Corrosion inhibitors for reinforced concrete

Citation

(2001), "Corrosion inhibitors for reinforced concrete", Anti-Corrosion Methods and Materials, Vol. 48 No. 6. https://doi.org/10.1108/acmm.2001.12848fad.006

Corrosion inhibitors for reinforced concrete

Corrosion inhibitors for reinforced concrete

Keywords: Sika, Corrosion inhibitors, Concrete

Steel corrosion in reinforced concrete structures has been a major problem across the USA. 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 acceleration admixtures.

FerroGard, a corrosion inhibitor, developed by Sika Corporation, penetrates hardened concrete to reduce corrosion by a reported 65 per cent 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, wth an anode (+) area and a cathode (–) area. Rust starts to form expanding the volume of the steel and causing cracks and spells. 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. According to Sika the product can be used as an admixture in the placement of new concrete, or topically applied to existing structures.

The product is said to be easily added to ready-mix concrete or to the surface of existing concrete. It is described as delaying the initiation of corrosion and greatly reducing the overall corrosion activity (65 per cent reduction), and providing corrosion inhibition in the presence of varying chloride concentrations, even high concentration of deicing or marine salts. The time of penetration is reportedly very fast, penetrating concrete to a depth of at least three inches in 28 days. It claims to cause no harm to the environment. It is also said to extend the service life of concrete structures and reduce maintenance costs. According to Sika if it is used in concrete restoration its application does not require concrete removal. They state that it can be applied to concrete that already exhibits corrosion. All the concrete properties and appearance are said to remain unchanged (it does not affect the plastic properties of concrete). No changes in mix design or placement operations are believed to be required. The product reportedly does not affect the properties of hardened concrete, such as compressive strengths, permeability, etc.

ASTM tests are said to show that FerroGard reduces corrosion currents by as much as 65 per cent. 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, and FerroGard 903 which is topically applied to existing structures.

Sika points out that 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.

Details available from: Sika Corporation. Tel: +1 630 9247900.