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Fine Limestone Additions to Regulate Setting in High Volume Fly Ash Mixtures

Published

Author(s)

Dale P. Bentz, Taijiro Sato, Igor de la Varga, Jason Weiss

Abstract

High volume fly ash (HVFA) concrete mixtures are being considered more frequently due to their cost and sustainability advantages. While the long term performance of these HVFA concretes typically meets or exceeds that of conventional concretes, their early age performance is often characterized by excessive retardation, delayed setting times, and low strengths. Extending an HVFA mixture to a ternary blend that incorporates a fine limestone powder may provide a viable solution to these deficiencies, particularly the retardation and setting issues. In this paper, a nano-limestone powder and two other limestone fillers of increasing median particle size (4.4 μm and 16.4 μm) are investigated for their propensity to accelerate early age reactions and reduce setting times in a Class C fly ash/cement blend. The fineness of the fly ash has measurable effects on its efficacy in accelerating hydration and decreasing setting times. Companion specimens prepared with a fine silica powder suggest that the fine limestone may act favorably through both a physical and a chemical mechanism. Isothermal calorimetry and Vicat needle penetration measurements on pastes are accompanied by strength measurements on mortars, to verify that the limestone powder substitutions are not negatively impacting strength development. A linear relationship with a reasonable correlation is found to exist between 1 d and 7 d compressive strengths of mortars and their accompanying cumulative heat release values as determined using isothermal calorimetry.
Citation
Cement and Concrete Composites
Volume
34
Issue
1

Keywords

Blended cement, high volume fly ash, isothermal calorimetry, limestone, particle size, setting, strength

Citation

Bentz, D. , Sato, T. , de, I. and Weiss, J. (2012), Fine Limestone Additions to Regulate Setting in High Volume Fly Ash Mixtures, Cement and Concrete Composites, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908529 (Accessed April 17, 2024)
Created January 2, 2012, Updated February 19, 2017