Origin, Evolution, and Effects of the Air Void System in Concrete. Part 3 - Influence of Water-Cement Ratio and Compaction*

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Title: Origin, Evolution, and Effects of the Air Void System in Concrete. Part 3 - Influence of Water-Cement Ratio and Compaction*

Author(s): James E. Backstrom, Richard W. Burrows, Richard C. Mielenz, and Vladimir E. Wolkodoff

Publication: Journal Proceedings

Volume: 55

Issue: 8

Appears on pages(s): 359-375

Keywords: no keywords

Date: 8/1/1958

Abstract:
Size distribution, frequencv of air voids, spacing factor, and freezing and thawing resistance of concret’e are influenced by many factors, among the most significant being water-cement ratio and degree of compaction. Increased freezing and thawing resistance generally reflects a reduction in void size and spacing factor. Such reductions are obtained, other factors being equal, through reduced water-cement ratio, increased amount of air-entraining agent, and in the case of void size through increased periods of vibration. Reduction of water-cement ratio increases the proportion of air-entraining agent necessary to produce a given air content but the air content required for maxi-mum durability is decreased as the water-cemen.t ratio is decreased. Increasing periods of vibration reduce the total air content and increase the specific surface of air voids, but have relatively little effect on spacing factor. For any one concrete there is an optimum air content and void spacing factor for optimum resistance to freezing and thawing. Spacing factor which obtains at optimum freezing and thawing resis tance of a single may or may not be the smallest in magnitude concrete variously vibrated