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Self-healing concrete with sloppy sludge used in sewer pipes

“World-first,” a project from the University of South Australia will look at using water treatment sludge to prevent sewer pipes from cracking in the form of self-healing concrete.

Concrete is one of the most widely used building products in the world because of its ability to be made locally, its cost-effectiveness, and its strength and durability. Because concrete has been around for so long, it might be difficult to imagine that such a well-established material could be improved upon, but it has. New concrete products and manufacturing methods are enhancing concrete’s performance to tackle modern challenges.One such product is Self-healing concrete. It is characterised as the capability of concrete to fix its cracks on its own autogenously or autonomously. It not only seals the cracks but also partially or entirely recovers the mechanical properties of the structural elements. In regard to this, Self-healing concrete, in the form of microcapsules filled with water treatment sludge is being used to mitigate microbial corrosion in concrete sewer pipes in Australia.

“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,” Prof Zhuge says.

A world-first project led by University of South Australia sustainable engineering expert Professor Yan Zhuge is trialling a novel solution to halt unprecedented levels of corrosion in the country’s ageing concrete pipelines.The project from the University of South Australia will look at using water treatment sludge to prevent sewer pipes from cracking in the form of self-healing concrete.

Led by sustainable engineering expert Professor Yan Zhuge, the research team is trialling the novel solution to halt “unprecedented levels of corrosion” in the country’s aging 117,000 kilometres of sewer pipes. The university reports say that this research could help save $1.4 billion in annual maintenance costs.

Corrosive acid from sulphur-oxidising bacteria in wastewater, along with excessive loads, internal pressure and temperature fluctuations are cracking pipes and reducing their life span, costing hundreds of millions of dollars to repair every year across Australia. Self Heal’ Cracked Concrete Using Sloppy Sludge could be an answer to this solution. 

“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,” Prof Zhuge says.

Researchers will develop microcapsules with a pH-sensitive shell and a healing agent core containing alum sludge – a by-product of wastewater treatment plants – and calcium hydroxide powder. The combination will be highly resistant to microbially induced corrosion (MIC).

It 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, microcapsules will release the healing agents.

“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,” Prof Zhuge says.

Existing repairs of deteriorating concrete not only cost millions and  methods to contain acid corrosion in sewer pipes are unsuccessful for a variety of reasons.

Chemicals can be added to wastewater to alter the sewer environment and stop corrosion, but they contaminate the environment and are also costly. Another option involves increasing the speed of sewage flow by amending the pipe hydraulics, but this is not always effective. Surface coating is another popular option, but it is time consuming, and the effect is temporary.

“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.”

To be carbon-neutral by 2050, the construction industry is being forced to transit to a circular economy, Prof Zhuge says.

“Industry by-products or municipal wastes that would normally be discarded in landfill sites, potentially generating pollution, may now be reused in the construction production chain.

“Mainland Australia alone has about 400 drinking water treatment plants, with a single site annually generating up to 2000 tonnes of treated water sludge. Most of that is disposed of in landfill, costing more than $6 million each year, as well as causing severe environmental issues.”

“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,” Prof Zhuge says.

The project is being partially funded by a $501,504 Australian Research Council grant and involves researchers from the University of South Australia and University of Queensland.

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