Navegando por Assunto "Geopolymer"

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Acesso aberto (Open Access)
Aplicação de resíduos da mineração de bauxita na síntese de geopolímeros
(Universidade Federal do Pará, 2022-04-08) BARRETO, Igor Alexandre Rocha; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
The process of extraction and beneficiation of bauxite deposits in the bauxite province of Paragominas/Rondon do Pará can generate large amounts of waste, mainly in two stages of the process: mining and processing. In the mining stage of the deposits, the “residue” comes from the removal of a thick layer of clay material (known as Belterra Clay). On the other hand, the “residue” from the beneficiation process is generated after the crushing, grinding and washing stages, which give rise to a large amount of clay material dispersed in a large amount of water. For the present study, it selected Belterra clay from the bauxite deposits of Rondon do Pará, a sample of Bauxite Washing Clay from the Hydro company and a sample of kaolin benefited from Imerys Company. The samples and geopolymers were characterized by X-ray Diffraction (XRD), X-ray Fluorescence (FRX), Gravimetric Thermal Analysis (TG), Differential Exploratory Calorimeter (DSC), Optical Emission Spectrometry with Coupled Plasma (ICP-OES) and Laser Particle Analyzer (APL). Geopolymers were synthesized from Belterra clay, microsilica and NaOH according to the Box-Benkhen design. Synthesis of geopolymers from Belterra clay and beneficiated kaolin was also carried out (a comparative study) using KOH and microsilica. Finally, geopolymers were synthesized from Bauxite washing clay with NaOH and microsilica according to the Doehlert design. In the study with only Belterra clay, the highest resistance result was 47.78MPa and the lowest result was 7.05MPa. In the comparative study between Belterra Clay and beneficiated kaolin, the best results of compressive strength were obtained with the beneficiated kaolin. The compressive strength results of the geopolymers synthesized from the Washing Clay ranged from 8.99 to 41.89MPa. These results demonstrate the positive potential of both samples for the synthesis of geopolymers that can be used as possible “Eco-friendly” substitutes for traditional materials, mainly ceramics and cement.
Acesso aberto (Open Access)
Ativação alcalina para a produção de geopolímeros a partir de resíduo industrial
(Universidade Federal do Pará, 2018-02-02) BRITO, Woshington da Silva; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
The sustainable construction of the future, and has low energy consumption and greenhouse gas emissions must also adopt the principle of reuse of wastes impacting the environment generated by the productive chain. The aluminum production chain has as one of the leading waste impact on the environment the gray generation. The present study focused on the research and development of a cement-based material. Refers to an inorganic polymer, formed by the activation of amorphous aluminosilicates (Al2O3. SiO2), which react in a strongly alkaline medium, called geopolymer. As a raw material furnace fly ash, mineral residue from the combustion of the boilers of the company of the municipality of Barcarena-PA; As a source of aluminosilicate, and the kaolin that underwent the process of burning at 800 ºC that became metakaolin; And the alkaline medium of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH), used as activators. As fly ash partially crystallizes during burning and loses some of its amorphous state, so are its reactive properties to chemically combine during the geopolymerization reaction are reduced. To increase reactive properties of fly ash and added metakaolin. As the main analyzes, no X-ray diffraction (XRD), X-ray fluorescence (FRX), scanning electron microscopy (SEM) and EDS. Tests of resistance to compression of the traces in the hardened state were also carried out and the rheological test of the geopolymer was carried out at the start of the reaction in the fresh state. For Davidovits ratios in the range of 2.5 to 3.23, the best geopolymers with compressive strength were obtained reaching 25 MPa in 24 hours of cure. For 60 days of cure at room temperature the geopolymers reached a resistance of 45, 36 MPa. The research carried out through the characterization analysis of the samples and the mechanical and rheological tests were presented in a satisfactory way and demonstrated that the residues of fly ash and metakaolin, when activated with sodium silicate and sodium hydroxide, are an alternative for the possible application of Geopolymer materials in construction.
