## 2 Materials and Methods
### Methods
#### 2.2.4 Polymer Nanomodified Binder: Compositions and Preparation Technology  
For the study, at least 12 compositions of polymer nanomodified binders (PNB) were prepared. The bitumen content was constant at 100%, while the content of the hydrocarbon plasticizer, SBS polymer, and MWCNTs was calculated in addition to 100% of the bitumen mass. The hydrocarbon plasticizer content was the same across all compositions at 3%. The SBS polymer content varied from 2.5% to 5.5% (in 1% increments). The MWCNT content was 0.0005% and 0.05%. Additionally, for each polymer percentage in the binder, compositions without the nanomodifier were also prepared.  
A detailed description of the technology for preparing nanomodified polymer-modified binders was previously selected and described by the authors in the study [26]. In general terms, the process is as follows: In the first stage, the \"carbon nanotubes-hydrocarbon plasticizer\" dispersion system is prepared. Then, in the second stage, the dispersion system is introduced into preheated bitumen at a temperature of 160-170 \({}^{\circ}\)C and mixed using a paddle mixer. Afterward, the polymer is slowly added. The modified binder is mixed until a homogeneous state is achieved. In the third stage, the modified binder undergoes \"maturation\" in a drying oven at 135 \({}^{\circ}\)C for 1-2 h to stabilize the structure of the modified binder.  
Figure 1: Technology for preparing hydrocarbon dispersions with carbon nanotubes.  
2.5 Study of Properties Characterizing the Resistance and Stability of the Polymer Nanomodified Binder's Structure  
The homogeneity of the resulting binders was determined according to Russian State Standard GOST R 52056-2003 [52]. The essence of the method involves visually determining the binder's homogeneity using a glass rod. Before the test, the binder sample should be heated to a temperature 10 \({}^{\circ}\)C higher than the preparation temperature of the modified binder and stirred for 5-6 min. The glass rod is dipped into the prepared sample for 3-4 s, then removed, and the binder's flow off the rod and the condition of the binder film on its surface are visually evaluated. The modified binder should flow off the rod evenly, and there should be no clumps, lumps, or granules on its surface. The homogeneity of the binder is determined by comparing the results of three tests. If two out of three tests give a positive result, the modified binder is considered to have passed the homogeneity test.  
The stability of the polymer nanomodified binder during storage was determined according to Russian State Standard GOST EN 13399-2013 [53]. The essence of the method is that a homogeneous sample of modified binder is kept in a tube (a vertical reservoir 100-120 mm in height) for three days at 180 \({}^{\circ}\)C. After cooling, the sample is cut into three equal parts, and the properties of the top and bottom parts are evaluated. In the Russian Federation, for the top and bottom parts, the needle penetration depth at 25 \({}^{\circ}\)C is determined according to Russian State Standard GOST 33136 [54] (EN 1426), and the softening point using the \"Ring and Ball\" method is determined according to Russian State Standard GOST 33142 [55] (EN 1427). The difference in values between the top and bottom parts is calculated. The modified binder is considered stable if the difference in the \"Ring and Ball softening point\" does not exceed 3 \({}^{\circ}\)C, and if the \"Needle penetration depth at 25 \({}^{\circ}\)C\" does not exceed 20 (0.1 mm). The test method is schematically shown in Figure 2.