THE CONCRETE BRIDGE MAGAZINE

Winter 2019

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/1064399

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40 | ASPIRE Winter 2019 CBP Concrete Bridge Preservation Migrating Corrosion Inhibitors: A Positive Invasion Against Corrosion by Julie Holmquist, Cortec Corporation Corrosion is a serious enemy of reinforced concrete bridges, especially those exposed to deicing salts or salt-water spray. As bridges age, the high pH environment of new concrete—which initially protects steel reinforcement from corrosion—declines through carbonation. When moisture, oxygen, and chlorides seep into the concrete pores, they foster an environment for the reinforcement to rust. The pressure of the rusting reinforcement causes the concrete to crack and spall. The damaged concrete allows corrosive elements greater access to the reinforcement, accelerating the corrosion cycle and damaging the bridge. Accelerated corrosion and damage are a serious concern because bridges are complex and expensive structures to design, build, and replace. Migrating Corrosion Inhibitor Technology While it is not possible to fully stop corrosion, there are many strategies to slow corrosion and extend service life. Among these are migrating corrosion inhibitors, which have been in use for more than 30 years. These products, including some that are patented, come in a variety of delivery methods, giving fl exibility for use in the construction, repair, or maintenance of new or existing bridge structures. Migrating corrosion inhibitors are based on salts of amine alcohols or amine carboxylates. They have the ability to work their way through concrete pores to reach the surface of the CBP CONCRETE BRIDGE PRESERVATION Migrating corrosion inhibitor powders were used to protect post-tensioning strands on the St. Croix Crossing Bridge between Minnesota and Wisconsin. During this multi-year project, tendon grouting was sometimes delayed by cold weather. Photo: Minnesota Department of Transportation. A 100% silane sealer containing migrating corrosion inhibitors was applied to the deck of the Francis Scott Key Bridge in Baltimore, Md., as part of routine mainte- nance in 2008. The manufacturer recommends another application this year. Photo: Cortec Corporation.

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