. The economic value of various types of structures (e.g. dams, bridges, airfields) and the high costs related to structural degradation including losses of functionality and the permanent or temporary unavailability (for repair and rehabilitation) could be an important overthrow. Thus thorough understanding of the earth materials requirements for concrete manufacture are of vital economic importance in view of the prevention of deterioration and aging of structures whose longevity and functionality must be guaranteed. It is imperative to provide the concrete producers with the necessary knowledge in order to avoid this type of concrete degradation. Particularly important is the recently approved Lisbon-Madrid High Speed Train railway construction. This expensive operation will require large quantities of aggregates for the construction of bridges and other concrete infrastructures. Three main sources of raw materials will be considered for the study: St. Eulalia, Montemor and Cano. These quarries are already major exploitation sites separated by 50 km and not far from the future High Speed Train railway. Two of them are granitoid rocks but the raw material from St. Eulalia is richer in quartz and poorer in ferromagnesian minerals than the Montemor aggregates. The enrichment in calcium of feldspar goes together with the iron and the magnesium. The Cano aggregates are very different materials. The main lithology is a dolomite rock with local microscopic enrichments in phyllosilicates and very deformed quartz. Mineralogical and textural characterization of the aggregates was done by optical microscopy. The crystallinity of quartz was also evaluated by XRD and FTIR. The aggregates were also studied by accelerated expansion mortar-bar and concrete-prism tests to evaluate their potentially alkali-reactivity. The relationship between aggregates characteristics and their behaviour in what concerns to alkali reactivity will be discussed.
Year: 2010
Number Pages:
1.
Author(s): Sabino, N.; Santos Silva, A.; Menezes, A. P.; Moita, P.; Candeias, A.; Mirão, J.
Editor: Department of Mineralogy, Geochemistry and Pterology, University of Szeged
Keywords: Dolomites; Granites; Alkali reactivity; Asr
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