Self-healing mix for future concrete pipes

Self-healing concrete containing water treatment sludge is being trialled to prevent concrete sewer pipes from cracking in the future without the need for any repair.

In a world-first project by University of South Australia, sustainable engineering expert and professor in structural engineering, Professor Yan Zhuge, is working on a novel solution to stop corrosion of Australia’s future concrete pipelines.

Corrosive acid from sulphur-oxidising bacteria in wastewater, along with excessive loads, internal pressure and temperature fluctuations, are cracking Australia’s 117,000 kilometres of concrete pipes and reducing their lifespan.

Annual maintenance costs are around the $1.4 billion mark, according to Professor Zhuge, while 20% of repairs only last five years and 55% fail after a decade. But sludge waste has shown promise to mitigate microbial corrosion in concrete sewer pipes because it works as a healing agent to resist acid corrosion and heal the cracks, Prof Zhuge revealed.

“Improving the concrete mixture design is the preferred method for controlling microbially induced corrosion [MIC],” she explained. “Using self-healing concrete that can seal cracks by itself without any human intervention is the solution.”

Prof Zhuge’s research team is developing microcapsules with a pH-sensitive shell and a healing agent core containing alum sludge, which is a by-product of wastewater treatment plants, and calcium hydroxide powder. This combination is highly resistant to microbially induced corrosion (MIC), she said, and will be embedded inside the concrete at the final step of mixing to protect it from breakage.

When the pH value changes as acid levels build up, the microcapsules will release the healing agents, Prof Zhuge said, extending the lifetime of the concrete structure and promoting a circular economy, something the construction industry is getting on board with.

To contribute carbon neutrality by 2050, what better use for treated water sludge that would be otherwise dumped into landfill, releasing tonnes of carbon dioxide emissions, costing $6 million a year, while causing severe environmental and health issues?

About the author

Desi Corbett

Desi is the Editor of Concrete in Australia and at the helm of our magazine for 8 years. She was behind the Institute's weekly news bulletins from 2016-2021 and is now writing our focused news items. Desi has been an engineering news and features journalist/editor across all disciplines since 2013 - part of a 30-year career writing for a wide range of industries.