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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 Fiorotti
This 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.
Quartzite tailings in civil construction materials : a systematic review.
(2023) Martins, Letícia Matias; Peixoto, Ricardo André Fiorotti; Mendes, Júlia Castro
The 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.
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 dos
The 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.
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 Silva
Eucalyptus 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.
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 Brigolini
In 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.
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 Leopoldino
Pathogens 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.
Optimized reinforcement distribution in reinforced concrete structures under plane stress state.
(2022) Silva, Amilton Rodrigues da; Ladeira, Artur Hallack
The 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.
Parametric study using a curved shell finite element to dynamic analysis of footbridge under rhythmic loading.
(2021) Becerra, Humberto Cardona; Silva, Amilton Rodrigues da
When 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.
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 Leão
Although 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.
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 Matte
The 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.
Study of mechanical, durability and microstructural properties of cementitious composite with addition of different iron ore tailings from Brazil.
(2022) Almada, Bruna Silva; Melo, Henrique da Silva Silveira; Duarte, Marlo Souza; Aguilar, Maria Teresa Paulino de; Garcia, Dayana Cristina Silva; Silva, Guilherme Jorge Brigolini; Santos, White José dos
Brazil is the second-largest global iron ore producer in the world. Consequently, a large volume of iron ore tailings (IOTs) is generated, which is associated with environmental impacts. IOTs present potential to be used as an addition in cementitious compounds, however, few studies assess how the heterogeneity of this waste can limit its utilization as a building material. Thus, the present study aims to assess whether the heterogeneity of IOTs influences mechanical, durability, and microstructural properties when added to the cementitious composite. Four IOTs samples from different origins were collected and added to cementitious composite at 40% addition content. Composites’ mechanical (compressive strength and modulus of elasticity) and durability properties (water absorption, porosity, electrical resistivity, carbonation, and pH pore solution) were correlated to the microstructure of the IOTs. Results showed that the IOTs from different mines exhibited different physical properties and chemical/mineralogical compositions. Moreover, the higher the degree of ore processing, the lower the heterogeneity, iron content, and specific gravity. Although the IOT samples are heterogeneous, this type of tailing can be used as a filler addition in structural mortars. IOT addition tends to improve the mechanical and durability properties. Heterogeneity most significantly influenced the properties in the fresh state, durability, and microstructural properties. The microstructure of the cement matrix tends to be denser in the IOT-added with higher SSA and silica content. Was observed higher-porosity in regions close to the interfacial transition zone in the samples with coarser IOT.
Educação empreendedora para mulheres : estudo de caso do curso online “Empreenda como uma Mulher”.
(2023) Fiuza, Nayara das Mercês Lúcio; Umbelino, Dulcineia Gomes; Marquetti, Isabela Toffolo; Cunha, Letícia Teixeira Matos; Barbosa, Lucas Silva; Hermenegildo, Nicolas Gomides; Silveira, Stella Cristine Ferraz; Amaral, Tanise Florentino Costa; Silva, André Luis; Mendes, Júlia Castro
O crescimento do empreendedorismo feminino favorece a economia do país, aumenta o número de mulheres em cargos de liderança e incentiva a sua realização pessoal. Entretanto, muitas mulheres empreendem por necessidade, sem instrução formal, enquanto lidam com a dupla jornada de trabalho. Assim, o curso “Empreenda como uma Mulher”, foi lançado visando capacitar empreendedoras em todo o Brasil. Como metodologia, as cursistas foram divididas em 2 grupos de WhatsApp com 20 empreendedoras cada. Nos grupos, a equipe lançou diariamente videoaulas de até 15 minutos, que abordavam aspectos fundamentais de empreendedorismo, como plano de negócios, gestão financeira, gestão de vendas, marketing, precificação, entre outros. Também foram realizadas mentorias e trocas de experiências. O projeto recebeu 133 inscrições de empreendedoras de todo o Brasil, das quais 40 foram selecionadas por critérios socioeconômicos. Dessas, somente 13 (32%) o finalizaram, com as demais alegando que “não tinham tempo”. As cursistas que preencheram o formulário de feedback destacaram o quanto o curso foi fundamental para a melhoria da gestão de seus negócios. Assim, o presente projeto proporcionou aos alunos-membros uma formação holística e socialmente contextualizada, além de contribuir com o aperfeiçoamento de empreendimentos gerenciados por mulheres. Foi possível observar o quão proeminente é a necessidade de capacitação entre mulheres empreendedoras e o quanto o cansaço resultante de suas longas jornadas de trabalho interfere no acesso a essas capacitações.
