ICI - C-MADE | Documentos por Auto-Depósito
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- Improving the Behaviour of Green Concrete Geopolymers Using Different HEMP Preservation Conditions (Fresh and Wet)Publication . Saez-Perez, Maria Paz; Jorge Alberto, Duran-Suarez; Castro-Gomes, JoãoThis paper evaluates a type of geopolymer concrete that uses hemp fibres as a natural aggregate due to the various advantages offered by these woody materials. These advantages include ease of cultivation and processing and their use in the essential structure of concretes used for green construction purposes. The sampling study was prepared using an environmentally friendly inorganic binder, based on geopolymerization reactions (Si-Na). The improvement in the hemp aggregate using two different preservation methods (fresh and wet) was assessed. The type of conservation enables anaerobic reactions to take place in the structure of the hemp, in such a way as to modify the proportions of the organic compounds contained in the hemp and the morphology of the fibres. It also encourages the proliferation of cellulose nanofibrils (CNC), which enhance the mechanical results, improving plasticity and thixotropy. The hempcrete studied in this paper could be a good alternative material for sustainable, environmentally friendly construction, as much less CO2 is emitted during the production process in comparison with conventional concrete. Using wet-preserved hemp means that less water must be added to the mix during preparation of the concrete. This also helps reduce production costs, and by extension, the cost of the final product.
- Microstructural properties of Asian hornet nest paper-like materials: Preliminary step towards biomimicry materials for civil engineering applicationsPublication . Sedira, Naim; Pinto, Jorge; Gomes, Ana; Nepomuceno, Miguel; Pereira, SandraThis paper presents a comprehensive examination of the microstructure and mineralogy of the paper-like material found in Asian hornet nests (referred to as AHN P-LM) and the nearby tree leaves, utilising scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The analysis conducted through SEM-EDS demonstrates that AHN P-LM is primarily composed of plant fragments, with slight traces of inorganic substances (such as CaOx). The thread-like morphologies observed in the SEM analysis, which are linked to the secretion of hornets, warrant attention due to their significance in understanding the microstructure of AHN P-LM. The presence of nitrogen (N) in the EDS analysis of AHN P-LM, in contrast to its absence in analysed leaves, strongly implies that the nitrogen originates from hornet saliva. Additionally, SEM-EDS analysis revealed the impact of chemical composition variations on colour differences within AHN P-LM. Furthermore, X-ray diffraction analysis on ash samples from AHN P-LM confirmed the presence of minerals such as quartz, lime, phlogopite, and microcline. These findings about mineral composition align closely with results obtained from SEM-EDS analyses, presenting various aspects related to understanding the structure and compositional makeup of AHN P-LM. Biomimicry principles can be applied to draw inspiration from the AHN P-LM for replication in the civil engineering field, facilitating innovative solutions. Understanding hornet behaviour and nest material composition is essential. Future outlook includes utilising these materials in wood construction, 3D printing for structural components, shelters, infrastructure repair, green building, and architectural innovation.
- Caracterização mecânica do material do ninho da vespa asiáticaPublication . Sedira, Naim; Santos, Moisés; Pereira, Fábio; Santos, Cristóvão; Pereira, Sandra; Nepomuceno, Miguel; Bentes, I.; Pinto, JorgeO ninho da vespa asiática (NVA) tem despertado o interesse de vários investigadores de diversas áreas do conhecimento. Na perspetiva da construção, este ninho revela uma complexidade funcional, arquitetónica, construtiva, estrutural e material deveras interessante. Alguns trabalhos de investigação foram publicados recentemente sobre o estudo desta construção animal. De uma maneira geral, estes trabalhos debruçaram-se sobre uma visão macro das estratégias construtivas, sobre a caracterização química do material de construção e sobre a descrição da solução arquitetónica e construtiva. Este trabalho de investigação pretende dar um contributo na caracterização mecânica do material do ninho da vespa asiática. Para o efeito, foram recolhidas algumas amostras de material de um ninho de vespa asiática, foram preparados diferentes provetes, ajustadas as técnicas de ensaio e realizados ensaios de tração. Com base nos resultados experimentais, foi possível obter de forma aproximada a capacidade resistente à tração do referido material. Importa acrescentar que este material é natural, de origem celulósica e bastante heterogéneo. Pensa-se que este trabalho possa dar contributo na temática dos materiais e das construções naturais.
