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Rheology and Setting of High Volume Fly Ash Mixtures

Published

Author(s)

Dale P. Bentz, Chiara F. Ferraris

Abstract

While high volume fly ash (HVFA) concretes can be designed and produced to meet 28-d strength requirements and often even exceed the durability performance of conventional concretes, a persistent problem is the potentially long delay in setting time that produces concurrently long delays in finishing the concrete in the field. Previously, based on isothermal calorimetry studies, two different powder additions, namely calcium hydroxide and a rapid set cement, have been suggested as potential solutions to mitigating this excessive retardation. In this paper, rheological measurements and conventional Vicat setting time studies are conducted to verify that these powder additions do indeed reduce setting times in paste systems based on both class C and class F fly ashes. The reductions obtained are dependent on the class of fly ash and suggest that trial mixtures would be a necessity to apply these technologies to each specific fly ash/cement/admixture combination being employed in the field. Potentially, for such screening studies, the rheological measurement of yield stress may provide an earlier indication of setting (and finishability) than conventional Vicat needle penetration measurements on pastes.
Citation
Cement and Concrete Composites
Volume
32
Issue
4

Keywords

Building technology, high volume fly ash, hydration, rheology, set time, sustainability.

Citation

Bentz, D. and Ferraris, C. (2010), Rheology and Setting of High Volume Fly Ash Mixtures, Cement and Concrete Composites, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=904150 (Accessed June 19, 2024)

Issues

If you have any questions about this publication or are having problems accessing it, please contact reflib@nist.gov.

Created April 1, 2010, Updated February 19, 2017