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Characterization of fly ash reactivity in hydrating cement by neutron scattering

Published online by Cambridge University Press:  31 January 2011

Walairat Bumrongjaroen
Affiliation:
Vitreous State Laboratory, The Catholic University of America, Washington, District of Columbia 20064
Richard A. Livingston*
Affiliation:
Materials Science and Engineering Department, University of Maryland, College Park,Maryland 20742
Dan A. Neumann
Affiliation:
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
Andrew J. Allen
Affiliation:
Ceramics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
*
a) Address all correspondence to this author. e-mail: rliving1@umd.edu
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Abstract

Partial replacement of hydrating Portland cement by fly ash produces competing effects: it contributes calcium hydrate silicate (C-S-H) gel through the pozzolanic and alkali-activated reactions but dilutes the contribution of the main Portland cement reaction. To investigate this, two neutron-scattering methods were applied to density-fractionated lignite-type and bituminous-type fly ash/Portland cement pastes (20% by mass replacement). Small-angle neutron scattering (SANS) measured the effect of the fly ash on the fractal C-S-H microstructure, whereas inelastic neutron scattering (INS) measured the pozzolanic reaction in terms of calcium hydroxide (CH) consumption. The CH consumption increased with the effective density fraction, and the fractal microstructure evolved more slowly for all fly ash mixes compared with the pure cement control. However, gel volume measured by SANS showed no correlation with the CH consumption measured by INS. The implications of these results are discussed.

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Articles
Copyright
Copyright © Materials Research Society 2009

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