Navegando por Linha de Pesquisa "TECNOLOGIA DOS MATERIAIS"

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Acesso aberto (Open Access)
Amido termoplástico: obtenção de nanocompósitos de amido de araruta termoplastificado com nanopartículas de óxido de zinco
(Universidade Federal do Pará, 2024-02-07) PINTO, Bianca Corrêa; PAULA, Marcos Vinícius da Silva; http://lattes.cnpq.br/7538211324097974; MAIA, Ana Áurea Barreto; http://lattes.cnpq.br/0820112425394964; https://orcid.org/0000-0002-1880-1442
The search for new materials with comparable performance to synthetics has driven the development of sustainable and biodegradable materials. The growing demand has stimulated the creation of innovative materials, such as starch-based films, biopolymers, and others, which offer excellent mechanical and barrier properties while being environmentally friendly. To achieve higher levels of sustainability, starch-based films, enriched with new components, gain prominence as possible candidates for food packaging applications. In this context, the present study aims to obtain and characterize thermoplasticized nanocomposites with arrowroot starch (TPA) and zinc oxide nanoparticles (ZnO NPs) in different proportions (1%, 3% and 5%). Films without ZnO NPs were used as controls. The thermoplasticized starch films were made using the casting solution technique (solvent evaporation). They were evaluated for the concentration of ZnO NPs, and were also submitted to laboratory techniques, such as moisture, solubility and swelling tests. In addition, they were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and tensile, strain at break and modulus of elasticity tests. For the moisture test, the results revealed that the addition of 1, 3 and 5% of ZnO NPs to the polymeric matrix provided a gradual decrease in the percentage of moisture when compared to the control TPA film. This fact is attributed to the interfacial interaction between the ZnO NPs and the arrowroot starch matrix, which in turn hinders the interaction of water molecules with the nanocomposite film. For the percentage of solubility of the films, a small change was observed after the addition of the NPs ZnO to the starch matrix, which becomes important for the maintenance of products stored in food packaging as well as the stability of the polymeric films. As for the swelling test, for the 1% TPA, 3% TPA and 5% TPA films, it was verified that when the SPL was added, they presented smaller variations compared to the TPA film containing only arrowroot starch in the polymeric matrix. In view of the above, the micrographs obtained by SEM revealed the presence of randomly dispersed aggregates of ZnO NPs in the polymeric matrix of arrowroot starch. The stress properties tests were conducted in 5 replicates, with a speed of 5 mm/min. The TPA film showed an average of 0.34 MPa and 59.80% for tensile strength and deformation at break, respectively. The incorporation of ZnO nanoparticles into the arrowroot starch matrix resulted in an increase in the tensile strength and deformation of TPA 1%, TPA 3% and TPA 5% films compared to TPA film. The mean strength for the films TPA 1%, TPA 3% and TPA 5% were 0.42 MPa, 0.45 MPa and 0.60 MPa, respectively. In addition, the mean strain at break for TPA 1%, TPA 3% and TPA 5% films were 77.14%, 86.34% and 86.05%, respectively. The FTIR spectra exhibited the same spectral behavior. This phenomenon is due to the presence of high starch content in the polymeric matrix of the films. The thermal stability for TPA, TPA1%, TPA 3% and TPA 5% films was investigated by thermogravimetric analysis (TGA). The results obtained for the TPA1%, TPA 3% and TPA 5% films presented similar data to the thermal stability of the TPA film and showed that the addition of ZnO NPs to the polymeric matrix did not cause a significant decrease in them. The results showed that it is possible to use the films produced in this work in the packaging sector.
Acesso aberto (Open Access)
Análise da viabilidade técnico-econômica de implantação de reciclagem de pneus para produção de CBUQ em Tucuruí
(Universidade Federal do Pará, 2019-02-21) MOUSINHO, Mateus Mamede; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
Population growth and rapid technological development have contributed to increased solid waste generation by improperly disposing of post-consumer tires, which are not biodegradable and their decomposition time is not yet precisely determined. To be defended that the recycling culture does not only show aspects of environmental and educational preservation, it is also necessary to justify recycling as an economic activity that generates employment and income to the city, contributing to the well-being and quality of life. Therefore, the main objective of this research was to quantify the discard of waste tires and to analyze the technical-economical feasibility for the implementation of the recycling process of waste tires in the production of rubber aggregate in the asphalt mixture at the city's asphalt plant. To do so, it was measured the disposal of waste tires in a given period in Tucuruí and estimated the disposal volume of the adjacent cities, in addition, it was analyzed the operational activities and production costs of the waste as a rubber aggregate. In the field survey, 98 questionnaires were applied in 30 neighborhoods where the establishments were in January 2018. Thus, there was a monthly amount of 1,664 tires in the rubber workshops, 2,347 tires in the mechanical stores, totaling 4,011 tires in the municipality, which allows to conclude that the city presents a large volume of this solid residue. Adjacent cities presented in their estimate a total of 8,031 tires unserviceable per month. For the production of the rubber aggregate asphalt mixture, the conventional CBUQ trait was used in relation to the modified CBUQ developed by Coelho (2018), in which it was estimated that one kilometer of asphalt mixture of thickness of 3,5 centimeters can be used approximately 11.72 tonnes of recycled aggregate (8.79 tonnes of rubber and 2.93 tonnes of wood sawdust), this is equivalent to 1,465 car tires or 5,170 motorcycle tires, leading to an economy in the purchase of raw material from R$ 56,075.41 per kilometer. It is concluded that the results of the three scenarios are satisfactory, the simulations of the study were only the resources available to produce the rubber aggregate generated by the municipality as a pioneer project, with the intention that other municipalities are part of this visual identity of sustainable city.
