Unlocking the reactivity of municipal solid waste incineration bottom ash through physicochemical co-activation toward improved cementitious performance

Neither mechanical refinement nor chemical activation alone typically provides sufficient reactivity enhancement or performance robustness for municipal solid waste incineration bottom ash (MSWIBA) when used as a supplementary cementitious material (SCM). This study proposes a physicochemical co-activation route combining planetary ball milling with Ca(OH)2 impregnation, and elucidates how the coupled treatment regulates hydration kinetics, strength development, and microstructural evolution in MSWIBA-blended binders. The results show that ball milling followed by immersion in a moderately concentrated Ca(OH)2 solution (~ 0.2 mol/L) establishes a dual activation pathway: particle disintegration and defect formation increase the accessible reactive surface, while alkaline–calcium conditioning promotes depolymerization of the aluminosilicate glass and exposes latent reactive sites. Consequently, early hydration is accelerated and sustained formation of C–S–H and AFt is promoted, yielding a compact and largely defect-free matrix. At 28 d, the optimized synergistically activated system achieves a compressive strength of 55.4 MPa, surpassing that of the ball-milled-only counterpart. Overall, the findings demonstrate a scalable physicochemical strategy for converting MSWIBA into a high-performance SCM.