Formulation of blast-furnace slag for use in hydraulically bound construction materials

Dry powder granulation of slag melts by gas atomization offers a means of reducing the resource expenditure associated with the conventional wet processing of blast furnace slags (BFS). Slags are a by-product of the iron production process and are subsequently processed to create a fine powder, which is then used in the manufacture of building materials.

The melt atomization process, which is widely used in metal powder production, was adapted to process the slag into fine, amorphous and spherical particles. Therefore, this study investigates the development of an adapted high-temperature atomization process utilizing a new developed atomizer, the resulting properties of the slag particles, and the suitability of atomized blast furnace slag powders (ABFS) for use in building materials.

It is demonstrated that BFS can be properly atomized to form spherical, amorphous particles that exhibit excellent flowability and a low Carr-Index. The utilization of heated atomization gas and high atomizing gas pressure increases the content of small particles below 200 μm in diameter with up to 60 % of the powder mass. The atomized slag powder exhibits comparable latent hydraulic properties as ground slag powders. The utilization of the atomized slag powder fraction below 90 μm in concrete approaches the results of formulations containing conventionally processed slag. In this way, the requisite water content in concrete formulations can be diminished, and the concrete formulation's CO₂ footprint may be reduced. Consequently, liquid BFS can be directly processed into spherical and amorphous particles through hot gas atomization and the resulting slag powder can be utilized in building materials.