Influência da adição de nanosílica e nano-metacaulim na formação de etringita tardia: estudos de dispersão das adições e caracterização microestrutural de pastas submetidas à cura térmica

• Ano de defesa: 2020
• Autor(a) principal: Cardoso, Juliana Oliveira Malta
• Orientador(a): Barreto, Ledjane Silva
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Programa de Pós-Graduação: Pós-Graduação em Ciência e Engenharia de Materiais
• Palavras-chave em Português: Engenharia de materiais; Sulfatos; Cimento; Sílica
• Palavras-chave em Inglês: Sulfate; Nanosilica; Ettringite
• Área do conhecimento CNPq: ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: https://ri.ufs.br/jspui/handle/riufs/14758

The pathological manifestation of heat-induced internal sulfate attack is quite aggressive and promotes the growth of ettringite crystals in the hardened cement matrix, which can lead the element to cracking or structural collapse. In order to mitigate this manifestation, additions of nanometric pozzolanic materials have been studied with promising results. In this work it was proposed on the influence of the additions of nanosilica (NS) and nano-metakaolin (NMK) in isolation and together, in the formation of delayed ettringite (DEF) in cementitious pastes under thermal curing. In order to take advantage of the reduced size of the nanoparticles, using them in the most dispersed form possible, a study on the characterization and stability of NMK suspension was carried out, analyzing potentiometric titration, zeta potential, average particle size, different types of dispersants and viscosity measurements over time. In addition, the characterization of pastes with the addition of NS and NMK by DRX, TG, FTIR and SEM was carried out, evaluating aspects of pozzolanicity and DEF formation. The results showed stable suspensions until the age of 24 h, with polycarboxylate being the dispersant that provided greater stabilization of the suspensions zeta potential over time. Regarding DEF, the single addition of NS did not show any influence on the reaction mechanism. The single addition of NMK postponed the onset of DEF from 28 to 180 days. In the paste with NS + NMK combined addition, despite the high pozzolanic activity, DEF occurred with 28 days of hydration, and with 180 days SEM images showed massive formation of ettringite.