Publications

Nanostructured coatings exhibit a high potential for corrosion protection of metallic materials, namely, the hybrid sol-gel coatings due to the synergic effect on the mechanical and chemical properties achieved by interconnecting organic and inorganic components. In this study, a nanostructured hybrid sol-gel coating with optimized anticorrosive properties was developed for protection of an aluminium alloy frequently used in the construction field. Its performance was assessed in different corrosive conditions, showing an effective ability to protect the alloy either individually or integrated an anticorrosive coating system usually applied in architecture, replacing the toxic Cr(VI) based pre-treatments.

The degradation of large concrete structures over time is well known. One of the main reasons is the reaction that occurs between the cement paste and some reactive siliceous aggregates, which causes a significant expansion that depends on the employed materials and exposure conditions of the structure. This process is known as alkali-silica reaction (ASR) and affects several structures worldwide, including major dams and bridges in long time run. In this work the effect of fly ashes from biomass combustion in the mitigation of the ASR was investigated. The fly ashes were collected from two industrial plants located in the central area of Portugal: (i) a thermal power plant (BFA1), (ii) co-generation process of a pulp and paper industry (BFA2). The fly ashes were characterized by different techniques to determine the following properties: particle size distribution (laser interference), loss on ignition and thermal behaviour (TG/DTA), chemical (XRF) and phases (XRD) composition and pozzolanic activity (EN 196-5:2005). These biomass fly ashes were irregular in shape and fine in size. The chemical characterization revealed significant differences in CaO and SiO2 contents, but both fly ashes can be considered as class C fly ashes if compared with those generated from the coal combustion. Accelerated mortar-bar tests were conducted according to ASTM C1260/ASTM C1567 to evaluate the behaviour of the biomass fly ash in the ASR inhibition mechanism. The expansive behaviour was studied on mortars where the cement was partially replaced (20–30 wt%) by the biomass fly ashes. This substitution tends to reduce the expansion upon accelerated curing conditions, and BFA2 is more effective than BFA1. But the incorporation of biomass fly ash in the blend along with metakaolin (MK), 20% BFA + 10% MK did a significant improvement in the expansion results, indicating the effective use of biomass fly ash along with metakaolin in mitigating the ASR.

A casa de Fresco de Sanches de Baena situado em Vila Viçosa é um exemplo gritante de um património cultural em risco, que apela a um estudo e intervenção urgentes para a sua salvaguarda e preservação. No âmbito do projecto MURAL2D: Murais em Risco no Alentejo – Degradação e Diagnóstico, pretende-se dar continuidade aos estudos já iniciados em 2008 pelo laboratório HERCULES da Universidade de Évora, ao nível das técnicas, materiais e estado de conservação dos elementos decorativos que revestem as paredes e a abóbada de aresta deste espaço do final do século XVI ou início do XVII (pintura mural, estuques modelados e embrechados). O objectivo é o levantamento de dados que possibilitem a obtenção de um conhecimento aprofundado dos materiais e dos mecanismos de degradação, para que, no futuro, estes possam servir de base à elaboração de uma proposta de conservação. No presente artigo, após enquadramento estilístico-histórico da decoração, são apresentados os primeiros resultados desta pesquisa pluridisciplinar a decorrer in-situ e em laboratório.

Lime-based mortars with admixtures of metakaolin (10,20 and 30 wt.%) and fine sepiolite (5 wt.%) were prepared with the aim of facilitating their use as repair mortars in low humidity conditions. The mechanical properties and the dynamic modulus of elasticity were studied after 28,90 and 180 days of curing. With increasing amount of metakaolin in lime mortars, improved mechanical strength was observed mainly after 90 days. Addition of fine sepiolite, due to its adsorption properties for storing water for later supply to the mortar system and its microfibrous morphology,led to an improvement of compressive and flexural strength of blended air lime/air lime-metakaolin mortars,especially at later ages of curing. Incorporation of fine sepiolite into air lime-metakaolin mortars resulted in comprehensive densification of the core of the mortars. Air lime mortar containing 5% of fine sepiolite and 20% of metakaolin appears to be an optimal admixture.