Cobertura verde como alternativa sustentável para geração de renda em habitações de interesse social.
(2021) Pereira, Rondinelly Geraldo; Araújo, Ernani Carlos de; Ribas, Rovadávia Aline de Jesus
Frente ao déficit habitacional nacional, fazem-se necessárias propostas de Habitações de Interesses Social (HIS) que possam atenuar esse problema, atendendo às necessidades dos usuários quanto a critérios de segurança e habitabilidade e, também, aos aspectos sociais e econômicos. Sistemas construtivos industrializados, como as estruturas em aço, por suas características inerentes, podem contribuir consideravelmente com esses fatores. Diante do exposto, este trabalho tem por objetivo investigar se a implantação de cobertura verde em condomínio de HIS na cidade de Ouro Preto, MG, configura uma alternativa sustentável, capaz de gerar renda para auxiliar no custeamento de financiamento da edificação. A metodologia é pautada em um estudo de caso de caráter dedutivo, tendo sido realizados trabalho de campo em parceria com universidades brasileiras e norteamericanas. Os resultados mostraram que, além dos diversos benefícios ambientais das coberturas verdes em maior ou menor escala, o cultivo de horta em HIS pode contribuir significativamente com a complementação da renda familiar para pagamento das parcelas de compra do imóvel. Foram avaliados dois cenários: o primeiro com o cultivo de três espécies distintas em mesma proporção de área e o segundo com maior disposição de área para a espécie mais rentável. O segundo cenário se mostrou mais lucrativo e a renda mensal gerada corresponde a 65% e 99% do valor da 1ª e 234ª parcelas do financiamento, respectivamente e, a partir dessa parcela, a renda simulada cobriria o valor das parcelas gerando lucro, podendo alcançar até 130% na 420ª parcela, a última do financiamento.
Análise experimental da resistência ao cisalhamento do conector HILTI X-HVB em vigas mistas de aço e concreto.
(2021) Silva, Marcos Antônio da; Paula, Geraldo Donizetti de; Ribas, Rovadávia Aline de Jesus
A construção estruturada em aço no Brasil surge por volta dos anos 1950, sendo o edifício garagem América a primeira edificação de grande porte a ser concebido nesse sistema. A partir daí outras edificações e empreendimentos foram surgindo impulsionados pela criação da Companhia Siderúrgica Nacional (CSN), que criou a Fábrica de Estruturas Metálicas (FEM). As construtoras especializaram-se na fabricação de estruturas metálicas com suporte de países que dominavam esse tipo de construção. Mesmo timidamente, houve avanços e temos na atualidade tecnologia e conhecimento fabril para realização de novas e complexas edificações, dentre as quais se destacam as construções mistas. Nesse tipo de construção, normalmente aplicam-se conectores de cisalhamento na interface laje-viga, que têm a função de diminuir o deslizamento horizontal que ocorre quando a edificação está sujeita a cargas laterais, transmitindo o cisalhamento na interface aço-concreto. Nas primeiras edificações no país, foi muito utilizado o conector tipo “U” de perfil laminado e, em outras ocasiões, o perfil “U” conformado a frio. O conector tipo pino com cabeça “stud bolt” começa a ser aplicado no Brasil no ano de 1980. Pode-se dizer que sua utilização está bem difundida e aprovada pelas normas nacional e internacional. Em 2010 surge o conector Hilti X-HVB, sendo que sua aplicação em maior escala está na Europa. Inicialmente, observamse esses conectores sendo mais aplicados em lajes com fôrmas incorporadas, podendo ser, no entanto, utilizados em lajes moldadas “in loco”, pré-moldadas e mistas. Nesse contexto, o objetivo dessa dissertação é fazer uma análise experimental de conectores de cisalhamento do tipo Hilti X-HVB em lajes maciças. Nos experimentos são avaliados três corpos de prova por meio de ensaios tipo Push out, conforme especificação do Eurocode 4, tendo sido avaliados o comportamento e determinada a resistência ao cisalhamento sob carregamento estático. Os resultados obtidos mostram que os conectores atendem em média os resultados especificados no catálogo do fabricante.
