Resumo em Português:

RESUMO Este trabalho teve por objetivo analisar a viabilidade da produção de pisogramas de concreto com a incorporação de fibras de papel kraft provenientes de embalagens de cimento pós-uso. As embalagens foram coletadas e processadas, resultando nas fibras de papel kraft (FPK). Foi adotado o traço de referência de 1:2,31:2,49:0,54 nas proporções de massa de cimento, agregado miúdo, agregado graúdo e fator água/cimento, respectivamente. Estudou-se duas composições com incorporação de FPK nos percentuais de 0,5% e 1,0% em relação à massa total de agregados. Para cada composição, foram moldados 4 corpos de prova e executados os ensaios de absorção de água e resistência à compressão aos 28 dias. Como resultado, todas composições apresentaram absorção de água abaixo do limite normativo de 6%. No ensaio de resistência à compressão, as composições de referência, de 0,5% e de 1,0% de FPK obtiveram 35,55 MPa, 30,61 MPa e 28,40 MPa, respectivamente. Como o concreto com 0,5% de incorporação de FPK obteve melhor desempenho mecânico, foram confeccionados 6 pisogramas para realização da inspeção visual e avaliação dimensional, os quais atenderam aos requisitos normativos. Este trabalho mostra a viabilidade de produção de concreto com FPK e a utilização deste na fabricação de pisogramas para áreas que exijam até 30 MPa.

Resumo em Inglês:

ABSTRACT This paper aimed to analyze the feasibility of the production of grass paver blocks of concrete with the incorporation of kraft paper fibers from post-use cement bag. The bags were collected and processed, resulting in kraft paper fibers (FPK). It adopted the reference composition of 1:2.31:2.49:0.54, in the proportions of mass of cement, fine aggregate, coarse aggregate, and water/cement factor, respectively. It was studied two compositions with FPK incorporation in the percentages of 0.5% and 1.0% in relation to the total mass of aggregates. For each composition, 4 specimens were molded, and the water absorption and compressive strength tests were performed at 28 days. As a result, all compositions showed water absorption below the normative limit of 6%. In the compressive strength test, the reference compositions, 0.5% and 1.0% FPK obtained 35.55 MPa, 30.61 MPa and 28.40 MPa, respectively. As the concrete with 0.5% FPK incorporation obtained better mechanical performance, 6 grass paver blocks were made to carry out the visual inspection and dimensional evaluation, which both met the normative requirements. This research presented the feasibility of the producing concrete with FPK and its use in the manufacture of grass paver block for areas requiring up to 30 MPa.

Resumo em Inglês:

ABSTRACT The utilisation of various resources, specifically industrial wastes, in the manufacturing of concrete is the main emphasis of today’s knowledge of concrete technology. One of the key concerns in the global protection of the environment is waste management. The growing growth of the Indian automobile industry has ultimately led to a rise in the garbage that is dumped, such as used tyres. Coal ash was also added to the improvised concrete mix (CRAC) in a frozen percentage within the cement mantle of the concrete matrix for the stabilization of the binding qualities. For sustaining the required qualities of supplied 30 MPa or other base values for concrete with reference to a specific purpose, it was found that an optimal proportional combination of 12% waste rubber tyre crumbs and 9% coal ash was the most technologically and economically effective solution. Flexural strength of 5.18 MPa, which was attained, confirmed that this optimum proportionate combination was the best and most durable.

Resumo em Inglês:

ABSTRACT Due to the rapid urbanisation and rapid population explosion, there is a vast essential requirement in the dispose of solid waste. Carbonization of Styrofoam is carried out at varying temperature ranges of 300°C to 675°C at an interval of 75°C using KOH as reagent. The Characterisation of power of hydrogen ion, ash and moisture content, fixed carbon, Volatile matter, iodine adsorption value, methyl blue value was conducted. It was found that the activate carbon obtain from the temperature of 525°C has a good carbon characteristic. The batch experiment such has pH, contact time, carbon dosage, agitation speed, potency of Nickel (II) was conducted with the purpose of ascertaining the efficiency of Nickel (II) adsorption. This analysis deals with fixed bed column to remove Nickel (II) from a solution. The results indicated that the sorption-second order kinetic model was the most appropriate fit for the data, and alternative models such as Adams-Bhorat, Thomas, and Yoon Nelson’s were also evaluated. Increasing a bed height resulted in better removal of Nickel (II) in all 3 models. Therefore, The utilization of Styrofoam-derived activated carbon as a medium for ongoing Nickel (II) adsorption from an aqueous solution.

Resumo em Inglês:

ABSTRACT Huge accumulations of Recycled asphalt pavement (RAP), scarcity of bitumen obtained from natural resources, RAP causing environmental pollution, and increased construction of flexible pavement all over the world led the researchers to reuse the improved aged bitumen by modifiers. Hence, in this research, the reclaimed aged asphalt improved by ABS (5% weight of virgin bitumen) was partially replaced by virgin bitumen (10 to 60% with an increment of 10%) used in the asphalt mix, and mechanical properties such as stability, flow, rutting resistance, fatigue life, Indirect Tensile strength, and resilient modulus were investigated. The research concluded that the aged reclaimed asphalt containing 5% ABS can be partially replaced up to 30% by conventional virgin bitumen, exhibiting better performance without compromising the mechanical properties of the asphalt mix.

