Mechanical activation improves reactivity and reduces leaching of municipal solid waste incineration MSWI bottom ash in cement hydration system

This laboratory study explores the effects of mechanical activation on the properties of municipal solid waste incineration (MSWI) bottom ash (BA) in a cement hydration system. The experimental results showed that the mechanical activation effectively reduced the particle size of municipal solid waste incineration bottom ash (MSWIBA), increased its specific surface area by about 770%, 1674%, and 1990%, and improved the 28d compressive strength of bottom ash-cement paste samples by about 5%, 14%, and 8% after milling of 15min, 30min, and 45min, respectively. The scanning electron microscopy revealed that the microstructure of the 30min-milled bottom ash-cement sample was more homogenous than other samples, which likely accounted for the difference in compressive strength. X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis were employed to shed light on the process, products, and degree of hydration of bottom ash-cement pastes. In addition, the leachate toxicity of heavy metals was evaluated and the 30min-milled bottom ash-cement paste showed the best binding effect in reducing the leaching of heavy metals. This work demonstrates the great potential of using mechanical-activated MSWI bottom ash as a supplementary cementitious material with acceptable environmental footprint.