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- Recomendações para a incorporação de agregados resultantes de RCD em betões de ligantes hidráulicos – Um contributoPublication . Oliveira, Miguel José; Lança, RuiNeste artigo apresentam-se recomendações técnicas gerais, com base nos resultados obtidos no âmbito do projeto de investigação “30307 – MULTIVALOR RCD – Otimização do Processo de Valorização de Resíduos de Construção e Demolição por Caracterização Mecânica, Física, Química e Ambiental”. As recomendações aqui apresentadas são relativas às medidas necessárias para incorporar os agregados resultantes de RCD em betões de ligantes hidráulicos. Pretende-se contribuir para a criação de condições mais favoráveis para a produção de agregados reciclados comerciáveis, respeitando os requisitos da regulamentação europeia em vigor. Procura-se assim produzir agregados reciclados que conduzam a betões mais sustentáveis e que ao mesmo tempo apresentem características de estabilidade, deformabilidade e durabilidade aceitáveis. O trabalho desenvolvido no âmbito do projeto permitiu identificar oportunidades de melhoria em todas as fases. Nomeadamente na fase de demolição, processamento e armazenamento, assim como na fase de produção do betão a partir das características intrínsecas dos agregados reciclados. São ainda apresentadas reflexões para a prescrição do betão com agregados reciclados em fase de projeto.
- Evaluating the potential of adaptive comfort approach using historic data to reduce energy consumption in buildings in southern SpainPublication . Bienvenido-Huertas, David; Rubio-Bellido, Carlos; Farinha, Fátima; Oliveira, Miguel José; Pérez-Ordóñez, Juan LuisThe application of adaptive comfort models is among the determinant factors to reduce greenhouse gas emissions in the building sector. This research studies the region of Andalusia (south of Spain). A cluster analysis is applied to 786 Andalusian municipalities, and 4 groups are established according to the potential of adaptive strategies. A town is chosen from each group, and an hourly specific study is conducted for the last 20 years, as well as a daily study of the old time series by using an artificial neural network based on the existing climate data. The possibility of application of the EN 16798-1:2019 standard during the days of the year is analysed, as well as the possibilities of using natural ventilation and the possibility of using adaptive setpoint temperatures in comparison with both 3 fixed heating temperatures and 3 fixed cooling temperatures by considering the energy saving. The results to apply the standard ranged 69.0 and 100% of the days of each year. The possibilities of natural ventilation considered were greater than 10% of the hours of the year in all the assumptions. The energy saving of cooling degrees reveals a greater potential in the area studied than that of heating degrees; this tendency is supported by the study of old temporary series which are part of the climate variation predicted throughout the 21st century.
- In-situ disinfection of wastes generated in dwellings by utilizing ozone for their safe incorporation into the recycling chainPublication . Marín-García, David; Bienvenido-Huertas, David; Moyano, Juan; Oliveira, Miguel JoséThe Covid-19 pandemic has certainly changed behaviour patterns in many aspects of life, such as the management of solid wastes inside residential spaces. The goal of this research work is to study an ozone generator device as a disinfection and sterilization tool for these wastes in dwellings themselves, thus re-establishing the selective collection to take them back to the recycling chain. In addition, an approach to the risk verification is made. The methodology is based on an experimentation with a device designed to be as cheap as possible. A room like a bedroom is used as a test bed to apply the device, but with no people inside the room to avoid risks. The results show that the device is feasible, concluding that risks are acceptable if its use is correct and appropriate equipment is available to be applied and controlled, all without prejudice of the rigorous control by the competent authorities that approve its use.
- Legal regulation of ventilation rates in homes in Europe 2010–2022: Evolution and comparison study regarding Covid-19 recommendationsPublication . González-Sancha, Rafael; Marín-García, David; Duarte-Pinheiro, Manuel; Oliveira, Miguel JoséThe airborne transmission of SARS-CoV-2, the virus that causes Covid-19 disease, has been recognized as an essential route of contagion, so adequate ventilation is vital indoors. For this reason, the research goal focuses on carrying out the study and evolutionary and comparison analysis of the regulation of ventilation rates in dwellings in Europe (2010-2022) and on determining whether modifications are necessary for the said regu-lation based on the recommendations of competent international organizations. To do this, the methodology followed initially starts from the study carried out in 2010 by Christine Dimitroulopoulou, in which the existing regulation in various European countries regarding ventilation in dwellings was studied. Once this study has been analysed, it continues to update and compare the regulation of the different European countries cited in the said work, detecting during the process if a modification is necessary based on the recommendations indicated by international organizations such as the WHO or ECDC. The results and conclusions indicate that few countries have significantly changed their ventilation rates. Although the existing ones may be admissible, requiring controlled ventilation in the different regulations would be convenient.