Resumo em Inglês:

ABSTRACT Water cooling systems usually receive additional chemical treatment and different features to prevent pitting corrosion on stainless steel which is dependent on medium factors such as species concentration. Chloride is an aggressive ion with which sulfate can act as an inhibitor. By applying cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and Mott-Schottky plots, the behavior of 304 stainless steel (304 SS) was evaluated in solutions containing chloride, sulfate and ammonium ions. The polarization curves indicated the inhibiting effect of sulfate ions against pitting corrosion and the increase of the repassivation potential with increasing ammonium concentration. The most pronounced inhibiting effect occurred with a smaller ratio between chloride and sulfate ions (1:2). By EIS, the values obtained for charge transfer resistance of 304 SS sample corroborated the results of the cyclic voltammetry, ranging between 0.4 and 0.7 MΩcm2. The passive film showed semiconductor behavior, in agreement with the model of the chromium oxide inner layer and iron oxide outer layer. The passive films formed were highly doped, with doping density values on the order of 1020-21 cm–1. The difference between the corrosion potential and the flat band potential was found in the solutions where the material was less susceptible to corrosion.

Resumo em Inglês:

ABSTRACT This study investigated the effects of electrokinetic treatments on mortar specimens using a range of experimental techniques. Ionic migration tests revealed that increasing voltage and duration led to higher charge transfer, with Ca(OH)2 electrolyte showing the highest cationic migration. X-ray fluorescence analysis indicated that Nano-Silica treatment resulted in the highest oxide content, transforming absorbed elements effectively. The chloride penetration test demonstrated that Ca(OH)2 treatment exhibited the lowest charge passed, suggesting minimal chloride penetration, while NaOH and KOH treatments showed higher charge passed. Field Emission Scanning Electron Microscopy analysis provided visual evidence of structural changes and material depositions. Calcium Hydroxide treatment reduced porosity, Sodium Hydroxide, and Potassium Hydroxide treatments displayed distinct particle distributions, and Nano Silica treatment led to the formation of hair-like crystal structures. These findings help to understand the microstructure and composition of cement mortar specimens after various treatments. The nano-silica electrolyte appeared as a viable choice for electro-kinetic therapy, whereas Ca(OH)2 treatment stated the potential to reduce chloride penetration in mortar specimens. The results offer insights into optimizing electrokinetic treatments for improved mortar performance.

Resumo em Inglês:

ABSTRACT Concrete, a vital material in construction, is facing challenges in enhancing its strength and durability. Researchers are exploring innovative approaches, such as using Fibre Reinforced Polymer (FRP) composites, to improve these properties. Structural flaws are often found during evaluations of existing buildings, especially older ones that may benefit from retrofitting. In this study, Manufactured sand was tested as a replacement for fine aggregate in concrete mixes to strengthen the mixes. The study utilized response surface methodology to predict the strength properties of sustainable Concrete mixes based on compressive strength. The flexure of reinforced concrete beams was evaluated using chopped strand mat (CSM) and glass-fiber reinforced plastic (GFRP) laminates. The study tested five RC beams using a 4-point bending configuration, with one beam serving as the control and the other four strengthened with FRP laminates. The results showed successful improvement in load-bearing capacity with GFRP + CSM laminates. However, thicker FRP sheets were not recommended as they can impact flexural strength. The GFRP + CSM enhanced beam achieved a 107% increase in ultimate load compared to the non-strengthened beams, according to experimental results. The strengthened beam had a greater rise load-carrying capability of 115 kN than the unstrengthen beam.

Resumo em Inglês:

ABSTRACT This research is to replace natural coarse aggregate as 20%, 40%, 60%, 80%, and 100% respectively, by weight in an M20 grade geopolymer concrete. The geopolymer concrete with different mixes is subjected to fresh, hardened, and durability tests. Utilization of thermal ash aggregates increased the slump and compressive strength of geopolymer concrete by about 15% and 9% respectively. Whereas the slump and compressive strength of geopolymer concrete decreased by about 30% and 38% respectively by using 100% Lightweight Expanded Clay Aggregate (LECA). Density reduction in geopolymer concrete was found by using both thermal ash aggregate and lightweight expanded clay aggregate for about 9% and 28% respectively. Thermal ash aggregate decreased the density of geopolymer concrete up to 1850 kg/m3 and improved the strength up to 24.50 N/mm2, on the other side using lightweight expanded clay aggregate, the density of geopolymer concrete drastically decreased up to 1250 kg/m3 with a huge decrease in strength up to 14 N/mm2. Other mechanical test results showed similar variations with respect to the compression test results. To ensure the durability of lightweight geopolymer concrete for mixes of GPC, TM5, and LM2 conducted tests like acid resistance, sulphate resistance, salt resistance, water absorption, accelerated corrosion, and sorptivity test.

Resumo em Inglês:

ABSTRACT The annual output of refinery waste sludge is huge in our country, and the resource disposal of sludge has become a difficult problem that needs to be overcome. In order to increase the content of renewable gas and light oil after pyrolysis of oil sludge at the bottom of refinery tank, nano-CuO and nano-γ-Al2O3 with good wave-absorbing property and good catalytic property were selected to study the effect of additive load on the characteristics of pyrolysis reaction products by experimental research and analysis. The results show that the highest oil and gas yields can be obtained when the nano-CuO content is 10%. When nano-γ-Al2O3 was loaded at 15%, the pyrolysis oil and pyrolysis gas yield reached the peak. Moreover, the light component of pyrolysis oil can be improved, and the proportion of gasoline and diesel (C4 ~ C12, C13 ~ C18) is 75.422%. H2 volume content reaches the highest at 15% load.

