INVESTIGATION OF VACUUM MIXING OF CONCRETE.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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Concrete mixtures for this study were proportioned to contain either 34-in. maximum-size limestone or 34-in. lightweight aggregate, both with and without entrained air. Each mixture was mixed both in the standard manner and under reduced pressure to determine the effect of vacuum mixing on properties of concrete. Additional batches of the concrete mixtures containing limestone aggregate were vacuum-mixed to determine the effect of the addition of ammonia water, and also to determine if additional air could be entrained by remixing concrete at normal pressure that had been previously vacuum-mixed. The results of the tests indicated that vacuum mixing decreased the air content of the concrete somewhat vacuum mixing also resulted in a slight increase in the strength of the mixtures containing entrained air and a slight decrease in the strength of the mixtures not containing entrained air with each of the two aggregates. The reduction in air content resulted in a considerable decrease in the resistance to freezing and thawing of the air-entrained concrete containing limestone aggregates. Results of this limited testing indicated that no apparent advantages are obtained through use of vacuum mixing. Author
- Ceramics, Refractories and Glass