The Effect of Air-Entrainment on a Pumped, High-Strength Concrete Used in a Severe Marine Environment

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Title: The Effect of Air-Entrainment on a Pumped, High-Strength Concrete Used in a Severe Marine Environment

Author(s): G. C. Hoff and R. Elimov

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 65-92

Keywords: Air-entrainment; durability; freeze thaw durability; high-performance concrete; high-strength concrete; lightweight aggregate; pumping.

Date: 7/1/1997

Abstract:
The paper describes the physical characteristics of pumped high-strength, high-performance concrete for a large (26,480m3) 50m high concrete slipform placement where the air content in the formwork was intentionally varied from 2-3% in the lower portion of the placement to 4-6% in the upper portions of the placement. Included are evaluations of the slump, air content and density of the unhardened concrete at the batch plant, in distribution hoppers after pumping, at the formwork before vibration, and in the formwork after vibration and re-vibration. A special tub test was developed to approximate the unhardened characteristics of the pumped concrete in the formwork without having to remove concrete from the formwork to do the testing. The concrete was a modified normal density concrete where a portion (45% by volume) of the normal weight coarse aggregate was replaced with structural lightweight aggregate to reduce the concrete density. High slumps (210-230mm) were used to facilitate pumping, and to accommodate extremely congested reinforcing bar situations. Concrete cylinder strengths of 74 to 78 MPA were obtained at 28-days age for concretes having air contents from 4 to 6%. Hardened concrete air-void parameters indicated fewer but larger air voids than what might normally be expected for durable concrete yet the freezing and thawing behavior in water (ASTM C666, Procedure A) for 500 cycles showed no change in the quality of the concrete.