Sustainable Mining and Metallurgy

Alkaline substances such as CaO in steel slag react with precipitation during storage, resulting in an increase in the pH value of surrounding soil, which leads to soil pollution. In addition to free calcium oxide, 2CaO·SiO₂ 3CaO·P₂O₅ is the main mineral phase of alkaline dissolution in steel slag. In order to reduce its formation, the steel slag was modified by adding SiO₂ and MgO in this paper, and the effectiveness of SiO₂ and MgO in inhibiting the alkaline dissolution of steel slag was investigated. The results show that the formation of free CaO and 2CaO·SiO₂ 3CaO·P₂O₅ phases in steel slag can be significantly reduced by using SiO₂ and MgO to modify steel slag. With the increase of SiO₂ and MgO addition, the content of Ca²⁺ in the dissolution solution is gradually reduced, and the maximum pH value is significantly reduced. When the addition amount of SiO₂ is 30% and the addition amount of MgO is 10%, the maximum pH value of the leaching solution is reduced to 10.1, which is very close to the maximum pH value (10.03) of the CaCO₃ leaching solution. It can be considered that the modified steel slag will not cause serious alkali dissolution problems in practical applications.