Steel making slag – a key ingredient in vital construction products

InfraBuild is already known for our extensive network of recycling centres – contributing about 1.4 million tonnes of recycled metals every year into our steel making operations.

But did you know we also reuse and repurpose by-products from our steel making?

Slag is one such material. Slag is produced when molten steel is separated from molten silicates and oxides – forming a type of artificial rock when cooled. Solidified slag, which looks and feels like rock, can be crushed and screened to various sizes – the same way natural rock is processed after being quarried to make aggregate for the construction industry.

InfraBuild produces about 130,000 tonnes of slag every year, and according to Giyas Mohammed, Manufacturing Manager at InfraBuild’s Sydney Steel Mill, InfraBuild was doing everything possible to use its slag in a safe and sustainable way so none of it goes to waste.

“We are re-using this material in a safe and sustainable way by substituting it for quarried rock and aggregate where possible,” he said.

“In addition to being used in road construction, other uses of slag are being developed, such around retaining walls and foundations.”

Slag produced by our steel making operations is crushed, screened, tested, and approved for use in various construction applications, including sealing, asphalt and filter aggregate, road pavement and road base, and engineered fill.

Prior to its reuse, the slag is subjected to various safeguards to ensure it presents no environmental risks.  Originating from the well-controlled manufacturing processes of InfraBuild, slag is a very stable and inherently safe material which is viewed as a valuable resource and not as a waste material.  InfraBuild maintains records to prove ongoing compliance with all regulatory requirements.

“By reusing slag in this way, we are diverting slag from landfill while producing an essential product for construction and reducing the need for mining and quarrying natural rock,” Mr Mohammed said.

In 2021, all slag produced by Infrabuild was available for reuse with none going to landfill.