A study on the process for formation of spherical cement through an examination of the changes of powder properties and electrical charges of the cement and its constituent materials during surface modification

In the initial stage of surface modification treatment to form cement particles into a spherical shape, the fine cement particles below 3 μm increased and the specific surface area also increased. However, in the final stage of treatment, both the fine particles and the specific surface area decreased when compared to raw cement. These results seem to endorse a process for formation of spherical cement, namely grinding of the particles in the initial stage and then adhering and fixing the fine particles to the surfaces of larger core particles in the next stage. Clinker powder had a positive charge, whereas gypsum powder had a negative charge. The difference observed in the electrical charge proved that the attachment of gypsum particles to clinker particles was caused by the attraction of opposite charges in addition to the van der Waals interaction. Therefore, gypsum played an important role as an adhesive agent. The fluidity of clinker powder after it was treated with finely ground gypsum improved. This was because the fine gypsum particles quickly attached to the surfaces of the larger particles of clinker, and consequently, the final process for formation was accelerated.