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Activation of Pozzolanic Reaction of Hydrated Portland Cement Fly Ash Pastes in Sulfate Solution
Author(s) -
Lorenzo Mari Paz,
Goñi Sara,
Guerrero Ana
Publication year - 2002
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2002.tb00581.x
Subject(s) - fly ash , portland cement , pozzolanic reaction , pozzolan , pozzolanic activity , sulfate , materials science , cement , chemical engineering , mineralogy , nuclear chemistry , composite material , chemistry , metallurgy , engineering
The activation of the pozzolanic reaction of fly ash in portland cement paste immersed in sulfate solution has been studied. Mixtures of two Spanish fly ashes (ASTM class F) with 0%, 15%, and 35% replacement of portland cement by fly ash were immersed in Na 2 SO 4 solution, of 2880 ppm SO 4 2− concentration, for a period of 90 days. The resistance of the different mixtures to the sulfate attack was evaluated using the Koch‐Steinegger test. The results showed that all of the mixtures were sulfate resistant, despite the high Al 2 O 3 content of the fly ash. The diffusion of SO 4 2− and Na + ions through the pore solution activated the pozzolanic reactivity of the fly ashes, causing microstructural changes, which were characterized by X‐ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). As a result, the flexural strength of the mixtures increased, principally for the fly ash of a lower particle size and 35% of addition.