Historical mortars from sixteenth to seventeenth century military forts located at the mouth of the Tagus River in Lisbon have been characterized by polarized light microscopy (PLM), thermal analysis (TG/DTA), X-ray diffractometry (XRD) and scanning electron microscopy / energy dispersive spectroscopy (SEM/EDS). The results indicate that the mortars used were all hydraulic lime-based. The presence of well-rounded lime lumps indicates a limited use of water during the lime hydration process. The detection of hydrated calcium chloroaluminate and carboaluminate compounds mostly at binder-aggregate interfaces provides evidence for the onset of pozzolanic reactions during mortar production as further confirmed by the presence of ceramic fragments in the aggregate fractions intentionally added by the fort builders to increase the hydraulic properties of the mortars. The higher mechanical strength and greater resistance to degradation processes imparted by these pozzolanic compounds could explain why, despite the extreme proximity of the investigated sites to the sea, salt weathering processes do not appear to have significantly affected the studied mortars.

Historical mortars from sixteenth to seventeenth century military forts located at the mouth of the Tagus River in Lisbon have been characterized by polarized light microscopy (PLM), thermal analysis (TG/DTA), X-ray diffractometry (XRD) and scanning electron microscopy + energy dispersive spectroscopy (SEM + EDS). The results indicate that the mortars used were all hydraulic lime-based. The presence of well-rounded lime lumps indicates a limited use of water during the lime hydration process. The detection of hydrated calcium chloroaluminate and carboaluminate compounds mostly at binder-aggregate interfaces provides evidence for the onset of pozzolanic reactions during mortar production as further confirmed by the presence of ceramic fragments in the aggregate fractions intentionally added by the fort builders to increase the hydraulic properties of the mortars. The higher mechanical strength and greater resistance to degradation processes imparted by these pozzolanic compounds could explain why, despite the extreme proximity of the investigated sites to the sea, salt weathering processes do not appear to have significantly affected the studied mortars.

In this work, we present the results of an analytical method developed for detailed pigment identification, stratigraphy, and degradation of the paint layers of mural paintings applied in the study of the 17th century frescoes from the Misericordia Church of Odemira (Southwest Portugal). In situ X-ray fluorescence spectrometry analyses were performed on three panels of the mural paintings and complemented by colorimetric measurements. The different color areas were also sampled as microfragments (approx. 1 mm2)that were studied as taken or mounted in epoxy resin to expose the different paint layers. The microfragments of paint layers and their cross sections were characterized by optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. Furthermore, elemental analysis was obtained with spatially resolved confocal synchrotron radiation micro-X-ray fluorescence spectrometry performed at ANKA synchrotron FLUO beamline. Occasionally, phase analysis by micro-X-ray diffraction was also performed. Results from the different techniques allowed pigment identification and, in some cases, the evaluation of color changes due to degradation processes and, considering the Southern Portugal geology, the identification of their possible provenance. The pigments used were essentially yellow, brown and red ochres, smalt blue, copper green, and black earths, probably from local sources.

An electrochemical study of prestressed steel in saturated Ca(OH)2 aqueous solutions (pH 12) was carried out in the absence and in the presence of chloride ions, in such a concentration that simulates the composition of seawater. Cyclic voltammetry, linear sweep voltammetry, open circuit potential transients, atomic absorption spectroscopy and scanning electron microscopy coupled to electron diffraction spectroscopy were employed. The linear polarisation curves analysis led to the determination of polarisation resistance, Rp, corrosion potential, Ecorr, corrosion current density, jcorr, Tafel slopes, breakdown potential, Eb and repassivation potential Erepass. A linear dependence of the breakdown potential, Eb, on the square root of scan rate was obtained, according to the Point Defect Model (PDM). A crossover characteristic of the nucleation processes was observed in the presence of chloride ions. SEM/EDS studies revealed, as expected, a strong influence of the presence of chloride ions observed in the transpassive and the active regions. In conclusion, chloride ions contribute to enhance the corrosion of steel, most probably due to their adsorption on both the active and the passive electrode surfaces.

