Polymer-cementitious composites containing recycled rubber particles

Waste from scrap tires is one of the most environmentally harmful waste since it leads to significant soil and air pollution. This work investigates the effect of recycled rubber particles incorporation into cementitious composites modified with epoxy polymer. A Design of Experiment (DoE) was conducted to identify the effect of epoxy polymer inclusion (35 and 50?wt%), rubber inclusion (10, 15 and 20?wt%) and rubber particle size (coarse and fine particles) factors on the bulk density, mechanical strength and stiffness of the composites. Third-order interaction effects were obtained, except for density which was affected by two second-order interactions. Larger epoxy polymer and rubber amounts decreased the bulk density of the composites. Epoxy polymer contributes to cement hydration, even without water content. Higher incorporation of coarse rubber particles leads to reduced mechanical performance. In general, lower amounts of epoxy polymer and finer rubber aggregates provide superior mechanical strength and modulus. The use of epoxy polymer also enhances the adhesion between cement and rubber aggregates. This rubber polymer-cementitious composite achieved promising results, being a feasible alternative to reuse end-of-life rubber tyres into structural applications

Sustainable construction: integrated projects management's contributions

No contexto do desenvolvimento sustentável, a indústria da construção avança na gestão integrada de projetos, entendida como a arte e a ciência de coordenar recursos humanos e materiais para concluir um projeto a tempo, com qualidade, dentro de um orçamento adequado, ambientalmente correto e sócio culturalmente aceito. Neste artigo são abordadas práticas como o Lean Construction (LC), Last Planner System (LPS), Advanced Work Packaging (AWP) e Building Information Modeling (BIM), cuja associação se mostra eficiente, na medida em que os contextos se integram e têm em comum o mesmo objetivo final. As ferramentas se mostram eficientes, se os atores da cadeia de valor, em todas as fases do projeto forem devidamente capacitados. Elas contribuem de forma decisiva para a melhoria dos resultados econômicos, para preservação ambiental, e, de forma modesta no viés sociocultural, considerando que a melhoria em saúde e segurança se dá em paralelo com a melhoria da produtividade.In the context of sustainable development, the construction industry advances in integrated project management, understood as the art and science of coordinating human and material resources to complete a project on time, with quality, within an adequate budget, environmentally correct and socio-culturally accepted. In this article, practices such as Lean Construction (LC), Last Planner System (LPS), Advanced Work Packaging (AWP), and Building Information Modeling (BIM) are discussed. The tools are efficient if the actors in the value chain, in all phases of the project, are properly trained. They contribute in a decisive way to the improvement of the economic results, to environmental preservation, and, in a modest way in the social and cultural perspective, considering that the improvement in health and safety happens in parallel with the improvement in productivity

Geopolimeric compounds: a contribution to the sustainability of Thermal Comfort Design

Nas construções, em geral, utilizam-se sistemas artificiais de climatização para se alcançar o Conforto Térmico dos ambientes, gerando um elevado consumo de energia elétrica. Do ponto de vista do Design do Conforto, é importante utilizar materiais sustentáveis, cujas propriedades contribuam para a eficiência energética no interior dos edifícios. Os compostos geopoliméricos são materiais de baixo impacto ambiental, boa resistência à compressão e alta durabilidade. Neste estudo, apresenta-se uma visão geral dos geopolímeros baseada na literatura. Os resultados mostram que os estudos sobre suas propriedades térmicas são recentes e os apontam como material capaz de produzir componentes para o Conforto Térmico. Fica evidente que a incorporação de resíduos contribui de forma ecológica e imprime melhores propriedades mecânicas e térmicas aos compostos. A trabalhabilidade, retração e fissuração por secagem merecem atenção especial. Os custos, cuidados de manuseio e a falta de normatização também são fatores dificultadores da sua prática. Embora haja muitos avanços, esforços são necessários para melhor se investigar suas propriedades térmicas, durabilidade, interação com o aço e previsões de vida em serviço.In buildings, in general, artificial air conditioning systems are used to achieve the Thermal Comfort of the environments, generating a high consumption of electrical energy. From the Comfort Design perspective, it is important to use sustainable materials whose properties contribute to energy efficiency inside buildings. Geopolymerics composites are materials with low environmental impact, good resistance to compression and durability. This study presents an overview of geopolymers based on the literature. The results show that studies on its thermal properties are recent and highlighting it as a material able to produce components for Thermal Comfort. It seems clear that the incorporation of residues, contributes ecologically, gives better mechanical and thermal properties to the compounds. The workability, shrinkage and drying cracking require special attention. Costs, careful handling, lack of standards, are also factors that hamper its practice. Although there are many advances, efforts are needed to better investigate its thermal properties, durability, interaction with steel, and predictions of service life

