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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

CCTRP 20-03: Protection Against Corrosion of Steel in Concrete Using Epoxy/LDH Coatings

Chloride-induced corrosion of steel is one of the most critical causes for the deterioration of reinforced concrete structures. This corrosion severely impacts the durability and service life of the reinforced concrete structures. In salt-contaminated environments, chloride ions diffuse into the concrete surrounding the steel reinforcement and act as a catalyst (rather than as a direct reactant) to promote corrosion of the steel. The corrosion of steel reinforcement is an electrochemical process and consists of two half-cell reactions. Both the anodic and cathodic areas are located on the steel surface. As a typical physical protection approach, the purpose of epoxy coating is to block the penetration of water (chloride is typically transported via water) and oxygen, two of the most critical compounds inducing corrosion. The barrier properties of epoxy coating against water and oxygen are decent but not ideal. Consequently, in the past few decades, numerous attempts have been made to improve the barrier properties of epoxy coatings. While some progress has been achieved, it is not sufficient to meet the demanding requirements for long-term protection of steel in concrete. Additionally, various chemical protection strategies have been developed and shown to be effective, but their complexity and expense militate against their displacement of the well-accepted epoxy coating method. In this research, the study team aims to seamlessly integrate both physical and chemical protection strategies into epoxy coating, the most widely adopted method to mitigate the corrosion of steel reinforcement, so that the developed technology can show superior corrosion protection over currently available strategies and have a relatively high chance to be commercialized.