Professor Gaurav Sant and colleagues in UCLA’s Department of Civil and Environmental Engineering have developed a new method of inhibiting corrosion in steel-reinforced concrete.
Modern and efficient infrastructure is a critical driver for economic growth. Aging and premature failure of US infrastructure limits the country's potential for economic recovery, to the extent that the restoration and improvement of urban infrastructure is identified by the NAE as a "grand challenge" facing society today. A substantial cause of such premature degradation is the electrochemical corrosion of reinforcing steel embedded in concrete infrastructure. In fact, the World Corrosion Organization estimates the cost of corrosion at $2.2 trillion across the globe which is around 3% of global GDP.
Corrosion mitigation in concrete bridge decks is particularly challenging, due to the combined effects of loading and environment. These typically include the application of Cl- containing de-icing chemicals, making Cl- induced corrosion common even in bridges remote from marine environments. At the same time, the potential for early age cracking in high surface-area elements is amplified, increasing the rate at which aggressive chlorides may penetrate to the steel rebar. In a time of limited financial resources and environmental constraints, there is a need for the emergence of technologies which can address environmental/structural conservation related to engineering infrastructure.
Professor Gaurav Sant and colleagues in UCLA’s Department of Civil and Environmental Engineering have developed a new method of inhibiting corrosion in steel-reinforced concrete. The approach uses calcium aluminate cement mixture (CAC) and NO3- anion exchange coatings to simultaneously bind large quantities of Cl- ions and release corrosion inhibiting NO3- species. The coating is expected to increase service life by a factor of 10. It is readily applied as a topical coating and can be used with existing corrosion inhibition practices. The formulations are also effective over a wider range of surface Cl- concentrations, spanning conditions from seawater, to exposure to deicing salts, or standing seawater that is concentrated by evaporation. Moreover, the coating is expected to exert beneficial effects even when the concrete is cracked.
The corrosion inhibition technology can also use anatase (TiO2) to provide the anion exchange species. The anions are formed by TiO2 oxidizing atmospheric NOx pollutants under UV excitation. Therefore, NO3- species capable of corrosion inhibition are always available as long as NOx pollutants and UV-light are in the vicinity. This technology can delay steel corrosion inhibition by a factor of 10, in comparison to Portland-based cement systems. Moreover, this technique reduces NOx levels in the atmosphere. The anatase can be applied either topically or integrally and is compatible with existing practices. Both formulations provide a convenient, cost-effective route for corrosion inhibition in high-value structural elements exposed to moisture and salt.
Prevent corrosion in structures that contain steel-reinforced concrete
|United States Of America||Issued Patent||9598314||03/21/2017||2012-702|
Concrete, corrosion inhibition, calcium aluminate cement mixture (CAC), anion capture exchange (ACE), anion exchange coatings, photoactivity, ion-exchange, anatase