- Microcimento: normalização e patologia construtivaPublication . Oliveira, José Miguel; Marçal Gonçalves, Marta; Renda, JorgeQuando novos materiais aparecem no mercado, a falta de normalização e uma eventual maior dificuldade na altura da aplicação podem originar patologias. É o caso do microcimento, que é um material de base cimentícia com um tamanho de grão menor que o cimento comum. Em termos comerciais, a designação de microcimento aplica-se a um sistema de materiais multicamadas, em que as argamassas modificadas por polímeros fazem parte e que, no final da aplicação, constituem um único revestimento contínuo. Tem uma espessura total muito fina e está aumentando a cota de mercado, principalmente na execução de revestimentos de pisos, paredes e tetos interiores. O seu uso também ocorre em elementos exteriores, incluindo revestimentos de móveis urbanos e paredes de piscinas. Com base num caso de estudo sobre a aplicação de um revestimento de microcimento, descrevemos as principais anomalias construtivas observadas e identificamos as causas prováveis. Foi realizado um breve estudo dos produtos comercializados em Portugal, bem como uma revisão da bibliografia específica e normalização aplicável. Da análise realizada, verificou-se que grande parte deste material é comercializado em Portugal sem atender aos requisitos da legislação portuguesa e europeia. Além disso, as informações técnicas fornecidas pela maioria dos fabricantes e comerciantes eram insuficientes. A formação prática dos aplicadores também é considerada essencial. Onão cumprimento de determinados requisitos em alguns materiais de construção e seus aplicadores pode levar a uma maior ocorrência de patologias, que, além dos aspetos estéticos, afetarão a funcionalidade, a durabilidade das soluções e a sustentabilidade dos edifícios.
- Strategies to mitigate shrinkage in self-compacting concretePublication . Oliveira, Miguel; Ribeiro, Antonio Bettencourt; Branco, Fernando GarridoO betão auto-compactável (BAC) apresenta propriedades especiais, que justificam a sua preferência em muitas aplicações. No entanto, são conhecidos vários casos de comportamento inadequado, devido principalmente ao comportamento deficiente deste material durante o processo de hidratação e secagem. A retração tem uma importância significativa na conceção, dimensionamento, processo construtivo e comportamento em serviço das estruturas de betão. As exigências normativas não consideram de forma adequada a influência dos fatores existentes. Além disso, a possibilidade de utilização de novos materiais limita fortemente a aplicação do conhecimento existente. De modo a contribuir para a resolução de uma das principais desvantagens deste material – a sua elevada retração, foi realizada uma campanha de ensaios, tendo em vista a avaliação dessa propriedade. Foi dada especial importância à utilização de adjuvantes redutores de retração e adições expansivas. Com base nos resultados obtidos foi possível avaliar a eficiência da utilização desses materiais. Obtiveram-se melhoramentos que permitiram formular uma hierarquização das estratégias de mitigação utilizadas.
- Sustainable competitiveness of tourism in the Algarve region. Critical stakeholders’ perception of the supply sectorPublication . Farinha, Fátima; Bienvenido-Huertas, David; Duarte Pinheiro, Manuel; Da Silva, Elisa Maria De Jesus; Lança, Rui; Oliveira, Miguel José; Batista, RicardoThe Algarve region, located in the south of Portugal, is a well-known tourism destination that seeks to be sustainable and competitive. The local administration looks to establish a collaborative network, where stakeholders take a crucial role. The research aims to appeal to the accommodations and food services stakeholders to have a shared vision of the issues and priorities related to sustainable tourism development. Their perception is a critical factor in making decisions regarding the region’s competitiveness. Algarve’s two major and leading associations of the tourism supply sector AIHSA and AHETA were invited to participate in the study. Based on the responses of an online questionnaire, an artificial intelligence algorithm was applied to the data to identify the common and divergent aspects. The conceptual model developed is based on a simplified model of psychological ownership. The results highlight a convergent perspective regarding sustainability challenges, namely, natural resources and biodiversity, safety, and supply chain. However, hotels and restaurants do not reflect the same perception regarding sustainability initiatives, e-tourism, or free internet access. These divergences are essential results since they indicated which issues require local authorities’ priority intervention.
