New concrete could beat 'bergs
Australian researchers have a developed a cement-free concrete that could solve old sewage problems.
RMIT University engineers say their new eco-friendly zero-cement concrete all but eliminates corrosion.
They say the concrete can withstand the corrosive acidic environment found in sewage pipes, while greatly reducing residual lime that leaches out.
It could be a key weapon in the fight against fatbergs.
Fatbergs are globs of congealed mass that clog sewers with fat, grease, oil and non-biodegradable junk like wet wipes and nappies. They have blocked cities around the world, sometimes growing to over 200 metres long and weighing tonnes.
These build-ups, as well as general corrosion over time, costs billions in repairs and replacement pipes.
But the new concrete eliminates free lime – a chemical compound that promotes both corrosion and fatbergs.
“The world’s concrete sewage pipes have suffered durability issues for too long,” says lead researcher Dr Rajeev Roychand.
“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.”
By-products of the manufacturing industry are key ingredients of the cement-less concrete – a zero cement composite of nano-silica, fly-ash, slag and hydrated lime.
Not only does their concrete use large volumes of industrial by-products, supporting a circular economy, it 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 said.
“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, and billions worldwide.
The environmental cost is greater – ordinary Portland cement accounts for about 5 per cent of the world’s greenhouse gas emissions.
However, a new RMIT study has proven certain by-products can be up to the job, replacing cement and able to withstand the high acidity of sewage pipes.
“Our zero-cement concrete achieves multiple benefits: it’s environmentally friendly, reduces concrete corrosion by 96 per cent 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.”