Valorization of municipal solid waste incineration bottom ash in ecological cement mortar: Mechanical enhancement, effective immobilization of hazardous heavy metals, and life cycle environmental benefits

This study investigates the utilization of municipal solid waste incineration bottom ash (IBA), pretreated via simple co-grinding and sieving, in ecological cement mortar (ECM) designed with a modified Andreasen–Andersen particle-packing model and an ultra-low water-to-binder ratio (w/b = 0.16). Mortars with 0–15 % IBA by mass replacing natural river sand were evaluated for mechanical, microstructural, and environmental performance. Strength improved at 5–10 % IBA, with the 10 % mix reaching a 28-day compressive strength of 127.6 MPa. XRD/TGA confirmed pozzolanic reactivity, showing ∼42.9 % consumption of Portlandite (Ca(OH) 2 ) and additional C–A–S–H formation. SEM and MIP revealed a densified matrix and refined pore structure. Leaching concentrations of Cu, Zn, Pb, and Cr were below regulatory thresholds, and mixes with 5–10 % IBA exhibited lower values than the control. Life-cycle assessment indicated that 15 % IBA reduced global warming potential by ∼9.8 % and yielded net benefits in ecotoxicity and human-toxicity categories due to avoided-burden credits. Overall, 10 % IBA provided the best balance between mechanical performance and environmental safety, whereas 15 % maximized environmental benefits, supporting the large-scale, low-cost use of IBA in sustainable construction materials.