Acesso aberto (Open Access)
Análise das propriedades tecnológicas da cinza do caroço de açaí na cerâmica vermelha
(Universidade Federal do Pará, 2019-09-16) FERREIRA, Taiana da Silva; SOUZA, Paulo Sérgio Lima; http://lattes.cnpq.br/4933212993218783; ISHIHARA, Júnior Hiroyuki; http://lattes.cnpq.br/3498874642887006; https://orcid.org/0000-0002-0081-7913
The raw materials from the exploration of deposits used for the manufacture of products used in construction and the environmental impacts caused by the red ceramic sector evolved as cities developed. The need for the use of alternative materials, such as waste biomass, has become increasingly necessary studies aimed at the reuse of waste in the process of production and manufacture of ceramic materials. Thus, this work has the objective of evaluating the incorporation of ash from the acai kernel residue (RCA) in the clay mass and to evaluate the technological properties of red ceramic. The materials were chemically and physically characterized, and then extruded specimens were molded using 0%, 10%, 15% and 20% RCA ash mixed in two types of clay, called red clay and dark clay. After firing at 950 ºC, the pieces were subjected to water absorption, apparent porosity, specific gravity, linear shrinkage and flexural strength stress tests. The results showed that the use of RCA ash contributed to the workability of the mixtures, reducing the need for additional water for molding. It was also verified that the 10% ash content as a partial substitute of red clay, and the mass containing 50% of red clay and 50% of dark clay, had a positive influence on the evaluated technological properties. However, for the 20% ash incorporation of RCA, the values were median and for the unsatisfactory porosity assay. Thus, it was possible to verify the technical feasibility of using açaí stone ash in partial substitutions, contributing to the reduction of raw material exploration, reduction of solid waste disposal and the reuse of the residual biomass of açaí stone in the production of ceramic materials.
Acesso aberto (Open Access)
Análise de atributos de classificação para o diagnóstico de falhas em rolamentos baseado em SVM
(Universidade Federal do Pará, 2019-08-06) SOUZA, Jusley da Silva; BAYMA, Rafael Suzuki; http://lattes.cnpq.br/6240525080111166; MESQUITA, Alexandre Luiz Amarante; http://lattes.cnpq.br/3605920981600245; https://orcid.org/0000-0001-5605-8381
In industries, the concern in total availability of machines and the mechanical equipment in the productive area it’s subject of research and tests to obtain more efficient techniques to be applied for monitoring and faults’ diagnosing. Bearings are machine elements of great application in the industrial area and they present high fault index that generate machine’s stops to carry out maintenance. For this reason, this paper presents Artificial Intelligence technique applied to the vibration signals of a rotary machine for fault diagnosis in its bearings. The vibration signals are part of an open database offered by Case Western Reserve University. In this paper the Support Vector Machine (SVM) classification algorithm is applied in two ways for the rolling bearings faults’ diagnosis. In the first case statistical predictors (Root Mean Square Value, Crest Factor, K Factor, Kurtosis and Skewness) are used as features for the SVM classifier. In the second case, the signal processing is performed by applying the Ensemble Empirical Mode Decomposition (EEMD), which generates several signals called Intrinsic Mode Functions (IMFs). For each IMF, it’s modeled using Autoregressive Modeling (AR), and the AR modeling coefficients of each IMF are used as features for the SVM classifier. The analyzes are performed for training and validation groups, with randomly chosen window and with temporal sequence chosen window, considering two classification problems within the same data, the first one considers the same severity and only changes the fault type and the other vary both severity and fault type. As result, both methodologies presented excellent reliability results for bearing faults’ diagnosis.
