Hydration of Portland Cement in the Presence of Highly Reactive Metakaolin

Alexey Brykov¹, Svetlana Krasnobaeva¹, Maxim Mokeev²

¹Faculty of Chemistry of Substances and Materials, St. Petersburg State Institute of Technology, St. Petersburg, Russia.
²Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia.

DOI: 10.4236/msa.2015.65044                

Abstract

The degree of conversion of highly reactive metakaolin in Portland cement metakaolin paste at different ages as well as the influence of metakaolin on the degree of hydration of Portland cement and composition of C-S-H is investigated by ²⁷Al- and ²⁹Si-MAS NMR spectroscopy. At the age of 7 days, in the paste with 10% of metakaolin, the additive is completely consumed. In the 30% substituted cement paste, the content of metakaolin remains quite high (about 40% of the initial amount) even after 3 months of hydration. At the age of 1 - 3 months, the degree of Portland cement hydration in the presence of metakaolin is of 15% - 20% less than without it, probably, due to deficit of water or spatial restrictions. After 7 days of hydration, about half of C-S-H consists of material derived from metakaolin. Metakaolin mainly contributes to Q² and Q² (1Al) species, whereas PC does to Q¹. After 1 day of hydration, an amount of ettringite in cement paste with high dosage of metakaolin is higher than in pure PC paste.

Keywords

Metakaolin, Portland Cement, Hydration, MAS NMR, Pozzolanic Reaction

Conflicts of Interest

The authors declare no conflicts of interest.

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