Regulating the phase transformation of γ → β in dicalcium silicate (C 2 S) can effectively improve the hydration activity and recycling rate of AOD slag; however, the evolution law for γ → β in C 2 S has not been extensively investigated. In this study, a novel “two-step” γ → α ′ L → β phase transformation method in C 2 S was designed based on the study of the pure C 2 S phase at a nonequilibrium state in the low- and middle-temperature ranges. The “two-step” method can be used to realize the transformation from needle-like nanostructured γ -C 2 S grains to lamellar-structured β -C 2 S grains, exhibiting the trend of interlaminar peeling accompanied by expansion of the particle volume and leading to the appearance of macroscopic lamellar cracking in β -C 2 S particles. In addition, the β -C 2 S mass fraction in AOD slag treated by water cooling at 680 °C reaches a maximum value of 47.5 wt pct, while the treated AOD slag presents abundant holes and defects, which can effectively enlarge the hydration contact area.
This study focuses on evaluating the carbonation potential of argon oxygen decarburization (AOD) slag and analyzing influence mechanism of carbonation on chromium leachability . Static thin-film accelerated carbonation and sequential leaching tests were carried out. Results show that the liquid to solid (L/S) ratio was the most influencing factor for AOD slag’s carbonation, and the maximum carbonation ratio of AOD slag was 50–52% (L/S = 0.4 mL/g, P CO2 = 7.5 bar, and t > 6 h). Dicalcium silicate’s carbonation resulted in the generation of amorphous calcium carbonate , crystalline calcite and silica gel . AOD slag’s smooth surface could be eroded by these products gradually with carbonation furthered. The mineral phase evolution clearly influenced the mineral phase hydrolysis and physical encapsulation, and thus affected the hydrolysis behavior of the primary phase and the generation behavior of the secondary phase in the carbonated slags. Chromium leachability (20 days) declined to its lowest value (1.7 mg/kg) as the carbonation ratio growing to 23% and then increased to its highest value (7.9 mg/kg) with the carbonation ratio increasing to 52%. Chromium leachability varies with the carbonation ratio. The optimal carbonation ratio that resulting in minimum chromium leaching risk must be taken full in mind before using AOD slag in carbonation-related production activities.
危险品化学品经营许可证（带存储）