Navegando por Autor "BRITO, Woshington da Silva"

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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)
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.