## 4 Discussion
### Ternary Systems \"Bitumen-AG-4I-AC-1\"  
It follows from the presented data that the introduction of AC-1 into bitumen compositions with a solution of polyisobutylene led to a deeper decrease in the specific surface energy \(\sigma_{\text{1-g}}\) and, as a result, a denser packing of surfactant molecules on the surface. Compaction of the hydrophobic layer with the addition of AC-1 shifted the contact angle of wetting to the region of large values and reached a maximum at C\({}_{\text{AG-4I}}\) = 1 g/dm\({}^{3}\) and C\({}_{\text{AC-1}}\) = 1 g/dm\({}^{3}\). At these concentrations, the composition \"bitumen--AG-4I--AC-1\" provided an increase in the contact angle of wetting with water by 20.85\({}^{\circ}\) relative to unmodified bitumen (\(\theta=95.05^{\circ}\)). For a comparative assessment of the water-repellent properties of additives in binary and ternary systems, we used a comparison of the indicators \(\theta_{\rm ex}\) and \(\theta_{\rm c}\). The data obtained (Table 9) indicate that in the entire studied range of concentrations (C; g/dm\({}^{3}\): 0.5 \(\div\) 2.0) there were deviations from the calculated data, except for the only ratio between the additives (C\({}_{\rm AG-4I}\) = 1 g/dm\({}^{3}\) and C\({}_{\rm AC-1}\) = 1 g/dm\({}^{3}\)), for which the contact angles of wetting with water, \(\theta_{\rm c}=115.46^{\circ}\) and \(\theta_{\rm ex}\) = 115.90\({}^{\circ}\), had almost equal values (\(\Delta\theta=-0.44\)). Beyond this ratio, the difference between the calculated and experimental wetting angles tended to increase (\(\theta_{\rm c}>\theta_{\rm ex}\)); however, in the region of increased concentrations of the sealing liquid (C\({}_{\rm AG-4I}\geq 1.5\) g/dm\({}^{3}\)), on the contrary, the experimental values of the contact angle of wetting exceeded the calculated ones. Thus, the maximum hydrophobic effect (\(\theta=105.90^{\circ}\)) was provided with the additive contribution of modifiers, i.e., in the absence of intermolecular interactions between surfactant molecules in the surface layer \"bitumen-air\". The results of subsequent tests of asphalt concrete samples using bitumen containing AG-4I and AC-1 in their composition confirmed their decisive role in the development of water saturation processes (Figure 3). With the simultaneous addition of two modifiers, the formation of a hydrophobic surfactant film on the bitumen surface reduced the water saturation of the modified samples with almost all variations in the quantitative contents of AG-4I and AC-1 (Figure 3). At the same time, the best indicator of water resistance (min W) was achieved with the same ratio of additives (C\({}_{\rm AC-1}\) = 1 g/dm\({}^{3}\) and C\({}_{\rm AG-4I}\) = 1 g/dm\({}^{3}\)) (Table 12) as the best hydrophobicity index (min cos \(\theta\), Figure 4). With this optimal content of two additives, the compacted hydrophobic film reduced the water saturation of the modified asphalt concrete sample by 2.6 times in comparison with the original bitumen and was 3.05%. This effect of water resistance was 1.3-1.6 times higher than with the individual use of additives. Correlation between the Marginal Angle of Wetting Bitumen Films with Water and the Indicator of Water Saturation of Asphalt Concrete  
Partial dependencies (Figure 6) were approximated by one-parameter equations that were combined into multi-factor mathematical models (Equations (7) and (8)). \[\theta=\frac{\left(-2.6166\mathrm{C}_{\rm AC-1}^{2}+7.9655\mathrm{C}_{\rm AC -1}+103.57\right)\left(-5.2137\mathrm{C}_{\rm AG-4I}^{2}+14.848\mathrm{C}_{\rm AG -4I}+100.58\right)}{107.612}\] (7  
The calculated values, according to Equations (3) and (4), of coefficients of nonlinear multiple correlation (R \(>\) 0.89) and significance (t\({}_{\rm R}\)\(>\) 2) indicate a satisfactory convergence of the experimental and calculated function values. To find the correlation between the contact angle of wetting of bitumen films and the water saturation index, generalized Equations (7) and (8) were used.