## 4 Discussion of the Results
### Pavement Durability  
Based on the results presented in Table 6, seven of the most important observations were listed.  
1. Analyzing the pavement fatigue life using the AASHTO criteria could cause a significant underestimation of the results when asphalt mixes are utilized in construction containing polymer asphalts (modified and highly modified). The fatigue life of such mixtures in the laboratory is definitely higher than that of those based on common asphalt [56; 57]. Binder usage affects not only the mix but also the entire structure's durability. Modeling results emphasizing the mentioned problem according to tests are presented in Figure 10. Obtained results also confirm that relying only on the stiffness modulus, horizontal tensile strain level, and volumetric parameters of the mixture in its current form is insufficient, and this problem should be examined.  
All pavement constructions' fatigue lives were decreased by water and frost and, in turn, by the independent road salt impact (implemented value). Moreover, water and frost impacts caused a higher decrease in fatigue life than road salt, regardless of the type of binder used in construction. The degradation level (fatigue life reduction) was presented in Figure 11.  
3. The degradation caused by road salt impact caused a smaller (from 18 to 63%) decrease in the pavement fatigue life than water and frost impact (Figure 11). The changes depended on the type of binder and air void content in the designed mixture.  
4. The pavement construction degradation caused by water, frost, or salt is significant and should be considered in the mix design and pavement fatigue criteria. The decrease in the fatigue life of the structure ranged from 7.9% to as much as 26.7% (Figure 11).  
5. The pavement consisting of highly modified asphalt (25/55-80 HIMA) turned out to be up to 2.00 times more resistant to water and frost impact and 2.77 times more resistant to road salt impact than pavement with common road asphalt in warm technology (35/50 WMA) (Figure 11). It is stated that mixtures based on polymer-modified bitumen ensure higher durability (environmental resilience) and should be used in constructions subjected to difficult environmental and traffic conditions.  
6. Pavement mixes made with warm technology can be up to 2.38 times less resistant to environmental factors such as road salt than those made with hot technology. The effect of the discussed susceptibility might be more frequent damage occurrences (Figure 11) to the structure and its shorter durability. It is not recommended to use mixtures in warm technology, e.g., for roads built in coastal regions, where the impact of salt on the pavement structure occurs throughout the year.  
7. The pavement fatigue life decrease ratio (\(DI_{r}\)), referring to the tested mixes' degradation, is at a similar level, regardless of the impact (water and frost as well as road  
Figure 11: The impact of road salt, water, and frost on pavement reduces its fatigue life.  
Figure 10: KR5 typical flexible pavement fatigue life variability caused by water, frost, or road salt.  
salt) and the type of binder. Its values were exposed in Figure 12. Values fluctuated between 1.80 and 1.91. This could mean that the stiffness modulus mixture decrease causes an almost two-fold decrease in the fatigue life of the pavement structure. It is stated that the value of this index might help to perform durability analysis of similar pavement constructions in a simplified way (the entire pavement construction durability decrease \(\Delta N_{j}\) is equal to \(\sim\)1.85 \(\Delta DI_{(S)}\) for the analyzed environmental factors.