Acesso aberto (Open Access)
Argamassa autonivelante para contrapiso: efeito do tipo de cimento no comportamento físico-mecânico
(Universidade Federal do Pará, 2020-04-24) ALVES, Brenda Maiara Oliveira; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
Self-leveling mortar (SLM) is inserted in the construction market as an innovative product due to its special properties when compared to conventional mortars due to the filling of empty spaces and self-compacting only under the effect of gravity, the ability to flow and level without the occurrence of segregation. The use of CP V – ARI cement is common for its production, since its high fineness favors the fluidity of the material and for providing fast hardening, fundamental characteristics that must be considered in self-leveling mortars (SLM’s). However, the rare availability of this type of cement becomes a limiting factor for its applicability in the region. Therefore, the objective of this research is to develop the study of SLM dosage for screed, adapting it to local materials that favor its design and evaluating its influence on rheological and mechanical characteristics. For the production of these mortars, we used the adaptation by Lopes et al. (2018) of Tutikian's methodology (2004) for self-compacting concrete (CAA), using fines in partial replacement of cement, adopting as controllable factors the type of cement (CP I, CP II-E, CP IV and CP V-ARI) and the type of mineral addition (silica fume and metakaolin). For the characterization of SLM in the fresh state, the mini slump, mini V-funnel, flow retention, mass density and incorporated air content, determination of exudation and healing time tests were performed. In the hardened state, the mechanical resistance to compression and traction in flexion and the retraction of these materials were verified, since it is one of the main pathologies of SLM. Analyzing the results obtained, it was observed that the surface area of the tested cements was the factor that most influenced the performance of the produced mortars, where cements with larger surface areas needed more additive to achieve fresh properties and had the highest rates of retraction. Mineral additions contributed to the cohesion of mortars and reduced shrinkage in mixtures with contents of up to 25% metakaolin and 15% silica fume.
Acesso aberto (Open Access)
Avaliação da eficácia dos óleos essenciais das especies piper divaricatum e eugenia caryophyllus como inibidores de corrosão em aço carbono
(Universidade Federal do Pará, 2023-07-13) MONTEIRO, Heloise Leal; PAULA, Marcos Vinicius da Silva; http://lattes.cnpq.br/7538211324097974; MAIA, Ana Áurea Barreto; http://lattes.cnpq.br/0820112425394964; https://orcid.org/0000-0002-1880-1442
This research reports the evaluation of essential oils (EOs) such as those from the plant Piper divaricatum and Clove (button) Eugenia caryophyllus, as green corrosion inhibitors in metallic materials precisely in this work, carbon steel, these oils being considered environmentally sustainable. Corrosion tests were carried out in corrosive media such as 1M HCl and 3.5% NaCl, the concentrations used for both essential oils were 0.5g/L; 1g/L; 2g/L and 4g/L, for periods of time such as 24h and 7 days. The method used to evaluate the efficiency of the oils was gravimetric (weight loss). The Scanning Electron Microscopy technique of the field emission gun type (SEM-FEG) was conducted to investigate the surface of the specimen, while its chemical composition was obtained through Electron Dispersion Spectroscopy (EDS). In this work, several aspects were discussed, such as the efficiency in relation to the time exposed to the test specimen to corrosive media and factors such as the adsorption isotherm of the oils on the metal surface, in addition to calculations of the corrosion rate of the test specimens in the absence and presence of inhibitors and their relationship with the oil concentrations used. The studies indicated that the essential oils of Piper divaricatum and Clove (Eugenia caryophyllus) showed excellent results in an acid medium of up to 98.3% for the concentration of 2g/L of Piper divaricatum EO in 24h, and 89.5% for the concentration of 1g/L of Eugenia caryophyllus EO in 7 days. In the neutral medium, the highest percentages of inhibition were 61.1% for the concentration of 0.5g/L of EO from Piper divaricatum in 24h, and 83.3% for the concentration of 1g/L of EO from Eugenia caryophyllus in 24h. the isotherms of the oils followed the Langmuir adsorption model, where both oils adsorbed on the metal surface, the best results of isotherms were for the acid medium, for the neutral medium due to the high variability of the data it was not possible to establish a consistent correlation. In view of the proposed results, it was possible to conclude that the essential oils of P. divaricatum and E. caryophyllus have the potential to be used as corrosion inhibitors mainly in an acid medium, thus providing new alternatives in order to reduce the toxicity of this process in comparison to inhibitors already on the market.
Acesso aberto (Open Access)
Avaliação da influência de sistemas de proteção na permeabilidade de água em placas cimentícias com incorporação de perolas de poliestireno expandido
(Universidade Federal do Pará, 2025-04-24) GOMES, Saulo de Almada; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
Water is one of the main elements responsible for the emergence and propagation of pathological events in coatings. Its permeated presence compromises the protective capacity, as well as directly influences durability, and can accelerate the deterioration of mortars, impairing their useful life. It is known that the use of surface protection instruments (painting system) and the use of waterproofing additives in the production of mortar coatings directly influence the protection against water permeability. Within this aspect, this study aimed to evaluate the degree of influence of protection systems for cement boards with the incorporation of Expanded Polystyrene (EPS). EPS was used in the cement board as a partial replacement for sand, in a volume of 20%. Two types of painting systems were evaluated, one for indoor environments and the other for outdoor environments, in addition to a type of waterproofing water-repellent additive, which was applied to the mortar mixture. This evaluation was carried out using two methods that analyze the permeability of mortar coatings: the Karsten tube test (pipe method) and the permeability test of ABNT NBR 15498/2021, which deals with the requirements for using cement boards. The mechanical properties of the mortars and boards were also characterized. The results of this work demonstrated that the protection systems evaluated caused different effects on the permeability of the boards. The waterproofing additive did not significantly influence the permeability of the panels, only the physical characteristics, with greater emphasis on the mass density and water absorption properties. The painting systems positively influenced the waterproofing capacity of the panels, with the external painting system being more efficient. Regarding the permeability assessment techniques, the Karsten tube showed great variability in the results, demonstrating that this technique is more sensitive to the conditioning variables. And, in the permeability test of NBR 15498, all panels passed the use requirement.
