Effect of Fly Ash on the Microstructure and Durability of Concrete

by K. W. Nasser, Univ of Saskatchewan, Canada,
P. S. H. Lai, Univ of Saskatchewan, Canada,



Document Type: Proceeding Paper

Part of: Serviceability and Durability of Construction Materials

Abstract:

The influence of fly ash on the microstructure and durability of concrete was investigated. It was found that the use of 50% fly ash in concrete reduced greatly its resistance to freezing-and-thawing even though the concrete was well cured and contained an adequate amount of air. On the other hand, the same concrete showed better resistance to sulfate attack. Results from the SEM examination indicated that the decrease in the resistance to freezing-and-thawing might be due to migration of the microcrystalline Ca(OH)₂ and fibrous ettringite from the dense C-S-H zone to the air voids during cycling. However, the improvement in the sulfate resistance might be due to the reduced amount of ettringite in fly ash concrete.

Subject Headings: Load and resistance factor design | Fly ash | Concrete | Sulfates | Microstructure | Freeze and thaw | Material tests

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