Feasible use of municipal solid waste incineration bottom ash in ultra-high performance concrete

In this study, municipal solid waste incineration bottom ash (IBA) was reused as fine aggregates to prepare ultra-high performance concrete (UHPC). The effects of IBA on the mechanical properties, workability, hydration, volume stability and microstructure of UHPC were investigated. The experimental results showed that the incorporation of an appropriate amount of IBA could improve the compressive strength of UHPC due to the internal curing effect. While the addition of excessive amount of IBA would reduce the strength significantly. From the microstructure analysis, the hydration of UHPC was promoted by adding IBA, leading to a higher hydration degree and denser microstructure of the paste compared to reference sample. The use of IBA in UHPC could effectively restrict the expansion due to the presence of metallic Al, glass, gypsum in the IBA as the UHPC matrix acted as a barrier in the vicinity of the IBA particles, which prevented the formation and propagation of cracks. Also, the highly impermeable UHPC cement paste, the use of supplementary cementitious materials and the high self-desiccation of UHPC further prevent the expansive chemical reactions from occurring. Thus, it was practicable to apply IBA in UHPC without considering the expansive risks and with easy pre-treatment, and it was demonstrated that the utilization of IBA in UHPC is a feasible solution for recycling IBA.