Os revestimentos interiores de paredes e tectos dos edifícios antigos portugueses têm sido raras vezes objecto de estudo, verificando-se um desconhecimento quase total dos materiais que entram na sua constituição. Neste estudo são apresentados os resultados da caracterização dos revestimentos interiores de edifícios portugueses antigos, constituídos por argamassas de cal e de cal e gesso, dos vários períodos da arquitectura nacional, com base na análise de amostras de vários casos de estudo, localizados em diversas zonas do País e pertencentes a épocas diferenciadas (romano, árabe, barroco e pós-barroco).

Alentejo religious buildings reflect undoubtedly the history and character of this southern Portugal region. These buildings conservation requires a deep knowledge of their masonry’s and renders’ lime mortars, to evaluate correctly their state of conservation, to avoid progression of pathological situations and to plan efficient interventions, with repair and substitution materials with similar characteristics. In this article we present a synthesis of the main results obtained in the mortars characterization of religious buildings from Alentejo, which include Évora and Elvas Cathedrals, Mértola Mosque and the church of Amieira do Tejo. For each monument, several samples were collected from different sites and a set of tests was carried out, including chemical, mineralogical and microstructural, as well as physical and mechanical tests. The tested mortars correspond to different phases of construction and interventions on the buildings, comprising mainly origin periods from the 12th to the 18th century; hence exhibited significant differences in composition and in application techniques. The obtained results of composition have given important information about the provenance of the materials used, including binder and sand types, and also about decay products and their correlation with the mortar’s conservation state, which gave important clues on the repair strategy to adopt.

A common degradation phenomenon in historical renders is the cohesion loss of the binder:aggregate system, which is often linked to the presence of soluble salts. Cohesion is recovered through the application of consolidant products, being inorganics preferred due to their compatibility and durability. The aesthetic function can be restored by chromatic reintegration. The aim of this paper is the assessment of the durability of consolidation and chromatic reintegration treatments applied on renders when exposed to marine environment. Mortar specimens with a simulated loss of cohesion were consolidated with commercial nanolimes, which were considered due to their stability and compatibility. Their combined application with ethyl silicate guarantees some benefits. Chromatic reintegration treatments were obtained by mixing pigments in the consolidant products. After treatments, dissolution-crystallization cycles were performed with a sodium chloride solution. Consolidation effects were monitored. Physical characterization was performed on specimens before and after contamination and the results were discussed.

Organic-inorganic hybrid (OIH) sol-gel coatings based on ureasilicate gels present promising characteristics to be used as eco-friendly coatings for hot dip galvanized steel (HDGS), in contact with cementitious media, allowing to mitigate the harmful effects of an initial excessive reaction between cement pastes and the zinc. The long term performance of HDGS reinforcement coated with OIHs and embedded in concrete, in the presence of chloride ions is, however, unknown. In this paper, the behavior of HDGS, coated with five ureasilicate hybrid coatings, in chloride-contaminated simulated concrete pore solution, was assessed by electrochemical measurements. HDGS plates, with an average Zn layer thickness of 16 ?m, were used. OIH sol-gel coatings were produced and deposited on the substrate by dip coating method. The ureasilicate matrices, U(X), were synthesized according to the literature. Concrete pore simulated solutions were prepared by the addition of 0.2 M KOH to a Ca(OH)2 saturated solution. Coatings performance was evaluated by polarization resistance, macrocell current density and polarization curves. SEM/EDS analyses of the coatings were also performed, before and after the tests. The results showed that the HDGS samples coated with the OIH coatings presented enhanced corrosion resistance to chloride ions, when compared to uncoated galvanized steel.