Resumo em Português:

RESUMO O concreto celular é um material cimentício de estrutura porosa e com baixa densidade, resultante do endurecimento de uma mistura constituída por aglomerantes, agregados miúdos e poros de ar. Uma das formas de inserҫão dos poros de ar é através de uma espuma pré-formada, composta por bolhas de ar, as quais influenciam o comportamento do concreto celular no estado fresco e endurecido. Trabalhos recentes propuseram a utilizaҫão de pequenas quantidades Goma Xantana (XG) como agente espessante da espuma, e verificaram que XG aumentou a estabilidade da mesma e proporcionou melhor desempenho ao concreto celular no estado endurecido. No entanto, o funcionamento da XG em diferentes teores ainda não está esclarecido. Assim, este artigo apresenta um estudo da influência de XG na qualidade da espuma pré-formada, como também nas propriedades físicas e mecânicas do concreto celular. Foram avaliadas amostras com duas densidades diferentes, 800 Kg/m3 e 1200 Kg/m3. A composiҫão que proporcionou melhor qualidade da espuma foi 2% de XG. No concreto celular, a adiҫão de XG mostrou-se mais eficiente para as amostras com densidade alvo de 800 Kg/m3, pois proporcionou uma diminuiҫão do índice de vazios e da interconectividade entre poros, além de maior resistência á compressão.

Resumo em Inglês:

ABSTRACT Cellular concrete has a porous structure and low density, resulting from a mixture of binders, fine aggregates and air pores. One way of inserting the air pores is through a preformed foam. The foam is composed of air bubbles, which influence the behaviour of cellular concrete both in the fresh and hardened state. Recent studies have proposed the use of xanthan gum (XG) as a foam thickening agent, which increases the foam stability and improves the performance of cellular concrete in the hardened state. However, the functioning of XG and the use of different contents is still unclear. Thus, this work presents a study of the influence of xanthan gum on the quality of preformed foam, as well as on the physical and mechanical properties of cellular concrete. Samples with two different densities (800 Kg/m3 and 1200 Kg/m3) were evaluated. The content that provided better foam quality was 2% of XG. In cellular concrete, the addition of XG proved to be more efficient for foamed concrete with a target density of 800 Kg/m3, since decreases the void ratio, as well as the interconnectivity between pores. Likewise, xanthan gum promoted an increase in compressive strength.

Resumo em Inglês:

ABSTRACT The main aim is to examine the behavior of laminated carbon fiber and glass fiber reinforced polymer (CFRP) and (GFRP) reinforced composite (RC) beams. The physical characteristics of these laminates, such as tensile strength, modulus of elasticity and strain capacity are examined. The capacity of load bearing, deflection, and cracking behavior of RCC beam specimens along with various types and numbers of laminates will be analyzed and compared. The results will provide insight into the outcome of using different kinds of laminates over RCC beams and identify the optimal configuration for their reinforcement. The findings of this research paper will have significant implications for the construction industry, particularly for rehabilitation and repairing of old buildings and other structures. The use of CFRP and GFRP laminates as a reinforcement material can extend the life of RCC beams, reduce the need for costly repairs and replacements, and increase the safety and sustainability of infrastructure. The paper will conclude with recommendations for the optimal use of carbon fiber and glass fiber reinforced polymer laminates in RCC beam reinforcement, including the selection of appropriate materials and design criteria for their successful application.

Resumo em Inglês:

ABSTRACT Predictive models are useful tools for reliable estimations of key mechanical properties when properly calibrated. Several research efforts have compared calibrated models in the literature, but the sampling techniques adopted in the model calibration, selection, and evaluation were not the focus of these studies. This work reviews different sampling techniques and employs hold-out and repeated k-fold cross-validation (CV) to evaluate three empirical dynamic modulus equations calibrated using a database containing 1,806 records from 65 asphalt mixtures. The results indicate that hold-out can induce unrealistic conclusions about the estimations, while repeated k-fold CV is a reliable methodology.

Resumo em Inglês:

ABSTRACT Waste management is one of the essential issues in the global domain of environmental conservation. The flourishing promotion of the Automobile Industry in India has eventually ended up with an increase in dumped waste material, such as a waste tyre. Steel slag was also added to the improvised concrete mix (CRAC) in a frozen percentage within the cement mantle of the concrete matrix for the stabilization of the binding qualities. It was discovered that an optimal proportional combination of 12% waste rubber tyre crumbs and 9% steel slag proved to be the most techno-economically viable solution for maintaining the mandated qualities of supplied 30MPa or other base values for concrete with reference to a specific purpose due to calcium oxides. The achieved split tensile strength (3.762MPa) validated this ideal proportionate combination as the best and most long-lasting.