Residues in cement-based composites : occurrence mapping in Brazil.
(2023) Lopes, Carolina de Melo Nunes; Mendes, Vítor Freitas; Garcia, Danielle Rios; Mendes, Júlia Castro
Scientific articles related to the incorporation of residues in civil construction materials are growing worldwide, although their practical application is still incipient. In this scenario, this paper produced an occurrence map of the most studied residues in Brazil when incorporated in cement-based composites. Initially, the most relevant residues were identified through a bibliometric analysis on the Scopus database, using the software VOSviewer. This analysis included scientific papers from Brazilian institutions published from 2001 to 2022 regarding the development of cement-based composites using residues, wastes, or tailings. Subsequently, to map the occurrence of these materials in each Brazilian state, we used public and private data on the country’s industrial production and waste disposal. From 1272 articles analyzed, we identified 49 residues with at least 2 citations. Among the most cited residues in Brazilian publications are construction and demolition waste, rice husk, glass waste, sugarcane bagasse, and tire rubber residue. The authors noticed the heterogeneity of the occurrence of the residues across the large Brazilian territory and found gaps on research trends involving them. These and other observations facilitate the decision-making process regarding logistics and investments related to the reuse and recycling of these materials.
Resistance factor calibration for perforated cold-formed steel compression members.
(2022) Jardim, Roberta Layra Faragó; Freitas, Marcílio Sousa da Rocha; Brandão, André Luis Riqueira
Cold-formed Steel profiles are structural profiles widely used in civil construction. They are often manufactured with perforations. The designing can be performed using the direct resistance method. Formulations were adapted by Moen and Schafer (2008) to consider the presence of perforations in these profiles. The objective of this study is to investigate the structural safety of columns with web perforations. The calculation of the resistance capacity was performed using the formulations proposed by the authors. The reliability indexes were determined using the First Order Reliability Method (FORM), First Order Second Moment (FOSM) and Monte Carlo Method (MCM), which are reliability methods for the Load and Resistance Factor Design (LRFD) and Limit States Design (LSD) philosophies. Following the same criteria performed by AISI S100, the resistance factors were obtained from the FOSM method. Based on the results, it was found that the desired security level for the LSD philosophy was not achieved. The calculated resistance factors are predominantly lower than the target. However, for the LRFD philosophy, the safety level was achieved, and the resistance factors were higher than the target.
Utilização de filtro biológico com diferentes meios de suporte para tratamento de águas residuárias de laticínios.
(2022) Carneiro, Rúbia Lemos Ferreira; Simpliciano, Anne Caroline; Souza, Tamara Daiane de; Mendes, Múcio André dos Santos Alves; Uliana, Eduardo Morgan; Gallardo, Nuria Pérez
The dairy industry has a prominent role in the Brazilian scenario, lacking alternatives that combine a good cost / benefit ratio in the management of its effluents. Thus, the objective of this work was to experimentally analyze the biological filter (BF) with two different media, sugar cane bagasse and wood sawdust, in the biological treatment of dairy effluent, in order to evaluate the effectiveness of the treatment and to identify which of the materials is more efficient. Analyzes of pH, BOD, turbidity, total solids, sediment solids, total dissolved solids, electrical conductivity (EC), nitrogen and phosphorus were performed. There were superior results of removal of BOD, nitrogen and turbidity for the filter filled with wood sawdust. The bagasse filter presented better results on average in the reduction of phosphorus concentration and total solids, which are 91.7% and 59.8, respectively. The reduction of TDS concentration and EC reduction, both filters demonstrated equivalence. The results of sediment solids indicate the need to implement the secondary settler to the system. It is recommended to use FB filled with wood sawdust for treatment of dairy wastewater.
Lignin-based admixtures : a scientometric analysis and qualitative discussion applied to cement-based composites.
