Journal of Thermal Analysis and Calorimetry
Volume/Issue:
Volume 80: Issue 3
Hypothetical transformation of Ca(OH)2 into CaCO3 in solid-state reactions of portland cement
Author:
Ewa T. Stepkowska Institute of Hydro-Engineering PAS 80-953 Gdańsk, Poland

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Pages:
727–733
Online Publication Date:
31 May 2005
Publication Date:
01 Jun 2005
Article Category:
Research Article
DOI:
https://doi.org/10.1007/s10973-005-0721-7
Keywords:
cement hydration; aragonite; vaterite; calcium carbonate; calcium carbonate hydroxide; calcium carbonate hydroxide hydrate; carbonation of portlandite
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Summary Previous study of the hydration and ageing products of two cement pastes created the basis for the postulate of the course of solid-state reactions between the portlandite Ca(OH)2 and the CO2 from air in the hydrated and air dry cement. XRD basal spacing d(001) of portlandite exceeded the nominal value and increased with ageing, with the wetting and drying procedure and with carbonate content of the paste, indicating that a part of OH- ions was gradually substituted by CO32- ions, which are about twice bigger. IR spectroscopy showed a considerable content of portlandite, of CO32- of water and silicates. Also HCO3- H2O and CO2 in cavities between hexagonal rings and hexagonal hydrates were indicated. By MS (mass spectrometry) in vacuum the evaporation of sorbed water was detected at 100-120°C, of gel water at 350°C of portlandite water at 400°C and of high temperature water between 500 and 700°C, simultaneously with CO2 escape. Slightly higher peak temperatures were found by the TG test either in air or in argon. From these results and from geometric considerations it is postulated that the solid-state reactions take place on ageing of the cement paste and on its heating: hexagonal portlandite?calcium carbonate hydroxy hydrate?calcium carbonate hydrate?hexagonal vaterite and/or orthorhombic aragonite?rhombohedral calcite The analysis of the standard files of the calcium carbonate hydroxy hydrates supports this postulate and indicates a gradual transformation.

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Cover Journal of Thermal Analysis and Calorimetry
Journal of Thermal Analysis and Calorimetry
Print ISSN:
1388-6150
Online ISSN:
1572-8943

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation		 1969
Volumes
per Year		 1
Issues
per Year		 24
Founder Akadémiai Kiadó
Founder's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher		 Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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