Resumo em Inglês:

ABSTRACT Due to their excellent mechanical properties, Carbon fiber reinforced aluminum laminates (CARALL) are widely used in aerospace, transportation, military and navigation fields. In this study, a method of preparing CARALL by molding process was introduced. We used this method to obtain two kinds of CARALL, Al-CFRP-Al laminated plate and CFRP-Al-CFRP laminated plate. Then we tested their tensile properties. The experimental results indicated that the tensile properties of Al-CFRP-Al laminates were 865.1 MPa, while the tensile properties of CFRP-Al-CFRP laminates were 718.2 MPa. In comparison to pure aluminum alloy, the tensile strength of both laminates had been significantly improved. By observing the microstructure of the fiber layer of the laminated plate, it was found that the carbon fiber is a brittle material, and its fiber bundle can effectively enhance the material properties during the tensile process. Finally, the tensile failure behavior of the prepared CARALL was analyzed by finite element simulation, which further confirmed that the use of carbon fiber composite can effectively enhance the tensile properties of aluminum alloy. Through this study, the tensile properties of aluminum alloy were successfully enhanced by CFRP, which provided a method for the study of aluminum alloy performance enhancement.

Resumo em Inglês:

ABSTRACT The principal objective of this study is to investigate the flexural characteristics of ferrocement slabs incorporating geopolymer and to evaluate the most effective composition. Using Carbon Fiber Reinforced Polymer (CFRP) wounded wire mesh, characteristics of Nano silica based geopolymer incorporated ferrocement slab elements have been experimentally examined in detail at both room temperature curing and hot curing at 60 °C. Cement can be replaced in mortar by fly ash, saving on the need for expensive disposal land. GGBS is applied in addition to fly ash to increase strength in room temperature curing. Geopolymer mortar of 1:2 is used for the ferrocement slab. This binder is made up of 25% sodium silicate, 10% sodium hydroxide, and 65% fly ash. By changing the fly ash's weight with GGBS, the percentage was changed by 20%, 40%, 60%, 80%, and 100%. 80% percent GGBS addition is deemed ideal, even though the compressive test results show that the best strength was achieved with 100% GGBS. Nano silica added as 0.5%, 1%, 1.5%, and 2% by weight of binder further enhances the performance of the chosen blend. The strength of the geopolymer mortar increased by about 240% when 1.5% nano silica and 80% GGBS were added.

Resumo em Inglês:

ABSTRACT Population growth and rapid pace of globalization have increased the demand for construction materials. River sand is one of the main materials used to make the fine aggregate for concrete. As a result, finding an alternative to sand has become crucial. Granite debris and M sand are employed in place of river sand in this experiment. In this experiment, granite debris as well as M sand are used in place for river sand. Concrete constructed using granite waste and alccofine was compared to ordinary concrete that had a 0.50 w/c ratio using the M25 mix design. 10% of alum is added to cement, and 0% to 30% of fine aggregate is replaced with granite waste enrich the physical properties by 23%, 9% and 41% in compressive, split tensile and flexural strength. The mechanical and microstructural characteristics are looked at in this investigation. According to the test results, concrete made with 10% alccofine, 15% granite waste, with 85% M sand performs satisfactorily. In addition, super plasticizers are acceptable in the M5 mix compared to the other mixes. The microscopic images show a densely packed cement matrix and the aggregate transition area, which points to strong bonding.

Resumo em Português:

RESUMO Este estudo teve por objetivo avaliar a resistência à compressão residual de argamassas de cimento LC3 após a exposição à elevadas temperaturas (200, 400, 600, 800 e 1000 °C), em comparação com uma argamassa de cimento Portland (CP). Paralelamente, o efeito da temperatura na mineralogia de ambas as composições foi avaliado através da técnica de difração de raios-X (DRX). Os resultados de resistência à compressão revelaram que as argamassas à base de cimento LC3 apresentaram um desempenho mecânico equivalente ao das argamassas à base de CP após 28 dias de hidratação, independentemente das temperaturas testadas (23, 200 e 320 °C). Adicionalmente, os resultados de DRX indicaram que, mesmo com a decomposição da etringita e das fases AFm a partir de 200 °C, não foram observadas reduções na resistência à compressão dos sistemas LC3 para temperaturas de até 320 °C. Foi identificada a formação da fase ghelenita nos sistemas LC3 para temperaturas superiores a 800 °C. Este estudo demonstrou que os sistemas LC3 exibiram um comportamento mecânico equivalente ao CP quando submetidos a altas temperaturas. Esses resultados oferecem contribuições significativas para a validação e potencial aplicação prática desse cimento alternativo com menor impacto ambiental.

Resumo em Inglês:

ABSTRACT This study aimed to evaluate the residual compressive strength of LC3 cement mortars after exposure to high temperatures (200, 400, 600, 800, and 1000 °C), in comparison to a Portland cement (PC) mortar. Concurrently, the effect of temperature on the mineralogy of both compositions was assessed using X-ray diffraction (XRD) analysis. The compressive strength results revealed that LC3 cement-based mortars exhibited mechanical performance equivalent to PC-based mortars after 28 days of hydration, regardless of the tested temperatures (23, 200, and 320 °C). Additionally, XRD results indicated that even with the decomposition of ettringite and AFm phases starting at 200 °C, there were no reductions in the compressive strength of LC3 systems up to 320 °C. The formation of ghelenite phase was identified in LC3 systems at temperatures above 800 °C. This study demonstrated that LC3 systems displayed mechanical behavior equivalent to PC when subjected to high temperatures. These findings offer significant contributions to the validation and potential practical application of this environmentally-friendly alternative cement.