A kinetic based comparison between expansion tests for alkali-aggregate reactivity was carried out deriving critical rates from test criteria, in an earlier paper. The present paper checks the assumptions and models of such earlier comparison against results with real aggregates varying in alkali reactivity. Using the same approach, for each aggregate, expansion rates for three expansion tests were estimated, corrected for alkalinity and depicted as an Arrhenius plot. The relationship used data from NF P18-590, ASTM C 1260 and ASTM C 227 tests and shows linear Arrhenius plots for several aggregates, aligned almost parallel to the line obtained for test criteria. Aspects related to the different experimental conditions on test-methods and their effects are discussed. The proposed conclusion is that both standards and aggregate results, at the given conditions, are not inconsistent under the kinetic point of view. Some suggestions are made for improving the accuracy of the relationship obtained.

As construções históricas são testemunhos físicos da história de um País mas também repositórios de conhecimentos científicos e técnicos e, em muitos casos, exemplos do gosto e da arte de uma época. O estudo dos materiais e das técnicas empregues desvenda informações importantes sobre a história construtiva e as condições em que ocorreu a sua evolução no tempo. No caso dos Fortes das Linhas de Torres os estudos experimentais realizados incidiram sobre os principais materiais de construção: argamassas e terras. Trata-se de materiais porosos e heterogéneos, com características dependentes não só das matérias-primas mas também dos processos de execução e alteráveis sob a ação do clima, do ambiente, do homem; por isso esses materiais evolutivos guardam uma “impressão digital” do seu percurso no tempo, apenas parcialmente legível por quem a saiba interpretar. As argamassas foram usadas principalmente nas zonas dos Fortes que exigiam maior resistência mecânica, segurança e durabilidade, como é o caso dos paióis. Os resultados dos ensaios realizados revelaram que se trata em todos os casos de argamassas de cal aérea, terra e agregados siliciosos e por vezes também calcários. Apesar da semelhança geral dos materiais, as argamassas são bem diferenciadas de Forte para Forte. As terras recolhidas das muralhas e dos través revelaram o uso de materiais locais e em alguns casos variação textural vertical, relacionada com os recursos terrosos disponíveis e mais facilmente escaváveis. Os estudos realizados permitiram conhecer as estratégias usadas na construção dos Fortes, e poderão ser mais desenvolvidos em futuras colaborações com as entidades envolvidas na recuperação e/ou manutenção e na valorização e divulgação das estruturas das Linhas de Torres.

Service life, in alkali-silica reaction (ASR) affected concretes, is reached when expansions no longer allow normal use of a structure. ASR expansions are detected only after a long period, accelerating after that, similarly to reactions having an induction period in Chemical Kinetics This study deals with service life as a conventional induction time, and uses kinetic methods in its estimate. The classical Unreacted Shrinking Core (USC) model with diffusion control and induction time was selected among other models. Both plane and spherical interfaces were considered adapting their models to expansion data. ASTM C 1260 setup and test conditions were selected, its near constant alkalinity being closer to initial conditions in concrete. Mortar bars prepared with a reactive Tagus river aggregate were tested at temperatures of 80, 70, 60, 50 and 37ºC. Plane and spherical expansion models were fitted to the isothermal curves obtained; depicting their kinetic parameters in Arrhenius plots suggests the spherical model as better. The main interest of this study is to, in what concerns the potential for alkali-silica Reaction (ASR), discuss and foresee possible problems allowing to schedule monitoring and/or the needs of adequate interventions at a stage as early as possible. The extension of service life allows savings in raw materials and energy, improvement of the investment economics and, on a long term basis, lower investment requirements, contributing to an improvement of the sustainability of all related sectors.

