*2.1. Materials*

#### 2.1.1. MSWI Bottom Ash

The MSWI bottom ash used in this research was sampled from a waste incineration power plant in Huai'an, China. The impurities and heavy metal ions in the samples were removed by washing treatment and magnetic separation. Ball-milling was conducted on an XQM-8 variable-frequency planetary ball mill to reduce the particle size to a maximum of 180 μm. Figure 1 shows the original and ground MSWI bottom ash. The particle size distribution of the BA was determined using a Bettersize 2000 laser particle analyzer, and the result is presented in Figure 2. Meanwhile a larger specific surface area of 6631 cm<sup>2</sup>/g was obtained.

**Figure 1.** Municipal solid waste incineration (MSWI) bottom ash before (**a**) and after (**b**) ball milling.

**Figure 2.** Particle size distribution for bottom ash (BA).

X-ray fluorescence spectroscopy (XRF) was performed using a Philips PW2400 instrument to determine the chemical composition of the MSWI bottom ash. The major, minor, and trace elements in the BA are presented in Table 1. Si, Al, Fe, and Ca together accounted for 68.59% of the total elements. Thus, the BA had a similar chemical composition to Portland cement. It belongs to a typical chemical system of CaO–SiO2–Al2O3–Fe2O3 and should have hydration activity.

**Table 1.** The chemical (oxide) composition of BA.

