Bond of Reinforcement to Superplasticized Concrete

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Title: Bond of Reinforcement to Superplasticized Concrete

Author(s): Barie B. Brettmann, David Darwin, and Rex C. Donahey

Publication: Journal Proceedings

Volume: 83

Issue: 1

Appears on pages(s): 98-107

Keywords: bond (concrete to reinforcement); concrete construction; consolidation; cover, plasticizers; pullout tests; reinforced concrete; reinforcing steels; vibration; water-reducing agents

Date: 1/1/1986

Abstract:
The effects of superplasticizers on concrete-steel bond strength were studied. Key variables were degree of consolidation, concrete slump, both with and without a superplasticizer, concrete temperature, and bar position. No. 8 deformed reinforcing bars were used with a 2 in. (51 mm) cover and a 10 in. (254 mm) bonded length. Concrete slumps ranged from 1 3/4 in. to 9 in. (44 to 229 mm). Three specimen depths were used. All specimens were modified cantilever beam specimens. The experimental results show that high-slump superplasticized concrete provides a lower bond strength than low-slump concrete of the same strength. Vibration of high-slump concrete increases the bond strength compared to high-slump concrete without vibration. The current ACI top bar requirements appear to be unconservative for top-cast bars with less than 12 in. (305 mm) of concrete below the bar and are possibly over-conservative for nontop-cast bars with more than 12 in. (305 mm) of concrete below the bar when low-slump concrete is used.