DECIV - Artigos publicados em periódicos
URI permanente para esta coleçãohttp://www.hml.repositorio.ufop.br/handle/123456789/497
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Item Use of steel slag and LAS-based modifying admixture in obtaining highly eco-efficient precast concrete products.(2023) Martins, Ana Carolina Pereira; Carvalho, José Maria Franco de; Duarte, Matheus do Nascimento; Pedroti, Leonardo Gonçalves; Ribeiro, José Carlos Lopes; Peixoto, Ricardo André FiorottiThis paper presents a study on improving the eco-efficiency of no-slump concrete for precast elements using Basic Oxygen Furnace Slag (BOFS). Recycled BOFS powders and aggregates have been produced to obtain mixtures with better particle size distribution and improved packing density based on a particle packing method. A comprehensive experimental investigation was carried out on mixtures with different cement contents (5%, 10%, and 15% vol.) and compaction energy levels (6, 10, and 20 blows in a sand rammer). A modifying admixture based on Linear Alkyl Benzene Sodium Sulfonate (LAS) has also been evaluated as a workability and cohesiveness enhancer for steel slag concretes. In addition, concrete eco-efficiency was evaluated by measuring the binder intensity (bi) and waste consumption. The highest compaction energy provided packing densities ranging from 0.78 to 0.80, and BOFS aggregates led to better mechanical performances. The BOFS concrete containing 15% cement obtained the best strength (52.1 MPa) and bi value (7.0 kg/m3 /MPa), with a waste consumption of 2356.57 kg/m3 . The mixture with the lowest cement consumption (5% - 121.56 kg/m3 ) and the highest consumption of waste (2637.82 kg/m3 ) reached 16 MPa, delivering a bi of 7.6 kg/m3 /MPa.Item Quartzite tailings in civil construction materials : a systematic review.(2023) Martins, Letícia Matias; Peixoto, Ricardo André Fiorotti; Mendes, Júlia CastroThe inadequate management of waste from the mining industry can lead to several environmental problems. For instance, the extraction of quartzite, an ornamental stone, generates quartzite waste (or residues or tailings) (QTZ), which is commonly deposited in the environment, causing landscape degradation, contamination by dust, and silting of rivers. To mitigate this scenario and stimulate the circular economy, this literature review focuses on the use of quartzite tailings in construction materials. A systematic search was carried out in the Scopus, Web of Science, and Google Scholar databases, including articles in English and Portuguese published between 2007 and 2022. The results showed that the use of QTZ as aggregate in cement-based composites is viable, as this waste has physical, chemical, mineralogical, and microstructural characteristics similar to conventional natural aggregate. Quartzite waste has been successfully adopted in precast concrete, cladding, and laying mortars, soil–cement bricks, and interlocking pavements. Many works brought the physical and mechanical characterization of the proposed construction materials, with gaps being observed mainly in terms of durability and performance. In conclusion, the use of QTZ in construction materials is a promising alternative, especially in cement-based composites. An important advantage is that this material requires little or no prior processing. However, the reuse of quartzite tailings is still limited, showing that more academic studies, private initiatives, and public policies are required.Item Evaluation of the microstructure and micromechanics properties of structural mortars with addition of iron ore tailings.(2023) Almada, Bruna Silva; Silva Neto, Gilberto Alves da; Prado, Dyala Fraga do; Aguilar, Maria Teresa Paulino de; Garcia, Dayana Cristina Silva; Silva, Guilherme Jorge Brigolini; Santos, White José dosThe Interfacial Transition Zone (ITZ) between the cement paste and aggregates is a region of great interest for concretes because it is the composites’ weakest region. ITZ presents a great amount of large calcium hydroxide and ettringite crystals, with the porosity being able to be up to 2.5 greater than that the rest of the paste. The microstructure, and consequently the ITZ, can be improved by mineral addition. These materials fill the pores in the composite, influence the hydration process and densify the matrix. Therefore, mineral additions, such as iron ore tailings (IOT), can modify microstructure of composites. There are few studies on the assessment of IOT heterogeneity on the microstructure and hardness of structural mortar. Thus, the present study analyzes the properties influences of four IOT types on the microstructure, porosity, and thickness of the structural mortars’ Interfacial Transition Zone (ITZ) with IOT addition, by different evaluation methods. The composites were characterized through the Scanning Electron Microscope by backscattered electrons (SEM-BSE), line scan by Energy Dispersive Spectroscopy and nanoindentation. Results presented that IOT improved particle packing and tended to reduce the ITZ. The IOT improved nucleation since it reduces the amount of anhydrous cement particles and increases the amount of calcium hydroxide particles in the cement matrix. The nanoindentation showed that IOT-added matrix presented greater hardness and indentation module. It can be concluded that the IOT heterogeneity may affect microstructural properties and that the methods presented can be good ways to evaluate the parameters.Item Alkali-activated materials produced using high-calcium, high-carbon biomass ash.