A Raman spectroscopic study of the evolution of sulfates and hydroxides in cement–fly ash pastes

Raman spectroscopy has been employed to study the evolution of sulfo-aluminate and hydroxyl phases in pastes made with ordinary Portland cement (OPC) and fly ash (FA). Three fly ashes with different CaO contents were used as a cement replacement at the level of 0 and 50% by weight. The pastes were a...

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Bibliographic Details
Published in:Cement and concrete research 2013-11, Vol.53, p.91-103
Main Authors: Garg, Nishant, Wang, Kejin, Martin, Steve W.
Format: Article
Language:English
Subjects:
Applied sciences
Buildings. Public works
Ca(OH)2 (D)
Cement (D)
Cement concrete constituents
Cements
Concretes. Mortars. Grouts
Evolution
Exact sciences and technology
Fly ash
Fly ash (D)
General (composition, classification, performance, standards, patents, etc.)
Hydroxides
Materials
Pastes
Properties and test methods
Properties of anhydrous and hydrated cement, test methods
Raman spectroscopy
Raman spectroscopy (nominated)
Spectroscopic analysis
Sulfates
Sulfo-aluminate (D)
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Summary:Raman spectroscopy has been employed to study the evolution of sulfo-aluminate and hydroxyl phases in pastes made with ordinary Portland cement (OPC) and fly ash (FA). Three fly ashes with different CaO contents were used as a cement replacement at the level of 0 and 50% by weight. The pastes were analyzed at 0, 0.2, 2, 4, 8, 12, 16, 20, 24, 48, 72h, and 7, 14, 21, 28, and 56days after mixing. The wavenumber ranges used for Raman spectroscopic analysis are 950–1050cm−1 for evolution of sulfates and 3600–3700cm−1 for evolution of hydroxides. Gradual disappearances of gypsum in parallel with the formation of ettringite (AFt) are clearly observed in most paste mixes. Evolution of hydroxides showed the gradual spatial growth of portlandite. In addition to the potential benefits, the limitations of using Raman spectroscopy in study of cement-based materials are also noted in this paper. •Raman spectroscopy characterizes raw cementitious materials effectively.•Raman spectroscopy clearly illustrates gypsum depletion and ettringite formation.•Raman spectroscopy is able to map Ca(OH)2 concentration and distribution with time.Raman spectroscopy is a simple technique for in-situ evaluation of cement hydration.
ISSN:0008-8846
1873-3948
DOI:10.1016/j.cemconres.2013.06.009