Resumo em Português:

RESUMO O lodo de Estação de Tratamento de Água (ETA) quando disposto inadequadamente pode ocasionar desequilíbrio ambiental e problemas de saúde pública, devido à lixiviação de metais pesados para os corpos hídricos. Dito isso, este trabalho objetivou caracterizar de maneira física, química, térmica e mineralógica o lodo da ETA da cidade de Palmeira dos Índios-AL. A metodologia empregada foi de caráter experimental através da realização dos ensaios de granulometria, limites de Atterberg, fluorescência de Raios X, difração de Raios X e análise termogravimétrica. Após o ensaio de granulometria o lodo apresentou característica de areia fina. Na análise química identificou-se presença do Ca (7,81%) e Mg (2,51%), que podem interagir com elementos formadores de fase vítrea Si (55,65%) e Al (12,03%) durante a sinterização. Ademais, os percentuais mais significativos de silício e alumínio apresentaram-se na forma de quartzo e caulinita, corroborando com os resultados de fluorescência de Raios X. Na análise térmica houve perda de massa em torno de 42% até a temperatura de 400°C, sinalizando a possibilidade de tratar termicamente o subproduto, antes de sua incorporação em cerâmicas. Por fim, o lodo apresenta potencial de aplicação em matrizes cerâmicas, dado a presença de elementos com características fundentes.

Resumo em Inglês:

ABSTRACT The sludge from Water Treatment Plants (WTP) when disposed of improperly can cause environmental imbalance and public health problems due to leaching of heavy metals into water bodies. Therefore, this work aimed to characterize the physical, chemical, thermal and mineralogical characteristics of the sludge from the WTP of the city of Palmeira dos Índios-AL. The methodology used was experimental, through the performance of granulometry tests, Atterberg limits, X-ray fluorescence, X-ray diffraction and thermogravimetric analysis. After the granulometry test, the sludge presented characteristics of fine sand. The chemical analysis identified the presence of Ca (7.81%) and Mg (2.51%), which may interact with glass phase forming elements Si (55.65%) and Al (12.03%) during sintering. Furthermore, the most significant percentages of silicon and aluminum were in the form of quartz and kaolinite, corroborating the X-ray fluorescence results. In the thermal analysis there was a loss of mass around 42% until the temperature of 400°C, indicating the possibility of thermally treating the by-product before its incorporation into ceramics. Finally, the sludge presents potential for application in ceramic matrices, given the presence of elements with melting characteristics.

Resumo em Inglês:

ABSTRACT The Design of Experiment (DOE) approach was employed to determine the optimum combination of progression variables, which included Jute fibres (JF), Kenaf fibres (KF), and Silica fumes (SF), aimed at improving the mechanical properties of concrete. To achieve this, the Central composite design (CCD) of Response Surface Methodology was used. The results indicated that the inclusion of KF, JF and SF contributed positively to enhancement of mechanical properties. However, it was observed that a higher level of 0.75% of Jute and kenaf fibres incorporation led to a reduction in strength. The analysis, which involved surface plots, Pareto charts, and regression models, demonstrated that the presence of silica fumes was the most influential factor affecting compressive strength at both 14 days and 28 days. On the other hand, for split tensile strength, both jute and kenaf fibres played significant roles. To assess the accuracy of the models, validation tests were conducted, and the percentage of error was found to be less than 3.5% for compressive strength and split tensile strength. This indicates the reliability of models in predicting the strength properties based on the chosen progression variables.

Resumo em Português:

RESUMO Os inibidores são um dos métodos mais antigos de combate à corrosão, que ainda hoje é um problema desafiador e caro. Porém, os inibidores tradicionais são tóxicos e não biodegradáveis, o que vai contra os princípios da Química Verde, assim denominada por valorizar o uso de produtos biodegradáveis e ambientalmente amigáveis. Os inibidores podem ser obtidos de plantas e seus resíduos que, quando submetidos a algum tipo de processamento, geram extratos ou óleos com importante potencial inibitório. Na maioria dos casos, os inibidores verdes são compostos orgânicos classificados, quanto ao mecanismo, como mistos, possuindo grupos funcionais polares que atuam como centros de adsorção na superfície metálica. Este estudo teve como objetivo realizar uma revisão sistemática da literatura sobre inibidores de espécies da flora brasileira e utilizados em ambiente ácido para prevenir a corrosão em aço carbono. O Brasil apresenta uma rica biodiversidade de flora, com mais de 46.200 espécies catalogadas em 2020, o que proporciona um amplo campo de pesquisa nesta área. A revisão incluiu 28 espécies de plantas diferentes. Os resultados encontrados foram promissores, com destaque para o uso de partes de vegetais que normalmente são descartadas e mostram o potencial de desenvolvimento e aprimoramento de inibidores verdes para futura aplicação em escala industrial.

Resumo em Inglês:

ABSTRACT Inhibitors are one of the oldest methods of mitigating corrosion, which is still a current challenging and costly problem. However, traditional inhibitors are toxic and non-biodegradable, which goes against the principles of Green Chemistry, so named for valuing the use of biodegradable and environmentally friendly products. They can be obtained from plants and their residues that, when subjected to some type of processing, generate extracts or oils with important inhibitory potential. In most cases, green inhibitors are organic compounds classified relating to the mechanism as mixed, having polar functional groups that act as adsorption centers on the metallic surface. This study aimed to carry out a systematic review of the literature on inhibitors from species of Brazilian flora and used in an acid environment to prevent corrosion in carbon steel in a specific medium. Brazil presents a rich biodiversity of flora, with more than 46,200 species cataloged in 2020, which provides a wide field of research in this area. The review included 28 different plant species. The results found were promising, with emphasis on the use of parts of vegetables that are normally discarded and show the potential for development and improvement of green inhibitors for future application on an industrial scale.

