Effect of Entrained Air on Bond Between Concrete and Reinforcing Steel

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Title: Effect of Entrained Air on Bond Between Concrete and Reinforcing Steel

Author(s): Eivind Hognestad and C. P. Siess

Publication: Journal Proceedings

Volume: 46

Issue: 4

Appears on pages(s): 649-667

Keywords: no keywords

Date: 4/1/1950

Abstract:
This paper reports an experimental investigation of the effect of entrained air on the bond properties of the new Laclede and the Hi-Bond bars, each in 1/2 in. and 7/8 in. sizes. Bond properties were studies through 108 pull-out tests with a constant bar embedment of 12 diameters. Bars were cast vertically as well as horizontally; in the latter case, with 6 and 30 bar diameters depth of concrete under the bars. A 5000 psi basic concrete mix was used, wiuth air content as a major variable. Within the scope of these tests it was found that up to the normal air content of 4 to 5 percent, the bond of all bars in all positions was reduced, in terms of percent, less than the flexural and compressive strength of the concrete. Where more than 5 percent of the air was entrained, however, the bond of the horizontal bars was reduced rapidly, probably due to rising air.