Posco forges sustainability path with new use for slag

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Posco forges sustainability path with new use for slag

Published: 08 Oct. 2024, 10:10

Posco Group strengthens soft ground for Posco International’s second LNG Terminal in Gwangyang, Gwangyang 2, using steel slag compression piles. [POSCO]

Posco’s steel slag is being used as an aggregate to pave roads on National Route 3. [POSCO]

Posco is advocating for a more sustainable circular economy and society by repurposing waste material from the steelmaking process.

The company is seeking to act on the significant amount of slag, dust and sludge produced daily as a byproduct in steelmaking.

Slag, formed when converting hot metal to crude steel as impurities are removed and minute adjustments to the iron composition are made, is a typical co-product of the steel industry that makes up over 75% of all industry byproducts.

Domestically, 25 million tons of slag is produced each year – enough to fill 5,000 Olympic-size swimming pools. Posco is taking action to convert such waste into a useful, economically sustainable resource.

Although slag has advantages over natural materials such as gravel or sand — namely, greater hardness — it is generally utilized in less profitable ways, such as construction aggregates. However, with depleting sources of natural aggregate and frequent damage to roads due to large vehicles and extreme summer heat, asphalt made with steel slag is an attractive alternative.

The steelmaker is tapping into market demand by partnering with a domestic asphalt-concrete manufacturer to use the byproduct as an aggregate, which has been used to pave five segments of roads on National Route 3 since late last June.

The slag has a more consistent and angular shape that generates an interlocking effect when used in paving that makes roads 2.2 times more durable than regular asphalt, lengthening durability to 64 months.

Posco plans to supply 100,000 tons of steel slag for use in roadwork in the metropolitan and central regions, while also pursuing markets for the product in the south, near its Pohang and Gwangyang steel plants.

The steelmaker is taking full advantage of the byproduct’s high durability, partnering with the Research Institute of Industrial Science & Technology (RIST) to develop a sand compaction pile method that incorporates slag, which was used at the construction site of the Gwangyang-2 LNG terminal at Gwangyang Port.

The compaction pile method, utilizing slag instead of sand, was used to improve the port’s fragile foundation, offering greater protection against erosion or soil liquefaction in the event of an earthquake. RIST confirmed that compaction piling with slag as an aggregate improved the strength of the foundation by 30 percent over natural materials.

Last April, Posco and RIST published “Steel Slag Compaction Pile Planning and Construction Guidelines” through the Korean Society of Civil Engineers to promote the broader use of steel slag compaction piles with consistent quality and performance.

Taking a page from its own book, the steelmaker plans to use steel slag compaction piles at the new industrial complexes near its Pohang and Gwangyang plants.

“Steel slag is not only more durable than natural aggregate, but it is also a sustainable resource that helps preserve our environment,” emphasized Lee Baek-hee, executive director of the health, safety and environment division, adding, “Through continued research and development, we will enhance the profitability and utilization of steel industry co-products like steel slag.”

Posco plans to keep searching for new uses for steel slag to conserve natural resources and promote the reuse of steel co-products.

BY KIM YEONSOO [kim.yeonsoo1@joongang.co.kr]

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