Resumo em Inglês:

ABSTRACT In this work, AA7075/SiC/ZrC hybrid metal matrix composite was successfully fabricated by powder metallurgy route. The influence of conventional and microwave sintering on the microstructural and mechanical properties of the composites were investigated. SEM, XRD and XRF Analysis were used to investigate the microstructure of the samples. The compression strength and hardness were determined using a Universal Testing Machine and Rockwell Hardness setup respectively. It can be concluded that the specimen which is fabricated with a reinforcement of 15% SiC and 3% ZrC with microwave sintering shows the best mechanical characteristics with hardness reaching 92HRB, a compression strength of 200 MPa and better microstructural property than the conventionally sintered specimens. This work has applications in the aerospace and automotive industries for the manufacturing of composite materials that can endure high temperatures.

Resumo em Português:

RESUMO O objetivo deste trabalho foi produzir e caracterizar o biocarvão a partir da palha de cana-de-açúcar, bem como investigar possíveis efeitos fitotóxicos às germinações de algodão, milho e soja. Para tanto, o biocarvão foi produzido em forno de duplo tambor e caracterizado por diferentes técnicas. Os ensaios de germinação foram conduzidos in vitro, com doses de biocarvão variando entre 0 e 100 t/ha. O biocarvão foi obtido com rendimento de 40%, pH igual a 9,10, condutividade elétrica de 2,22 dS/m e área superficial específica de 20,3 m2/g. A análise elementar mostrou razões atômicas H/C e O/C de 0,41 e 0,21, respectivamente. A FTIR mostrou a presença de grupos C=C, enquanto a MEV/EDS mostrou estrutura porosa tipo favo de mel e nutrientes, como o Mg, K e Ca. O ensaio de germinação classificou o biocarvão como fitoestimulante para o milho e mostrou ausência de fitotoxicidade para soja. Por outro lado, para o algodão, as doses mais elevadas (50 e 100 t/ha) causaram fitotoxicidade. Os resultados deste trabalho vêm ao encontro das demandas globais por técnicas verdes. O biocarvão feito da palha de cana-de-açúcar é uma tecnologia promissora para melhorar a infertilidade de solos pobres e gerir o sequestro de carbono.

Resumo em Inglês:

ABSTRACT The objective of this work was to produce and characterize biochar from sugarcane straw, as well as to investigate possible phytotoxic effects on the germination of cotton, maize, and soybean. To this end, the biochar was produced in a double-drum oven and characterized by different techniques. The germination trials were conducted in vitro, with biochar doses varying between 0 and 100 t/ha. The biochar was obtained with a yield of 40%, pH equal to 9.10, electrical conductivity of 2.22 dS/m and specific surface area of 20.3 m2/g. The elemental analysis showed H/C and O/C atomic ratios of 0.41 and 0.21, respectively. The FTIR showed the presence of C=C groups, while SEM/EDS showed a honeycomb porous structure and nutrients such as Mg, K and Ca. The germination test classified the biochar as a phytonutrient for corn and showed no phytotoxicity for soybeans. On the other hand, for cotton, the highest doses (50 and 100 t/ha) caused phytotoxicity. The results of this work meet the global demands for green techniques. Biochar made from sugarcane straw is a promising technology to improve the infertility of poor soils and manage carbon sequestration.

Resumo em Inglês:

ABSTRACT ABS resins have wide application in the market, mainly in the manufacture of household appliances, telephones, automotive industry and others, and need to be processed by extrusion for the manufacture of products. The variables used in the process of extrusion of polymers have a direct influence on their mechanical properties. The objective of this study was to evaluate the different speeds of the extruder screw (15, 30, 45 and 60 rpm) on the mechanical properties of raw ABS after the extrusion process. Izod impact resistance and tensile tests, were also performed. The fractures of the samples tested by Izod impact were observed via optical microscopy, scanning electronic microscopy (SEM), and roughness was measured. Calorimetric tests (DSC) and thermogravimetry (TGA), as well as melt flow index (MFI), were also performed. The most significant results were observed for the extruder screw speed of 60 rpm. For the impact test, a reduction in impact energy of approximately 3% was observed, with the same result for tensile resistance. However, an increase in the value of the elastic modulus and the MFI was observed due to the increase in the degree of crystallinity, which was caused by the higher shear of the polymer mass in the screw of the extrusion equipment. Additionally, an atypical case occurred for the ABS polymer in the highest rotation, since it was the polymer that suffered the greatest shear in the polymer chains due to the degradation of the butadiene phase.

Resumo em Inglês:

ABSTRACT Shearer reliability is considered as one of the most important indexes in longwall mining production. However, the traditional reliability methods are based on the specific distribution of the failure parameters, which are incongruent in the actual practice. Therefore, a novle shearer reliability prediction method based on support vector machine (SVM) with chaotic particle swarm optimization (CPSO) is proposed. It combines the advantages of the high accuracy of SVM and the fast convergence of CPSO, where the chaos idea is introduced to particle swarm optimization for the particle initialization, inertia weight coefficient optimizing and premature convergence treatment. Then this CPSO is used to select and optimize the important parameters of SVM. Ultimately, the optimized parameters are used to obtain a superior CPSO-SVM method for reliability prediction. To show the effectiveness of the proposed method, two numerical comparisons are designed respectively using the literature data and the actual shearer data from the coal mine enterprise. The research results reveal the prediction accuracy and validity of the proposed method.

