University of Oulu

Hoang Nguyen, Wolfgang Kunther, Katrijn Gijbels, Pieter Samyn, Valter Carvelli, Mirja Illikainen, Paivo Kinnunen, On the retardation mechanisms of citric acid in ettringite-based binders, Cement and Concrete Research, Volume 140, 2021, 106315, ISSN 0008-8846,

On the retardation mechanisms of citric acid in ettringite-based binders

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Author: Nguyen, Hoang1; Kunther, Wolfgang2; Gijbels, Katrijn3;
Organizations: 1Fibre and Particle Engineering Research Unit, University of Oulu, Pentti Kaiteran katu 1, 90014 Oulu, Finland
2Department of Civil Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
3Nuclear Technological Centre, Hasselt University, Agoralaan, Gebouw H, 3590 Diepenbeek, Belgium
4IMO, Applied and Analytical Chemistry, Hasselt University, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium
5Department A.B.C., Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milan, Italy
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Version: published version
Access: open
Online Access: PDF Full Text (PDF, 10.1 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2020-11-30


This study aims to obtain insights into the retardation mechanism of citric acid in an ettringite-based binder from ladle slag and gypsum. The hydration kinetics and phase assemblage of the binder were experimentally investigated and thermodynamically modelled. Additionally, the effects of citric acid on synthetic ettringite were studied to obtain further understanding of the interaction between this organic ligand and the crystal. Experimental results reveal that citric acid works as an inhibitor of ettringite’s formation leading to the precipitation of monosulfate and gypsum; the ettringite surface blockage by citrate ligand effectively prevents precipitation of this crystal. This leads to an overestimation in the precipitation of ettringite in the thermodynamic model due to this kinetic barrier imposed by the ligand. Thermodynamic modelling suggests ettringite, monosulfate, aluminum hydroxide, and strätlingite as main hydrates in this binder, whereas an intermixed C–(A–)S–H gel was observed experimentally instead of strätlingite.

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Series: Cement and concrete research
ISSN: 0008-8846
ISSN-E: 1873-3948
ISSN-L: 0008-8846
Volume: 140
Article number: 106315
DOI: 10.1016/j.cemconres.2020.106315
Type of Publication: A1 Journal article – refereed
Field of Science: 212 Civil and construction engineering
215 Chemical engineering
216 Materials engineering
Funding: This work is a part of the FLOW Project (project number 8904/31/2017) funded by Business Finland in the ERA-MIN 2 Innovation program (EU Horizon 2020 program). Hoang Nguyen gratefully acknowledges financial support from travel grant of UniOGS (the University of Oulu Graduate School) for his research visit in Technical University of Denmark. P.K. acknowledges financial support from Academy of Finland (grants 322085, 329477 and 326291).
Academy of Finland Grant Number: 322085
Detailed Information: 322085 (Academy of Finland Funding decision)
329477 (Academy of Finland Funding decision)
Copyright information: © 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (