Yuanhang Sun

Steel slag is generally regarded as a supplementary cementitious material in cement-based materials, which is conducive to the realization of the goal of carbon peak and carbon neutralization. However, the lower cementitious activity and poorer volume stability of steel slag limit its high dosage in cement-based materials. In this paper, steel slag ultrafine powder (SSUP) was prepared in the laboratory through mechanical activation combined with grinding aids. Furthermore, the grinding time was optimized. The particle size, specific surface area, and microstructure characterization were evaluated for the SSUP compared with steel slag powder (SSP). The hydration properties of SSUP were studied by means of cement paste hydration heat and mortar strength. Meanwhile, the soundness of SSUP and SSP was compared by the Le chatelier soundness test. The process of preparing SSUP in the laboratory is as follows: the steel slag is ground by a horizontal ball mill for 50 min and then ground with a planetary ball mill mixing with the grinding aids for 15 min. The experimental results show that the hydration degree and rate of SSUP are better than that of SSP, and the activity index of SSUP is 94.19%, which is much higher than that of SSP (69.62%). The X-ray diffractometry (XRD) result shows that the content of the hydration products for SSUP is higher than that of SSP. The soundness test shows that the stability of SSUP is superior to that of SSP when the dosage is the same. Therefore, ultra-fining can effectively improve the cementitious activity and soundness of steel slag.