This paper compares expansion model estimates and experimental data. In an earlier paper, a diffusion controlled topochemical model fitted to isothermal curves yielded kinetic parameters (induction time and kinetic constant). Linear regression of their Arrhenius plots modelled the constants dependence on temperature, allowing to predict induction times at given temperatures and times in laboratory. Comparing expansions thus estimated with experimental values at 37 ºC in mortar-bars immersed in 1M NaOH solution ASTM C 1260 adapted test, the expansion start matched the modelled induction time. The experimental and modeled expansion after that time follow different patterns. The model may use known correlations for correcting for different alkalinities and humidity’s,. The model possibilities were checked with published data on ASR-affected concrete . The estimates matched real values despite high errors in statistical processing and environment data. Improvements are proposed for reducing errors, in modeling major factors , and application to other cases.

Coimbra é uma cidade milenar, de elevado valor histórico e arquitetónico, hoje classificada como Património Mundial pela UNESCO (Alta de Coimbra e Universidade). Nas zonas históricas de Coimbra, encontram-se ainda, edifícios medievais em bom estado de conservação. No entanto, os revestimentos e acabamentos históricos, que perduraram ao longo dos séculos, têm vindo recentemente a ser substituídos, perdendo-se assim testemunhos únicos dos materiais e técnicas tradicionais de construção. No âmbito do Projeto “Os revestimentos e os acabamentos nos centros históricos entre tradição e modernidade - bases para um plano de ação e de salvaguarda do Centro Histórico de Coimbra (CHC) – PTDC/AUR-URB/113635/2009”, que tem como objetivo geral a análise dos revestimentos, das superfícies arquitetónicas, das suas cores, texturas e outros elementos que marcam a imagem urbana do Centro Histórico de Coimbra, foi realizada uma caracterização e avaliação do estado de conservação de amostras de argamassas de revestimentos de alguns edifícios do CHC. Na presente comunicação apresenta-se o estudo realizado no Laboratório Nacional de Engenharia Civil (LNEC) sobre os revestimentos de um número limitado de edifícios históricos, que foram considerados representativos dos principais tipos de revestimentos do CHC. Descreve-se sucintamente a metodologia utlizada para a análise da constituição e composição dos revestimentos e para a avaliação do seu estado de conservação; são ainda descritas as amostras selecionadas e os ensaios realizados, e apresentam-se e interpretam-se os resultados dos ensaios efetuados e extraem-se conclusões. Os resultados da caraterização da composição dos revestimentos mais antigos mostraram que o ligante usado é de cal aérea, predominantemente de origem dolomítica. Constatou-se que as argamassas, cuja estratigrafia indica serem mais recentes, são à base de cal aérea calcítica. Em termos do tipo de areia empregue verificou-se ser sempre de natureza siliciosa, embora com variações em termos de mineralogia e granulometria de amostra para amostra. Nas amostras de argamassa mais antigas foram detetados vários produtos de neoformação (nomeadamente resultantes da ação da água e de reações da cal com agregados alterados) e ausência de produtos de degradação, apresentando estas resistências mecânicas e coeficientes de capilaridade compatíveis com argamassas antigas de cal em bom estado de conservação, o que fundamenta a recomendação de se optar pela sua preservação e manutenção. Este conhecimento, além da sua importância como registo histórico, deverá fundamentar o plano de conservação dos revestimentos.

A ocorrência de reações álcalis-sílica (RAS) em estruturas de betão foi reconhecida pela primeira vez em Portugal no início da década de 90 do século passado. Desde então um grande volume de trabalho tem vindo a ser desenvolvido com o objetivo de estudar os agregados para betão, criar medidas preventivas da reação, monitorizar e reparar as estruturas afetadas. No presente trabalho resume-se o estudo realizado para a caracterização de oito granitos portugueses provenientes de pedreiras atualmente em exploração para obtenção de agregados para betão. A caracterização seguiu os procedimentos previstos nas normas nacionais e internacionais em vigor e incluiu um conjunto de ensaios que se distribuem em dois métodos principais: petrografia com análise petrográfica; ensaios de expansão envolvendo a produção de barras de argamassa e prismas de betão expostos a diferentes condições ambientais. Os ensaios permitiram determinar a reatividade potencial de alguns destes agregados e tecem considerações sobre possíveis modificações a propor na revisão das normas nacionais.