- Material de Construção do Ninho da Vespa Asiática - Um contributoPublication . Sedira, Naim; Gomes, Ana; Nepomuceno, Miguel; Paiva, Anabela; Bentes, I.; Pinto, Jorge Tiago Queirós da Silva; Pereira, SandraMuitos trabalhos de investigação têm vindo a ser desenvolvidos no sentido de encontrar novas soluções para os diversos contextos da ciência através da bio-inspiração. Este trabalho está centrado no estudo do ninho da vespa asiática e, em particular, no estudo do seu material de construção. Esta construção natural é complexa em todas a vertentes. A sua complexidade arquitetónica, estrutural, material, funcional, entre outros aspetos técnicos, são fatores que despertam a curiosidade, esta construção pode ainda apresentar dimensões relativamente grandes. Ela é construída e usada aproximadamente meio ano e não volta a ser reutilizada. Este é outro aspeto técnico que motiva um estudo tendo em conta a escassez de habitação a nível mundial. O material de construção também é interessante e inovador. Neste ponto, tentou-se compreender a constituição deste material através da realização de ensaios MEV-EDS de amostras do material do ninho retiradas em diferentes zonas. Amostras de folhas de árvore foram analisadas para serem usadas como referência. As imagens de MEV mostram que o ninho da vespa asiática é feito de fibras vegetais e pedaços de madeira mastigadas, com sulcos e poros para manipulação, troca de gases e regulação de temperatura e humidade. A análise EDS do material do ninho de vespas asiáticas indica origem vegetal, com elementos como carbono (C) e oxigénio (O) formando 82,31%, e magnésio (Mg), potássio (K), cálcio (Ca) e ferro (Fe) constituindo 9,43%. Alumínio (Al) e silício (Si) representam 7,41%. A saliva das vespas é crucial para a construção. Importa acrescentar que este material é utilizado na construção da fachada do ninho, a qual, apesar de estar diretamente exposta às intempéries, proporciona uma durabilidade adequada. O interior do ninho da vespa asiática também garante o conforto necessário para a reprodução destes insetos. Este trabalho tem como principal objetivo partilhar com a comunidade cientifica alguns dos resultados alcançados por esta equipa de investigação neste contexto.
- Perfil tendencial de comportamento dos ocupantes em caso de incêndioPublication . Cordeiro, Elisabete da Cunha; Coelho, António; Nepomuceno, MiguelA importância do comportamento humano em situações de evacuação é reconhecida por todos os que de algum modo estão relacionados com a segurança contra incêndios em edifícios, como é comprovado pelo elevado número de estudos e projetos de investigação que têm sido desenvolvidos. Nesta comunicação apresentam-se os resultados de um projeto de investigação, que deu origem a uma tese de doutoramento, cujo objetivo foi o de prever esse comportamento e analisar os fatores que mais fortemente o condicionam. Nesse trabalho, a informação que suporta as conclusões foi obtida a partir de 4 tipos de inquéritos destinados a pessoas distintas (pessoas que viveram uma situação de incêndio, pessoas que participaram em exercícios de evacuação, pessoas no geral e bombeiros que estiveram envolvidos nas operações de combate e salvamento). No total obtiveram-se mais de mil inquéritos convenientemente preenchidos, a partir dos quais, e após uma análise e tratamento estatístico, foi criado um perfil tendencial de comportamento dos ocupantes em caso de incêndio. Com recurso a um modelo de simulação de evacuação foi avaliado o impacto desse perfil no tempo total de evacuação em diferentes edifícios que foram desenhados especificamente para o estudo. Nesta comunicação apresentam-se os resultados fundamentais desse estudo, incluindo as conclusões sobre o que importa alterar em termos metodológicos de abordagem do tema de modo que se possa incorporar, no futuro, o conhecimento adquirido com este trabalho.
- Carbon Fiber Epoxy Composites for Both Strengthening and Health Monitoring of StructuresPublication . Salvado, Rita; Lopes, Catarina; Szojda, Leszek; Araújo, Pedro; Górski, Marcin; Velez, Fernando J.; Castro-Gomes, João; Krzywon, RafalThis paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the “wet process”, which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring.
- A Qualitative Analysis Using Thermography for Characterization of the Built EnvironmentPublication . Ferreira, Ana Vaz; Ferreira, Pedro; Santos, Michael M.The revised Energy Performance of Buildings Directive (EPBD) recognizes nearly zero-energy buildings (nZEB) and building renovation as essential steps in the decarbonization of the built environment. A thorough understanding of existing buildings is a prerequisite for improving their thermal performance and ensuring that interventions are based on pre-existing conditions. This study investigates the use of thermography as a tool for identifying construction solutions and assessing the thermal performance of buildings. Initially, it addresses the benefits and limitations of this technique, as well as some results of a qualitative analysis and standard application of this technology. Specific conditions for capturing images on-site were identified, along with the relevant factors for interpreting thermograms under natural conditions. These images enabled the identification of previous works, changes in buildings, and the use of different materials and construction techniques, thereby contributing to the characterization of buildings. Consequently, they can be used in the diagnostic phase to enhance the accuracy of intervention solutions based on a better understanding of existing conditions.
