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Corrosion Inhibitors for Reinforced
Concrete
The Need
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Steel corrosion in reinforced concrete
structures has been a major problem across the U.S. Steel-reinforced concrete structures
are continually subject to attack by corrosion brought on by naturally occurring
environmental conditions such as carbonation and the introduction of chlorides from
sources such as salt water, deicing salts, and accelerating admixtures. |
The Technology
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FerroGard, a corrosion inhibitor, developed by
Sika Corporation, penetrates hardened concrete to dramatically reduce corrosion by 65% and
extend the structure's service life. Steel in concrete is naturally protected by the high
pH level in the concrete. Over time the pH drops due to environmental conditions. Once
corrosion occurs an electrochemical corrosion cell forms on the concrete rebar, with an
anode (+) area and a cathode (-) area. Rust starts to forms expanding the volume of the
steel and causing cracks and spalls. FerroGard penetrates the concrete via diffusion and
features a dual action providing a protective layer on both the anode and cathode parts of
the steel. This protective layer further acts to displace chlorides from the steel. The
product can be used as an admixture in the placement of new concrete or topically applied
to existing structures (see figure). |
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The Benefits
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The product is easily added to ready-mix
concrete or to the surface of existing concrete. Dramatically delays the initiation of
corrosion and greatly reduces the overall corrosion activity (65% reduction). Provides
corrosion inhibition in the presence of varying chloride concentrations, even high
concentration of deicing or marine salts. The time of penetration is very fast,
penetrating concrete to a depth of at least 3 inches in 28 days. Causes no harm to the
environment. It extends the service life of concrete structures and reduces maintenance
costs. If it is used in concrete restoration its application does not require concrete
removal. It can be applied to concrete that already exhibits corrosion. All the concrete
properties and appearance remains unchanged (It does not affect the plastic properties of
concrete). No changes in mix design or placement operations are required. The product does
not affect the properties of hardened concrete, such as compressive strengths,
permeability, etc. |
Status
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ASTM tests show that FerroGard reduces
corrosion currents by as much as 65%. It has been implemented in several DOT projects and
was also selected for use in an extensive Federal Highway Administration research project.
FerroGard comes in two types; FerroGard 901 which is used as an admixture in the placement
of new concrete or FerroGard 903 that is topically applied to existing structures. |
Barriers
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The product is able to reduce corrosion but
not to stop it. A combination of this product with other protective systems is required if
the level of durability of the concrete structure needs to more than double. |
Points of Contact
- Sika Corporation, 2190 Gladstone Court, Suite A, Glendale
Heights, IL. 60139. Phone (630) 924-7900 or (800) 933-SIKA
References
- 'The Sika Edge', Issue No. 1, July 1997, Page 4.
- Sika FerroGard 'Corrosion Inhibitors for Reinforced
Concrete',Sika Catalog 1997
Disclaimer Statement
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Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
LHM03
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