Acesso aberto (Open Access)
Avaliação do emprego de agregado miúdo reciclado na produção de peças pré-moldadas para pavimentação tipo “paver”
(Universidade Federal do Pará, 2021-02-05) VIEIRA, Marília de Oliveira; SOUZA, Paulo Sérgio Lima; http://lattes.cnpq.br/4933212993218783
Acesso aberto (Open Access)
Avaliação microestrutural e mecânica das fibras de cotia e dos compósitos de matriz poliéster
(Universidade Federal do Pará, 2025-01-20) NASCIMENTO, Damares da Cruz Barbosa; OLIVEIRA, Michel Picanço; http://lattes.cnpq.br/6383844066460475; https://orcid.org/0000-0001-9241-0194; CANDIDO, Verônica Scarpini; http://lattes.cnpq.br/8274665115727809; https://orcid.org/0000-0002-3926-0403
The search for sustainable and low-cost materials has driven the use of natural fibers in the development of polymer composites, due to their mechanical and sustainable properties. The aim of this work is to study and characterize a new natural fiber, as well as to study the mechanical properties of composites made with in natura fibres (FC) and mercerized fibres (FM) in volumetric percentages of 10, 20 and 30%. The fibres and composites were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetry (TGA), Scanning Calorimetry (DSC), Energy Dispersive Spectroscopy (EDS) and Raman Spectroscopy, as well as mechanical characterization. The physical characterization of the fiber indicated an average density of around 0.34 g/cm3. The FTIR of the FC and FM fibers indicated chemical structural changes, which were confirmed with Raman, SEM and EDS. The thermal stability of Cotia fiber in natura was close to 145 and 272 ºC. The mechanical properties of the FC and FM fibers showed average strengths of around 151.32 and 99.98 MPa, respectively. The FTIR and Raman scans of the composites showed few changes related to the variation in chemical treatment, but differences when percentages of fibers were added. The tensile and flexural results indicated that the CF fibers were stronger and stiffer in relation to the matrix than the modified fibers. The SEM confirmed the existence of defects and flaws that caused early rupture of the composites with FM fibers. The single and double F ANOVA confirmed that both factors, chemical modification and increase in volume percentage, had an impact on the final properties. Although the results of the FM fibers did not have a positive impact, the properties of the in natura fibers stand out as efficient reinforcements for engineering applications.
Acesso aberto (Open Access)
Captura de carbono em placas de concreto permeável
(Universidade Federal do Pará, 2020-06-12) SANTOS, Caio José Bastos Marques; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
The production of cement has an impact on the environment from the release of co2 where carbon dioxide acts directly on the phenomenon of "greenhouse effect". Although cement production generates high rates of carbon dioxide, cement hydration products have the ability to reabsorb carbon dioxide from a physical-chemical phenomenon called carbonation. This research related this physical-chemical phenomenon to a material considered sustainable, such as permeable concrete. This type of concrete can be used on non-reinforced floors. The research focuses on analyzing the ability to capture co2in permeable concrete slabs. As for carbonation, mixtures produced with two granulometric bands of pebble and CP II F agglomerate with a/c ratios of 0.33 and 0.37 were analyzed in protected and unprotected environments, and in an accelerated environment in a co2 chamber. A chemical phenolphthalein indicator was used to assess the occurrence of carbonation in five ages of reading and image analysis software to study the carbonated surfaces. The material showed satisfactory results in terms of mechanical, water and carbonation depth parameters, having reabsorbed the atmosphere gas from the cement paste that surrounds the aggregate grains of the material's granular skeleton.