- Sustainable Vernacular Architecture to Improve Thermal Comfort in African CountriesPublication . Santos, Michael M.; Ferreira, Ana Vaz; Lanzinha, JoãoThis study highlights the importance of bioclimatic design, passive solar cooling and heating systems, and traditional building materials in improving the sustainability and thermal comfort of vernacular architecture in Africa. The lack of available technology, financial resources, and increasing urban populations are significant challenges in implementing sustainable vernacular architecture. To overcome these challenges, this study suggests creating awareness, providing financial aid, preserving traditional buildings, and implementing sustainable urban-development strategies. The study also emphasizes the need for further research to evaluate the impact of renewable energy solutions, energy-responsive designs, and climate change reduction in traditional settlements to inform the development of sustainable vernacular architecture in Africa. Achieving sustainable vernacular architecture presents an opportunity to promote ecological embeddedness, sustainable architecture, land-use planning, and integrated green infrastructure, leading to improved indoor air quality, reduced energy consumption, and protection of occupant health. Therefore, it is crucial to develop strategies that promote sustainable design, community engagement, and locally sourced materials to create a more sustainable future for African countries, thereby contributing to climate change resilience and adaptation.
- Reducing cement consumption in mortars by waste-derived hydrocharsPublication . Santos, Michael M.; Marques Sierra, Antonio Luis; Amado Fierro, Álvaro; Suárez, Marta; Blanco, Francisco A.; González La Fuente, José Manuel; Diez, Maria Antonia; Centeno, Teresa A.Waste-derived hydrochars are presented for the first time as promising materials to reduce the consumption of natural resources and the carbon footprint of the cement industry, while eliminating waste and sequestering a high amount of carbon in civil infrastructures. Rice husk (RH) and stabilized organic waste from a mixed municipal waste mechanical-biological treatment plant (SOW) were subjected to hydrothermal carbonization at 200 °C for 2 h and the resulting hydrochars were thoroughly evaluated as cement substitutes in fresh and hardened mortars. Compared to the control, mortars with 1.25–5 wt% of cement replaced by hydrochar from stabilized organic fraction caused a decrease in compressive strength of about 50–60% at 28 days of curing, while flexural strength was diminished by about 38–47%. The use of rice husk-derived hydrochar led to a reduction of 32–47% in compressive strength and of 22–34% in flexural strength. With compressive and flexural strengths of 27–41 and 3.31–4.92 MPa, respectively, blended mortars (28 days) display good prospects for use in plastering, rendering, masonry, partition panels and low-load paving. On the other hand, substituting 5 wt% of cement by hydrochar decreases the thermal conductivity and increases electrical resistivity of the mortar by 25–30%, which enhances thermal insulation properties and potential durability. This approach opens a new avenue for large-scale application of biowaste hydrochars as secondary raw materials for sustainable construction.
- Innovative particleboard material from the organic fraction of municipal solid wastePublication . Santos, Michael M.; Diez, Maria Antonia; Suárez, Marta; Centeno, Teresa A.This study presents a challenging approach that addresses the efficient management of the organic fraction of municipal solid waste (OFMSW) by hydrothermal carbonization (HTC) for the development of novel sustainable low-CO2 building materials. Mild HTC treatment at 180 °C for 2 h transformed low-grade OFMSW into a renewable carbonaceous solid (hydrochar), which displays promising properties for application in particleboards. Taking advantage of the presence of extractives acting as natural binders, the hydrochar particles with sizes of <0.3 mm, 0.3–1 mm, and 1–2 mm agglomerate successfully by simple pressing at 3 MPa for 7 min at room temperature (∼ 25 °C). The resulting binderless monolithic probes display a density of 838 and 883 kg/m3 for the finest and coarsest grain sizes, respectively, and approximately 30% porosity. The mechanical resistance is enhanced by the use of larger particle sizes, and values of modulus of rupture and tensile strength of 21.64 MPa and 18.99 MPa are reached, respectively. The thermal conductivity of the probes in the range of 0.091–0.132 W/(m∙K) suggests the potential of OFMSW-derived hydrochar for thermal insulation panels.