GEOSLAGS

Conception of a geopolymer binder made with slag from aluminium production.

The environmental impacts caused by concrete is mostly due to cement. Despite the fact that it constitutes only 12% of the total mass of concrete, cement represents around 92% of its carbon footprint. The goal of the project GEOSLAGS is to produce an eco-friendlier alternative to current cement by formulating a new hybrid geopolymer binder incorporating slags.  During the production of stainless steel, a finer fraction called slag which has lower chemical and physical properties is formed on the steel mill site of Aperam. Orbix who handles this flow of waste doesn’t have any solution to recycle all the slags produced.

In order to tackle this issue, Geogrind has developed a method to upcycle slags by increasing their free lime content. These slags are then mixed with geopolymer to create a low-carbon binder. The enhancement of free lime content occurs through a thermo-mechanical process that activates the slags. The resulting geopolymer hybrid binder is capable of two different types of bonding: hydraulic bonding, facilitated by activated slag, and polymer bonding, ensured through metakaolin activated by sodium silicate. The combination of these two types of bonding results in the formation of a binder that is more efficient than the two separate binders. Its strength is similar to, or even greater than, that provided by standard concrete. Additionally, it would have adaptable mechanical and thermal properties to ensure its use to manufacture different prefabricated elements and even heat insulator. In the end, commercial and industrial buildings would be erected from the ground with a former local waste and by using the expertise and knowledge of ICM.  All the stakeholders are located in Wallonia thus, a complete circular system would be created.

To sum-up, this new binder would bring many advantages:

• carbon dioxide emissions would be reduced by 75%
• a decrease of sand in concrete by using inactivated slag as aggregate
• heat insulator based on GPH binder more resistant to fire.
• facilitated recycling cause same for prefabricated elements, insulator
• promoting circular economy.

The project is carried out by an exclusively Walloon consortium composed of ICM (Mettet), Orbix (Farciennes), Geogrind (Strépy), scientifically supported by INISMa (Mons), CRM (Liège), and the University of Liège (Liège) and is helped by Greewin.