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Effect of Gypsum on the Early Hydration of Cubic and Na-Doped Orthorhombic Tricalcium Aluminate

1
Department of Civil Engineering of Federal, University of Rio Grande do Sul (UFRGS), Porto Alegre 90035-190, Brazil
2
Department of Structures and Civil Construction, Federal University of Santa Maria (UFSM), Santa Maria 971015-900, Brazil
3
School of Engineering, University of Edinburgh, King’s Buildings, Sanderson Building, Edinburgh EH9 3BF, UK
4
Malvern PANalytical, 117 Flanders Rd # 120, Westborough, MA 01581, USA
5
Department of Civil and Environmental Engineering, University of California, Berkeley, CA 1792, USA
6
Polytechnic School of the University of São Paulo—POLI/USP, São Paulo 05508-010, Brazil
*
Author to whom correspondence should be addressed.
Materials 2018, 11(4), 568; https://doi.org/10.3390/ma11040568
Received: 5 March 2018 / Revised: 30 March 2018 / Accepted: 2 April 2018 / Published: 7 April 2018
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

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. View Full-Text
Keywords: cubic tricalcium aluminate; orthorhombic tricalcium aluminate; gypsum; hydration; calorimetry; in situ XRD cubic tricalcium aluminate; orthorhombic tricalcium aluminate; gypsum; hydration; calorimetry; in situ XRD
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Kirchheim, A.P.; Rodríguez, E.D.; Myers, R.J.; A. Gobbo, L.; M. Monteiro, P.J.; C. C. Dal Molin, D.; De Souza, R.B.; Cincotto, M.A. Effect of Gypsum on the Early Hydration of Cubic and Na-Doped Orthorhombic Tricalcium Aluminate. Materials 2018, 11, 568.

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