(2023) Carvalho, Victor Rezende; Costa, Laís Cristina Barbosa; Baeta, Bruno Eduardo Lobo; Peixoto, Ricardo André Fiorotti
The development of lignin-based admixtures (LBAs) for cement-based composites is an alternative to valorizing residual lignins generated in biorefineries and pulp and paper mills. Consequently, LBAs have become an emerging research domain in the past decade. This study examined the bibliographic data on LBAs through a scientometric analysis and in-depth qualitative discussion. For this purpose, 161 articles were selected for the scientometric approach. After analyzing the articles’ abstracts, 37 papers on developing new LBAs were selected and critically reviewed. Significant publication sources, frequent keywords, influential scholars, and contributing countries in LBAs research were identified during the science mapping. The LBAs developed so far were classified as plasticizers, superplasticizers, set retarders, grinding aids, and air-entraining admixtures. The qualitative discussion revealed that most studies have focused on developing LBAs using Kraft lignins from pulp and paper mills. Thus, residual lignins from biorefineries need more attention since their valorization is a relevant strategy for emerging economies with high biomass availability. Most studies focused on production processes, chemical characterizations, and primary fresh-state analyses of LBA-containing cement-based composites. However, to better assess the feasibility of using different LBAs and encompass the multidisciplinarity of this subject, it is mandatory that future studies also evaluate hardened-sate properties. This holistic review offers a helpful reference point to early-stage researchers, industry professionals, and funding authorities on the research progress in LBAs. It also contributes to understanding the role of lignin in sustainable construction.
Influence of residual stress models prescribed in design codes for steel I-section behavior.
(2022) Lemes, Igor José Mendes; Silva, Jéssica Lorrany e; Batelo, Everton André Pimentel; Silveira, Ricardo Azoubel da Mota
Non-uniform cooling of steel cross-sections during the manufacturing process generates a state of residual stresses in the cross-section. Design codes describe the distribution of these stresses in different ways. This work aims to numerically investigate the influence of these models on the behavior of bare steel and steel-concrete composite sections by the curves: flexural stiffness-bending moment, moment-curvature and yield curves (initial and full yield). These procedures are important for the study of the simplified curves used in some methodologies of the refined plastic hinge method (RPHM) analysis. The study will use the strain compatibility method (SCM), where, if the axial strain of the cross-section point is known, the section stiffness is obtained using the tangential Young's modulus derived from the materials constitutive relationship. A fiber discretization algorithm is applied and the residual stresses are explicitly inserted into the fibers automatically. The methodology was calibrated using the moment-curvature relationship and the flexural stiffness-bending moment curve. These results were numerically stable and good convergence with literature data was obtained. In general, the residual stress model of the American standard (AISC, 2016) defines a larger elastic region within the interaction diagrams then European model (CEN, 2005). The results obtained showed that the initial yield curves for steel I-sections under minor axis bending require revision for application to RPHM, mainly due to the loss of symmetry in relation to the ''M'' axis in the normal force-bending moment (''NM'') interaction diagram.
Comparison between recent implicit time integration methods with frequency dissipation for nonlinear structural applications.
(2022) Fernandes, William Luiz; Barbosa, Gustavo Botelho; Greco, Marcelo; Silveira, Ricardo Azoubel da Mota
The present paper aims to test recent (Truly self-starting two sub-step method and three-parameter singlestep implicit method) and classical (Generalized-α, HHT-α, and WBZ-α methods) time integration methods using the geometrically nonlinear Positional Finite Element Method (PFEM). The numerical formulation is based on the total Lagrangian approach and uses the Hessian matrix to obtain the response. The mixed hardening inelastic model applied to PFEM is also presented. Two examples validate the time integration algorithms and the inelastic model. In the first example, the mixed hardening inelastic model is compared with the the bilinear stress-strain model and the elastic-perfectly plastic hinge model, and aspects such as amplitude decay and period elongation are discussed. In the second example, the implemented algorithms are verified in a severe geometrically nonlinear example, considering the influence of numerical dissipation, time interval, and the number of elements in the response. Results show the relevance of numerical damping for numerical stabilization and the good performance of the Generalized-α algorithm.

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