Waste generation has been a source of environmental concern in case of inadequate management. However, the potential for resource recovery from waste has been highlighted, and circular economy strategies have been greatly promoted to achieve sustainability goals. Municipal solid waste incineration bottom ash (IBA) and mine tailings represent two relevant waste streams under study for geotechnical applications. The present work aims at investigating the physical, mechanical, chemical, and ecotoxicological characteristics of two mixtures of 90 % bottom ash and 10 % of two different mine tailings (one of iron and another of tungsten, tin, and copper) to evaluate their safe utilization. The results indicated that mixtures of IBA and mine tailings have good compressibility, permeability, and shear strength properties, comparable to granular soils. Additionally, adding 10 % mine tailings in the mixtures had minimal effect on the mechanical behaviour of IBA alone. No substantial concentration of potentially toxic metals or relevant ecotoxic effects were found in any of the analysed materials and their eluates. These results suggest that mixing IBA with mine tailings for geotechnical use, e.g., in embankments or road base/subbase may be a safe option. This represents a promising alternative for valorising both waste streams while promoting sustainable and circular solutions.

The rational disposal and resource utilization of municipal solid waste incineration bottom ash (MSWI-BA) is an urgent problem to be solved. This study explores the impact of MSWI-BA and its finely ground powder (MSWIBAP) as fine aggregates and solidifying agent components in pre-mixed fluidized solidified soil (PM-FSS) by conducting tests on the unconfined compressive strength and volume stability. Additionally, it analyzes the composition and microstructure properties of hydration products using techniques such as XRD, TG-DSC, MIP, and FTIR. The results demonstrated that the PM-FSS incorporating MSWI-BA and MSWI-BAP exhibited a dense microstructure and excellent mechanical properties, with the main hydration products being Aft, C-(A)-S-H gel, square crystal, etc. The volume deformation of PM-FSS with MSWI-BA and MSWI-BAP increased, but it did not affect the development of its mechanical strength. MSWI-BA can be used as a solidifying agent component and fine aggregate for the preparation of PM-FSS, achieving its resource utilization.