- Strategies to mitigate shrinkage in an intermediate strength self-compacting concretePublication . Oliveira, M. J.; Bettencourt Ribeiro, Antonio; Branco, Fernando G.Self-compacting concrete (SCC) is a concrete that does not require vibration for casting and consolidation. It is able to flow under its own weight, completely filling the formwork and achieving full consolidation, even in the presence of congested reinforcement. SCC possesses special technical features and properties that recommend its application in a considerable amount of applications. Nevertheless, an inadequate behavior of the material at early ages has been observed in some situations, due to shrinkage. Shrinkage has a significant importance in the design, construction and in-service performance of concrete structures. The regulatory requirements were derived from experience with traditional concrete, which is not always suitable for SCC. In addition, the option of using new materials, such as binders with large amount of pozzolanic or latent hydraulic additions, strongly limits the validity of existing rules. In order to contribute for a better understanding of the major drawback of this material-its high potential shrinkage, experimental research was carried out using different commercial shrinkage-compensating products. This study focuses on the use of a shrinkage reducing admixture and an expansive agent. The results obtained demonstrate the efficiency of the individual or combined use of these products and allowed identifying three different strategies to control the shrinkage, with distinct levels of efficiency.
- Influence of steel slag type on concrete shrinkagePublication . Rubio-Cintas, Maria Dolores; Parron-Rubio, Maria Eugenia; Perez-Garcia, Francisca; Bettencourt Ribeiro, António; Oliveira, Miguel JoséBuilding construction and building operations have a massive direct and indirect effect on the environment. Cement-based materials will remain essential to supply the growth of our built environment. Without preventive measures, this necessary demand in cement production will imply a substantial increase in CO2 generation. Reductions in global CO2 emissions due to cement consumption may be achieved by improvements on two main areas: increased use of low CO2 supplementary cementitious materials and a more efficient use of Portland cement clinker in mortars and concretes. The use of ground granulated blast furnace slag in concrete, as cement constituent or as latent hydraulic binder, is a current practice, but information of concrete with ladle furnace slag is more limited. Specific knowledge of the behavior of mixtures with steel slag in relation to certain properties needs to be improved. This paper presents the results of the shrinkage (total and autogenous) of five concrete mixtures, produced with different percentages of two different slags in substitution of cement. The results show that shrinkage of concrete with the two different slags diverges. These different characteristics of the two materials suggest that their use in combination can be useful in optimizing the performance of concrete.
- Slag substitution as a cementing material in concrete: mechanical, physical and environmental propertiesPublication . Parron-Rubio, María Eugenia; Perez-Garcia, Francisca; Gonzalez-Herrera, Antonio; Oliveira, Miguel José; Rubio-Cintas, Maria DoloresA circular economy is a current tenet that must be implemented in the field of construction. That would imply the study of the possibilities of the use of waste generated, for obtaining materials the used in construction as replacements for the raw material used. One of these possibilities is the substitution of the cement by slag, which contributes to the reduction of cement consumption, decreasing CO2 emissions, while solving a waste management problem. In the present paper, different types of concrete made by cement substitution with different type of slags have been studied in order to evaluate the properties of these materials. Cement is replaced by slag from different steel mills, both blast furnace and ladle furnace slag. The percentages of slag substitution by cement are 30%, 40% and 50% by weight. Mechanical, physical and environmental properties have been evaluated. Compressive and flexural strength have been analysed as the main mechanical properties. As far as physical properties go, density and porosity tests were be reported and analysed, and from an environmental point of view, a leachate study was performed. It has been found that some kinds of slag (blast furnace slag) are very suitable as substitutes for cement, providing properties above those of the reference concrete, while other types (ladle furnace slag) could be valid for non-structural applications, contributing in both cases to a circular economy.
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