Guide to Design and Construction Practices to Mitigate Corrosion of Reinforcement in Concrete Structures

Description

Guide to Design and Construction Practices to Mitigate Corrosion of Reinforcement in Concrete Structures Corrosion of metals in concrete is a serious type of deterioration that affects concrete in service. Corrosion is seen in parking structures, marine structures, industrial plants, buildings, bridges, and pavements. The Federal Highway Administration published a report in 2001 that the estimated cost of corrosion of highway bridges was between$6.43 and $10.15 billion (FWHA-RD-01-097 2001).

This problem drains resources in both the public and private sectors. Implementation of solutions is needed, both in thedesign of structures resistant to corrosion and the rehabilitation of structures suffering the effects of corrosion. Concrete provides a highly alkaline environment, which results in the formation of a passivating film that protects thes teel from corrosion. Corrosion of embedded metals in concrete can occur, however, if concrete quality and details such as concrete cover and crack control are not adequate; if the functional requirement of the structure is not as anticipate dor is not adequately addressed in the design; if the environment is not as anticipated or changes during the service life ofthe structure; or a combination of thereof. For moredetails on the mechanism of corrosion of metals in concrete, refer to ACI 222R.

Once corrosion begins, it is aggravated by factors such asmoisture and elevated ambient temperatures. Cracking, straycurrents, and galvanic effects can also exacerbate corrosion.Other causes of corrosion include steel directly exposed tothe corrosive elements due to incomplete placement orconsolidation of concrete, and industrial or wastewaterchemicals that attack the concrete and the reinforcing steel.Reinforced concrete structures should be designed either toavoid these factors when they are present or be protectedfrom these factors when they cannot be avoided.