# Long-Term Monitoring of the Behavior of Modified Bitunens of RC Type
## 7 Test Results and Interpretation  
This section discusses the results of the binder tests that were recovered from the cores taken during the period of use of the roadways. The binder tests focus on the rheological tests (DSR) as they aptly describe the binder properties. In addition, empirical tests, which  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test Section** & **Domasov** & **Lednice** & **Opava** \\ \hline Asphal mixture & AC surf 11+ & AC bin 22 S & AC bin 22 S \\ Sieve size [mm] & & & Passing percent [\%] \\
32 & 100 & 100 & 100 \\
22 & 100 & 99 & 100 \\
16 & 100 & 79 & 82 \\
11 & 98 & 65 & 59 \\
8 & 83 & 51 & 51 \\
4 & 60 & 39 & 40 \\
2 & 44 & 27 & 30 \\
1 & 32 & 21 & 24 \\
0.5 & 21 & 16 & 17 \\
0.25 & 15 & 12 & 10 \\were mentioned before, and BBR tests were performed to provide an idea of the evolution of binder behaviour over time of asphalt pavement use. Figure 1 shows that the needle penetration of the binders recovered from the three experimental sections does not change significantly with time. There is some variation over time, but there is no obvious trend of further increase in stiffness (i.e., decrease in needle penetration value) caused by the ageing of the binders. The readings before time (0) are the values of the neat bitumen in the laboratory before it was mixed in the mixing plant and laid down at the construction site. There is a big difference between the laboratory tests and time (0), which are caused by the short-time ageing of the bitumen during the mixing process. Figure 2 shows that the softening point does not change significantly with time. There are some variations over time, but there is no obvious trend of increasing stiffness due to the ageing of the binders. Figure 3 shows the critical temperature calculated from the bending beam rheometer (BBR) test at a flexural creep stiffness value of S = 300 MPa. Again, the results from the individual tests are close to each other. It can be observed that the value increases slightly for all test sections. In the case of the Domasov section, after 93 months, but since then without further change, a temperature of \(-19\)\({}^{\circ}\)C is still an excellent level. On the Lednice section, the critical temperature value has decreased to \(-18.3\)\({}^{\circ}\)C over the past 8 years, which is still an excellent value for the binder layer. In the case of the Opava experimental section, the increase in critical temperature over 44 months was 1.6\({}^{\circ}\)C. Figure 4 shows the evolution of the critical temperature determined at m-value = 0.3 and Figure 5 summarizes the evolution of the critical temperature difference \(\Delta\)Tc determined from the flexural creep stiffness and the m-value. It is clear from the graph that the critical temperature obtained from the m-value is in all cases higher (i.e., worse) than the critical temperature obtained from the creep stiffness. The diagram shows that \(\Delta\)Tc is decreasing over time due to ageing, but \(-2.8\)\({}^{\circ}\)C (Domasov) and \(-4.1\)\({}^{\circ}\)C (Lendnice) are still good after 8 years. Due to this, it is not expected that the pavement layers will be damaged by low temperature cracking in the coming years [53; 54]. Figure 1: Penetration of fresh PmB 45/80 RC binder and recovered binder at 0 years, half a year, 1 year, 2 years, approx. 4 years and approx. 8 years. Figures 6 and 7 show the DSR values for AC surf 11+ in Domasov. All test results for the first 44 months (blue) are still close to the target curve after the mixture was laid (green line--PmB 45/80-65) and no significant changes are visible over time. A slight stiffening can be observed in the past 4 years (see black line with cross). The same is true for the phase angle. The curves for the first 44 months follow the shape of the target curve. In the past 4 years, we can observe that the shape of the curves changes a little towards the aged bitumen, but only slightly, and the typical S-shaped curve is still visible, which clearly shows that the PmB properties are excellent and still active.