Influence of Particle Size Distribution on the Effectiveness of Type-F fly Ash in Suppressing Expansion Due to Alkali-Silica Reactivity

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Title: Influence of Particle Size Distribution on the Effectiveness of Type-F fly Ash in Suppressing Expansion Due to Alkali-Silica Reactivity

Author(s): M. A. Berube, A. Carles-Gibergues, J. Duchesne, and P. Naproux

Publication: Special Publication

Volume: 153

Issue:

Appears on pages(s): 177-192

Keywords: accelerated tests; alkali-aggregate reactions; concretes; expansion; fly ash; limestone; particle size distribution; tests; Materials Research

Date: 6/1/1995

Abstract:
The effectiveness of fly ash (FA) in suppressing concrete expansion due to alkali-silica reactivity (ASR) is thought to be largely affected by its particle size distribution and composition, in particular, the glass and alkali contents. This study is particularly concerned with the effect of particle size. A low alkali Type F fly ash was screened to obtain different size fractions. The fly ash was also ground to obtain different Blaine fineness, from 3100 (natural fly ash) to 8800 cm 2/g. The activity index of the various fly ash samples, including the bulk fly ash, was determined on mortar samples made with 25 percent fly ash by mass as cement replacement. The effectiveness of the same samples was investigated through the Accelerated Mortar Bar Method ASTM C 1260 (or CSA A23.2-25A), in the presence of a well known alkali-silica reactive aggregate from Canada, a siliceous limestone (Spratt Quarry, Ottawa, Ontario), at a 30 percent cement replacement by mass. High-performance concrete was also made with the same fly ash samples at a 25 percent cement replacement level, using a high-range water-reducing admixture (HRWRA), with an alkali-silica reactive aggregate from France (Tournesis Quarry), then stored in air at 100 percent relative humidity and 60 C. Such an accelerated expansion test is currently under investigation in France to test the potential for ASR expansion of job concrete mixtures. This study indicated that, irrespective of the procedure used to get a finer sample (screening or grinding), the finer the fly ash under investigation, the higher its activity index and the greater its effectiveness in suppressing expansion due to ASR.