Navegando por Assunto "Cimento geopolimérico"

Agora exibindo 1 - 2 de 2

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.
Acesso aberto (Open Access)
Estudo de ligante geopolimérico obtido a partir de metacaulim e escória granulada de alto forno
(Universidade Federal do Pará, 2022-12-06) MORAES, Mario Henrique Moreira de; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357
The need for alternative materials to replace Portland cement is a contemporary discussion. Those new and alternative materials must have a sustainable character and good durability to supply the demand of the civil construction sector and mitigate the environmental crises caused by the industry, such as the high emission rate of CO2. In this context, geopolymeric binders appear as materials produced by different solid precursors in contact with an alkaline activator, with zero CO2 emission and mechanical properties and durability compatible or superior to that of Portland cement. Thus, this study aimed to evaluate the geopolymeric binder obtained from the combination of metakaolin (MK) and ground granulated blast furnace slag (GGBFS) with three different molar concentrations of sodium hydroxide (8, 10, and 12 M) for the alkaline activator. Dosages were established from the partial mass substitution of MK by GGBFS, coded as G0 (100% MK 0% EAF), G20 (80% MK 20% EAF), and G40 (60% MK 40% EAF). XRD, XRF, and SEM analyses were conducted for solid precursors. Geopolymer pastes properties were evaluated in the fresh state regarding setting time and in the hardened state based on physical tests, average compressive strength, and fracture morphology. Results showed that the MK and the GGBFS have adequate reactivity and chemical composition for the geopolymer synthesis, with the presence of calcium in the GGBFS actively contributing to the reduction of the setting time and gain of mechanical resistance of the dosages. As for the hardened state, higher levels of water absorption are intrinsically related to a decrease in mechanical strength, with fracture analysis revealing the presence of pores and micropores that favor the propagation of cracks. Statistical analysis found that the interaction between the analyzed factors significantly influenced the properties of the materials, with 85.35% (R2 = 0.8535) of the model being able to explain the variation in compressive strength of geopolymers as a function of the factors used in the regression, limited to the chosen range of variables. The G40M12 formulation showed the highest compressive strength value (38.08 MPa) and the ideal synthesis parameters defined were the rotational frequency at 150 RPM, a partial replacement of MK by GGBFS of 40%, and the NaOH concentration of 12 M. Finally, from the correlation of the evaluated characteristics, the developed geopolymeric binders showed technological potential as alternative and sustainable materials, with properties comparable to those of Portland cement.