Acesso aberto (Open Access)
Caracterização de tintas industriais aplicadas na região amazônica a partir de análises físico-químicas, mecânicas e de durabilidade
(Universidade Federal do Pará, 2024-02-28) LUCAS, Mathaus Moraes; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287
In Brazil, the industrial sector of paints and varnishes is among the five largest in the market. The manufacture of paints for various applications, with technology and technical responsibility, equals the most advanced global production centers. The durability of a paint refers to its resistance to weathering. For weathering, a weather-resistant paint is necessary so that fading does not occur on the substrate where it will be used, which can occur among some factors, due to the incidence of sunlight and heavy rains. The North region, with high rainfall, influenced by instability lines, presents significant spatial and seasonal heterogeneity of rainfall and has the highest annual rainfall total. Given this reality, a paint commercially applied in the Amazon region was developed. In the standard formulation, variations of mineral loads (Kaolin, Dolomite and Precipitated Calcium Carbonate) were made and subsequently analyses and tests were carried out to evaluate the performance of this paint, compared with the original formulation, such as abrasion resistance and weathering resistance. The paint production methodology will be according to Castro (2009) using Hare’s technique (1974). The characterization of the paints in the fresh state was carried out through the Viscosity, pH and specific weight tests, while the characterization of the paints in the hardened state was carried out through the abrasion resistance tests, weathering resistance test and Scanning Electron Microscopy. The physico-chemical tests revealed that, in relation to Stormer viscosity, all formulations exceeded the standard (130 KU), with the exception of the paints containing 30% Dolomite, 15% PCC, 15% Dolomite and the ternary combination of 5% Kaolin, 5% Dolomite and 20% PCC. As for the specific weight, the formulation that came closest to the standard was the binary paint with 15% Kaolin and 15% PCC, presenting an average value of 1.43 g/cm³. In terms of pH, all formulations showed alkalinity, with values ranging between 7.5 and 9.6. After a period of exposure of 180 days, none of the mixtures, including the standard formulation, showed the formation of pathologies, demonstrating resistance to weathering. The formulations with 30% Dolomite; 15% PCC and 15% Dolomite; 5% PCC, 5% Kaolin and 20% Dolomite; 10% Kaolin, 10% PCC and 10% Dolomite, exhibited respectively 300, 290, 240, 270 cycles of abrasion resistance, indicating the potential of these paints for a variety of applications, such as floor paints, external paints and road paints.
Acesso aberto (Open Access)
Caracterização do tecido fibroso de tururi e avaliação de propriedades mecânicas de compósitos de matriz poliéster reforçados com tecido fibroso de tururi
(Universidade Federal do Pará, 2023-01-30) SANTOS, Avener Gleidson Andrade; CÂNDIDO, Verônica Scarpini; http://lattes.cnpq.br/8274665115727809; https://orcid.org/0000-0002-3926-0403
In recent decades, the search for materials with high mechanical performance and that are in accordance with sustainability requirements has become increasing. In the context of sustainability, the United Nations (UN) established in 2015 the Sustainable Development Goals (SDGs), in order to guide the paths to sustainable development. The use of waste to produce new materials is beneficial, because the use of these materials represents a solution for environmentally friendly disposal, thus covering the requirements established by the SDGs. The use of natural fibers in the production of new materials has increased significantly in the last decade. The use of natural fibers as reinforcement in polymer matrix composites is already well established. This is due to the fact that some fibers have high mechanical performance and good thermal stability, two highly attractive properties in composite materials. Composites reinforced with natural fibers have a vast field of application, and can be used in civil construction, aerospace, and automotive industries, among others. In this scenario, the use of tururi fabric as a reinforcement agent in composites of polymeric matrix emerges as a viable alternative for sustainable disposal of this waste coming from the harvesting stage of its fruits. Thus, this study aims to characterize the tururi fibrous tissue by optical microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy (FTIR), as well as to determine physical properties such as density, moisture content and weight. The composites were produced using a 2.5, 5.0 and 7.5% by mass percentage of reinforcement. Additionally, tensile, flexural and charpy impact tests were performed. The characterizations revealed that the tururi fibrous tissue is composed of fibers of various diameters and has regions of bifurcation, indicating that the tissue can act in different ways when incorporated as reinforcement. The density, moisture content and weight had average values of 1.17 g/cm3, 16.58% and 146.61 g/m2, respectively. The thermal analysis revealed good thermal stability for the tururi fabric. The mechanical tests pointed out that as the incorporation of reinforcement occurred, the composites tested in traction had a loss of resistance, presenting a loss of 15MPa in relation to the matrix. When requested in flexion the composites reinforced with up to 2.5% showed better mechanical performance, with values of 63.9 MPa. The impact test revealed that the energy absorption capacity increased by 371% compared to the matrix, which indicates that the fabric acted as a good reinforcement agent.
Acesso aberto (Open Access)
Concreto auto adensável com agregado miúdo reciclado de concreto
(Universidade Federal do Pará, 2019-03-29) BERNARDO, Karen Suely Martins; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
A more sustainable approach in the production of self-compacting concrete (SCC) aims to replace the natural aggregates by recycled concrete aggregates, however this substitution affects the properties of the concrete produced. This research propose evaluate the effect of the fine recycled aggregate on the properties in the fresh and hardened state of self-compacting concrete using a methodology of dosage focused on the rheology of materials. The dosage study was performed through an adaptation of the Gomes method, and four levels of FNA substitution by FRCA were determined (10%, 20% and 30%). Were analyzed the fresh state properties according to the parameters established according to the specifications on the subject and by the normative prescription of reference, and the properties in the hardened state. In this study, was observed a decrease in apparent viscosity, passing ability and segregation resistance, proportional to the increase in FNA substitution. However, all mix designs have attend the required of self-compacting, with minimum adjustments. All concretes obtained axial compressive strength at which fit in the structural concrete class. Therefore, through the responses founded during the dosing study, it was possible to produce self-compacting concretes with 30% of FRCA that met the requirements established.
