SABINE

Steel mill slag as a binder for geotechnical building materials

The SABINE project is investigating how steel mill slag can be treated, processed and activated in order to make it usable as an alkali-activated binder in building materials. In alkali-activated binders, the addition of a highly alkaline activator to a precursor in the form of slag, ash or rock flour initiates strength development. Previous research has shown that crystalline steelworks slags in particular, such as electric furnace slag, are not as easy to activate as glassy or amorphous granulated blast furnace slag. In particular, it has not yet been possible to achieve comparable strengths.

Within the framework of SABINE, the alkaline activability of electric furnace slag in a typical mortar system has been investigated. Both process-typical slags with a high crystalline content and amorphous slags prepared by water granulation have been used. However, the latter are not yet available on an industrial scale.

As expected, mortars with amorphous electric furnace slag developed a significantly higher strength than when crystalline slag was used. With regard to early strengths, it is noticeable that up to approx. 90 % (amorphous slag) or up to approx. 65 % (crystalline slag) of the reference strength after 28 days is typically achieved after just 7 days. This shows that electric furnace slag is an interesting potential field of application for the geotechnical building materials focussed on in the SABINE project.

Now that the basic feasibility has been demonstrated, the next step will be to optimise the combination of alkaline activator and ground slag. The material will then be analysed with regard to environmental hygiene in contact with groundwater. Finally, installation tests for the application "annular gap mass in mechanised tunnelling" will be carried out on a large-scale demonstrator.