Potential application of MSWI bottom ash as substitute material in Portland cement concrete: Filler or binder

In recent years, the rapid industrialization and urbanization led to the explosive growth of municipal solid waste incineration (MSWI) bottom ashes (BA) production. However, most of them are directly landfilled, which not only brings environmental burden but also results in loss of potential resources. Present researches have proved that MSWI BA could be utilized as a replacement in Portland cement concrete. However, several drawbacks such as volume expansion, leaching behaviour, and relatively lower strength have been reported. In this study, as-received BA was pretreated to remove the metallic aluminium which is responsible for the hydrogen-induced expansion when blended in OPC concretes. Subsequently, the treated BA samples were used as a substitution for cement at the replacement level of 10%. Micronized sand (M300) was selected as reference materials to investigate the role of treated BA in blended cement system, either as filler or binder material. In the experimental program, the hydration process of different mixtures was monitored by isothermal calorimeter and hydration products were determined by X-ray diffraction (XRD) and Thermalgravimetric analysis (TGA). Results showed that the pretreatment effectively removed the metallic aluminum in BA and no severe expansion or strength decrement were detected. The treated BA showed limited reactivity comparing with Portland cement, however, it still worked better than micronized sand as a filler substitution.