## 3 Test Results  
### Physical Parameters  
The results of tests on physical properties of industrial waste are presented in Table 1, and Figure 3 shows the grain size curves of the tested materials. The grain size composition of the tested waste deserves a detailed discussion. Changes in the grain size composition due to mechanical disintegration resulting from the material compaction or weathering caused changes in the values of shear strength parameters [2; 6]. The analysis of the grain size composition of the tested waste before and after the test (the compaction index \(\mathrm{I_{S}}=1.00\)) showed significant differences in the content of each fraction.  
The grain size composition of the finest material, i.e., fly ash, was dominated by the silt fraction, which was over 78%, the sand fraction was 17%, and the clay fraction nearly 5% (Table 1). According to the geotechnical nomenclature, grain size composition of the fly ash corresponded to well-graded medium silt.  
On the other hand, the grain size composition of coarse unburnt coal waste was dominated by the gravel fraction, which was 84%. The sand fraction (nearly 10%) and silt fraction (about 5%) were in much smaller quantities, and the clay fraction content was the smallest (1.5%). However, in their grain  
Figure 3: Grain size curves of the materials.  
Figure 2: Scheme of the calculation model of the embankment with slope inclination of 1:1.5.  
size composition after the test, the content of gravel fraction decreased by 10%. In turn, the content of other fractions increased, by about 8% of the silt fraction, 1.5% of the clay fraction, and by nearly 1% of the sand fraction. According to the geotechnical nomenclature, these wastes, in terms of grain size composition, corresponded to well-graded medium gravels (before the test) and clayey medium gravels (after the test). Similarly, the composition of the burnt coal waste was dominated by the gravel fraction, which was 71%, while the sand fraction was 26%. On the other hand, the silt and clay fractions before the test were just over 3%. However, after the test, the content of gravel fraction decreased by 11%, and the sand, silt, and clay content increased by 4%, 5.5%, and over 1%, respectively. These wastes were classified as well-graded sandy medium gravels, before and after the test. It can, therefore, be stated that the tested coal wastes were susceptible to mechanical disintegration, mainly because of compaction, and, to a much lesser extent, because of shearing or grinding resulting from grain rotation during shearing of the sample.  
The grain composition of the composite was dominated by the gravel fraction (61%). There was almost 15% of the sand fraction, 23% of silt, and slightly over 2% of clay. According to the geotechnical nomenclature, the composite was a well-graded silty medium gravel.  
The specific density of the ash was the lowest and equaled 2.40 g\(\cdot\)cm\({}^{-3}\), whereas in the case of the burnt coal waste it was the highest, 2.78 g\(\cdot\)cm\({}^{-3}\). However, the specific density of the unburnt coal waste and the composite was similar and amounted to 2.25 and 2.33 g\(\cdot\)cm\({}^{-3}\), respectively.  
The maximum dry density of the fly ash was the lowest, 1.16 g\(\cdot\)cm\({}^{-3}\) at the optimum moisture content of 34%, which was the highest among the tested materials. However, the maximum dry density of the coal waste and the composite ranged from 1.69 to 1.76 g\(\cdot\)cm\({}^{-3}\) at the optimum moisture content from 6.7% to 17.6%. Similar values, as well as changes in compaction parameters along with the addition of fly ash were also noticed by [PERSON] [6], [PERSON] [2], [PERSON] [5], and [PERSON] et al. [18]. It should be stated that the compactability of all wastes met the requirements for earth materials used for road construction in Poland [41].