Title: Techniques to Improve the Reliability of Blended Cement Concretes Made with Collie Fly Ash

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Publication: CIA

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Date: 2/13/2011

Abstract:
Substantial research investigations have been undertaken in recent years at Boral Laboratories and the School of Civil & Environmental Engineering at the University of New South Wales to determine why Collie fly ash has behaved unreliably compared to other sources of fly ash when used in concrete. Previously published papers have described research into the issues of admixture incompatibility and characterization of this fly ash source. The presence of high surface area carbon particles and sulphide minerals was found to strongly influence the behaviour of air entraining and water reducing admixtures. In particular, when used in slab-on-ground construction, concretes made with Collie fly ash have required very high dosages of air entraining admixture and reported unpredictable air content and bleeding. Several techniques have been trialed to control the variability and improve the efficiency of Collie fly ash in concrete. This paper describes the development of these production processes and testing programs that have resulted in a fly ash with greatly improved reliability and performance in concrete. These product improvements have now made Collie fly ash a reliable supplementary cementitious material for inclusion in Australian concrete.