Resumo O metacaulim é a principal matéria-prima utilizada na síntese de geopolímeros, embora a relação entre os teores de sílica e alumina não seja a ideal. Normalmente, o teor de SiO 2 é ajustado com o uso de silicatos presentes na solução ativadora. Uma opção ecoeficiente seria o uso de resíduos de vidro como fonte adicional de sílica. Este trabalho avalia a eficiência da ativação alcalina do metacaulim, utilizando hidróxido e silicato de potássio, com e sem substituição de 12,5% de metacaulim por micropartículas de vidro. A eficiência da ativação alcalina foi avaliada por difratometria de raios x, espectroscopia na região infravermelha com transformada de Fourier, espectroscopia de ressonância magnética nuclear do 27 Al e 29 Si, massa específica e resistência à compressão. Os resultados indicam a ocorrência de geopolimerização com e sem uso de resíduo de vidro. Observou-se que a substituição de 12,5% favorece o desempenho mecânico dos compósitos aos 28 dias, com aumentos de 37% e 47% da resistência mecânica do material com cura em estufa e na temperatura ambiente, respectivamente.

Abstract Metakaolinis the principal raw material utilized in the synthesis of geopolymers, although its ratio of silica and alumina contents is not ideal. Normally, the SiO2 content is adjusted with the use of silicates present in the activating solution. An eco-efficient alternative would be the use of glass waste as an additional source of silica.This work evaluates the efficiency of the alkaline activation of metakaolin, using potassium hydroxide and silicate, with and without the substitution of 12.5% of metakaolin by microparticles of glass. The efficiency of the alkaline activation was evaluated by X ray diffractometry, spectroscopy in the infrared region with the Fourier transform, nuclear magnetic resonance spectroscopy of 27Al and 29Si, specific mass and compressive strength. The results indicate the occurrence of geopolymerization with and without the use of glass waste. It was observed that the substitution of 12.5% favors the mechanical performance of the compounds at 28 days, with increases by 37% and 47% in the mechanical strength of the material with thermal curing and ambient temperature curing, respectively.

RESUMO 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.

ABSTRACT Soda-lime-silica glass is a material with high recycling potential. However, its processing generates microparticles that are suspended in the water used for cooling the tools. This residue is inert and generally not reused. For disposal, the microparticles of glass are decanted using flocculants and the mud produced is deposited in landfills. According to the literature, these glass microparticles could act as supplementary cementitious material in Portland cement production. However, information on the thermal performance of these materials is scarce. This study investigates the thermal diffusivity of mortars for structural purposes made with Portland cement and pozzolanic soda-lime-silica glass mud. The mortars were produced with and without cement replacement for 10 and 20% natural mud and washed mud to remove the flocculant. The mortars were characterized for compressive strength and thermal diffusivity. The specific mass, the thermal conductivity and the heating profile of the mortars were also determined, requirements to evaluate the thermal diffusivity. The results indicate that glass mud with and without flocculant could be used in place of cement without compromising compressive strength due to its pozzolanic characteristics. In mortars with 10% mud without flocculant an increase of approximately 8% in compressive strength is observed. However, in all samples with glass mud, washed or not, there is a decrease of 3 to 4% in the specific mass and 17 to 18% in the thermal conductivity, indicating that the pozzolanic reaction did not occur to its full extent. Diffusivity, determined with the aid of infrared thermography, presents results compatible with the literature and indicates that the use of the residue does not significantly influence the thermal inertia of the mortars. Thus, glass mud in place of 10% and 20% Portland cement could be used in structural mortars without compromising the thermal performance of the system, in addition to contributing to the environment by providing adequate destination to the waste and reducing the withdrawal of raw materials for cement production.

Severe plastic deformation (SPD) of metals leads to their strengthening and grain refinement, but to low uniform elongations. Low Strain Amplitude Multi Directional Forging (LSA-MDF) is an important method for increasing this low uniform elongation. The application of workpieces of SPD-processed materials requires that their distributions of mechanical properties, microstructures and deformation be as homogeneous as possible. Analyses of these distributions after LSA-MDF have not been found in the literature, and are presented in the current investigation utilizing microhardness measurements, optical and electronic microscopy and finite element simulations. LSA-MDF causes higher strains, mcrohardeness and structural distortions in the central regions of the specimens than at their edges and corners. In addition, LSA-MDF utilizing confined compressions seems to be the preferred processing route, due to its ease and to the more homogeneous microhardness, microstructure and strain distributions in relation to other experimental procedures.

