Effects of Powder Additive on High-Volume Fly Ash Mixtures
Mitigation of problems in high-volume fly ash (HVFA) paste mixtures was explored using powder additives. Class C fly ash substitution levels of 25, 50, and 70% were examined at two levels of water reducer, gypsum, lime, and rapid-set cement (RSC) each. Compressive strength at 1, 3, 7, 28, and 56 days; semi-adiabatic calorimetry; Vicat setting time; and miniature slump were used for evaluation. Lime, RSC, or gypsum by themselves were not helpful in significantly improving early strengths. However, gypsum-lime was in some cases effective, but lowered later strength. Gypsum-RSC improved strengths at all ages. Gypsum by itself helped restore (retard) the fly ash-accelerated HVFA calorimeter curve positions, as did gypsum-RSC and gypsum-lime. Early stiffening tendencies were alleviated by gypsum and gypsum-lime, but made worse by gypsum-RSC. Diagnostic plots of semi-adiabatic peak heights, curve positions, and early stiffening were developed to aid in prediction of mixture combination behavior.
D. N. Richardson et al., "Effects of Powder Additive on High-Volume Fly Ash Mixtures," ACI Materials Journal, vol. 112, no. 4, pp. 535-546, American Concrete Institute (ACI), Jul 2015.
The definitive version is available at https://doi.org/10.14359/51687395
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Additives; C (programming language); Calorimeters; Calorimetry; Compressive strength; Concrete beams and girders; Fly ash; Lime; Mixtures; Adiabatic calorimetry; Class C fly ashes; Early strength; High volume fly ash; Peak height; Rapid set; Setting time; Water reducers; Gypsum; High-volume fly ash; Mixture incompatibilities; Semi-adiabatic calorimetry
International Standard Serial Number (ISSN)
Article - Journal
© 2015 American Concrete Institute (ACI), All rights reserved.
01 Jul 2015