Acesso aberto (Open Access)
Avaliação do comportamento reológica e mecânico de geopolímero sintetizado com reaproveitamento de resíduo
(Rede Latino-Americana de Materiais, 2018-10) BRITO, Woshington da Silva; BRUM, Sebastião Martins; SILVA, André Luis Mileo Ferraioli; FELIPE, Augusta Maria Paulain Ferreira; SOUZA, José Antônio da Silva
The sustainable construction of the future, besides low energy consumption and greenhouse gas emissions must also adopt the principle of reusing wastes generated by the production chain that impact the environment. One of the most impacting wastes generated by the aluminum production chain is fly ash. Geopolymers are cementitious materials with a three-dimensional structure formed by chemical activation of aluminosilicates. According to studies some ashes have proven to be suitable sources of Al and Si for the geopolymerization reaction. One of the most important aspects in the commercializing these products is their behavior in a plastic state. The workability of fresh geopolymer paste can be measured using several common tests used for Portland cement concrete, such as flow and slump; however, a more in-depth characterization of their rheology is essential for understanding their basic setting mechanisms. The objective of this work was to evaluate the rheological behavior of the Davidovits (SiO2/Al2O3) geopolymer paste at 2.65; 3.04 and 4.11. The mechanical resistance to compression at 24 hours, 7 days and 28 days of geopolymer cure was also evaluated. The geopolymerization reaction was conducted at ambient temperature of 28°C and 15 Molar sodium hydroxide (NaOH) and 10 Molar sodium silicate (Na2SiO3), were used as the activator. Fly ash and metakaolin were used as source of Al and Si was used. XRD, XRF, SEM techniques were used in the characterization of raw materials and geopolymers. The geopolymer with a lower Davidovits ratio of 2.65 presented better workability in its fresh state and higher mechanical strength at 40.80 MPa compression with 28 days cure at ambient temperature. The Herchel Bulkley rheological model was the one that was best adjusted to the geopolymers.
Acesso aberto (Open Access)
Concreto permeável geopolimérico aplicado na pavimentação
(Universidade Federal do Pará, 2023-03-07) ARAÚJO, Wendel Melo Prudêncio de; MACEDO, Alcebíades Negrão; http://lattes.cnpq.br/8313864897400179
In the recent scenario, groundwater retention plays a key role in achieving environmental sustainability. This can be achieved by using pervious concrete as a paving material in roads, parking lots, garden areas and low traffic road applications. Due to its mechanical limitation, much research has been carried out to develop a more resistant material. Geopolymeric permeable concrete is synthesized by the alkaline activation of materials rich in aluminate and silica in an alkaline medium. This work aims to produce samples of geopolymer permeable concrete, using red ceramic residue and metakaolin as precursors, for application in permeable paving. The results showed that the use of red ceramic in the production of pervious geopolymer concrete up to a concentration of 30% is feasible, since higher concentrations can compromise the physical, hydraulic and mechanical properties.
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)
Influência da temperatura de síntese do metacaulim para uso em pastas geopoliméricas
(Universidade Federal do Pará, 2022-12-09) BRANDÃO, Luis Felipe Alencar; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357; https://orcid.org/0000-0001-7313-1229
Geopolymers are a type of alkali-activated cement, composed of one or more precursors (sources of aluminosilicates), in general metakaolin, and an alkaline activating solution. This type of cement is known to have low carbon emissions and high initial strength gain, besides being able to incorporate several industrial wastes in its structure and also be compatible for the creation of reinforced concrete or not. Therefore, this work aims to study the influence of kaolin processing temperature for its transformation into metakaolin, in addition to evaluating the best proportion of SiO2/Al2O3 between the range of 3.5, 4 and 4.5 regarding compressive strength. For this purpose, kaolin of commercial origin was used as raw material for the production of the precursor, solutions based on sodium silicate and sodium hydroxide as an alkaline activator. The kaolin was processed at 3 different temperatures (550 °C, 650 °C and 750 °C), originating 3 different precursors, MK- 550, MK-650 and MK-750, respectively. From this, cylindrical specimens were made to evaluate the compressive strength of the geopolymer paste. And by combining with the evaluation of the 3 sio2/Al2O3 contents, 9 analysis points were established. Through diphratometry (XRD), it is possible to notice that there was full amorphization of the kaolin at 750 °C. And when rehearsing the test specimens with cure for 7 days at room temperature, it was found that the best formulation was for SiO2/Al2O3 = 4.0, with 25.2 MPa. After a reduction in the total water content of the system, there was an increase in resistance to 46 MPa at 7 days and when waiting 28 days for the cure of this series, a reduction was noticed to 29 MPa, possibly related to alkali excesses. Further tests show that the water absorption and porosity of the material is 40 % and 48 % respectively. It is concluded that by calcinar kaolin at 750 °C it is possible to produce a precursor for geopolymers of good resistance, being more economical energetically than usual in the literature researched.
