<p>Electric Arc Furnace Slag (EAFS) possesses excellent mechanical properties; however, it has serious volume stability issues that could pose a significant threat to the safety performance of structures. This study selected EAFS from three different steelmaking plants to analyze the possible causes of expansion and the benefits of autoclave stabilization in improving its volume stability using tests of pulverization rate, accelerated aging of mortar bars, accelerated aging of mortar cubes, and free oxide content before and after stabilization. Additionally, the relationship between the volume stability of EAFS and its pulverization rate was explored. The pulverization phenomenon of EAFS during the autoclave stabilization process mainly occurs within the first 3 h of treatment. Using size #4 as the sample size (particle size range of 9.52 to 4.75 mm), the calculated pulverization rate of EAFS showed a consistent trend with the corresponding volume stability performance of the EAFS samples, which can serve as an important basis for analyzing its degree of stabilization. The volume expansion of EAFS may be caused by both free calcium oxide (ƒ-CaO) and free magnesium oxide (ƒ-MgO) together or individually, but this phenomenon can be significantly improved after autoclave stabilization treatment. Depending on the differences in the characteristics of the EAFS, the time required for different samples to achieve stabilization may vary from 0.5 h to over 5 h.</p> Graphical Abstract <p></p>