Relationship between Reinforcing Bar Corrosion and Concrete Cracking

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Title: Relationship between Reinforcing Bar Corrosion and Concrete Cracking

Author(s): Aimin Xu and Ahmad Shayan

Publication: Materials Journal

Volume: 113

Issue: 1

Appears on pages(s): 3-12

Keywords: chloride; concrete cover; corrosion; reinforcing steel; time-to-cracking

Date: 1/1/2016

Abstract:
This paper presents results of an investigation on the relationship between reinforcement corrosion rust growth at the concrete-steel interface and cracking of concrete cover, based on study of laboratory specimens containing various amounts of chloride ions. The corrosion depth of steel bars to cause cover cracking (critical depth) was found to vary from 5 µm (0.2 mil) for 24 mm (0.9 in.) bar under 25 mm (1 in.) cover, to 150 µm (5.9 mil) for 6 mm (0.2 in.) bar under 73 mm (2.9 in.) cover. The steel corrosion rate was found to be closely related to the amount of chloride in concrete. The applicability of existing equations on cover cracking is assessed and a new mathematical equation is proposed. The predicted critical corrosion depth by the equation matched with the experimental data reasonably well. A mathematical equation has been proposed for calculation of the time-to-cracking, which uses this model in combination with the law of chloride diffusion in concrete.