Portland cement-blast furnace slag mortars activated using waterglass: Effect of temperature and alkali concentration

•Portland cement with 50% slag was alkali activated to improve the early strength.•Activation with 4%Na2O was not effective compared to nonactivated mortars.•The alkali activation delayed the portland cement hydration and strength development.•For the blended cements, increased temperature and/or %N...

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Bibliographic Details
Published in:Construction & building materials 2014-09, Vol.66, p.323-328
Main Authors: Escalante-Garcia, J.I., Castro-Borges, P., Gorokhovsky, A., Rodriguez-Varela, F.J.
Format: Article
Language:English
Subjects:
Alkali activated blended
Analysis
Backscattered electron imaging
Cement
Granulated blast-furnace slag
Hydration
Hydration (Chemistry)
Mechanical properties
Microstructure
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Summary:•Portland cement with 50% slag was alkali activated to improve the early strength.•Activation with 4%Na2O was not effective compared to nonactivated mortars.•The alkali activation delayed the portland cement hydration and strength development.•For the blended cements, increased temperature and/or %Na2O enhanced the reactivity.•The formation of hydration products N–C–S–H contributed to the reduced strengths. Mortars of portland cement with 50% of blast furnace slag were alkali activated with 0–10%Na2O using waterglass and cured at 10–40°C. The presence of the slag reduced the strength of 0%Na2O blends and the alkaline activation with 4%Na2O resulted in even lower values; 6%Na2O gave similar results as 0%Na2O and 10%Na2O rendered strengths similar or higher than those of neat portland cement. The combination of higher temperature and higher alkalinity favored the reactivity and strength. The formation of N–C–S–H and delayed hydration of portland cement appeared to be the causes of the low strengths observed in alkali activated systems.
ISSN:0950-0618
1879-0526
DOI:10.1016/j.conbuildmat.2014.04.120