The unique features of SF that make it ideal for use as supplementary cementitious components are its fineness, really amorphous in nature and elevated content material of SiO2. The little SF spheres act as fillers given that they occupy many of the space in between the rather coarser cement grains https://www.tjcyindustrialchem.com/news/cement-additives-and-concrete-admixtures-key-differences.html