ArcelorMittal Tubarão makes as many as 30 new products from Linz-Donawitz (LD) slag, which is a by-product of steel
Steel is an infinitely recyclable material and we recycle about 25 million tonnes of it annually, saving about 36 million tonnes of carbon dioxide. But the process of steelmaking produces a number of by-products that can potentially be recycled. One of these is Linz-Donawitz (LD) slag. At a major steel unit, such as the one in Tubarão, Brazil, we produce as much as 800,000 tonnes of LD slag every year, and ArcelorMittal has been researching ways to re-use this material. After a comprehensive study of its properties, we now make as many as 30 new products from LD slag.
These are used for building roads and fence posts, for sewage filtration, as a raw material for cement and as railway ballast. We now have two trademarked products for building roads: Revsol® and Acerita®. Revsol® has been used to pave 230km of primary roads since 2006, and we have sold 400,000 tonnes of Acerita® since 2005, which was also awarded a national prize for technological innovation in Brazil.
Reducing our environmental footprint
ArcelorMittal Tubarão sells about 200,000 tonnes of slag to the cement industry every year and can save up to 700kg of carbon dioxide (CO2) emissions for every tonne of granulated slag that is re-used in concrete.
Following the success of the recycling project at Tubarão, our steel unit in Asturias, Spain, sold more than one million tonnes of slag to the cement industry, saving 700,000 tonnes of CO2 in a year.
Another imaginative use of the slag was to build artificial reefs in Brazil, for which we worked with the Ekos Institute. The reefs were built to help preserve marine life, and in turn sustain the local fishing industry.
The project for recycling LD slag, which is now a success, did encounter some challenges early on. At the initial stage, we had to understand the specific properties of the material and improve the quality of slag produced at our plant, for which we enlisted external researchers and universities. We also had to work with potential customers to show them the benefits and how to use slag products correctly.
José Geraldo Cavalini Tardin, manager of internal infrastructure at ArcelorMittal Tubarão, explained: “Re-using LD slag brings a myriad of advantages, both economic and environmental, not only to the steel industry but also to construction industries and society in general. Waste that would otherwise be sent to a landfill is being transformed into innovative new materials.”