## 3 Results and Discussion
### Dynamic Shear Rheometer Investigation--Rheological Behavior  
The rheological responses of extended bitumens were investigated and compared with the behavior of the reference material in order to verify the possibility of using the extenders as a replacement for neat bitumen. Hence, we checked that the extended bitumens did not show performance degradations at the binder level.  
At first, the amplitude sweep test was carried out to define the linear visco-elastic (LVE) range of neat and extended bitumens, and the most restrictive ranges were defined at 10 \({}^{\circ}\)C. The limits of samples non-destructive deformation that corresponded to the 95% of initial storage modulus were:  
1. \(\gamma\) BRO1_1:1 = 1.61%
2. \(\gamma\) BRO2_1:1 = 1.51%
3. \(\gamma\) BRO1_1:2 = 1.46%
4. \(\gamma\) BRO2_1:1 = 1.14%
5. \(\gamma\) B-50/70 = 1.61%  
The B-50/70 and BRO1_1:1 had the same LVE limit; it seems that the substitution of standard bitumen with the compound O1-R in the proportion 1:1 does not weaken the resulting binder while the same extender made with O2 reduced the LVE limit of the binder, leading it to withstand a lower deformation until structural changes occur. Regarding the effect of different R-REOB ratios, double the amount of REOB than R into the extender strongly influences the response of binders, and the results confirmed the more detrimental effect of O2 than O1.  
The complex shear modulus (G*) and phase angle (\(\delta\)) master curves obtained from the frequency sweep tests are shown in Figure 4. Concerning the complex shear modulus master curves, all extended bitumens showed a stiffness reduction with respect to B-50/70 at high frequencies that corresponded to low temperatures. Lower values of G* may turn into a greater thermal cracking resistance, which may be related to the addition of REOB. At intermediate conditions, the G* values of extended bitumens were still lower than B-50/70; however, the differences between the binders decreased. By decreasing the frequencies, an inverted trend could be observed in the G* master curves. About all of the extended bitumens showed a greater complex modulus than neat bitumen at low frequencies or high temperatures; only the BRO1_1:1 sample had a similar response of B-50/70 and their master curves overlapped. The higher values of G* at low frequencies means that almost all extended bitumens can better withstand permanent deformations. This improvement may be ascribed to the presence of R; as a matter of fact, the binders made with R-REOB ratio equal to 1:1 had a greater stiffness than those made with a ratio 1:2 over all tested frequencies. Nevertheless, the samples BRO1_1:1 and BRO1_1:2 showed the opposite behavior at low frequencies/high temperature, which could be related to the production and/or test issues (e.g., non-well homogenization of components or the sample is not representative). On the other hand, the phase angle master curves of the extended bitumens showed lower values than that of neat bitumen, especially at low frequencies or high temperature. The introduction of R particles improves the elastic response of all bituminous binders. Moreover, the addition of a polymer (i.e., R) leads to changes in the shape of the binders' phase angle master curves. The curves of the extended binders showed two different slopes, while the curve of the neat bitumen was continuous.