Early-age Bond Strength in Reinforced Concrete

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Title: Early-age Bond Strength in Reinforced Concrete

Author(s): Ralph A. Chapman and Surendra P. Shah

Publication: Materials Journal

Volume: 84

Issue: 6

Appears on pages(s): 501-510

Keywords: age; anchorage (structural); bond (concrete to reinforcement); concrete construction; cracking (fracturing); curing; loads (forces); pullout tests; reinforced concrete; reinforcing steels; slippage; Materials Research

Date: 11/1/1987

Abstract:
An investigation was conducted to determine the bond strength between reinforcing steel and concrete loaded at early ages. Bond tests were conducted using a specially developed pullout test. Load-slip characteristics of smooth bars were compared for specimens with different bar-embedment lengths and tested at various ages from 1 to 28 days of curing. Smooth bars did not exhibit any age effect. However, the bond characteristics of deformed bars showed a significant age effect. It was observed that the ACI Code-suggested equation for development length overestimated test results for very early ages. An alternate relationship is examined for structures loaded at early ages.