Resumo em Português:

RESUMO A técnica de Hard Anodization foi desenvolvida para otimizar o processo de anodização porosa de alumínio, gerando altas taxas de anodização, com crescimento acelerado e organizado da camada de óxido aliando altas tensões aplicadas no processo com eletrólitos em baixa temperatura. Já o licor pirolenhoso é um produto conhecido no meio agrícola, sendo uma mistura de compostos orgânicos líquidos derivados da condensação da fumaça da produção de carvão vegetal. Assim, o objetivo deste estudo é avaliar a viabilidade técnica do uso do licor pirolenhoso como eletrólito de anodização para alumínio por meio de Hard Anodization. Foram definidos os parâmetros de anodização (tempo, temperatura, tensão e densidade de corrente) adequados a Hard Anodization, em eletrólito de licor pirolenhoso e comparado ao ácido acético 1%. Os testes eletroquímicos foram conduzidos em modo galvanostático e potenciostático. As amostras foram avaliadas morfologicamente, por meio de microscopia eletrônica de varredura (MEV) e microscopia ótica, e por suas características de molhabilidade. Os resultados mostraram que o licor pirolenhoso é capaz de anodizar alumínio, em baixas velocidades de crescimento de óxido, e que o melhor modo de anodização foi o galvanostático. Nas condições de processo utilizadas, o ácido acético comportou-se como eletrólito de eletropolimento para o alumínio.

Resumo em Inglês:

ABSTRACT The Hard Anodization technique was developed to optimize the porous aluminum anodizing process, generating high anodization rates, with accelerated and organized growth of the oxide layer, combining high voltages applied in the process with electrolytes at low temperature. The pyroligneous liquor is a well-known product in the agricultural environment, being a mixture of liquid organic compounds derived from the condensation of smoke from charcoal production. Thus, the aim of this study is to evaluate the technical feasibility of using pyroligneous liquor as an anodizing electrolyte for aluminum using Hard Anodization. The anodizing parameters were defined (time, temperature, voltage and current density) suitable for Hard Anodization in pyroligneous liquor electrolyte and compared to 1% acetic acid. Electrochemical tests were conducted in galvanostatic and potentiostatic mode. The samples were evaluated morphologically, by scanning electron microscopy (SEM) and optical microscopy, and for their wettability characteristics. The results showed that the pyroligneous liquor is capable of anodizing aluminum at low oxide growth rates, and that the best anodizing mode was galvanostatic. Under the process conditions used, acetic acid behaved as an electropolishing electrolyte for aluminum.

Resumo em Português:

RESUMO Zamac é uma liga metálica composta de zinco, alumínio, magnésio e cobre. Suas propriedades de processamento, como baixo ponto de fusão e alta fluidez a quente faz com que a indústria reprocesse o refugo da produção de zamac sem enviá-lo a uma usina para refino, podendo ocasionar diferenças de composição química na liga original e consequentemente nas suas propriedades mecânicas e microestruturais. Este trabalho visa avaliar as variações oriundas do reprocessamento de zamac 5 na forma de sucata contendo eletrodeposição de cobre alcalino quanto à microestrutura e às propriedades mecânicas. As amostras reprocessadas foram comparadas com amostras de zamac 5 como recebidas e analisadas por meio de ensaios de dureza, resistência à compressão, microestrutura por microscopia eletrônica de varredura e de composição química por EDS. Os resultados de ensaio de resistência à compressão e composição química mostram que houve a formação de uma liga nova, com aumento da concentração de aproximadamente 4% de cobre, muito semelhante à liga ternária Zn-15Al-4Cu. Embora essa liga nova tenha apresentado resultados de dureza alta e resistência à compressão relativamente baixa, preliminarmente, pode-se dizer que é adequada para fabricação de peças que não recebem esforços compressivos significativos, como enfeites para roupas, bolsas, calçados e acessórios.

Resumo em Inglês:

ABSTRACT Zamac is a metallic alloy composed of zinc, aluminum, magnesium and copper. Its processing properties, such as low melting point and high hot fluidity, make the industry reprocess the waste from zamac production without sending it to a plant for refining, which can cause differences in chemical composition in the original alloy and consequently in its mechanical and microstructural properties. This work aims to evaluate the variations arising from the reprocessing of zamac 5 in the form of scrap containing alkaline copper electrodeposition in terms of microstructure and mechanical properties. The reprocessed samples were compared with zamac 5 samples as received and analyzed using hardness, compressive strength, microstructure tests using scanning electron microscopy and chemical composition tests using EDS. The results of the compressive strength and chemical composition tests show that a new alloy was formed, with an increase in copper concentration of approximately 4%, very similar to the ternary alloy Zn-15Al-4Cu. Although this new alloy has shown results of high hardness and relatively low compressive strength, preliminarily, it can be said that it is suitable for manufacturing parts that do not receive significant compressive stresses, such as decorations for clothes, bags, shoes and accessories.