Grand Challenges Scholars Program - GCSP at the Engineering School, Universidade Federal de Minas Gerais / Programa Acadêmico Grandes Desafios para a Engenharia, Escola de Engenharia, Universidade Federal de Minas Gerais

The structure of the Grand Challenges Scholars Program (GCSP) of the Universidade Federal de Minas Gerais -UFMG, School of Engineering, linked to the National Academy of Engineering (NAE) former initiative, is presented. This academic program has an aspirational vision of educating professionals for facing the challenges of engineering in the twenty-first century. The approach is based on an integrative methodology, geared toward the formation of critical competencies, with a focus on solutions to global problems. It creates opportunities for cooperation, as well as develops multicultural and multidisciplinary competencies, social ability, and commitment. Currently, the courses at the UFMG School of Engineering are adapting to meet the new national guidelines for Engineering courses in Brazil, published in January 2019, and the GCSP is a pilot program, capable of transforming the methodology, the mentality, and the educational and technological tools it uses, into an alternative for all engineering courses at UFMG. The Program started its activities in the School of Engineering in 2020, despite the challenges and limitations imposed by the Covid-19 pandemic. The operational criteria and the internal organization were defined, and the Program was introduced to the students. The first initiatives of the Program - with broad access to engineering students and open to the participation of students from other areas - included the Call No.01/2020 - Covid-19 and the I Sustainability Workshop, held in 2021

Microstructure and hardness of cement pastes with mineral admixture

Portland cement pastes are highly heterogeneous material and exhibits heterogeneous features over a widerange of length scales. Mechanical properties of microstructure can be determined using depth-sensing indentation.Coupled indentation/SEM technique can be used to location the indents and provides a way to determinethe mechanical properties of a specific phase. Thus, the present paper aims to determine the hardness ofdifferent phases of cement pastes prepared with different mineral admixtures including sugarcane bagasseash. The microstructure of cement pastes prepared with different mineral admixtures is analyzed by X raydiffraction, scanning electron microscopy and dynamic hardness tests on polished sections. The differentbackscatter coefficient allows to differentiate anhydrous phases from C-S-H, calcium hydroxide, silica fumeand quartz. A grid of indentation is used to determine the hardness of the different phases and a completephase segmentation of the different samples is achieved. The results show that the hardness of the differentphases follow the sequence (from higher to lower hardness) quartz, anhydrous particles, calcium hydroxide,C-S-H and agglomerated silica fume. The presence of agglomerated silica fume is clearly observed in scanningelectron microscopy images and the poor mechanical properties of these areas might compromise thecement pastes. The microstructure of cement pastes prepared with sugarcane bagasse ashes is similar to theobserved in samples with crushed quartz

Durability of Mortar Made with Fine Glass Powdered Particles

Different studies investigate the use of waste glass in Portland cement compounds, either as aggregates or as supplementary cementitious materials. Nevertheless, it seems that there is no consensus about the influence of particle color and size on the behavior of the compounds. This study addresses the influence of cement replacement by 10 and 20% of the colorless and amber soda-lime glass particles sized around 9.5 μm on the performance of Portland cement mortars. Results revealed that the partial replacement of cement could contribute to the production of durable mortars in relation to the inhibition of the alkali-aggregate reaction. This effect was more marked with 20% replacement using amber glass. Samples containing glass microparticles were more resistant to corrosion, in particular those made of colorless glass. The use of colorless and amber glass microparticles promoted a reduction in wear resistance

Influência do uso de lama de vidro na difusividade térmica de argamassas estruturais utilizando termografia

