Environmental life cycle assessment of concrete made with fine recycled concrete aggregates

The majority of worldwide structures use concrete as its main material. This happens because concrete is economically feasible, due to its undemanding production technology and case Of use. However, it is widely recognized that concrete production has a strong environmental impact in the planet. Natural aggregates use is one of the most important problems of concrete production nowadays, since they are obtained from limited, and in some countries scarce, resources. In Portugal, although there are enough stone quarries to cover coarse aggregates needs for several more years, Supplies of fine aggregates are becoming scarcer, especially in the northern part of the country. On the other hand, as concrete structures' life cycle comes to an end, an urgent need emerges to establish technically and economically viable solutions for demolition debris, other than for use as road base and quarry fill. This paper presents a partial life cycle assessment (LCA) of concrete made with fine recycled concrete aggregates performed with EcoConcrete tool. EcoConcrete is a tailor-made, interactive, learning and communications tool promoted by the Joint Project Group (JPG) on the LCA of concrete, to qualify and quantify the overall environment impact of concrete products. It consists of an interactive Excel-spreadsheet in which several environmental inputs (material quantities, distances from origin to production Site, production processes) and outputs (material, energy, emissions to air, water, soil or waste) are collected in a life cycle inventory, and are then processed to determine the environmental impact (assessment) of the analysed concrete, in terms of ozone layer depletion, smog or "greenhouse" effect

Durability performance of concrete made with fine recycled concrete aggregates

Fine recycled aggregates are seen as the last choice in recycling for concrete production. Many references quote their detrimental influence on the most important characteristics of concrete: compressive and tensile strength; modulus of elasticity; water absorption; shrinkage: carbonation and chloride penetration. These two last characteristics are fundamental in terms of the long-term durability of reinforced or prestressed concrete. In the experimental research carried out at IST, part of which has already been published, different concrete mixes (with increasing rates of substitution of fine natural aggregates sand - with fine recycled aggregates from crushed concrete) were prepared and tested. The results were then compared with those for a reference concrete with exactly the same composition and grading curve, but with no recycled aggregates. This paper presents the main results of this research for water absorption by immersion and capillarity, chloride penetration (by means of the chloride migration coefficient), and carbonation resistance, drawing some conclusions on the feasibility of using this type of aggregate in structural concrete, while taking into account any ensuing obvious positive environmental impact

Verificação probabilística da segurança das estruturas

Neste artigo, abordam-se as técnicas probabilísticas desenvolvidas para a anáilse da segurança de estruturas: as metodologias baseadas nas técnicas clássicas de fiabilidade, nomeadamente os métodos do segundo momento, de primeira (FORM) e de segunda ordem (SORM), e as baseadas nas técnicas de simulação numérica. Destas últimas, que são as de uso mais divulgado, destaca-se o chamado método de Monte Carlo, em relação ao qual se apresentam ainda alguns métodos para redução da variância

The impact of the 2008 and 2010 financial crises on international stock markets: Contagion and long memory