RESUMO Um método alternativo para produção de concretos ecoeficientes seria a substituição parcial de cimento Portland por resíduos de pastas e argamassas submetidas a um tratamento termomecânico. Neste contexto, este estudo avalia a influência da relação água/cimento (a/c) e do tamanho médio das partículas na decomposição térmica do cimento hidratado. Pastas de cimento com três relações a/c (0,40, 0,50 e 0,60) e curadas por 28 dias foram moídas para obtenção de granulometrias com tamanho médio de 0,60 mm e 0,15 mm. A decomposição térmica das pastas foi analisada por termogravimetria (TGA), difração de raios X (DRX) e espectroscopia no infravermelho por Transformada de Fourier (FTIR). A análise de TGA indica que o teor de água quimicamente combinada é favorecido pelo aumento da relação a/c entre 0,40 e 0,50, mas é constante para a/c de 0,50 e 0,60. A redução do tamanho médio quase não interfere nas curvas de TGA. De acordo com as análises por DRX e TGA, a maior parte dos hidratos se decompõe até 500-550°C, enquanto que silicatos de cálcio e aluminatos de cálcio similares às fases anidras do cimento Portland foram detectados na pasta aquecida a 750°C. Assim, temperaturas mais altas seriam necessárias para a completa recuperação do cimento anidro em pastas hidratadas.

ABSTRACT A possible method for producing eco-efficient concrete would be the partial replacement of Portland cement by pastes and mortars residues subjected to thermal-mechanic treatment. In this context, this study evaluates the influence of water/cement (w/c) ratio and average particle size on the thermal decomposition of hydrated cement. Cement pastes with three w/c ratios (0.40, 0.50 and 0.60) and cured by 28 days were ground to obtain two particle distributions with average sizes of 0.60 mm and 0.15 mm. The thermal decomposition of pastes was analysed by thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). TGA analysis indicates that chemically bounded water content is improved by the increasing of w/c ratio between 0.40 and 0.50, but it is constant between w/c of 0.50 and 0.60. Particle size reduction almost does not interfere with TGA curves. According to XRD e TGA analysis, most hydrates are decomposed at 500-550 °C, while calcium silicates and calcium aluminates similar to the anhydrous phases of Portland cement were detected on the heated paste at 750 °C. Thus, higher temperatures would be required for the complete recovery of the anhydrous cement in hydrated pastes.

Resumo Sistemas alimentares têm sido, tradicionalmente, objeto de estudo das ciências sociais e agrícolas. Mais recentemente, a pesquisa em Design vem desenvolvendo estratégias que buscam compreender as relações entre a sustentabilidade e o sistema alimentar. Não como meio de produção de uma commodity tangível a ser comercializada, mas como resultado de um sistema sociotécnico intangível, que pode ser projetado para melhoria da qualidade de vida. Este trabalho tem como objetivo analisar as interseções entre os conceitos de Sistema Produto-Serviço (PSS) em Comunidades que Sustentam a Agricultura (CSA). Nesse contexto, são analisadas duas CSAs como alternativas capazes de transformar positivamente a forma com a sociedade produz, distribui e comercializa os alimentos. Também se discute as limitações do estudo e o papel do design no desenvolvimento de modelos de CSAs mais eficientes e sustentáveis no que se refere ao sistema alimentar como um todo. Os resultados permitem contextualizar o funcionamento das CSAs estudadas e identificar os particulares desafios que possam ser superados utilizando-se processos e habilidades do PSS.

Abstract Food systems have traditionally been the subject of social and agricultural sciences research. More recently, design research has been developing strategies that help understand the intersections between sustainability and the food system. It is not seen as a means of producing a tangible commodity to be marketed but as a result of an intangible sociotechnical system, which can be designed to improve life quality. This work aims to analyze the intersections between the concepts of Product-Service System (PSS) in Communities that Support Agriculture (CSA). In this context, two CSAs are analyzed as alternatives capable of positively transforming the way society produces, distributes and markets food. The limitations of this study and the role of design, in the development of more efficient and sustainable CSA models for the food system, are also discussed. The results allow to contextualize the functioning of the CSAs studied and to identify the particular challenges that can be overcome using PSS’ processes and skills.