(2022) Silva, Thiago Henrique; Lara, Luis Felipe dos Santos; Silva, Guilherme Jorge Brigolini; Provis, John Lloyd; Bezerra, Augusto Cesar da SilvaEucalyptus ash (EA) was used in this study as a high calcium ash (HCA) precursor for alkali-activated binders. The EA used also has high carbon unburned (High loss on ignition). This type of ash is one of the waste products from biomass-fuelled thermoelectric plants, and annually thousands of tons are discarded as a by-product of the energy generation process in Brasil, but it is rich in unburnt carbon which means that it is challenging to use in cementitious systems. Eucalyptus is a biomass that removes CO2 from the atmosphere by photosynthesis and part of this carbon content remains in the ashes, generating CO2 capture when EA is incorporated in the production of alkali-activated binders. The objective of the present study was to evaluate the properties of the material obtained by the alkali-activation of the high-calcium high-carbon biomass ash to generate a cementitious binder, with different pastes proportions of EA and silica fume (SF), activated by sodium hydroxide. With the different pastes, mortars were produced using standardized sand. The results obtained from the pastes and mortars were satisfactory in several aspects. The mechanical results of the alkali-activated mortars were comparable those of Portland cement mortars. Mortars degraded methylene blue more efficiently in illuminated conditions, even after high adsorption for 24 h in the dark. The content of leached ions in the remaining solutions met potability standards.Item Effects of glass wool residue recycled admixtures on the properties of portland cement-based composites.(2022) Silva, Keoma Defáveri do Carmo e; Cotta, Jéssica Fernandes; Elói, Fernanda Pereira da Fonseca; Carvalho, José Maria Franco de; Peixoto, Ricardo André Fiorotti; Silva, Guilherme Jorge BrigoliniIn this study, the effects of a recycled mineral admixture based on glass wool residue (GWR) in microstructural and mechanical properties of ordinary portland cement (OPC)-based composites are examined. The GWR was dried and milled into a fine powder, whereby it was physicochemically characterized. Physicomechanical tests, quantitative X-ray diffraction, and scanning electron microscope observation were performed in pastes and mortars at 28, 56, and 90 days of age. Moreover, the potential application of the GWR was evaluated by determining the pozzolanic activity and the fiber reinforcement effect. The results showed that the partial replacement of cement by 25% by weight of GWR presented no reductions in flexural strength at 28 and 56 days of curing, whereas the long-term flexural strength increased by 17%. This replacement also increased the long-term compressive strength of the composites—reaching a strength activity index of 1.06. The results also showed that GWR presented some fiber reinforcement effect—depending on the particle size. Promising properties were observed for samples blended with GWR, yielding technical, environmental, and economic benefits.Item Inactivation of Escherichia coli in photobioreactors with microalgae and illuminated by light emitting diodes.(2022) Silva, Ludymyla Marcelle Lima; Santiago, Aníbal da Fonseca; Silva, Gilmare Antônia da; Lima, Lívia Bastos de; Amaral, L. P.; Nascimento, Rafael Souza LeopoldinoPathogens in wastewater must be inactivated to prevent the spread of waterborne diseases and allow reuse of the water after treatment. One of the options for wastewater treatment is to use photobioreactors with microalgae. Such systems can inactivate pathogens by diferent mechanisms, and Escherichia coli can be used as an indicator of inactivation. Therefore, this study aimed to evaluate inactivation of E. coli in wastewater by means of light emitting diodes (LED)-illuminated photobioreactors with microalgae, without the emission of ultraviolet radiation (UV). Two optimization steps were carried out, in which LED-illuminated photobioreactors without UV emission were set up for the treatment of wastewater, and various exposure times and luminous fuxes were tested for three wavelengths (white, blue and red); they were compared with photobioreactors illuminated by sunlight and in the dark. Additionally, using the results obtained in the optimization, a scaled-up reactor approximately 8.5 times larger in volume was operated to evaluate whether the behavior would be maintained at this scale. The removal efciency was 5.06 logarithmic units. Photobioreactors illuminated with a blue LED with luminous fux of 700 µmol m−2 s −1 and operated for 15 days showed the best performance in the inactivation of E. coli. LED-illuminated photobioreactors with microalgae, without the emission of ultraviolet radiation (UV) presents inactivation of pathogens and has the advantage of the low cost of the lamps, and the ease of operation.Item Optimized reinforcement distribution in reinforced concrete structures under plane stress state.(2022) Silva, Amilton Rodrigues da; Ladeira, Artur HallackThe strut-and-tie model is widely used for analysis and design of reinforced concrete structures. To apply this model, it is necessary to defne strut-and-tie systems that represent the fow of stresses generated in the analyzed structure. In many situations, this strut-and-tie model is defned through an evolutionary structural optimization (ESO) considering linear isotropic material. The results obtained from this model are not always satisfactory Query ID="Q1" Text="Please confrm the inserted city name and country name in afliations 1 and 2 are correct and amend if necessary." because of the nonlinear behavior of the concrete, mainly because of the great diference in the behavior under tension and compression. Because of this, an evolutionary algorithm is developed in this article to defne the optimized reinforcement distribution in reinforced concrete structures under plane stress state, considering the nonlinearity of the materials. This algorithm adopts the same principle as the ESO algorithm; however, it does not