Acesso aberto (Open Access)
Desenvolvimento de Redes Semi-Interpenetrantes de PCL-pHEMA-copaíba para potencial uso com scaffolds na Engenharia de Tecidos
(Universidade Federal do Pará, 2024-02-22) LIMA, Tainara de Paula de Lima; PASSOS, Marcele Fonseca; http://lattes.cnpq.br/0588450144351187; https://orcid.org/0000-0002-5616-2127
Tissue engineering is an alternative to replace organs and tissues in the biological system affected by an illness. Therefore, it is necessary to study the material used as a scaffold in depth. Among the materials in this area, polymers and hydrogels stand out, such as poly (ε-caprolactone) (PCL) and poly (2-hydroxyethyl methacrylate) (PHEMA), respectively. PCL is a bioresorbable, biodegradable, and biocompatible polymer. However, it is hydrophobic.On the other hand, pHEMA is a biocompatible and hydrophilic hydrogel but does not show good degradability. Furthermore, it is possible to intersperse bioactive compounds through the use of Amazonian vegetable oils in these structures to further enhance tissue regeneration and combat possible infections by microorganisms. Therefore, this work aimed to obtain and characterize PCL-PHEMA-copaíba semi-IPN networks for scaffolds in tissue engineering using the rotospinning technique. The results successfully demonstrated the processing of PCL fibers (with and without copaiba oil) and the formation of PCL-C-PHEMA semi-IPN networks. Gas chromatography confirmed the presence of bioactive components in copaiba essential oil, the majority being (β)-caryophyllene (40.75%). The FTIR spectrum showed interactions of the materials' functional groups, confirming the incorporation of the oil into the PCL structure and the formation of semi-interpenetrating networks. Micrographs and topographies revealed tangled and disorganized microfibers in all samples, with different diameters, porosities, and roughness. The PCL, PCL-C, and PCL-C-PHEMA samples presented fiber diameters ranging from 18.40 to 19.50 μm, 3.11 to 24.44 μm, and 6.29 to 8.14 μm, respectively. Contact angle analyses (PCL: 86.96°, PCL-C: 93.99°, PCL-PHEMA: 29.42°, and PCL-C-PHEMA: 56.02°) and swelling test (PCL: 4.49%, PCL-C: 2.73%, PCL-PHEMA: 21.57%, and PCL-C-PHEMA: 10.11%) demonstrated that the addition of the hydrogel to the PCL structure optimized the hydrophilic properties of material. The sol-gel tests indicated that the PCL-PHEMA and PCL-C-PHEMA materials presented 73.5 74.3% gel fractions. Thermograms confirmed that the material did not significantly change in thermal stability with the addition of the hydrogel and oil. Microbiological tests confirmed the antimicrobial action of copaiba oil, PCL-C-PHEMA, and PCL-C scaffolds against the gram-positive bacterium Staphylococcus aureus, with an inhibition halo of 9, 7, and 5 mm, respectively. Moreover, the cytotoxicity tests concluded that the PCL, PCL-PHEMA, and PCL-C scaffolds showed good cell viability. However, optimizing the photopolymerization process of the semi-IPN network is necessary, given that the PCL-C-PHEMA materials were moderately toxic. Finally, a new biomaterial is expected to be developed for use in tissue engineering, valuing the use of natural Amazonian resources.
Acesso aberto (Open Access)
Desenvolvimento de um aplicativo móvel para promover o reaproveitamento de resíduos na dosagem de concreto
(Universidade Federal do Pará, 2019-09-04) MESQUITA, Felipe José Marques; FÜLBER, Heleno; http://lattes.cnpq.br/5018616409948511; ISHIHARA, Júnior Hiroyuki; http://lattes.cnpq.br/3498874642887006; https://orcid.org/0000-0002-0081-7913
Concrete is the most widely used building material in the world, resulting in high consumption of natural materials, thus, the reuse of waste in substitution of cement and aggregates in the production of concrete enables reduction of greenhouse gas emissions, reduction in extraction of natural raw materials, in addition to the reduction on the disposal of these wastes in nature. Given the need to develop solutions that contribute to the efficient reuse of waste, this paper aimed to analyze the state of the art of national production of concrete with waste reuse, to develop a mobile application to promote the reuse of waste in concrete production. Through bibliometric analysis of Brazilian publications on concrete with reuse of waste, we analyzed works published over a period of 20 years in the Web of Science database, revealing growing interest on the subject, especially the construction and demolition waste, being this the most published and protagonist residue of the most influential article on the subject. The analysis of the publications allowed the creation of a knowledge base on the use of waste in concrete production. These data were used in the development of an application for Android mobile devices, which allows the user to have easy access to concrete dosages with reuse of residues, obtain information on potential waste suppliers and calculate the production costs of this concrete. The system has 41 different mix proportioning, including 7 concrete types and 10 waste options, allowing the user to achieve environmental gains by replacing up to 100% of natural concrete aggregates with waste and saving up to 11.82% over cost. of concrete produced without waste. Keyword: concrete, waste, database, application, bibliometrics.
