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n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Effect of activator dosage, water-to-binder-solids ratio, temperature and duration of elevated temperature curing on the compressive strength of alkali-activated fly ash cement pastes : technical paper

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Abstract

In this paper the effect of sodium oxide concentration, the water-to-binder-solids ratio, temperature, and the duration of elevated temperature curing on the compressive strength of alkali-activated fly ash cement pastes was investigated. Alkali concentration varied between 3% and 15% NaO of fly ash mass. An increase in NaO from 3% to 9% greatly improved the compressive strength of the pastes from 26.1 MPa to 50.8 MPa at 28 days. A further increase in NaO up to 15% did not provide an increase in the strength, but a decrease was observed, as well as higher strength variation. The paste activated with 9% NaO had the highest strength at 28 days and a low standard deviation, and 9% NaO was thus considered as the best value in the present study. The temperature and the duration of elevated temperature curing were found to be critical factors affecting the compressive strength at early age, but their effect decreased significantly in the long term. The water-to-binder-solids ratio affected the compressive strength considerably. An increase in the water-to-binder-solids ratio of the pastes from 0.18 to 0.29 resulted in a decrease in the compressive strength from 49.3 MPa to 21.3 MPa.

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/content/civileng/56/3/EJC161373
2014-10-01
2016-12-08
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