UCT research shows corrosion of concrete can be prevented

RESULTS OF research at UCT have shown that it is possible to delay and even prevent corrosion of concrete, an important factor in managing deteriorating structures.

A team of researchers at the Department of Civil Engineering recently determined that a liquid solution can be used to create a passive film that prevents the steel used in concrete from corroding.

According to Head of Department, Professor Mark Alexander, the findings will assist practising engineers make better decisions regarding the management of deteriorating structures. "For UCT the work is an opportunity to continue to build strong links with industry and particularly, Sika, the international company which sponsored the work," he added.

The Department is also active in investigating sustainable solutions for problems in different fields, such as structures, water, urban settlements and transport.

According to Marianne Vanderschuren, a senior lecturer in the Department, the problem of corrosion is widespread in all areas of reinforced concrete structures, both in South Africa and overseas. "Concrete needs to be reinforced with embedded steel when used to resist tensile and flexural loading, and it is the potential for corrosion of this steel that is of major concern in structural deterioration."

Vanderschuren describes corrosion as the "destructive attack of a metal due to an oxidation reaction". "Corrosion of steel in concrete is a similar process. If steel embedded in concrete is in contact with highly alkaline pore solution, it forms a stable passive film on the steel surface. This passive film prevents corrosion," she explained. "However, this passive film is not always maintained and can be broken down by aggressive environments. A liquid solution can be used to create a passive film that prevents the steel from corroding."

Colleague Rukshani Heiyantuduwa investigated various possibilities using these liquids (called inhibitors) on new and existing structures. Her research shows that these liquids are capable of delaying corrosion. Moreover, existing corrosion can be slowed down. "Penetration into existing concrete structures is not a problem, especially not if the concrete is porous," Vanderschuren noted.

The results of this research have been presented in a thesis and a major industry report will also be made available soon.

"It is this type of work that will be presented at the South African Institution of Civil Engineering's centennial congress in Cape Town during May next year," Vanderschuren said. "The Congress will reflect on the past century but will focus on finding solutions for a sustainable future in the civil engineering field."

For more information, contact Marianne Vanderschuren at 021 650 2584.

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