Acesso aberto (Open Access)
Desenvolvimento e caracterização de bioplásticos de fécula de mandioca com extrato alcoólico de Vismia Guianensis
(Universidade Federal do Pará, 2024-08-27) SANTOS, Josiel Ferreira; PASCA, Gabriel Adolfo Cabrera; http://lattes.cnpq.br/5642784995274060; https://orcid.org/0000-0002-9411-0889
This work investigates the incorporation of the alcoholic extract of Vismia Guianensis (EAVG) cassava starch, aiming to improve its bioplastic properties. Cassava starch was dissolved in distilled water at the following concentrations with 0.2%, 0.5% and 1.0% EAVG under controlled temperature at the gelatinization point (~70 °C) and then molded to form bioplastics. The prepared samples were characterized by Attenuated Total Reflectance/Fourier Transform Infrared Spectroscopy (ATR/FTIR), Thermogravimetric and Thermal Differential Analysis (TGA-DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Spectroscopy Dispersive (SEM/EDS), Atomic Force Microscopy (AFM) and mechanical assays, providing insights into chemical composition, thermal stability, crystallinity, surface morphology and mechanical properties. These techniques comprehensively characterized cassava starch bioplastics with EAVG addition, highlighting their enhanced mechanical properties. The results demonstrated that EAVG played an effective role as a plasticizer, increasing the flexibility, resistance and stability of the biofilm that has a thickness of 0.8 mm, and supports a traction of 4.19 to 18.43 MPa. This study justifies EAVG as a promising additive for the production of biocompatible and sustainable materials, suitable for numerous applications in biodegradable plastics. EAVG presents a path forward for the advancement of bioplastics with improved mechanical, thermal and functional properties, with a promising future in terms of their contribution to new developments in these areas.
Acesso aberto (Open Access)
Estudo da colmatação em concretos permeáveis para tráfego leve e de pedestres
(Universidade Federal do Pará, 2020-05-28) TEIXEIRA, Mísley da Cruz; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
Permeable concrete is a material mostly used as paving coating to reduce the effects of surface sealing. The material’s susceptibility to clogging is considered as a disadvantage, and it became an object of study in research about this material, as this one which evaluated the effect of clogging on permeable concretes used as pavement coating to light traffic. To this end, an experimental program was elaborated to characterize the material, designed with different percentages of fine aggregate, and to evaluate the evolution of clogging in permeable. The specimens were submitted to characterization and permeability tests after deposition cycles of different types of sediments (sand and clay) and cleaning by aspiration. The results of fresh material characterization corroborated the common assertion in the academic community that the insertion of fine aggregate in mix compositions increases the unit mass and the mechanical strengths and reduces the void percentage and the permeability of the concretes. The clogging tests proved that larger particle size sediments (sand) caused a loss of permeability due to sealing of the upper layer of the specimen, with loss ratios up to 21,13% at the end of the 20th sedimentation cycle, while the smaller particle size sediments (clay) induce to a deeper clogging, with a permeability reduction varying of 8,45% to 16,46%. The maintenance efficiency was proven by total recovery of clogging by sand, and a recovery percentage of 96,85% to clogging by clay. These results make it possible to declare that any particle size can clog the material, but also it is easy to recover its permeability by maintaining/cleaning of the pavement, which confirms that the pavement lifespan and raining capacity are directly associated to its periodic cleaning.
