The impact of alkali oxides Na2O and Rb2O on the phase composition and hydration of C3A

Authors

  • Simona Ravaszová Brno University of Technology, Faculty of Civil Engineering, Institute of Technology of Building Materials and Components, Veveří 95, 602 00 Brno, Czech Republic
  • Karel Dvořák Brno University of Technology, Faculty of Civil Engineering, Institute of Technology of Building Materials and Components, Veveří 95, 602 00 Brno, Czech Republic
  • Andrea Jančíková Brno University of Technology, Faculty of Civil Engineering, Institute of Technology of Building Materials and Components, Veveří 95, 602 00 Brno, Czech Republic
  • Michal Křištof Brno University of Technology, Faculty of Civil Engineering, Institute of Technology of Building Materials and Components, Veveří 95, 602 00 Brno, Czech Republic
  • Martin Boháč Research Institute for Building Materials, Hněvkovského 65, 617 00 Brno, Czech Republic

DOI:

https://doi.org/10.14311/AP.2026.66.0209

Keywords:

tricalcium aluminate, dopants, sodium, rubidium, solid-state synthesis

Abstract

Portland cement clinker contains C3A as one of its key phases. During firing, it forms a melt that is essential for the formation of C3S and C2S. Commonly, two polymorphs of C3A are present: cubic and orthorhombic, and their presence influences the kinetics of cement hydration. This study focused on the effects of Na2O and Rb2O dopants on the polymorphic modifications of C3A. It was found that Na2O in concentrations of 0–2.5 % promotes the formation of the cubic polymorph, while higher concentrations, above 2.5 %, lead to a transition to the orthorhombic polymorph. For Rb2O, incompatibility with calcium was observed, resulting in the formation of new phases and the leaching of rubidium oxide at high firing temperatures. In terms of hydration, samples containing Na2O exhibited higher reactivity due to the presence of orthorhombic C3A, whereas Rb2O slowed down hydration, which remains an issue for further research.

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Published

2026-05-15

Issue

Vol. 66 No. 2 (2026)

Section

Articles

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Copyright (c) 2026 Simona Ravaszová, Karel Dvořák, Andrea Jančíková, Michal Křištof, Martin Boháč

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This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite

Ravaszová, S., Dvořák, K., Jančíková, A., Křištof, M., & Boháč, M. (2026). The impact of alkali oxides Na2O and Rb2O on the phase composition and hydration of C3A. Acta Polytechnica, 66(2), 209–218. https://doi.org/10.14311/AP.2026.66.0209