Susceptibility to Expansive Reactions of a Greener UHPC: Micro to Macro-Scale Study

Nowadays, in Europe, several infrastructures, such as bridges, viaducts, and maritime structures, are in an advanced state of degradation. Therefore, novel repair/rehabilitation techniques are sought. Recent advances in ultra-high-performance fibre-reinforced cement-based composites (UHPFRC) represent a significant step towards resilient structures. In addition to their remarkable mechanical properties (compressive strength > 150 MPa), they present extremely low permeability and, as a premise, very high durability. Despite their relatively high cost, UHPFRC can be a competitive solution for rehabilitation/strengthening applications where smaller volumes are needed. UHPFRC applied in thin layers (with or without reinforcement) can replace carbonated and/or cracked concrete acting as a protective watertight and/or strengthening layer. The structural capacity increases (stiffness, ultimate strength), and the durability is expected to improve significantly while keeping cross-sectional dimensions. Additional advantages are expected, such as reduced intervention time, fewer maintenance routines, reduced life-cycle cost, and longer service life. Although much of the focus on UHPFRC has centred on mechanical and/or structural performance, durability is inevitably linked with mechanical properties. The current work evaluated the durability of non-property and greener UHPC concerning expansive reactions, alkali-silica reactions and expansion due to external sulphates, by macro and micro-scale integrative study. Linear expansion tests were performed in UHPC specimens according to ASTM C 1260 and LNEC E−364. At the macro level, no deleterious expansion due to ASR or external sulphate occured. Expansion due to ASR was 0.0018% after 14 days of immersion in an alkali-rich environment, and no expansion was recorded regarding sulphate attack. However, SEM analysis reveals reactive products of ASR and sulphate attack, namely, ASR gel and ettringite, respectively, in UHPC specimens

3D Construction Printing Standing for Sustainability and Circularity: Material-Level Opportunities

Three-dimensional Cementitious materials Printing (3DCP) is a cutting-edge technology for the construction industry. Three-dimensional printed buildings have shown that a well-developed automated technology can foster valuable benefits, such as a freeform architectural design without formworks and reduced human intervention. However, scalability, commercialization and sustainability of the 3DPC technology remain critical issues. The current work presents the ecological fragility, challenges and opportunities inherent in decreasing the 3DCP environmental footprint at a material level (cementitious materials and aggregates). The very demanding performance of printable mixtures, namely in a fresh state, requires high dosages of cement and supplementary cementitious materials (SCM). Besides the heavy carbon footprint of cement production, the standard SCM availability might be an issue, especially in the longer term. One exciting option to decrease the embodied CO2 of 3DCP is, for example, to incorporate alternative and locally available SCM as partial cement replacements. Those alternative SCM can be wastes or by-products from industries or agriculture, with no added value. Moreover, the partial replacement of natural aggregate can also bring advantages for natural resource preservation. This work has highlighted the enormous potential of 3DCP to contribute to reducing the dependence on Portland cement and to manage the current colossal wastes and by-products with no added value, shifting to a Circular Economy. Though LCA analysis, mixture design revealed a critical parameter in the environmental impact of 3DCP elements or buildings. Even though cement significantly affects the LCA of 3DCP, it is crucial to achieving adequate fresh properties and rheology. From the literature survey, mixtures formulated with alternative SCM (wastes or by-products) are still restricted to rice husk ash, Municipal Solid Waste ashes and recycled powder from construction and demolition wastes. Natural aggregate replacement research has been focused on recycled fine sand, mine tailing, copper tailing, iron tailing, ornamental stone waste, recycled glass, crumb rubber, rubber powder and granules, recycled PET bottles and steel slag. However, flowability loss and mechanical strength decrease are still critical. Research efforts are needed to find low-carbon cement replacements and mix-design optimization, leading to a more sustainable and circular 3DCP while ensuring the final product performance

Estudo de argamassas com substituição parcial de cimento por resíduos de vidro moídos

Tese de mestrado integrado. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 201

O fantástico no século XIX: contos escolhidos

Mestrado em Estudos EditoriaisEste projecto propõe-se a produzir uma edição de contos literários com o tema do Fantástico no Século XIX. A criação de um produto atraente e coerente foi tentada através da pesquisa de conteúdo apropriado, complementada pela produção de pequenos textos biográficos para o enquadramento dos autores escolhidos nesta edição. Foi ainda incluída uma proposta gráfica de apresentação do livro, compreendendo a concepção da estrutura interna, a paginação e o design da capa. Desta forma, o projecto apresenta tanto o texto e o raciocínio das escolhas e motivações para a sua escolha numa proposta completa para um livro potencialmente publicável.The objective of this project is to create an edition of literary tales focused on the Fantastic in the 19th century. The establishment of a coherent and attractive product has been attempted through research into appropriate content, supplemented subsequently by the production of small biographical texts for the reader to better understand how the authors fit into this edition. In addition, a proposal with respect to the graphic presentation of the book has been included, dealing with the conception of its internal structure and pagination, along with its cover design. In this manner, the project presents both the text and the rationale behind the text as a complete proposal for a potentially publishable book

The role of social and emotional competence on risk behaviors in adolescence

The purpose of this study was to investigate the relation between social and emotional competence and substance use in adolescence, including tobacco, alcohol and illicit drugs. The sample included 3,494 students, mean age 15 years old, in the 8th and 10th grades of the public school system from Portugal. Data were collected using the Health Behavior in School-aged Children (HBSC) survey. For the purpose of this study, the questionnaire included questions about social and emotional competence and risk behavior, specifically past 30-day tobacco use, drunkenness, and illicit drugs use. Results showed that adolescent social and emotional competence was negatively related to substance use. All social-emotional competence subscales were significantly associated with illicit drug use. In addition empathy, cooperation and communication, and goals and aspirations subscales, were significantly associated with tobacco use. Results demonstrate the potential importance of social and emotional competence in levels of substance use among Portuguese adolescents, and may be used to inform the development of Portuguese substance use prevention programspeer-reviewe