## 3 Results and Discussion
### Physicochemical Properties of the Raw Materials
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Chemical Composition** & & & & & & & \\
**(wt.\%)** & **OPC** & **BFA1** & **BFA1\_S** & **BFA1\_GS 1** & **BFA2** & **BFA2\_S** & **BFA2\_GS 1**  \\ \hline SiO\({}_{2}\) & 14.44 & 38.14 & 30.00 & 38.14 & 21.79 & 13.29 & 21.79 \\ CaO & 64.25 & 26.97 & 31.93 & 26.97 & 32.34 & 25.74 & 32.34 \\ Al\({}_{2}\)O\({}_{3}\) & 4.01 & 11.86 & 11.48 & 11.86 & 8.74 & 5.64 & 8.74 \\ K\({}_{2}\)O & 0.95 & 6.56 & 7.89 & 6.56 & 9.28 & 11.35 & 9.28 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.36 & 5.45 & 5.45 & 5.45 & 4.40 & 2.99 & 4.40 \\ MgO & 1.42 & 3.19 & 3.31 & 3.19 & 4.40 & 2.76 & 4.40 \\ SO\({}_{3}\) & 3.47 & 2.41 & 2.95 & 2.41 & 3.74 & 3.23 & 3.74 \\ Na\({}_{2}\)O & 0.20 & 1.34 & 1.28 & 1.34 & 6.04 & 18.04 & 6.04 \\ P\({}_{2}\)O\({}_{5}\) & 0.04 & 1.33 & 1.35 & 1.33 & 1.30 & 0.86 & 1.30 \\ TiO\({}_{2}\) & 0.34 & 0.80 & 0.71 & 0.80 & 0.55 & 0.34 & 0.55 \\ MnO & 0.05 & 0.54 & 0.67 & 0.54 & 0.91 & 0.75 & 0.91 \\ Cl & 0.07 & 1.12 & 2.65 & 1.12 & 6.21 & 14.66 & 6.21 \\ SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\) + Fe\({}_{2}\)O\({}_{3}\) & & 55.46 & 46.93 & 55.46 & 34.92 & 21.91 & 34.92 \\ (CaO + MgO)/SiO\({}_{2}\) & & 0.79 & 1.17 & 0.79 & 1.69 & 2.14 & 1.69 \\ LOI & 7.25 & 6.05 & 12.34 & 6.05 & 10.48 & 15.02 & 10.48 \\ Mean particle diameter (\(\upmu\)m) & 15.89 & 306.40 & 21.95 & 14.64 & 30.91 & 17.71 & 9.30 \\ Particle size fractions (\(\upmu\)m) & & & & & & \\ D10 & 0.68 & 8.63 & 2.25 & 1.30 & 2.37 & 1.60 & 1.07 \\ D50 & 11.66 & 260.50 & 17.20 & 11.39 & 19.05 & 12.53 & 6.20 \\ D90 & 37.68 & 705.50 & 48.62 & 33.32 & 75.95 & 42.20 & 22.93 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical composition, LOI, and particle size of OPC and BFA samples. Figure 2 shows micrographs of OPC, BFA1 and BFA2, as received and pre-treated. The detail of the surface of the particles of OPC, BFA1 and BFA2 is patent in Figure 2a,c,d, respectively. BFA particles have a rougher surface than OPC ones. As-received BFA (BFA1--Figure 2e and BFA2--Figure 2f) is composed of irregularly shaped particles with a broad particle size range (between only a few microns and more than 100 \(\upmu\)m). OPC (Figure 2b) is constituted by smaller and less angular particles and a narrower size distribution when comparing to BFAs. In Figure 2g,h is clear the smaller particle size that results from the sieving procedure. Grinding and sieving lead to a BFA with a very different particle morphology. The mean particle diameter was decreased and the particle size distribution was narrowed (Figure 2i,j) by turning irregularly shaped particles into smaller and less angular ones, so more similar to OPC ones. These observations are in accordance with the Coulter results (Table 2 and Figure 1). Figure 1: Particle size distribution (volume basis) of the OPC, and BFA as received and pre-treated: (**a**) differential, and (**b**) cumulative lower. Figure 2: SEM micrographs of the materials under study: (**a**) OPC, (**b**) OPC, (**c**) BFA1, (**d**) BFA2, (**e**) BFA1, (**f**) BFA2, (**g**) BFA1_S, (**h**) BFA2_S, (**i**) BFA1_GS and (**j**) BFA2_GS. The XRD results showed that the main crystalline phases present in BFA1 and BFA2 samples are \(\alpha\)-quartz, calcite, microcline, muscovite and illite, which is in good agreement with XRF results. As pointed by [PERSON] et al. [19] the mineralogical composition of BFA from fluidized bed combustion depends on fuel and quantity of chemical additions, but quartz and calcite are commonly found [4; 18; 19; 36].