Nesta tese estudamos os efeitos de contágio financeiro e de memória longa causados pelas crises financeiras de 2008 e 2010 em alguns mercados acionistas internacionais. A tese é composta por três ensaios interligados. No Ensaio 1, recorremos à teoria das cópulas para testar a existência de contágio e revelar os canais “investor induced” de transmissão da crise de 2008 aos mercados da Bélgica, França, Holanda e Portugal (grupo NYSE Euronext). Concluímos que existe contágio nestes mercados, que o canal “portfolio rebalancing” é o mecanismo mais importante de transmissão da crise, e que o fenómeno “flight to quality” está presente nos mercados. No Ensaio 2, usando novamente modelos de cópulas, avaliamos os efeitos de contágio provocados pelo mercado acionista grego nos mercados do grupo NYSE Euronext, no contexto da crise de 2010. Os resultados obtidos sugerem que durante a crise de 2010 apenas o mercado português foi objeto de contágio; além disso, conclui-se que os efeitos de contágio provocados pela crise de 2008 são claramente superiores aos efeitos provocados pela crise de 2010. No Ensaio 3, abordamos o tema da memória longa através do estudo do expoente de Hurst dos mercados acionistas da Bélgica, E.U.A., França, Grécia, Holanda, Japão, Reino Unido e Portugal. Verificamos que as propriedades de memória longa dos mercados foram afetadas pelas crises, especialmente a de 2008 – que aumentou a memória longa dos mercados e tornou-os mais persistentes. Finalmente, usando cópulas mais uma vez, verificamos que as crises provocaram, em geral, um aumento na correlação entre os expoentes de Hurst locais dos mercados foco das crises (E.U.A. e Grécia) e os expoentes de Hurst locais dos outros mercados da amostra, sugerindo que o expoente de Hurst pode ser utilizado para detetar efeitos de contágio financeiro. Em síntese, os resultados desta tese sugerem que comparativamente com períodos de acalmia, os períodos de crises financeiras tendem a provocar ineficiência nos mercados acionistas e a conduzi-los na direção da persistência e do contágio financeiro.In this thesis we study the effects of financial contagion and long memory caused by the 2008 and 2010 financial crises to some international stock markets. The thesis consists of three connected essays. In Essay 1, we use copula models to test for financial contagion and to unveil investor induced channels of financial contagion to the Belgian, French, Dutch and Portuguese stock markets (NYSE Euronext group), in the context of the 2008 crisis. We find that contagion is present in these markets, the "portfolio rebalancing" channel is the most important crisis transmission mechanism, and the "flight to quality" phenomenon is also present in the markets. In Essay 2, using copula models again, we assess contagion effects of the Greek stock market to the markets of the NYSE Euronext group, in the context of the 2010 crisis. Our findings show that, during the 2010 crisis, contagion existed only in the Portuguese market, and that contagion effects of the 2008 crisis were clearly more intense than those caused by the 2010 crisis. In Essay 3, we address the subject of long memory by studying the Hurst exponents of stock markets of Belgium, France, Greece, Japan, the Netherlands, Portugal, UK and US. We find that the long memory properties of the markets were affected by the crises, especially the 2008 crisis – which moved markets towards long memory and persistence. Finally, we use copula models once more to observe that crises caused, in general, an increase in correlation between the local Hurst exponents of the markets of origin of the crises (US and Greece) and the local Hurst exponents of the other markets, suggesting that the Hurst exponent can be used in the assessment of financial contagion. In summary, the results of this thesis suggest that compared to tranquil periods, the crisis periods tend to cause inefficiency in stock markets and to lead the markets towards persistence and financial contagion

The influence of curing conditions on the mechanical performance of concrete made with recycled concrete waste

Research on the use of Construction and Demolition Waste (CDW) as recycled aggregate (in particular crushed concrete) for the production of new concrete has by now established the feasibility of this environmentally-friendly use of otherwise harmful waste. However, contrary to conventional concrete (CC), no large applications of concrete made with recycled concrete have been made and there is still a lack of knowledge in some areas of production and performance of recycled aggregate concrete (RAC). One issue concerns curing conditions: these greatly affect the performance of concrete made on site and some potential users of RAC wonder how RAC is affected by far-from-ideal curing conditions. This paper shows the main results of experiments to determine the influence of different curing conditions on the mechanical performance of concrete made with coarse recycled aggregate from crushed concrete. The properties analyzed include compressive strength, splitting tensile strength, modulus of elasticity, and abrasion resistance. The general conclusion in terms of mechanical performance is that RAC is affected by curing conditions roughly in the same way as CC. (C) 2011 Elsevier Ltd. All rights reserved

Development of a penetration test for timber impregnation products for use in old buildings

