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Researchers create stronger concrete from steel slag


RMIT University engineering researchers have found a way to reuse a steel slag by-product to create concrete that is 17 per cent stronger than regular concrete aggregates.

Steel slag used in wastewater treatment has been proven to create stronger concrete than conventional concrete aggregates, according to a new study from RMIT University.

Steel slag is a by-product of smelted ore and has been used as a substitute aggregate for making concrete in the past. It has also shown its potential to absorb contaminants such as phosphate, magnesium, iron, calcium, silica and aluminium in wastewater treatment.

However, the problem with the slag’s use in wastewater treatment is that it loses effectiveness over time. RMIT’s study has shown the possibility for its reuse remains, and is more effective when using slag to make concrete.

The ‘“sewerage-enhanced”’ properties of the wastewater steel slag has the benefit of being a stronger material, according to water engineer Dr Biplob Pramanik at RMIT University.

“The global steel making industry produces more than 130 million tonnes of steel slag every year,” he said.

“A lot of this by-product already goes into concrete, but we’re missing the opportunity to wring out the full benefits of this material.”

RMIT’s research team discovered that steel slag sourced from wastewater produces concrete that is 17 per cent stronger than its conventional alternative.

“Making stronger concrete could be as simple as enhancing the steel slag by first using it to treat our wastewater,” Dr Pramanik explained.

“Normal aggregate has a physical bond with cement but slag from waste and underwater treatment has a chemical bond. So compared to any normal aggregate that we use for construction, slag before and after water treatment will give you more stamp because of the chemical bond.

“The things that we want to remove from water are actually beneficial when it comes to concrete, so it’s a perfect match.”

The slag used in the study was sourced from Australian Steel Mill Services in Port Kembla, New South Wales.

Dr Pramanik believes this new method of producing steel slag concrete will help boost the concept of a circular economy, with a zero-waste approach.

“We are able to have 50 per cent replacement with normal coarse aggregates and we have a better stamp compared to conventional concrete,” he said.

“While there are technical challenges to overcome, we hope this research moves us one step closer to the ultimate goal of an integrated, no-waste approach to all our raw materials and by-products.”

RMIT civil engineer Dr Rajeev Roychand said further research will be necessary for this form of steel slag to be adopted on a larger scale.

“Steel slag is currently not in widespread use in the wastewater treatment industry – just one plant based in New Zealand uses this by-product in its treatment approach,” he said.

“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.”

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