Influence of water vapour and carbon dioxide on free lime during storage at 80°C, studied by Raman spectroscopy

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 111; pp. 299 - 303
• Main Authors: Dubina, E., Korat, L., Black, L., Strupi-Šuput, J., Plank, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2013
• Subjects: Calcium carbonate polymorphs; Calcium oxide; Carbonation; Micro-Raman; Moisture; SEM/EDX; Carbonation; SEM/EDX; Calcium oxide; Calcium carbonate polymorphs; Moisture; Micro-Raman
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2013.04.033

[Display omitted] •Micro-Raman spectroscopy was used to monitor the reaction of CaO with water vapour.•At low RH values, total conversion of CaO to Ca(OH)2 was observed.•Ca(OH)2 underwent partial carbonation into amorphous calcium carbonate.•At low RH, only Raman spectroscopy revealed the formation of amorphous CaCO3.•Importance of Raman spectroscopy in the study of amorphous products is shown. Micro-Raman spectroscopy has been used to follow the reaction of free lime (CaO) exposed for 24h to moist air at 80°C under conditions of different relative humidities (10–80% RH). X-ray diffraction and SEM imaging were applied as complementary techniques. The conversion of lime to calcium hydroxide and its subsequent carbonation to various calcium carbonate polymorphs was found to strongly depend on the relative humidity. At low RH (10–20%), only Raman spectroscopy revealed the formation of early amorphous CaCO3 which in the XRD patterns was detected only at ⩾40% RH. However, XRD analysis could identify the crystalline polymorphs formed at higher relative humidities. Thus, between 20 and 60% RH, all three CaCO3 polymorphs (calcite, aragonite and vaterite) were observed via XRD whereas at high relative humidity (80%), calcite was the predominant reaction product. The results demonstrate the usefulness of Raman spectroscopy in the study of minor cement constituents and their reaction products on air, especially of amorphous character.