Alkalis incorporated into tricalcium aluminate: effects in hydration

Authors

  • Ana Paula Kirchheim Universidade Federal do Rio Grande do Sul
  • Rui Barbosa de Souza
  • Denise Carpena Coitinho Dal Molin Universidade Federal do Rio Grande do Sul
  • Paulo José Melaragno Monteiro University of California at Berkeley

Keywords:

Cubic and orthorhombic tricalcium aluminate, Ettringite, Hydration

Abstract

Tricalcium aluminate (C3A) is the phase that reacts more quickly in the cement hydration when in contact with water. Generally, the crystalline form of C3A synthesized during clinkerization is cubic. However, Na+ can be incorporated into
the crystalline lattice of C3A, replacing the Ca2+, leading to the formation of orthorhombic C3A (Na-C3A). Although some studies have investigated the influence of this polymorphous on cement hydration, some knowledge gaps still exist. This study uses pure phases synthesized in laboratory to analyze the reactions independently, isolating the reactions from the others phases. Hydration
reactions of C3A in presence of gypsum were investigated by isothermal calorimetry, scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic mode rheology. The results showed differences in the hydration of each aluminate, indicating that the orthorhombic phase is more reactive at early ages in the presence of gypsum, consuming them very quickly. The pastes mixed with orthorhombic C3A and gypsum presented a total heat released at least 10 times greater than the ones made with cubic C3A. The SEM images and the XRD patterns demonstrate that the pastes containing orthorhombic C3A reacted at a faster rate, and the ettringite crystals formed were also longer.

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Author Biographies

Ana Paula Kirchheim, Universidade Federal do Rio Grande do Sul

Engenheira Civil, doutora em Engenharia Civil (UFRGS), bolsista de pós-doutorado, Programa de Pós-Graduação em Engenharia Civil (PPGEC/NORIE), Universidade Federal do Rio Grande do Sul 

Denise Carpena Coitinho Dal Molin, Universidade Federal do Rio Grande do Sul

Engenheira civil, doutora em Engenharia Civil (USP), professor adjunto, Programa de Pós-Graduação em Engenharia Civil (PPGEC/NORIE), Universidade Federal do Rio Grande do Sul

Paulo José Melaragno Monteiro, University of California at Berkeley

Engenheiro Civil, PhD  (UC, Berkeley), professor adjunto, Department of Civil and Environmental Engineering, University of California at Berkeley

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Published

2010-03-03

How to Cite

KIRCHHEIM, A. P.; SOUZA, R. B. de; DAL MOLIN, D. C. C.; MONTEIRO, P. J. M. Alkalis incorporated into tricalcium aluminate: effects in hydration. Ambiente Construído, [S. l.], v. 10, n. 1, p. 177–189, 2010. Disponível em: https://seer.ufrgs.br/index.php/ambienteconstruido/article/view/11616. Acesso em: 25 jun. 2025.

Issue

Vol. 10 No. 1 (2010)

Section

Artigos

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ISSN 1678-8621

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