Navegando por Autor "FELIPE, Augusta Maria Paulain Ferreira"

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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)
Determinação do ponto de carga zero da bauxita da região nordeste do Pará
(2012-12) PINTO, Rayssa Luana da Silva; SILVA, Kelly Cristina Sarmento da; CARDOSO, Dilson Nazareno Pereira; MACÊDO, Emanuel Negrão; FELIPE, Augusta Maria Paulain Ferreira
In the northeast of Pará, Brazil, the transport of bauxite pulp is through pipeline, being the viscosity a parameter which can interfere in the pumping. This study illustrates the influence of pH on pulp rheology through of determination of the zero point of charge. Were done particle size analysis, SEM, EDS, potentiometric tests testing ammonia chloride as indifferent electrolyte and rheological tests at different pH values. The results revealed that ammonia chloride can be used as indifferent electrolyte and showed a decrease in viscosity when there is far of the zero point of charge.
Acesso aberto (Open Access)
Efeito de aditivos no comportamento reológico do rejeito da bauxita
(Universidade Federal do Pará, 2015-03) GONÇALVES, Silvane Gonçalves e; BRUM, Sebastião Martins; FELIPE, Augusta Maria Paulain Ferreira; SOUZA, José Antônio da Silva; FERREIRA, Keylla Castro
In the bauxite mining in Parogominas, PA, Brazil, tailings are discarded in the processing with 33.5% of solids content and small particle size with D50 below 5 µm. These factors contribute to this suspension basically formed by silicoaluminates, with high concentrations of kaolinite clay, increase the viscosity and the yield stress, these factors are important during the pumping. It was performed granulometric analysis and determined the chemical and mineralogical composition of the material. It was studied the use of the sodium hexametaphosphate and polyacrylamide 25% anionic to decrease the viscosity. The result show that the viscosity decrease with use of 23.8 g/ton for the polyacrylamide and 101.75 g/ton for the sodium hexametaphosphate. The particle size and the pH have influence in the behavior of the additives.