NaAlO₂ activated slag and MSWI bottom ash: Phase assemblages and thermodynamic assessment of long-term leaching behavior

Long-term leaching (heavy metal ions) behavior of municipal solid waste incineration bottom ash (MSWI BA) is one of the issues limiting its application in alkali activated materials (AAMs). This study investigates NaAlO₂ activated slag (partially replaced by MSWI BA) in terms of the reaction process and leaching behavior. A combined approach of experimental observation and thermodynamic modeling is utilized. The hardened pastes were evaluated by reaction kinetics, mineralogy, microstructure, strength, and leaching. The thermodynamic modeling included consideration of the raw materials chemistry and activator types. Results show that the modeled C(N)−A−S−H is in line with quantitative results. Specifically, modeled hydrotalcite content (3g/100g binder) is slightly higher than the experimental results (2g/100g binder) at 28 days. Furthermore, the uptake of Cu dramatically increases at 20 days by the generated C(N)−A−S−H gels, while the binding capacity of Sb, sulfates, and chlorides increases with the formation of hydrotalcite formation over time.