Abstract: ObjectiveIn order to improve the activity of steel slag, the steel slag was physically activated by rod mill, and the activated steel slag was used as raw material to prepare gel materials. MethodThe steel slag raw materials and the prepared gel materials were characterized by XRD, FT-IR, SEM and laser Particle size analysis, and the influence of rod mill time on material properties was explored. ResultRod mill can increase the activity of steel slag and promote the formation of gel phase. With the extension of rod grinding time to 90 min, the specific surface area of steel slag increased from 1.08 m²/g to 1.99 m²/g, and the particle size increased from 5.57 μm dropped to 3.02 μm. The open porosity of gel material prepared from steel slag decreases with the increase of rod milling time, while the bulk density and compressive strength increase with the increase of rod milling time, which are 8.47%, 1.76 g/cm³ and 3.04 MPa, respectively. ConclusionUnder alkaline conditions, the reaction process of steel slag includes not only the hydration process of C₂S, C₃S, etc., but also the geological polymerization reaction process, and the impact of rod grinding time on the latter is more significant.