This paper studies the application of commercial biocides to old maritime pine timber structures (Pinus pinaster Ait.) that have previously been impregnated with other products. A method was developed in the laboratory to be used in situ to determine the impregnation depth achieved by a new generation biocide product applied to timber from an old building. This timber had once been treated with an unknown product difficult to characterize without extensive analysis. The test was initially developed in laboratory conditions and later tested on elements of the roof structure of an 18th century building. In both cases the results were promising and mutually consistent with penetration depths for some treatments reaching 2.0 cm. The application in situ proved the tests viability and simplicity of execution giving a clear indication on the feasibility of possible re-treatments

Mechanical performance of lap joints of flat roof waterproofing membranes subjected to artificial weathering

The flat roof of a building, here understood as the whole of every construction element from the ceiling to the surface exposed to climatic agents, is made of a set of horizontal or quasi-horizontal layers that satisfy its functional demands. The waterproofing layer is fundamental in most flat roofs and, of the various options, single-layer systems made of prefabricated membranes and mechanically fastened are one of the most frequently used in Portugal. This solution is also used to repair roofs’ waterproofing systems without having to remove the existing layers, thus reducing the cost. However, it is well known that the performance of these systems is strongly influenced by the efficiency of the membrane fastenings, which is directly related to the membranes’ nature and the design and execution of the lap joints. Many of the anomalies that occur are related to the deficient execution of the membranes’ lap joints1–3 and the consequent faulty performance when subjected to average environmental agents. Studies undertaken in Portugal on the behavior of lap joints in membranes made or commercialized in this country4,5 have corroborated other studies in this area and shown that certain membranes perform worse than others when used in single-layer systems. Three different solutions were tested: amyloid precursor protein (APP)- and Styrene-Butadiene-Styrene (SBS)-modified bituminous membranes and polyvinyl chloride (PVC) membranes. Of the bituminous membranes, the SBS ones produced and commercialized in Portugal presented, as expected, much more satisfactory mechanical characteristics than the APP ones, thus justifying a more thorough study of their suitability for use in mechanically fastened single-layer systems.info:eu-repo/semantics/publishedVersio

Building Thermal Envelope

This book results from a Special Issue published in Energies, entitled “Building Thermal Envelope"". Its intent is to identify emerging research areas within the field of building thermal envelope solutions and contribute to the increased use of more energy-efficient solutions in new and refurbished buildings. Its contents are organized in the following sections: Building envelope materials and systems envisaging indoor comfort and energy efficiency; Building thermal and energy modelling and simulation; Lab test procedures and methods of field measurement to assess the performance of materials and building solutions; Smart materials and renewable energy in building envelope; Adaptive and intelligent building envelope; and Integrated building envelope technologies for high performance buildings and cities

Reliability of in-situ diagnosis in external wall renders

This study focuses on the reliability of in-situ diagnosis performed on external rendered façades. This analysis was based on a set of parameters drawn from different visual observation, in-situ and laboratory testing techniques. The results were collected based on the previous inspections of 98 rendered façades of buildings and individual testing walls with different components, ages and degradation types. For that purpose, a reliability indicator was proposed and applied for better results interpretation of multiple testing techniques. In each case study, the parameters with higher reliability are defined. The final reliability indicator was established based on the average of three partial indicators, namely a reliability indicator for the established base criteria' uncertainty in laboratory testing (reference reliability indicator); a reliability indicator for the assessment techniques' uncertainty (verification method reliability indicator); and a reliability indicator for the results' uncertainty (number of the tests and their accuracy; reliability indicator of results obtained in-service). The reference parameters for each testing technique were synthesised. The relevant aspects, such as uncertainty associated with the reference parameter and type of verification method (quantitative, qualitative, and intervals), were defined. The analysis of the relationships between the parameters (exemplified for mechanical properties) and their correlation coefficients were assessed. Selection matrices were proposed that qualitatively identify the set of parameters that contribute to indirectly analyse the characteristics and performance relevant to the behaviour of the renders applied on façades. (c) 2020 Elsevier Lt