Navegando por Assunto "Geopolymers"

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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.
Acesso aberto (Open Access)
Estudo de rotas tecnológicas para a síntese de geopolímeros com adição de micropartículas de vidro: análise da influência do tamanho e forma das partículas
(Universidade Federal do Pará, 2025-02-14) MODESTO, Alex da Silva; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287
The sustainable construction of the future requires materials that consume less energy, emit fewer greenhouse gases and reuse waste that is harmful to the environment, such as discarded glass, one of the main waste products in the production chain. This research developed geopolymers, inorganic polymers formed by the activation of amorphous aluminosilicates in an alkaline medium, using me-takaolin and blast furnace slag as precursors and recycled glass microparticles as an additive. Com-positions were formulated with glass contents ranging from 0% to 60%, in particle size ranges of < 38 μm, 38-45 μm, 45-75 μm and 75-180 μm, and alkaline hydroxide and sodium silicate activators. Compression tests carried out on cylindrical specimens after 7 days of curing revealed that the addi-tion of 40% glass with a grain size of 38-45 μm resulted in an 80% increase in compressive strength compared to the unmodified material, reaching values of over 40 MPa. Microstructural analysis by SEM and EDS confirmed greater density and reduced porosity in the geopolymer matrix. Tensile adhesion tests also indicated the viability of the material as a substrate for coatings, meeting the demands of the construction industry. It is concluded that geopolymers with added recycled glass combine high mechanical performance and sustainability, promoting circular economy and repre-senting a viable alternative to the use of Portland cement.
Acesso aberto (Open Access)
Síntese e caracterização de geopolímeros, a partir de argila, caulim ferruginoso e cinzas volantes - classe c
(Universidade Federal do Pará, 2021-08-12) PREZA, Carmen Raiza Aires Soares; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
The high demand in the civil construction sector has caused a negative scenario for the environment. With this, researches arise with the objective of discovering sustainable alternatives to the existing technology, because, it is known that over the years, the concern with nature was significantly lost. With that in mind, the situation can be softened with some of the techniques that have been around for millennia and are still relevant. Studies on geopolymers are growing, especially in developed countries. The main application of this material, composed of minerals and industrial residues, is the replacement of Portalnd cement. Thus, this work aimed to produce geopolymers with superior physicochemical properties. The elaboration of geopolymers was directed from different concentrations of clay/flying ash and ferritic kaolin/flying ash. The raw materials were analyzed in natura and calcined at 600 ºC/2 hours and 800 ºC, using Xray diffraction, X-ray fluorescence and laser particle size analysis. The results showed that the raw materials are technologically viable for the study, due to their SiO2 and Al2O3 contents, being: 63.89% and 16.65% for clay; 38.57% and 36.85% for ferritic kaolin; and 42.53% and 16.40% for fly ash, respectively. The raw materials presented fine grain sizes, being more reactive. Geopolymers A3 (80% clay/20% fly ash) and C3 (80% kaolin/20% fly ash) showed the best results for compressive strength, 13.19 MPa and 31.22 MPa, in the 28th day, respectively. The values found are within the limits found for some Portland cements.