# The Use of Construction Waste to Remediate a Thermally Active Spoil Heap
## 3 Results and Discussion
### Chemical Composition of Tailings  
At the Hermanice spoil heap, which is thermally active, both the tailings found in the upper part of the spoil heap body and the burnt tailings that are being removed have been analyzed. In unburnt tailings, which were in the centre of attention, the prevailingelements included Si (27%), Fe (25%), and Al (11%). It constituted the most decisive share of inorganic components. Considering the percentage presence of silicon, it can be assumed that acidification does not occur due to the loss of Si, but due to the lack of basic cations during the decomposition of aluminosilicates. The content of Si (48%) and Al (19%) in burnt tailings increased, while the content of Fe (15%) decreased. In unburnt tailings from the surface of the Hermanice spoil heap body, the total sulphur content was 3.5%. [PERSON] et al. also states that the total sulphur content of the anhydrous sample in OKC coal is generally low, and that the average in the individual layers and areas are usually lower than 1%, and reach an average of 0.78% in working seams [36]. Pesek presents a much larger range of total sulphur values of 0.4-4.8% with a mean value of 2.1% [39]. In burnt tailings, the total sulphur content is reduced to 0.5% due to endogenous combustion. [PERSON] also states that similar to sulphur content, fluoride and chloride content is highly variable but generally low, and phosphorus, fluorides, and chlorides are bound to the occurrence of hydroxylapatite. However, the chloride content in the black coal of the Upper Silesian Basin is usually lower than 0.025% [39]. Unburnt tailings from the Hermanice spoil heap contained 0.3% of P and 0.5% of chlorides. Their higher representation in tailings in the Hermanice spoil heap may be related to secondary halite contamination. The content of elements such as Na (<0.01%), Ca (0.7%), Mg (0.2%) in the unburnt tailings is very low. [PERSON], [PERSON], and [PERSON] (2018) report that heavy metals such as copper, nickel, and zinc are often linked with pyrite and other sulphide minerals. Increased levels of heavy metals in the soil solution can be toxic to plant roots and microbes, and they can also pose a risk to water quality [40]. However, the content of heavy metals in the OKCA carboniferous rocks is very low and their representation does not exceed the volume of other industrial emissions from an ecological point of view. That is why it does not represent a serious environmental burden (see Table 4). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**\%** & **Burnt Tailings** & **Tailings** & **\%** & **Burnt Tailings** & **Tailings** \\ \hline
**Na** & \textless{}0.01 & \textless{}0.01 & **Mo** & 0.0007 & 0.0011 \\
**Ag** & \textless{}0.0002 & \textless{}0.0002 & **Nb** & 0.0066 & 0.0054 \\
**Al** & 19.04 & 11.16 & **Nd** & 0.0313 & 0.0292 \\
**As** & 0.001 & 0.020 & **Ni** & 0.03 & 0.03 \\
**Ba** & 0.2815 & 0.678 & **P** & 0.19 & 0.30 \\
**Bi** & \textless{}0.00010 & \textless{}0.00010 & **Pb** & 0.01142 & 0.0272 \\
**Br** & 0.0006 & 0.0082 & **Pr** & 0.0066 & \textless{}0.00020 \\
**Ca** & 1.99 & 0.68 & **Rb** & 0.0608 & 0.0543 \\
**Cd** & 0.0017 & 0.00047 & **S** & 0.54 & 3.50 \\
**Ce** & 0.0342 & 0.011 & **Sb** & 0.0021 & 0.00043 \\ Cl & 0.01 & 0.49 & **Se** & \textless{}0.0005 & 0.0006 \\
**Co** & 0.01 & 0.005 & **Si** & 48.09 & 26.70 \\
**Cr** & 0.06 & 0.04 & **Sn** & 0.0036 & 0.00081 \\
**Cs** & 0.0110 & 0.014 & **Sr** & 0.0388 & 0.0532 \\
**Cu** & 0.02 & 0.03 & **Ta** & 0.0118 & 0.0115 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Elemental analysis of samples using XRF method in %.