ABSTRACT Sugar cane bagasse is a residue of the sugar-alcohol industry, and its main destination is represented by burning boilers 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 Portland cement production. International Standards indicate the use of pozzolan with up to 50% substitution. In the present work, we investigate the use of SCBA as an addition in Portland cement. For this purpose, Portland cement was prepared by substituting cement with 0, 10, 20, and 30% processed SCBA in volume. The ashes were processed by re-burning and grinding and were then characterized by scanning electron microscopy, X-ray diffraction, laser granulometry, X-ray fluorescence spectrometry, the Chapelle method, and pozollanic activity. To evaluate the cement with substitution, we used the mortar recommended by NBR 7215. The mechanical properties of the cements with replacement were analysed through tests of the compressive strength and flexural strength of mortars. The results appear interesting and support the possible use of SCBA in the production of cement from the aspect of mechanical properties evaluated.

ABSTRACT Portland cement pastes are highly heterogeneous material and exhibits heterogeneous features over a wide range 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 determine the mechanical properties of a specific phase. Thus, the present paper aims to determine the hardness of different phases of cement pastes prepared with different mineral admixtures including sugarcane bagasse ash. The microstmcture of cement pastes prepared with different mineral admixtures is analyzed by X ray diffraction, scanning electron microscopy and dynamic hardness tests on polished sections. The different backscatter coefficient allows to differentiate anhydrous phases from C-S-H, calcium hydroxide, silica fume and quartz. A grid of indentation is used to determine the hardness of the different phases and a complete phase segmentation of the different samples is achieved. The results show that the hardness of the different phases 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 scanning electron microscopy images and the poor mechanical properties of these areas might compromise the cement pastes. The microstructure of cement pastes prepared with sugarcane bagasse ashes is similar to the observed in samples with crashed quartz.

The work presents the characterization of clays from sterile mining of the concentrated phosphatic materials of Araxá in Minas Gerais as pozzolanic materials. Three clays of distinct tones, namely, yellow (YC), red (RC), and intermediate (IC) clays, were used at different levels of excavation depth. The clays were calcined at three temperatures (680, 760, and 840 °C) in a muffle-type electric oven. The pozzolanic activity levels of the calcined clays was measured through the conductivity change in saturated Ca(OH)2 solutions and also from the result of the compressive failure load achieved by mortars with 35% of the Portland cement replaced with the calcined material. The results indicated that the calcined clays showed a high level of pozzolanic activity and can be used as a partial substitute for Portland cement, thus suggesting the possibility of recovering this sterile material.

The use of residues, in partial or total substitution of aggregates or binders in concrete, presents interesting possibilities for obtaining eco-efficient concretes. Research has investigated the use of glass residue in Portland cement composite, whether as an aggregate or a supplementary cementitious material. However, there is still no consensus on the influence of the chemical composition of glass on the behaviour of the composites in which it is used. This paper analyse the influence of this composition on the performance of cement composites produced with microparticles of colourless and amber glass. Pozzolanicity was assessed by direct (Modified Chapelle, electrical conductivity) and indirect test (chemical characterization, X-ray diffraction, thermogravimetric analysis, differential thermal analysis and Strength Activity Index testing. The results show that microparticles of both glass display pozzolanic activity, with no significant differences between them. This confirms the potential for the use of glass microparticles as a supplementary material in cement composites.

Nodular cast irons (NCIs) involve the inoculation and nodulization of 0.03 to 0.06wt% Magnesium, as well as the addition of Molybdenum, Chromium, Nickel, Copper and Vanadium, although the presence of Niobium is not common. The literature reports that Niobium leads to better mechanical properties of the NCIs, and recent results indicate that 0.5wt% Niobium increases the strength and the Charpy notch toughness of NCIs, but decreases its hardness, in relation to a similar NCI without Niobium. The present report studies the addition of 0.23, 0.47, 0.67, and 0.85wt% Niobium to a NCI covering the effects on the microstructures, yield and tensile strengths, tensile elongations and Charpy toughness. The NCIs were prepared in a 120 kg medium frequency induction furnace, and samples were obtained following the ASTM A842 standard; the various test specimens were extracted from these samples according to specific standards for each test. Fracture analysis was performed in fractures specimens after the Charpy tests. It was shown that the volume fraction of pearlite increases as the Niobium content is raised, leading to increments in the yield and tensile strengths and hardness of these materials. Modest increment of tensile ductility and Charpy toughness are observed only for an addition of 0.23% Niobium. Fracture analysis revealed typical brittle cleavage surfaces and decohesion between grains and grain - graphite nodules interfaces, and very low porosity

