Mechanism of hydration activity enhancement of typical mineral phase C12A7 in LF refining slag

Abstract

As a byproduct of the secondary refining process, LF refining slag can lead to ecological and environmental issues such as soil degradation, water pollution, and threats to human health when stored for long periods. To address this problem, this study explores an effective method to enhance the hydration activity of LF refining slag by optimizing cooling process parameters to regulate the crystal structure of the typical mineral phase mayenite (Ca₁₂Al₁₄O₃₃, C₁₂A₇) under medium to low temperature conditions. The results indicate that air cooling treatment significantly improves hydration activity, with the accumulative heat release over 24 hours increasing by 18.41% for pure phase C₁₂A₇ and 13.48% for LF refining slag after air cooling at 950°C and 800°C for 25 minutes respectively. The cooling treatment facilitated the transformation of C₁₂A₇ microstructure from a smooth, flat plate-like structure to a porous structure rich in crack defects. This process generates vacancies and defects within the lattice and exhibits localized amorphization induced by lattice distortion. Consequently, this leads to a reduction in the grain size of C₁₂A₇ and an increase in interplanar spacing, thereby enhancing the number of hydration active sites and permeability of LF refining slag. The findings of this study provide significant guidance for improving the resource utilization rate of LF refining slag, thereby alleviating the environmental pressures associated with waste slag storage.