DOSECOPS

Development of sustainable electrochemical corrosion protection systems for reinforced concrete structures

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 Obiettivo del progetto (Objective)

'Corrosion of reinforcing steel in concrete structures is a worldwide problem and affects a large number of infrastructures. Two major causes connected to corrosion of reinforcing steel are the carbonation and chloride attack. Concrete carbonation produces a carbonated surface layer in which the pore solution pH value is depressed to near-neutral levels. A fall in pH to values below 10 at the steel can render the steel passive film thermodynamically unstable and thus cause steel corrosion. While chloride attack causes localised breakdown of the passive film that initially forms on steel as a result of the alkaline nature of the pore solution in concrete. The harmful chloride ions can be originated from the use of contaminated mix constituents or from the surrounding environment such as deicing salts or seawater. The corrosion of steel not only reduces the strength of reinforcement but also can lead to cracking and spalling of cover concrete because of the substantial volume increase that accompanies the transformation of iron to rust. To promote the effective application of reinforced concrete it is important to protect the reinforcing steel from corrosion during its service life. This proposal is to explore a new electrochemical remediation of reinforced concrete structures by combining conventional electrochemical processes, such as the electrochemical chloride removal for chloride contaminated concrete and the electrochemical realkalisation for carbonated concrete, with electrochemical nanoparticle injection. Using the new electrochemical processes, not only can they remove chlorides from concrete and increase alkalinity in concrete pore solution but also simultaneously inject nanoparticles into the concrete to enhance its mechanical properties as well as improve its porosity to stop the further penetration of chlorides and CO2 from its surrounding environment, and thus provide a permanent solution for concrete repair suffered from carbonation and chloride attack.'

Introduzione (Teaser)

Corrosion of the embedded steel in reinforced concrete significantly decreases service life with potentially dangerous consequences. Modern electrochemical methods and nanotechnology will solve the problem in both existing and future buildings.

Descrizione progetto (Article)

Most of the existing reinforced concrete building stock in Europe was built before 1970, incurring significant expenses for rehabilitation and renovation due to corrosion. Novel technology under development with EU support of the DOSECOPS project will remove and prevent corrosion while improving the material's bond and tensile strength.

The consortium brings together an international team of experts from China and Europe. Both have a vested interest in the problem given the ageing European infrastructure and the many new buildings in China already showing signs of corrosion. The proposed solution exploits electrochemical remediation together with electrochemical injection of nanoparticles.

Carbonation and chloride ions are the targeted offenders. Cement paste is highly alkaline (has a high pH), primarily due to calcium hydroxide or lime content. The alkalinity passivates the steel surface with an oxide film, protecting it from corrosion. Carbonation occurs when carbon dioxide (CO2) becomes dissolved in rain water and reacts with the limestone in the cement. Chloride ions from contaminated mixes or from ions in the environment such as de-icing salts or saltwater cause localised breakdown of the film. Carbonation and chloride attack both lower the pH, rendering the passive film unstable.

Electrochemical technologies are facilitating realkalisation of carbonated concrete, chloride removal and nanoparticle injection. Proven cathodic prevention systems enabling current injection to suppress corrosion are also under development for new reinforced concrete structures.

Now at its midpoint, the project is validating the new processes with experimental and numerical studies. Carbonated and chloride-contaminated concrete are being treated with processes exploiting carbon fibre-reinforced polymer meshes and embedded microcapsules, respectively. Novel performance-based cathodic prevention systems for marine structures are also being tested.

The technologies will remove chlorides from the concrete and increase alkalinity. They will also seal pores, preventing further entry of chlorides and/or CO2 from the environment and enhancing mechanical properties for a permanent solution.

Carbonation is an increasing problem given the rising levels of CO2 in the atmosphere. DOSECOPS technology will benefit both existing and future reinforced concrete buildings and infrastructure. It is expected to have major socioeconomic impact, reducing the costs of maintenance and monitoring while increasing safety.