Effect of Humidity on Steelmaking White Slag Weathering

Abstract

Slag waste from the steelmaking industry is generated in high amounts, so its reuse and recycling technologies are matters of industrial and academic interest. To get information for seeking new alternatives for reuse and/or recycling, white steelmaking slag obtained at the end of a ladle campaign was subjected to environmental conditions with different humidity (wet, normal and dry), with the aim of evaluating how the weathering process was modified. Slag degradation was monitored under these conditions for 49 days (7 weeks) via the evaluation of granulometric and mineralogical changes. Moreover, thermal treatments at 150 C and 650 C were performed on degraded samples to obtain additional information of the weathering process. The results showed that modifying the humidity by the used procedures can be an effective way to control the slag degradation. However, the weathering mechanism was not altered in the different environments, since the hydration of CaO and calcium aluminates was mainly responsible for the degradation just during the first 24 hours, even in a dry environment. Under wet conditions, a significant acceleration in weathering caused higher slag pulverization and the complete hydration of the lime; non-reacted MgO and calcium aluminates still remained at the end of the evaluation.