A world-first project that uses 'self-healing' concrete to repair sewage pipes

This technology will not only extend the lifespan of concrete structures, but also promote a circular economy.
Deena Theresa
A flooded sewer tunnel.
A flooded sewer tunnel.

Vladimir Zapletin/iStock 

Sewer pipe corrosion, or crown corrosion, occurs when sewage pipe material comes into contact with sulphuric acid. The aging pipe material corrodes, and the pipes crack. Over the past few years, engineers have developed sewer bots to inspect sewage pipes and go to places unsafe for humans.

But that also means the robots would have to go to places where existing wireless communications cannot reach them. Hurdles are aplenty.

Professor Yan Zhuge, an engineering expert at the University of South Australia, is trialing a novel solution. It involves no humans or bots but self-healing concrete.

The world-first project, if successful, could be a significant help. It could prevent 17,000 kilometers of sewer pipes in Australia from cracking in the future without any intervention by humans, helping to save $1.4 billion in annual maintenance costs, as per a release.

"We are confident this novel self-healing concrete based on advance composite technology will address issues of sewer pipe corrosion and sludge disposal in one hit," Zhuge said in a statement.

The microcapsules will release healing agents when pH value changes

Every year, hundreds of millions of dollars are required to treat sewage pipes buckling under internal pressure, temperature fluctuations, and corrosive acid. Self-healing concrete, in the form of microcapsules filled with water treatment sludge, could change everything.

"Sludge waste shows promise to mitigate microbial corrosion in concrete sewer pipes because it works as a healing agent to resist acid corrosion and heal the cracks," Zhuge said.

According to the release, researchers will develop microcapsules with a pH-sensitive shell and a healing agent core with alum sludge, a by-product of wastewater treatment plants, and calcium hydroxide powder. This combination will be resistant to microbially induced corrosion.

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The alum sludge will be embedded inside the concrete at the final step of mixing to protect it from breakage. And when the pH value changes, the microcapsules will release the healing agents.

Self-healing concrete is the solution

"This technology will not only extend the lifetime of concrete structures, saving the Australian economy more than $1 billion, but it will promote a circular economy as well by reusing sludge that would normally end up in landfill," Zhuge said.

"Mainland Australia alone has about 400 drinking water treatment plants, with a single site annually generating up to 2,000 tonnes of treated water sludge. Most of that is disposed of in a landfill, costing more than $6 million each year, as well as causing severe environmental issues," Zhuge continued.

"Improving the concrete mixture design is the preferred method for controlling microbially induced corrosion. Using self-healing concrete that can seal cracks by itself without any human intervention is the solution," she added.