eliminate the mesh element that discretizes the analyzed domain, but it eliminates the reinforcement of the elements that do not meet an efciency criterion. A three-node triangular fnite element is used for nonlinear analysis of the reinforced concrete structure under plane stress state. The structure domain is discretized by this element, which can be of four types: with reinforcement in two fxed orthogonal directions, only in one direction, or without reinforcement. During the evolutionary process of the algorithm using a rejection criterion based on the level of reinforcement strain, the elements with reinforcement are changed to elements without reinforcement or with reinforcement in only one direction. Three practical applications were evaluated to verify the efciency of the algorithm proposed in this article. Two of them had their results compared with results provided in the literature, verifying the efciency of the proposed algorithm.Item Parametric study using a curved shell finite element to dynamic analysis of footbridge under rhythmic loading.(2021) Becerra, Humberto Cardona; Silva, Amilton Rodrigues daWhen designing structural systems, the relation between form and structure is not always considered, because architects and engineers work independently. Structures with mutual collaboration such as surface-active (e.g., shells) when well-designed can optimize specific behaviors. This work proposes an analysis of some parameters that influence the dynamic behavior of footbridges under rhythmic loading. The variation of these parameters allows defining different mass distribution along the footbridge with a constant total weight. The relation between form and structure was also analyzed in this parametric study considering two architectural models for the footbridges. The parametric study proposed required a dynamic analysis of shells with variable thickness. Therefore, the formulation of a curved shell finite element is presented. This element is based on a degenerate three-dimensional solid element and is restricted to the behavior of shell under the Reissner–Mindlin approach. Two classic examples from the literature and the analytical solution of a long cylindrical shell under membrane and bending behavior were used in the validation of the curved shell finite element used in numerical analysis. From the proposed parametric study, results are presented for the parameters that define a better response in relation to the vibration fundamental frequencies of the footbridge and its maximum accelerations due to a rhythmic loading. It is concluded that the form of the curved shell supporting the flat slab significantly affects the footbridge dynamic behavior.Item Equisetum hyemale‑derived unprecedented bioactive composite for hard and soft tissues engineering.(2022) Silva, Rosangela Maria Ferreira da Costa e; Diniz, Ivana Márcia Alves; Gomes, Natália Aparecida; Silva, Guilherme Jorge Brigolini; Ferreira, José Maria da Fonte; Freitas Filho, Rubens Lucas de; Freitas, Erico Tadeu Fraga; Martins, Darliane Aparecida; Domingues, Rosana Zacarias; Andrade, Ângela LeãoAlthough Bioactive Glasses (BGs) have been progressively optimized, their preparation often still involves the use of toxic reagents and high calcination temperatures to remove organic solvents. In the present work, these synthesis related drawbacks were overcome by treating the ashes from the Equisetum hyemale plant in an ethanol/water solution to develop a bioactive composite [glass/ carbon (BG-Carb)]. The BG-Carb was characterized by scanning electron microscopy, and transmission electron microscopy; and its chemical composition was assessed by inductively coupled plasmaoptical emission spectroscopy. Brunauer–Emmett–Teller gas adsorption analysis showed a specifc surface area of 121 m2 g−1. The formation of hydroxyapatite (HA) surface layer in vitro was confrmed by Fourier-transform infrared spectroscopy analysis before and after immersion in simulated body fuid (SBF) solution. The Rietveld refnement of the XRD patterns and selected area electron difraction analyses confrmed HA in the sample even before immersing it in SBF solution. However, stronger evidences of the presence of HA were observed after immersion in SBF solution due to the surface mineralization. The BG-Carb samples showed no cytotoxicity on MC3T3-E1 cells and osteodiferentiation capacity similar to the positive control. Altogether, the BG-Carb material data reveals a promising plant waste-based candidate for hard and soft tissue engineering.Item Characterization of magnetic tailings from phosphate-ore processing in Alto Paranaíba.(2023) Silva, Fernando Brandão Rodrigues da; Araújo, Fernando Gabriel da Silva; Krüger, Fernando Leopoldo von; Silva, Guilherme Jorge Brigolini; Batista, Ronaldo Junio Campos; Manhabosco, Taíse MatteThe characterization studies of tailings from mining are crucial for the development of its reuse processes and the reduction of impacts caused by its conditioning on the earth’s surface. This study characterizes the magnetic tailings from phosphate-rock processing using X-ray diffraction, X-ray fluorescence spectrometry and quantitative electron microscopy techniques. Samples were obtained from the magnetic tailings deposit of a mining company in the Alto Paranaíba region, Minas Gerais. The tailings are mainly composed of hematite/magnetite (74.92%), ilmenite (8.91%), fluorapatite (8.8%), anatase (3.07%), calcite (1.67%), goethite (1.62%), and quartz (1.02%). The particle size of the tailings is smaller than that specified for the production of sinter feed. The hematite/magnetite phase is strongly associated with ilmenite and fluorapatite. New stages of comminution and separation are needed due to the low degree of liberation of these minerals for a possible reuse of the components.