Corrosion-Induced Concrete Cracking for Uncoated and Galvanized Reinforcing Bars

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Title: Corrosion-Induced Concrete Cracking for Uncoated and Galvanized Reinforcing Bars

Author(s): Matthew O’Reilly, Omid Farshadfar, David Darwin, JoAnn Browning, and Carl E. Locke Jr.

Publication: Materials Journal

Volume: 115

Issue: 6

Appears on pages(s): 825-832

Keywords: chlorides; corrosion; cracking; galvanized reinforcement; steel reinforcement; zinc

Date: 11/1/2018

Abstract:
Corrosion-related cracking in reinforced concrete is caused by expansive corrosion products and the resulting tensile stresses. While the amount of corrosion to cause cracking has been studied for uncoated conventional reinforcement, significantly less is known about the corrosion loss at cracking for galvanized reinforcement. Conventional and galvanized bars were cast in chloride-contaminated concrete. Clear cover to the bar ranged from 0.5 to 2 in. (12.7 to 51 mm). Specimens were tested both with and without the use of impressed current to drive corrosion. It was found that galvanized reinforcement requires greater corrosion losses to crack concrete than conventional steel reinforcement. Visual observations at autopsy suggest that the cracking of the concrete specimens containing galvanized reinforcement was not due to zinc corrosion products, but rather to corrosion products from intermetallic iron-zinc layers or from the underlying steel. Further study is needed to determine the exact nature of these corrosion products. Tests using impressed current may be used to establish the corrosion loss required to cause cracking.