Leaching Mechanism of Harmful Substances in Alkali-Activated Blast Furnace Slag-Secondary Aluminum Ash Sintered Fine Powder Cementitious Materials

To achieve the goals of utilization of secondary aluminum ash in building materials, this study investigated the leaching of harmful substances and mechanism analysis of alkali-activated ground granulated blast furnace slag-secondary aluminum ash sintered fine powder (GGBS-MP) cementitious materials with different fineness and content of MP. The assessment was conducted through experiments on heavy metal leaching concentrations, long-term heavy metal leaching concentrations, and ammonia nitrogen leaching concentrations. Additionally, X-ray photoelectron spectroscopy (XPS) was employed to investigate the transformation mechanisms of harmful substances within the alkali-activated GGBS-MP cementitious materials. The results showed that with an increase in MP content, the leaching concentrations of heavy metals, long-term heavy metal leaching concentrations, and ammonia nitrogen leaching concentrations in the alkali-activated GGBS-MP cementitious materials exhibited an upward trend. This was attributed to the higher content of heavy metals introduced by the increased MP content. Similarly, as the fineness of MP increased, these leaching concentrations also rose due to the increased specific surface area of the particles, which led to a larger leaching surface area for heavy metals. However, the concentrations of heavy metal and ammonia nitrogen leaching observed in the tests were all below the regulatory limits, indicating a high level of safety. XPS analysis revealed that harmful elements such as fluorine (F) and nitrogen (N) in the alkali-activated GGBS-MP cementitious materials were present in low concentrations and had largely been transformed into stable and safe compounds, posing minimal environmental risks. The findings not only validate the feasibility of using MP in the production of green cementitious materials but also highlight the potential of the alkali-activated GGBS-MP cementitious materials in resourcing utilization of secondary aluminum ash.