Coating an aluminium alloy in building and automotive industries requires its surface pre-treatment to promote adherence of the organic coating. Chromate based chemical conversion layers (CCC) have been extensively used for that purpose since they not only provide very good adhesion of organic coatings, but also afford corrosion protection, both by barrier and self-healing effect. However, the use of these surface treatments has been under severe restrictions in the European Community due to Cr (VI) toxicity and carcinogenic effects. Within building industry, several “green” alternative inorganic treatments are already being applied, but they lack the anticorrosive action of the Cr(VI) compounds. Coating via the sol-gel process has been pointed out as a promising environmentally friendly alternative to chromate pre-treatments. This type of coatings, namely the organic-inorganic hybrid sol-gel silane based ones provide corrosion protection by barrier effect and when corrosion inhibitors are incorporated in their structure active protection is conferred as well. The sol-gel coating is also able to promote adherence between the metallic substrate and an organic top layer. In this work, several organic-inorganic hybrid (IOH) sol-gel coatings with different organic content were synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide (TPOZ) precursors by the sol-gel process. Cerium nitrate was added during synthesis to be incorporated in the final coating and act as corrosion inhibitor. The synthesized OIH coatings were applied on EN AW-6063 alloy by dip-coating. The corrosion protection performance of coatings was evaluated in chloride medium by means of Electrochemical Impedance Spectroscopy (EIS) and by Salt Spray Test (NSS). A solely inorganic zirconium based sol-gel coating was also prepared and tested for comparison. The chemical composition with depth was analysed by means of Glow Discharge Optical Emission Spectroscopy (GDOES) and the thickness of coatings was estimated based on elemental depth profiles. Finally the aluminium alloy coated samples were bent to evaluate coatings adhesion to the substrate. The morphology of the aluminium coated samples after corrosion and deformation tests was observed by scanning electron microscopy (SEM-EDS). Electrochemical measurements provided evidence that the hybrid sol-gel coatings are much more corrosion protective than the solely inorganic ones. Additionally, it was observed that an increase in the organic content by the introduction of the epoxysilane in the coating formulation improves its corrosion resistance, but above a certain limit is detrimental to coating adherence, as shown by the bending test. The Salt Spray test confirmed EIS ranking of coatings’ corrosion resistance. GDOES elemental profiling revealed that sol-gel coatings thickness increases with organic content. However, this had not necessary implied a better corrosion behaviour. The best corrosion performance was achieved by the hybrid coating with a Zr/Si molar ratio of 0.26.

Although the use of HDGS (hot-dip galvanized steel) in reinforced concrete structures shows improved corrosion resistance due to the presence of the zinc layer, when in contact with fresh concrete is strongly affected by the hydrogen evolution. Surface treatments such as chromate conversion layers are usually used to prevent this initial corrosion process which involves the use of reagents that have high impact in environment and ecosystems. In this work sol-gel process was used to produce environmental friendly corrosion protection coatings based on organic-inorganic hybrid (OIH) gels with embedded corrosion inhibitor agents. The corrosion behavior of HDGS samples coated with different ureasilicate based gels doped with distinct inhibiting ionic species: sodium heptamolibdate, potassium hidrogenofosphate, K2HPO4 and zinc nitrate, Zn(NO3)2 – were tested in contact with simulate concrete media, by monitoring the current variation with the time. The electrical properties of the used OIH gels were characterized to allow the correlation of the data obtained by the two techniques (polarization curves and impedance). Both OIH gel films and coatings were prepared and HDGS coated samples were characterized according to the procedure reported in the literature.

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.

Vários

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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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.

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.