# New Insights into Cement-Soil Mixtures with the Addition of Fluidized Bed Furnace Bottom Ashes
## 2 Materials and Methods  
### Materials  
To replace cement in mortars and soil-cement mixtures, bottom ash (BA) from coal combustion at the Jaworzno power plant (fluidized bed slag from E. Jaworzno III, code 10 01 24) was used. The leachability of chemical contaminants was determined in accordance with the PN-EN 12457-4 standard [27]. The leachability of heavy metals is very low, which is crucial from an environmental perspective. An increase in grain size was observed to significantly reduce the leachability of sulfates. The finest fraction exhibited very high sulfate leachability, exceeding 2800 mg/dm\({}^{3}\), while the 0.63-2 mm fraction had significantly lower leachability at 508 mg/dm\({}^{3}\), and the leachability of sulfates in the fraction above 2 mm was 54 mg/dm\({}^{3}\). The amount of leached calcium also decreased with increasing grain size in the respective fractions. This is likely due to the penetration of sulfur removal by-products into the bottom ash. Such significant variations in the leachability of sulfates can be of significant importance for the utilization of bottom ash. In the case of a significant exceedance of permissible limits for the leachability of chemical contaminants from an environmental or technical perspective, which would prevent the use of waste, the separation of the finest fraction containing high levels of soluble sulfates proved to be helpful. Based on the obtained data, it was decided to separate grains larger than 2 mm, which, for technological reasons cannot be introduced into the cement-water mixture, especially in JG technology. Subsequently, the material obtained after separation, with a grain size of 0-2 mm, was subjected to grinding in a planetary mill for 5 and then 30 min, followed by sieve analysis. The authors conducted grinding in two periods to compare the particle size. This size is limited due to the JG technology. The main components of bottom ash are: SiO\({}_{2}\), CaO, Al\({}_{2}\)O\({}_{3}\), SO\({}_{3}\), and Fe\({}_{2}\)O\({}_{3}\). As the particle size increased, the amount of SiO\({}_{2}\) in the individual fractions increased, with the highest value, exceeding 56%, recorded in the BA +\({}_{2}\) mm bottom ash fraction. A similar trend was observed for Al\({}_{2}\)O\({}_{3}\) and Fe\({}_{2}\)O\({}_{3}\)--their content increased in coarser fractions. However, in the case of CaO, the situation was the opposite: the highest amount, exceeding 36%, was recorded in the finest fraction (0-0.63 mm), while in the coarsest fraction (greater than 2 mm), the amount of CaO was negligible, at 0.47%. This is likely related to the particle size of the calcium sorbent added to the fluidized bed boiler and desulfurization products that passed into the bottom ash. Loss on ignition shows a decreasing trend with increasing particle size in the separated fractions, ranging from 5.8% to 3.8%. The comparison is presented in Table 1. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Contain [\%]**} \\ \cline{2-5}  & **BA Fraction** & **BA Fraction** & **BA Fraction** & **BA Fraction** \\  & **0–10.0 mm** & **0–0.63 mm** & **0.63–2.0 mm** & **+2 mm** \\ \hline P\({}_{2}\)O\({}_{5}\) & 0.09 & 0.10 & 0.09 & 0.05 \\ Mn\({}_{2}\)O\({}_{5}\) & 0.03 & 0.03 & 0.03 & 0.03 \\ SiO\({}_{2}\) & 41.90 & 31.20 & 43.30 & 56.60 \\ TiO\({}_{2}\) & 0.08 & 0.02 & 0.08 & 0.02 \\ Al\({}_{2}\)O\({}_{3}\) & 12.80 & 8.99 & 14.25 & 18.77 \\ Fe\({}_{2}\)O\({}_{3}\) & 2.31 & 2.32 & 2.51 & 13.19 \\ CaO & 25.75 & 36.23 & 25.77 & 0.47 \\ MgO & 0.81 & 1.12 & 0.80 & 0.59 \\ Na\({}_{2}\)O & 0.35 & 0.24 & 0.45 & 0.26 \\ Li\({}_{2}\)O & 0.01 & 0.01 & 0.01 & 0.02 \\ K\({}_{2}\)O & 0.74 & 0.48 & 0.76 & 1.20 \\ SO\({}_{3}\) & 5.86 & 10.76 & 6.03 & 7.80 \\ Al\({}_{2}\)O\({}_{3}\)/SiO\({}_{2}\) & 0.3 & 0.3 & 0.3 & 0.3 \\ SiO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\)+Fe\({}_{2}\)O\({}_{3}\) & 2.8 & 2.8 & 2.6 & 1.8 \\ Al\({}_{2}\)O\({}_{3}\)/Fe\({}_{2}\)O\({}_{3}\) & 5.5 & 3.9 & 5.7 & 1.4 \\ Loss on ignition [\%] & 5.22 & 5.82 & 4.55 & 3.86 \\ \hline \hline \end{tabular}
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