Effect of gypsum on the early hydration of cubic and Na-doped orthorhombic tricalcium aluminate

• Autor(a) principal: Kirchheim, Ana Paula
• Data de Publicação: 2018
• Outros Autores: Rodriguez Martinez, Erich David, Myers, Rupert J., Gobbo, Luciano de Andrade, Monteiro, Paulo José Melaragno, Dal Molin, Denise Carpena Coitinho, Souza, Rui Barbosa de, Cincotto, Maria Alba
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRGS
• Texto Completo: http://hdl.handle.net/10183/179233
• topic: Aluminato de cálcio; Gesso; Calorimetria; Cubic tricalcium aluminate; Orthorhombic tricalcium aluminate; Gypsum; Hydration; Calorimetry; In situ XRD

The tricalcium aluminate (C3A) and sulfate content in cement influence the hydration chemistry, setting time and rheology of cement paste, mortar and concrete. Here, in situ experiments are performed to better understand the effect of gypsum on the early hydration of cubic (cub-)C3A and Na-doped orthorhombic (orth-)C3A. The isothermal calorimetry data show that the solid-phase assemblage produced by the hydration of C3A is greatly modified as a function of its crystal structure type and gypsum content, the latter of which induces non-linear changes in the heat release rate. These data are consistent with the in situ X-ray diffraction results, which show that a higher gypsum content accelerates the consumption of orth-C3A and the subsequent precipitation of ettringite, which is contrary to the cub-C3A system where gypsum retarded the hydration rate. These in situ results provide new insight into the relationship between the chemistry and early-age properties of cub- and orth-C3A hydration and corroborate the reported ex situ findings of these systems.