O vidro soda-cal-sílica é um material com alto potencial de reciclagem. No entanto, o seu beneficiamento gera micropartículas que ficam suspensas na água utilizada para resfriamento das ferramentas.  Esse resíduo é inerte e, comumente, não reaproveitado. Para seu descarte é feita a decantação das micropartículas de vidro utilizando floculantes, sendo a lama produzida depositada em aterros sanitários. De acordo com a literatura, essas micropartículas de vidro poderiam atuar como material cimentício suplementar na produção de cimento Portland. Contudo, as informações sobre o desempenho térmico desses materiais são escassas. Neste estudo investiga-se a difusividade térmica de argamassas para fins estruturais confeccionadas com cimento Portland e lama de vidro soda-cal-sílica com características pozolânicas. Foram produzidas argamassas com e sem substituição do cimento por 10 e 20% de lama in natura e lama lavada para retirada do floculante. As argamassas foram caracterizadas quanto à resistência mecânica e difusividade térmica. Também, foram determinadas a massa específica, a condutividade térmica e o perfil de aquecimento das amostras, parâmetros necessários para avaliar a difusividade térmica. Os resultados indicam que a lama de vidro, com e sem floculante, poderia ser utilizada em substituição ao cimento sem comprometer a resistência mecânica devido às suas características pozolânicas. Nas argamassas com 10% de lama sem floculante se observa um aumento de aproximadamente 8% na resistência. Contudo, em todas as amostras com lama de vidro, lavada ou não, observa-se uma diminuição de 3 a 4% na massa específica e de 17 a 18% na condutividade térmica, indicando que a reação pozolânica não ocorreu em toda a sua extensão. A difusividade, determinada com auxílio da termografia infravermelha, apresenta resultados compatíveis com a literatura e indica que o uso do resíduo não influencia significativamente a inércia térmica das argamassas. Dessa forma, a lama de vidro em substituição a 10% e 20% de cimento Portland poderia ser utilizada em argamassas estruturais sem comprometer o desempenho térmico do sistema, além de contribuir com o meio ambiente ao dar destino adequado ao resíduo e reduzir a retirada de matérias primas para a produção de cimento. Palavras-chave: lama de vidro soda-cal-sílica; difusividade térmica; termografia infravermelha.

Preservação do patrimônio urbano por termografia passiva: estudo em fachadas de cerâmica em Belo Horizonte

Belo Horizonte is a city with a significant number of façades covered in ceramics due to the strong European and American influence, which turns the city an important urban heritage. However, this heritage is constantly threatened by the appearance of pathologies throughout its useful life. The most common are adherence’s loss and infiltrations. Destructive techniques are used to identify such pathologies, but its damage the façade. A non-destructive technique capable of detecting defects in large areas is infrared thermography, which captures the thermal radiation emitted by the material’s surfaces. In this article, passive thermography was used to inspect façades submitted to direct sunlight at different times. An experimental model was built, for control, and five façades with different ages were evaluated. The data indicate that the thermography allows to distinguish punctual and/or generalized detachments. It was possible to identify humidity, the presence of thermal insulation, as well as the color’s influence and the material’s type. The environmental interference conditions (measurement time and cloudiness) in the collected data were also verified.Belo Horizonte é uma cidade com expressivo número de fachadas revestidas em cerâmica devido à forte influência europeia e americana, o que torna a cidade um importante patrimônio urbano. No entanto, esse patrimônio é constantemente ameaçado pelo surgimento de patologias ao longo da sua vida útil. As mais comuns são a perda de aderência e as infiltrações. Para identificar tais patologias, são utilizadas técnicas destrutivas que danificam a fachada. Uma técnica não destrutiva capaz de detectar defeitos em grandes áreas seria a termografia infravermelha, que capta a radiação térmica emitida pelas superfícies dos materiais. Neste artigo, utilizou-se a termografia passiva para inspecionar fachadas submetidas à insolação direta em diferentes horários. Um modelo experimental foi construído para controle e cinco fachadas com idades diferentes foram avaliadas. Os dados indicam que a termografia permite distinguir descolamentos pontuais e/ou generalizados. Foi possível identificar a umidade, a presença de isolamento térmico, assim como a influência das cores e do tipo de material. Também se verificou a interferência de condições ambientais (horário de medição e nebulosidade) nos dados coletados

Effect of partial replacement with thermally processed sugar cane bagasse on the properties of mortars

Sugar cane bagasse is a residue of the sugar-alcohol industry, and its main destination is represented by burningboilers for power generation. The bagasse cogeneration of power produces a sugar cane bagasse ash(SCBA) residue that does not have a useful destination. Ashes are commonly studied as pozzolan in Portlandcement production. International Standards indicate the use of pozzolan with up to 50% substitution. In thepresent work, we investigate the use of SCBA as an addition in Portland cement. For this purpose, Portlandcement was prepared by substituting cement with 0, 10, 20, and 30% processed SCBA in volume. The asheswere processed by re-burning and grinding and were then characterized by scanning electron microscopy, Xraydiffraction, laser granulometry, X-ray fluorescence spectrometry, the Chapelle method, and pozollanicactivity. To evaluate the cement with substitution, we used the mortar recommended by NBR 7215. The mechanicalproperties of the cements with replacement were analysed through tests of the compressive strengthand flexural strength of mortars. The results appear interesting and support the possible use of SCBA in theproduction of cement from the aspect of mechanical properties evaluated