Of Rebar, Corrosion Prevention
FORMS & REINFORCEMENT » BY IVANA LIPOSCAK, ANA JURAGA
Photo Credit: The Peljesac bridge, Croatia/ Cortec
Nearly 40% of failure of concrete structures occurs due to corrosion of embedded steel reinforcement. There are numerous causes but most often it is related to environment, quality of concrete, and quality of construction practices. Among the commercial technologies available, migrating corrosion inhibitors (MCIs) show versatility as admixtures, surface treatments, and in rehabilitation programs.
Organic inhibitors use compounds that work by forming a monomolecular film between the metal and the water— one end of the molecule is hydrophilic and the other hydrophobic. MCIs can be incorporated as an admixture at the plant or into the ready-mix truck, surface impregnation of existing concrete structures, or coated rebar cast in concrete. The inhibitor migrates through the concrete capillary structure, first by liquid diffusion via the moisture that is normally present in concrete, then by its high vapor pressure, and finally by following hairlines and microcracks. The diffusion process requires time to reach the rebar’s surface and to form a protective layer. With surface impregnation, diffusion transports the migrating corrosion inhibitors into the deeper concrete layers—even in the presence of chlorides. Results of one study showed that the products successfully inhibited corrosion of the rebar in a 3.5% NaCl solution for the duration of testing; protected samples showed an average corrosion rate of 0.4 µA/cm2 (compared to untreated samples 5.10 µA/cm2). According to this data, using MCIs can have the potential to increase the life expectancy of a concrete reinforced structure by more than 40 years.
By using MCIs, structures should have a stronger resistance to corrosion and therefore possess greater durability. Such increased durability would then mean fewer repairs, greater structural integrity, and longer service life—all leading to greater sustainability. In order to earn certain LEED credits, ensure that the MCI you want to use is made from a renewable raw material.
Ivana Liposcak is MCI Technical Sales Manager and Ana Juraga is a content writer at Cortec Corp.
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18 CONCRETE CONTRACTOR OCTOBER/NOVEMBER 2021 www.ForConstructionPros.com/Concrete