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Advancing the circular economy

circular economy

9 April 2020 

A steel making waste product can be used to treat wastewater and improve the strength of concrete. 

Muriel Cozier 

The global steel making industry produces more than 130 million tonnes of steel slag each year. Much of this by-product goes into producing concrete, where it is used as a substitute aggregate material. Steel slag can also be used to absorb contaminants such as phosphate, magnesium, iron, calcium, silica and aluminium and therefore it is used in the treatment of waste water. However steel slag used for treating water loses its effectiveness over time and has to be replaced. 

Researchers from RMIT University in Melbourne, Australia have found that concrete made with post wastewater treatment slag is about 8% stronger that concrete made with raw steel slag. ‘Making concrete stronger could be as simple as enhancing the steel slag by first using it to treat our waste water,’ said Dr Biplob Pramani, Water Engineer in the Department of Civil and Infrastructure Engineering at RMIT University. 

In their study the researchers found that the chemical properties of the slag are enhanced through the wastewater treatment, so it performed better when used in concrete. ‘The things that we want to remove from water are actually beneficial when it comes to concrete, so it’s a perfect match,’ Dr Biplob added. 

The research team said that while the initial study was promising, further work was needed to implement their approach on a larger scale, including investigating the long-term mechanical and durability properties of enhanced slag. 

‘Steel slag is currently not in widespread use in the wastewater treatment industry – just one plant in New Zealand uses this by-product in its treatment approach. But there is great potential here for three industries to work together – steel making, wastewater treatment and construction – and reap the maximum benefits of this by-product,’ said Dr Rajeev Roychand, Civil Engineer at RMIT University. 

Resources, Conservation and Recycling: DOI:10.1016/j.resconrec.2019.104533

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