Physical and mechanical study of municipal solid waste incineration (MSWI) bottom ash with different particle size distribution

Municipal solid waste incineration (MSWI) bottom ash has poor reactivity, and the regenerated powder is difficult to directly replace cement as the supplementary cementitious material in concrete. However, there is a significant difference in the reactivity of bottom ash particles with different material compositions. In this research, MSWI bottom ash was divided into three groups with particle sizes of 2.36-9.5 mm, 0.6-1.18 mm and 0.0-0.3 mm respectively. Then the morphology, particle distribution, chemical ingredients, mineral composition and pore structure of the treated bottom ash particles were investigated. In addition, the influence of bottom ash as fine aggregate or supplementary cementitious material on the properties of concrete or mortar was determined. The results show that the addition of bottom ash can optimize the particle distribution of natural sand, reduce the apparent density and improve the strength of concrete. It is easier to obtain the finer powders by milling the bottom ash particles with a larger size, and those powders have higher reactivity. The 90-day compressive and flexural strengths of the mortar, which is prepared by replacing 30% cement with the powder regenerated from bottom ash with the size of 2.36 over bar 9.5 mm, are about 30% and 14% lower than that of the reference mortar respectively. The leaching amount of heavy metals in cement paste with 30% bottom ash powder meets the requirements of Chinese legislation.