Silicomanganese slag: Hydration mechanism and leaching behavior of heavy metal ions

Metallurgy slags were regarded as suitable supplementary cementitious materials (SCMs). However, the environmental risk of metallurgy slag containing a certain amount of heavy metal ions has limited their wide application in the building materials field. In this study, a metallurgy slag named silicomanganese slag (SMS) was selected as the SCMs, its hydration mechanism and leaching behaviors of heavy metal ions were evaluated. Higher hydration activity of SMS than that of local granulated blast furnace slag (GBFS) was observed. And the hydration mechanism of SMS is similar to that of reported GBFS, the addition of SMS could increase the aluminate hydrates and promote the C3S hydration. In addition, heavy metal ions leaching results of SMS powder with different pH condition leaching tests showed the pH value of eluate changed due to SMS powder would react with acid and alkaline, and the leaching concentration of Mn ions was up to 75 × 10-3 mg/L under acid attack. Nonetheless, the leaching concentrations of heavy metal ions in SMS were still below the standard requirements. However, mortars with cement replaced by 30–50 wt% SMS showed excessive Mn leaching concentration (up to 31 mg/L) through the sulfuric acid-nitric acid leaching tests, which indicated the high environmental risk of SMS utilization under special service conditions.