Acesso aberto (Open Access)
Estudo da potencialidade da cinza da casca do murumuru, um resíduo agro industrial amazônico como filler ao concreto estrutural
(Universidade Federal do Pará, 2022-11-17) SOUZA, Milleno Ramos de; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
The use of agro-industrial waste in the partial replacement of cement in concrete has been the subject of research that analyzes the possible improvements in mechanical and physical properties and durability of the concrete, in addition to providing the use of mineral additions of natural origin or partial replacement in relation to the constituent materials of the composite, waste that would have inappropriate disposal, such as open-air landfills and burning. With this scenario, the study aims to research the use of murumuru husk ash (MHA), an agro-industrial waste generated specifically in the Amazon region as partial replacement of cement in structural concrete and evaluate the physical, chemical and mineralogical characteristics of the ash to act as filler in concrete, and its properties in the fresh and hardened state in concrete. With this purpose, the MHA underwent the physical-mechanical characterization tests such as specific mass, pozzolanic activity with Portland cement, pozzolanic activity with lime and BET test, also performing the mineralogical and chemical analysis of the ash. For concreting, a mix 1:1.6:2.4 (by mass) with water/cement ratio of 0.43 was considered, with replacement levels of 0%, 6%, 9% and 13% of the cement mass by MHA. After the dosage, the tests were performed on the concrete in its fresh and hardened state: slump test, specific mass, compressive strength (28 days), tensile strength in diametrical compression, water absorption by capillarities, specific mass in the hardened state, modulus of elasticity and morphological evaluation, through the Scanning Electron Microscope (SEM). Checking first the properties of concrete in the fresh state, it is evaluated that the insertion of the waste decreased the consistency and decreases the specific mass, except the concrete for the content of 6% that there was a 10% increase in the specific mass in relation to the concrete reference. Regarding the properties in the hardened state, the replacement by CCM showed an increase specifically in compressive and tensile strength in the 6% content at 28 days around 1% and 9% respectively, occurring a decrease in the contents of 9% and 13%. The results showed that there is a technical feasibility with partial replacement of 6% of MHA in cement, using plasticizer additive to improve workability
Acesso aberto (Open Access)
Estudo das propriedades de argamassa geopolimérica produzida com resíduos de caulim e escória de alto-forno da Região Amazônica
(Universidade Federal do Pará, 2025-02-27) SANTANA, Rayanne Oliveira Leão; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287
The growing demand for sustainable solutions in the construction sector has driven research into the use of industrial waste as alternatives to conventional materials. This study investigated the utilization of kaolin industry residues in the production of geopolymers, focusing on the substitution of soft metakaolin with flint metakaolin and conventional sand with sandy kaolin residue in geopolymer mortars. The research was conducted in three stages: first, a physicochemical characterization of the raw materials was performed, including tests to determine mineralogical, chemical, granulometric compositions, and specific mass. In the second stage, the substitution of soft metakaolin with flint metakaolin at different percentages (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) was evaluated, and the compressive strength of geopolymer pastes was analyzed. Although a linear relationship between the increase in flint metakaolin substitution and compressive strength was not observed, the highest strength (52 MPa) was achieved with the full substitution of soft metakaolin by flint metakaolin. In the third stage, geopolymer mortars were produced by combining geopolymer paste with aggregates, testing substitution percentages of conventional sand with sandy kaolin residue (0%, 25%, 50%, 75%, and 100%). Physical tests revealed that substituting 50% of the conventional aggregate with sandy residue resulted in a more compact matrix with lower water absorption, higher specific mass, and reduced porosity. The results showed that replacing 50% of conventional sand with sandy residue led to the highest compressive strength (46 MPa), suggesting that this proportion enhanced matrix densification and improved interaction between the residue and the paste. Morphological analysis using SEM confirmed that the formulation with 50% sand substitution presented a densely compacted matrix with good cohesion between the paste and aggregates and an adequate distribution of N-A-S-H and C-A-S-H gels. These findings highlight that partial replacement of sand with sandy kaolin residue improves the densification and strength of geopolymeric mortars while demonstrating the potential of flint metakaolin and sandy residue as sustainable alternatives in construction.
Acesso aberto (Open Access)
Estudo das propriedades mecânicas e microestruturais de materiais cimentícios geopoliméricos produzidos a partir de metacaulim e escória de alto forno
(Universidade Federal do Pará, 2023-06-21) ALMEIDA, Bianca Mendes; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287
The environmental impacts caused by the production of Portland Cement point to the urgency of reducing the use of this binder mainly due to the CO2 emission and energy consumption that occur during its production process. In the search for alternative materials, geopolymeric cement has shown promise, both in terms of mechanical performance and conservation of natural resources. These cements are obtained from natural raw materials containing aluminosilicates activated by an alkaline solution. In this work, geopolymeric cement paste, mortar and concrete were developed using metakaolin, blast furnace slag and alkaline solution of sodium hydroxide and sodium silicate. The main objectives included evaluating the influence of blast furnace slag on the mechanical properties of geopolymer pastes, varying its addition in mass (30% to 60%), evaluating the influence of sand in geopolymer mortar varying its addition in the paste with better performance of 20% to 70%, and finally, the addition of gravel 0 in two mixtures. The results showed that the paste reached a maximum compressive strength of 36.5 MPa with 35% slag in the matrix. This value rose to 41.15 MPa in the mortar with the incorporation of 40% sand. For concrete, the best result was found for the mixture that contained less crushed stone. The results of the concrete were compared with the CPV-ARI Portland cement concrete by setting some dosing parameters such as binder consumption and water/binder ratio. Other properties investigated included setting time, slump, flexural tensile strength and microstructural analysis by SEM. Geopolymeric concrete was superior to Portland by up to 21.16%, reaching compressive strength of 41.8 MPa, flexural traction of 4.87 MPa and better matrix/aggregate adhesion in the mixture with less addition of gravel 0. The results obtained for geopolymers enable their application in civil works that demand materials that reach high strenght in the initial ages, precast and paving industries.