Substantial study on use of Prefoam-type Air-entraining Admixture for Fly Ash Concrete

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Increased use of fly ash is expected from the standpoint of the effective use of natural resources and measures against alkali-silica reaction. However, it is difficult to adequately control the air content of fly ash concrete, as unburnt carbon contained in fly ash adsorbs the air-entraining admixture, posing a risk of reducing the resistance of concrete to frost damage. In this study, a prefoam-type air-entraining admixture of a whipped cream consistency, which is less prone to the effect of unburnt carbon, was used to entrain fine air bubbles into concrete, in an attempt to enhance its resistance to frost damage. The prefoam-type air-entraining admixture was found to be capable of reducing the spacing factor of fly ash concrete and thus effective against freezing and thawing action.