A structural engineering professor at the University of South Australia is developing a way to prevent cracks in concrete by mixing in microcapsules that have a pH-sensitive shell and a core made of alum sludge and calcium hydroxide powder. The sludge is a byproduct of wastewater treatment, and the self-healing concrete is resistant to microbially induced corrosion.
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.
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-healing concrete, in the form of microcapsules filled with water treatment sludge, could be the answer.
“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, but they are often short-lived, with 20 per cent failing after five years and 55 per cent failing after 10 years.