Mechanical properties of incineration bottom ash: The influence of composite species

The mechanical properties, including strength, deformational behavior, and wetting softening phenomena of municipal solid waste incinerator (MSWI) bottom ash are one of the major concerns for reuse applications. However, owing to the complex constituents of municipal solid waste, the properties of MSWI bottom ash are often highly variable. A series of artificial specimens with controlled chemical components were tested in this study. The test results show that the artificial bottom ash possesses the following mechanical characteristics: (1) for the strength, the frictional angles of the bottom ash under dry and saturated conditions vary from 34.8° to 51.1° and 26.0° to 37.2°, respectively; (2) for the deformation, the shear stiffness increases with the normal stress arises and degrades upon increased shearing; (3) significant wetting degradation of the strength and stiffness were observed.The multi-variable regression analysis was conducted to evaluate the associated influence of the chemical components on the strength. Among the evaluated components, Fe₂O₃ and Al₂O₃ are key factors; an increase in either results in higher strength at both dry and saturated conditions. The results were used to propose empirical relationships for φ_dry and φ_sat, expressed in terms of Fe₂O₃ and Al₂O₃. Accordingly, a strength classification chart is proposed for engineering purposes.