The thermotreatment of MSW incinerator fly ash for use as an aggregate: a study of the characteristics of size-fractioning

Abstract

Abstract During the sintering process, after heating, particles of municipal solid waste incinerator (MSWI) fly ash bind to one another giving greater strength. However, the driving force required to reach the sintered state at the ash powder contact points is proportional to the surface area of the ash particles, and is thus affected by the particle size of the MSWI fly ash. This study focuses on the effects of the particle size on the characteristics of ash sintering for the production aggregate set. The experiments were conducted with sintering temperatures ranging from 400–1000 °C, with sintering times varying from 1 to 4 h. The particle sizes were divided into six intervals. For specimens sintered at 400–1000 °C, for not less than 0.5 hours, the compressive strength peaked at 800 °C, at greater than 68.5 MPa. The compressive strength was far above the building material standards. Specimens sintered at higher temperatures, ranging from 800–1000 °C, showed a much higher Cr content than did the untreated specimens, because that Cr compounds were converted into more soluble or more extractable forms after sintering. However, for a specimen with a different particle size, sintered at 400–1000 °C, the heavy metal concentration in regulatory tests was in compliance with the current regulatory threshold.