Acesso aberto (Open Access)
Produção de agregados sintéticos para construção civil a partir de materiais geopoliméricos
(Universidade Federal do Pará, 2023-06-20) CRUZ, Kamila Sindy Pinheiro da; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; http://lattes.cnpq.br/7389345867032737
The civil construction industry is one of the sectors of the economy that consume the most natural resources, from the production of inputs to the execution of the work, which can significantly affect the environment and the quality of life of the population. Geopolymers are inorganic polymers with great ecological potential, produced from aluminosilicates and synthesized by alkaline solutions, providing the material with better mechanical resistance. Geopolymeric cement is a high-tech material developed using clay minerals, with characteristics such as durability, mechanical resistance, strong adhesion, heat resistance, in addition to being easily mixed and applied. The present study sought, through a correct proportion of the components that constitute the geopolymer, the production of a Geopolymeric Synthetic Aggregate (ASG), making variations with percentages of blast furnace slag and variations in the alkaline concentration of sodium hydroxide (NaOH). Soon after, physical tests were carried out on the powdered materials to verify the fineness index, loss on fire and moisture content of kaolin, metakaolin and blast furnace slag. The samples underwent characterization and the main analyzes involved in the process were: X-ray diffraction (DRX), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and EDS. A compression test was also carried out on the geopolymer synthetic aggregate specimen. The results of the compressive strength test indicated that the specimen with a percentage of 35% blast furnace slag and an alkaline concentration of sodium hydroxide at 10 molar presented better results. In the analysis of the microstructure of the paste, a dense morphology was observed, which gives the material high resistance to compression.
Acesso aberto (Open Access)
Uso de resíduo caulins da amazônia para a produção de precursores geopoliméricos utilizados na indústria da construção civil
(Universidade Federal do Pará, 2024-04-25) BRITO, Woshington da Silva; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500; https://orcid.org/0000-0003-0739-7592; SOUZA, Jose Antonio da Silva; http://lattes.cnpq.br/6157348947425968
The region of the Capim River (Northeast of the State of Pará), due to its large reserves of kaolin for covering paper, stands out nationally. The extraction of the ore occurs on average at a depth of 20 meters, covered by clayey-sandy sediments from the barrier formation, and from a level of hard kaolin, also known as flint or semi-flint kaolin(Ferruginous), considered stable depending on the content high iron content, which makes its application for roofing unfeasible. The research aims to address the development of geopolymers synthesized from waste containing aluminum silicate. Geopolymers are amorphous, threedimensional alkalis. Aluminosilicate binder materials synthesized from alkaline activation of clays, calcined clays, calcined kaolin, minerals, industrial waste, fly ash and other aluminosilicates. The fly ash generated in the Bayer process boilers under conditions of 900 °C and 120KPa was also used as a source of aluminosilicate in the geopolymerization reaction. To increase the reactivity of the reaction, the use of soft kaolin and flint and semi-flint(ferruginous) kaolin calcined at different temperatures(450,550,650, 700 and 800 °C) was evaluated. And, also at different calcination times(15,30,60 ,90 and 120 minutes). Sodium hydroxide (NaOH, 5-30 M) and sodium silicate (Na2SiO3, SiO2/Na2O = 3.2) as alkaline reaction medium. The residues were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). And, compressive strength tests were also carried out on the geopolymeric samples to evaluate the degree of polymerization, since the more polymerized the structure is, the greater the resistance. For the geopolymer based on (soft kaolin and fly ash), the best results were obtained for the SiO2/Al2O3 ratio of 2.65 and 3.4. For the geopolymer based on (flint kaolin and fly ash) the best result was for the SiO2/Al2O3 ratio of 2.95 and 3.57. The best results for the geopolymers based on (ferruginous metakaolin and fly ash) were obtained with a SiO2/Al2O3 ratio of 2.88 and 3.54. The geopolymeric ceramic plate obtained showed satisfactory performance in relation to mechanical resistance to compression and was also synthesized with raw material that contaminates the environment, as it is considered kaolin residue due to its high iron content.