## 2 Materials and Methods
### Methods  
The heavy metal content in the HS was determined by atomic absorption spectrometry (AAS). The content of Cr, Fe, Zn, Cu, Mn, Ni, Pb, and Cd has been determined using an iCE 3500 spectrometer (Thermo Scientific, Bremen, Germany) with a detectability of 0.0033 ppm. Before testing, the specimens were vacuum filtered using PTFE 0.45 \(\upmu\)m filter and buffered with hydrochloric acid to pH = 2. The pH was measured in a water solution of the HS and concrete samples using a Hach HQ40d pH meter with PHC 301 electrode. The electric conductivity was determined by a potentiometric method using the conductometer. The specimens were ground in the mortar and immersed in the distilled water. The content of organic substances in HS and HC was determined according to the standard ISO 14688-2 at the temperature of 650 \({}^{\circ}\)C.  
The HC specimens for the thermal testing were prepared from earlier manufactured cubes with the size 100 mm \(\times\) 100 mm \(\times\) 100 mm. The specimens were then cut in half. Thermal measurements were conducted on the exposed cores of the specimens after cutting. The tested HC specimens were stored in dry laboratory conditions until their masses were stabilised. The thermal conductivity was determined via the non-stationary method using the apparatus Isomet 2104. The measurements were carried out for each HC in the middle sections. Four cubes with a size of 100 mm were used for thermal tests of each HC. Two measurements were performed for each surface of the tested specimen; thus, eight measurements of thermal properties were carried out for each HC. The thermal conductivity, volumetric specific heat, and thermal diffusivity coefficient were determined. The average values, standard deviations, and coefficients of variation were calculated. Very high repeatability of the results has been achieved. The coefficients of variation for the thermal conductivity did not exceed 5% for all tested materials. The compressive strength of HC was tested on the dry specimens after 28 days of curing. The tests were performed on the testing machine (Toni Technik, Berlin, Germany) with a maximum load of 100 kN. Compressive strength HC was tested on cubes with dimensions of 150 mm \(\times\) 150 mm \(\times\) 150 mm. The strength was determined with an accuracy of 0.1 MPa. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **Binder/** & **Water/** & **SP a** & **ST a** & \\
**Concrete** & **Type of** & **Shives** & **Binder** & **[\% of** & **[\% of** & **Dry** \\
**Designation** & **Binder** & **Ratio** & **Ratio** & **Binder** & **Water** & **Density** \\  & & **(by Mass)** & **(by Mass)** & **Mass]** & **Mass]** & **[kg/m3]** \\ \hline HC0 & 100\% C a & 2.0 & 1.3 & 1.5 & 2 & 382 \(\pm\) 13 \\ HC1 & 100\% L a & 5.3 & 0.7 & - & - & 655 \(\pm\) 22 \\ HC2 & 40\% L a & 5.3 & 0.7 & 1.5 & - & 988 \(\pm\) 17 \\ HC3 & 100\% C a & 5.3 & 0.7 & 1.5 & 2 & 1026 \(\pm\) 11 \\ \hline \hline \end{tabular} a  
\end{table} 
Table 1: Characteristics of HC concrete. The antimicrobial properties of HC against Gram-negative bacteria _Escherichia coli_ K12 (ATCC 29425) and Gram-positive bacteria _Staphylococcus epidermidis_ (ATCC 49461) and mould fungi--_Aspergillus niger_ (strain N2 from Faculty of Chemical Technology and Engineering collection)-- isolated from the air were determined. The model bacteria were cultivated in nutrient broth (NB, BioMaxima, Poland) for _E. coli_ and Brain-Heart Infusion (BHI, BioMaxima, Poland) for _S. epidermidis_ and incubated at 37 \({}^{\circ}\)C for 24 h. The bacterial cells were centrifuged at 5000 g at 25 \({}^{\circ}\)C for 10 min and resuspended in sterile 0.85% sodium saline buffer to the final concentration of 0.5 in McFarland standard (bioMerieux, France) and concentration approx. 1 \(\times\) 108 CFU/mL (working solution). _Aspergillus niger_ was cultured aerobically on MEA (Merck, Germany) slants at 25 \({}^{\circ}\)C for 72 h (or until they reached total growth).