Resumo em Inglês:

ABSTRACT This work used a novel technique known as powder metallurgy to create Aluminium (Al) 2024 matrix composites using Al 2024 reinforced with graphene quantum dots at concentrations ranging from 0.25 to 1 wt.%. Here, Al alloy 2024 is presented as a metal matrix composite reinforced with graphene quantum dots. Graphene quantum dots (GQDs) are fragments of graphene that are smaller than 100 nm in size. Graphene quantum dots are added to Al 2024 in proportions of 0.25%, 0.5%, 0.75%, and 1% to create composites. Atomic force microscopy, X-ray diffraction analysis, Fourier transform infrared, TG/DTA, transmission electron microscopy, and scanning electron microscopy experiments have been carried out to determine the characteristics of the synthesized GQD nanoparticles doped with Al 2024. This powder metallurgy process in Al 2024 offers a number of advantages. Shape and material flexibility, application variety, and cost-effectiveness are all made possible by these characteristics. The results showed that powder metallurgy is a suitable method for incorporating and dispersing nanoparticles into Al 2024.

Resumo em Inglês:

ABSTRACT Despite the increasing use of plaster as a construction material, due to its numerous advantages when compared to cement, its use is still restricted, because of its low mechanical resistance and high solubility in water. In this context, research has been carried out related to the addition of nanomaterials to improve the mechanical and physical properties of plaster in civil construction. A highly available, low-cost nanomaterial with excellent properties is nanotalc. In this work, nanocomposites with dimensions of 40 × 40 × 160 mm were produced with ultrafine micronized nanotalc replacing plaster in proportions of 0%; 0.5%; 1%; 1.5% and 2%. The physical and mechanical properties of the nanocomposites were evaluated according to standards. The nanocomposites produced with 1% nanotalc showed satisfactory results for physical and mechanical properties, with an increase of 1.8% in apparent density and 24.12% in compressive strength, and a decrease in water absorption of 6.23%, compared to the composite without the incorporation of nanotalc. The production of nanocomposites with the incorporation of 1% nanotalc is viable and shown to be promising, presenting potential for application as linings and internal partitions, since they showed low water absorption due to the hydrophobicity of nanotalc.

Resumo em Inglês:

ABSTRACT Fly ash is used partially as a replacement to cement to make the concrete. Fly ash contains SiO2 and Al2O3, which contribute to increase the strength of concrete. In the current investigation, fly ash has been replaced with varying percentages of nanosize in concrete, and the strength of the resulting hardened concrete has been evaluated. The production of nanosized fly ash has been made by the ball milling process and the analyses has been completed using scanning electron microscope (SEM) and X-ray diffraction (XRD), in order to determine the chemical and physical composition of the nanoparticles of fly ash. The nano fly ash concrete (NFAC) have been undergone for the durability tests of acid, sulphate and chloride attack. The concrete with 23% of nano fly ash replaced with cement performs well against these adverse conditions. The comparison has been made between the conventional (CC), raw fly ash (RFAC) and NFAC. Nano fly ash makes concrete much denser and more resistant to cracking. So the durability behaviour of NFAC is much better than CC and RFAC. The percentage of reduction in strength after durability aspects is varies from 0.03% to 10.75% for the NFAC.

Resumo em Português:

RESUMO Dada a dificuldade em se usinar aços endurecidos e a complexidade das geometrias comumente observadas em moldes de injeção, além da qualidade da superfície necessária para a geração de peças plásticas sem defeitos, uma estratégia adequada de fresamento deve ser escolhida, o que implica na definição não apenas dos parâmetros de corte e da ferramenta, mas também de sua trajetória. Assim, o presente trabalho tem como foco a investigação da influência de duas diferentes estratégias de corte no fresamento sobre a qualidade de uma superfície convexa (de curvatura constante) em dois tipos de materiais. A qualidade foi avaliada a partir de diferentes parâmetros de rugosidade, os quais foram correlacionados com o brilho percebido e analisados juntamente às características de cada material, como dureza e microestrutura. A partir dos resultados encontrados na etapa final de acabamento, foi possível constatar a influência positiva da estratégia de corte em paralelo na obtenção dos menores valores de rugosidade média Sa e máxima Sz em ambos os aços estudados, VH13IM e VTMPlus, em comparação com a estratégia zig-zag. O conjunto de baixos valores de rugosidade com um perfil topográfico homogêneo da superfície levou a um maior brilho e grau de espelhamento.

Resumo em Inglês:

ABSTRACT Given the difficulty in machining of hardened steels and the complex geometries commonly observed in injection molds, besides the necessary surface quality to produce plastic parts without defects, an adequate milling strategy must be chosen, which consists in defining not only the cutting parameters and the tool, but also its trajectory. Thus, the present work focuses on investigating the influence of two different cutting strategies in milling process on the surface quality of a convex (constant curvature) surface on two types of material. The quality was evaluated through distinct roughness parameters, which were correlated to the perceived gloss and analyzed in combination with the characteristics of each material, such as hardness and microstructure. From the results obtained after the finishing operation, it was possible to verify the positive influence of the parallel tool path, which led to the lowest values of average Sa and maximum Sz roughness in both steels, VH13IM and VTMPlus, in comparison to the zig-zag tool path. The combination of low roughness values with a homogeneous topographic profile of the surface led to a higher gloss level and mirror effect.