## 3 Results and Discussion  
### Characterization of the Materials  
Results of the compositional analysis of the cement, FA and MIBA are presented in Table 2. It is clear that the cement complies with EN 197-1 [37]. According to the LOI results, FA can be classified as category B (LOI = 5.10%) in accordance with EN 450-1 [38]. Moreover, it presents the sum of Al\({}_{2}\)O\({}_{3}\) + SiO\({}_{2}\) + Fe\({}_{2}\)O\({}_{3}\) equal to 84.8%, exceeding the minimum value established (i.e., 70%). It is evident that the LOI value for MIBA is within the permitted range for category B in compliance with EN 450-1 [38]. However, the sum of the oxides Al\({}_{2}\)O\({}_{3}\), SiO\({}_{2}\) and Fe\({}_{2}\)O\({}_{3}\) is lower than the minimum value established, showing a resemblance closer to that of ground granulated blast furnace slag than that of FA. Still, according to ASTM C618 [39], MIBA can be classified as class C FA, wherein the minimum value of the sum of Al\({}_{2}\)O\({}_{3}\), SiO\({}_{2}\) and Fe\({}_{2}\)O\({}_{3}\) is 50%. Generally, 66% of the MIBAs in the literature satisfied this limit [10]. The relatively high Cl\({}^{-}\) content of MIBA, of about 0.7%, may prove to be problematic in terms of durability due to the presence of internal chloride ions. From an industrial point of view, to limit the total chloride content of the binder, the realistic maximum replacement level of cement with MIBA may be somewhere near 10-15%. The results of the XRD analysis are presented in Figure 1. The spectra of MIBA shows that the main crystalline phases were silica (SiO\({}_{2}\)) and calcite (CaCO\({}_{3}\)) (Figure 1a). These crystalline phases were found in the samples after the incineration process of MIBA up to 1000 \({}^{\circ}\)C. Figure 1b shows that the main crystalline phases of cement type CEM I 42.5 R were gypsum (CaSO\({}_{4}\)), calcium aluminates (tricalcium aluminate and tetracalcium aluminonferrite--3 CaO\(\cdot\)Al\({}_{2}\)O\({}_{3}\) and 4 CaO\(\cdot\)Al\({}_{2}\)O\({}_{3}\cdot\)Fe\({}_{2}\)O\({}_{3}\), respectively), and calcium silicates (both dicalcium and tricalcium silicates--2 CaO\(\cdot\)SiO\({}_{2}\) and 3 CaO\(\cdot\)SiO\({}_{2}\), respectively), which are characteristic of this type of cement. In Figure 2, the morphology of MIBA can be observed, in which most of the particles have an angular shape with a porous microstructure. According to this morphology, it is probable that a greater amount of water is needed to cover the particles' surface area for given workability [40; 41]. EDS test was carried out, the results of which are presented in Figure 2c. The elemental composition of MIBA corresponds to around 23.3% for oxygen, followed by calcium with 15.2%, 8.7% for silicon, 6.63% of aluminium and 4.1% of iron. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Materials** & **CEM I** & **FA (\%)** & **MIBA (\%)** \\ \hline Al\({}_{2}\)O\({}_{3}\) & 5.24 & 24.70 & 4.10 \\ CaO & 62.71 & 2.63 & 22.99 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.17 & 5.40 & 9.21 \\ K\({}_{2}\)O & - & 1.11 & 1.57 \\ MgO & 2.23 & 1.01 & 2.37 \\ Na\({}_{2}\)O & - & 0.89 & 2.40 \\ SiO\({}_{2}\) & 19.59 & 54.70 & 51.84 \\ SO\({}_{3}\) & 3.13 & 1.38 & 2.42 \\ Cl\({}^{-}\) & 0.01 & \textless{}0.01 & 0.70 \\ Insoluble residue & 1.37 & - & - \\ LOI & 2.94 & 5.10 & 2.40 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical composition of raw materials, cement type I, fly ash (FA) and municipal solid waste incinerator bottom ash (MIBA) (% by mass). Modified Chapelle test determined, by titration with 0.1 M HCl, the content of unconsumed Ca(OH)\({}_{2}\) (free content) by the reactive phases present in the FA and MIBA during 16 h of reaction at 90 \(\pm\) 5 \({}^{\circ}\)C of 2 g CaO grade laboratory and one gram of the by-product diluted in distilled water. The reactions presented in the titration are the following:  
\[\mathrm{CaO}+2\mathrm{HCl}\rightarrow\mathrm{CaCl}_{2}+\mathrm{H}_{2}\mathrm{O} \tag{1}\]  
Figure 1: X-ray diffraction (XRD) pattern for MIBA (**a**) and for CEM 142.5 R (**b**).