Cement-free concrete beats corrosion and gives fatbergs the flush
Sewage systems around the world are plagued by concrete corrosion and fatbergs, leading to costly and disruptive maintenance. But an eco-friendly zero-cement concrete developed by researchers at RMIT University could hold the solution.
Led by Dr Rajeev Roychand, the research team created a concrete that eliminates free lime — a chemical compound that promotes corrosion and fatbergs.
The research findings are published in Resources, Conservation & Recycling.
The concrete can withstand the corrosive acidic environment found in sewage pipes and reduce leaching of residual lime, which contributes to fatbergs. Fatbergs are globs of congealed mass clogging sewers with fat, grease, oil and non-biodegradable junk like wet wipes and nappies, some growing to be 200 metres long and weighing tonnes. The build-up of fat, oil and grease in sewers and pipelines, as well as general corrosion over time, costs billions in repairs and replacement pipes.
Dr Roychand said the solution is more durable than ordinary Portland cement, making it perfect for use in major infrastructure, such as sewage drainage pipes.
“The world’s concrete sewage pipes have suffered durability issues for too long,” he said.
“Until now, there was a large research gap in developing eco-friendly material to protect sewers from corrosion and fatbergs. But we’ve created concrete that’s protective, strong and environmental — the perfect trio.”
The cement-less concrete is a composite of manufacturing industry by-products including nano-silica, fly-ash, slag and hydrated lime. In addition to using large volumes of industrial by-products, supporting a circular economy, the concrete surpasses sewage pipe strength standards set by ASTM International.
“Though ordinary Portland cement is widely used in the fast-paced construction industry, it poses long-term durability issues in some of its applications,” Dr Roychand explained.
“We found making concrete out of this composite blend — rather than cement — significantly improved longevity.”
Replacing underground concrete pipes is a tedious task — ripping up the ground is expensive and often has a ripple effect of prolonged traffic delays and neighbourhood nuisances.
The Water Services Association of Australia estimates maintaining sewage networks costs $15 million each year. The environmental cost is greater, with ordinary Portland cement accounting for about 5% of the world’s greenhouse gas emissions.
“Our zero-cement concrete achieves multiple benefits: it’s environmentally friendly, reduces concrete corrosion by 96% and totally eliminates residual lime that is instrumental in the formation of fatbergs,” Dr Roychand said.
“With further development, our zero-cement concrete could be made totally resistant to acid corrosion.”
Dr Roychand and his team are looking to collaborate with manufacturers and government to develop more applications for their zero-cement concrete.