Concrete Proof for Corrosion Inhibitors by Marjorie Lynch, PE Image © BigStockPhoto.com EACH YEAR, THE AMERICAN SOCIETY OF CIVIL ENGINEERS RELEASES ITS REPORT CARD ON THE STATE OF THE NATION'S INFRASTRUCTURE. ALMOST INVARIABLY, PUBLIC WORKS SUCH AS BRIDGES, WATER/ WASTEWATER FACILITIES, AND DAMS GARNER A GRADE OF "C"--OR OFTEN LOWER. ONE OF THE CHIEF CAUSES OF THE POOR CONDITION OF OUR OLDER STRUCTURES IS CORROSION OF THE CONCRETE'S REINFORCING STEEL. Corroding steel expands several times its original size, creating pressure that fractures the concrete, causing spalls and eventually diminishing the structure's load-carrying capacity. Engineers and architects who followed the applicable building codes in effect at the time of construction designed these now-failing infrastructure projects. However, the industry now knows much more about concrete's characteristics than was understood years ago, and changes in practice and codes have evolved to reduce the likelihood of rebar corrosion in newly built structures. 28 the construction specifier | july 2009 Bar coatings, corrosion-resistant steel, lessporous concrete, corrosion-mitigating admixtures, crack control detailing, and overlays or coatings can be used to reduce or eliminate corrosion. Nevertheless, corrosion continues, and concrete repair remains a multi-billion-dollar industry. Over the last several decades, manufacturers have developed chemicals that are applied to the surface of hardened concrete and are purported to arrest, or even reverse, corrosion in reinforcing steel. Going by names such as `surface-applied,' `topically applied,' `migratory,' `penetrating,' and `impregnating,' these products come from manufacturers ranging from large multi-national chemical companies to smaller producers of concrete repair products. These materials are intended to reduce corrosion of reinforcement by merely spraying or otherwise applying a solution of chemicals to the surface of the concrete. How can a specifier know how likely these claims of arresting corrosion are to be accurate and verifiable? At present, manufacturers offer test results on their Web sites or in their product CS_July09.indd 28 6/11/09 11:26:32 AM