## 3 Results and Discussion  
### Nuclear Magnetic Resonance Measurements--T\({}_{2}\) Relaxation Time and Diffusion Coefficient  
The basic of spectroscopic analysis is the evaluation of the nuclei behavior that underwent an inhomogeneous external field, which perturbs the equilibrium in a steady uniform magnetic field. In fact, at equilibrium, nuclei are distributed among the energy levels according to the Boltzmann distribution with a specific net magnetization vector, but this state can be disrupted by the absorption of radio-frequency energy such as that caused by a NMR instrument [21]. After the removal of the disruption field, the nuclear spin system returns to its equilibrium state and the transverse component of the magnetization vector exponentially decays. The time constant T\({}_{2}\) characterizes the signal decay, which is called spin-spin relaxation time because it is related to the exchange of energy between spins via flip-flop mechanisms [22]. Usually, the collected signal decay is an envelope of multi-exponential attenuation since the relaxation time varies in the sample due to the heterogeneity or surface relaxation differences [23]. In this study, the relaxation time T\({}_{2}\) of pure oils and extenders was evaluated by the use of the L-NMR device [24]. The trend of spin-spin relaxation time and the resulting T\({}_{2}\) value of both pure \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Extended Bitumen**} & \multicolumn{3}{c}{**Percentage of Constituent Materials**} \\ \cline{2-4}  & **B** & **R** & **O1/O2** \\ \hline BRO1\_1:1 & 75.0 & 12.5 & 12.5 \\ BRO2\_1:1 & 75.0 & 12.5 & 12.5 \\ BRO1\_1:2 & 75.0 & 8.3 & 16.7 \\ BRO2\_1:2 & 75.0 & 8.3 & 16.7 \\ \hline \end{tabular}
\end{table} 
Table 1: Percentage of extended bitumens’ constituents. oils and extenders are reported in Figure 1 and Table 2, respectively. In general, a short T\({}_{2}\) time corresponds to more rigid supra-molecular particles; while, higher T\({}_{2}\) times refer to low intra-molecular interactions [25]. The pure oils show the highest relaxation time over the corresponding extenders made with themselves, and it means a lower intra-molecular interactions of Ox. The introduction of rubber particles into Ox leads to a decrease in the T\({}_{2}\) values. The oil absorption by the rubber limits the mobility of the oil's molecules, therefore the T\({}_{2}\) relaxation times, which reflects a more rapid relaxation decay. This trend is more evident in the extenders made with O1, which means a higher compatibility between the rubber and O1 than the R-O2 compounds. The relaxation time of the O1-extenders was reduced from 5.39\(\times\)10\({}^{-3}\) s for O1 to about 4.00\(\times\)10\({}^{-3}\) s for those extenders with an R content up to 50% by total weight. Then, more changes in the T\({}_{2}\) value can be observed in samples with a higher quantity of R than O1. In fact, their curves almost overlapped each other. On the other hand, the samples of R:O2 = 1:3 and R:O2 = 1:2 and pure O2 had similar T\({}_{2}\), as shown by the overlapping curves (see Figure 1). The amount of R in these two extenders does not seem to affect their relaxation time more than the reference one of pure O2. When the quantity of R is equal or higher than 50%, the reduction in T\({}_{2}\) values can be observed. Based on the collected data, the R-REOB ratios 1:1 and 1:2 represent the latest ratios after which some changes occurred in the relaxation time. Therefore, these two R-REOB proportions were defined as optimal. The NMR measurements with the self-diffusion H-NMR probe allowed the evaluation of the self-diffusion coefficient (D) of oil into the extenders. The present measurements provide information