Os compósitos cimentícios, comumente, são avaliados em função de sua trabalhabilidade, do teor de ar incorporado, do seu módulo de elasticidade e de resistência à compressão. Essa resistência é determinada através de ensaios de compressão axial de corpos-de-prova moldados especialmente para essa finalidade. Na execução do ensaio de compressão, é necessário que as superfícies, onde se aplicam as cargas, sejam planas, paralelas e lisas, de modo que o carregamento seja uniformemente distribuído. Para isso são utilizadas diversas técnicas e materiais, como capeamentos aderentes, não aderentes, sistemas de desgaste mecânico ou moldes especiais. Atualmente, os capeamentos mais utilizados são os que utilizam argamassas de enxofre ou almofadas de neoprene. O presente trabalho avalia, experimentalmente, a interferência de diferentes tipos de regularização das bases dos corpos-de-prova para compósitos cimentícios de diferentes classes de resistência.

Cementitious composites are commonly evaluated considering their workability, level of incorporated air, elasticity modulus and compression strength. Data from compression testing commonly present a high dispersion, which has been attributed to effects of the specimen geometry, dimensions and of the degree of material compaction, as well as to problems in the specimen end-faces, such as their parallelism, orthogonality in relation to the compression axis and surface regularity. Specimen end-face regularization has been achieved through various techniques, such as adhering or non-adhering capping with various materials, mechanical grinding and systems involving special moulds. The regularization methods utilized more frequently employ sulfur mortar capping, neoprene cushions and surface grinding. The present work covers the experimental compression tests of cementitious composites of different classes of strength employing sulfur mortar capping and neoprene cushions. It was concluded that there is a strong influence of the chosen regularization technique on the measured compression strengths.

Grain refinement in magnesium is evaluated in the present paper. Equal Channel Angular Pressing is used to process commercially pure magnesium. Processing was carried out at 523 K which is lower than the temperature used in other papers on the literature. The grain structure was evaluated throughout the deformation zone. The low processing temperature prevents significant grain growth. The evolution of the grain structure is compared to a recent model for mechanism of grain refinement in magnesium. The present results confirm the validity of the model.

Cold forming is usually associated with the "work hardening" of the material being formed. The work hardening behavior of metals subject to complex processing paths is different from that in monotonic deformation. The results show that, after some initial hardening, there is a possibility that further deformation will cause softening in the material ("work softening"). Recent work showed that cyclic torsion applied to drawn products causes changes in the subsequent tensile behavior of low carbon steel, and that the effect will depend on the previous "history" of the material. For annealed samples, the cyclic torsion leads to an increase in the yield strength, but does not affect the tensile strength and elongation. For the case of previously drawn bars, the cyclic deformation caused a decrease in the yield and tensile strength and an increase in the total elongation. The present paper discusses the dislocation structure changes associated with different strain paths in mild steel.

Equal Channel Angular Pressing (ECAP) is the most prominent SPD (Severe Plastic Deformation) method for the production of ultrafine and nanostructured metals, and has been extensively employed and analyzed. This technique was applied to a Pb-4%Sb alloy at room temperature, in order to study its effect on a low melting point and multiphase metallic material. The material was subjected to effective strains higher than 9, after 8 passes of processing, where dynamic and static recrystallization are expected during and after each pass. This eliminates any grain refinement and allows the analysis only of the microstructural effects associated with second phase redistribution and eventual precipitate dissolution. ECAP followed route C, which eliminates structural alignment after each even ECAP pass, facilitating the study of the microstructural evolution. It is shown that three ECAP passes are necessary to completely break the lamellar structure of the as cast strucure and that antimony dissolves into the lead rich matrix. Dynamic recrystallization and structural changes reduce the material strength and change the flow curve format.

The work hardening of metals subjected to complex processing paths is different from that in monotonic deformation. Changes in the deformation mode can promote transients in the strain-hardening rate, leading to anomalous softening or hardening of the material. This paper investigates the influence of strain path changes on the tensile behavior of drawn 0.12% steel rods. Annealed or predrawn specimens were submitted to cyclic twisting and then tested in tension. The results show that the cyclic deformation causes changes in the mechanical behavior of the metal, and the effect will depend on the previous "history" of the material. Cyclic twisting causes hardening in annealed samples, but leads to softening of the drawn bars. These phenomena are in line with the corresponding substructural aspects.