# Methodology for Efficient Bitumen Storage with Reduced Energy Consumption
## 3 Results and Discussion
### Penetration Index and Temperature Susceptibility
In the case of the BP + TC + RTFOT + PAV sample, the changes in the carbonyl functional group at 1700 cm\({}^{-1}\) and the sulfoxide functional group at 1030 cm\({}^{-1}\) reflect the change in the aromatic ring components, which are the main components in BP. These changes can reflect the oxidation degree of BP during the pressure-ageing vessel test (PAV), which resulted in broad sulfoxide and carbonyl peaks. These results are in good agreement with those cited in the literature, as [PERSON] et al. have cited in their work on the FTIR spectroscopy characterization of asphalt binders' ageing-related properties, during the ageing of the asphalt, the resins and asphaltenes react with oxygen and produce more aromatic hydrocarbons and polar functional groups. This can be an explanation as to why ketones in the asphalt increase after PAV ageing [31]. Figure 11 shows that the BP + RT sample exhibited no carbonyl peak, although it presented a visually larger sulfoxide peak (1030 cm\({}^{-1}\)) at its unaged state, compared to BP and BP + TC. After short-term ageing, a weak carbonyl peak appeared at 1740 cm\({}^{-1}\) (aldehydes), and the sulfoxide peak increased slightly. After long-term ageing, such as in the BP + TC FTIR spectra, a broad carbonyl peak appeared at 1700 cm\({}^{-1}\) (ketones). In order to obtain a clearer idea of the samples' chemical composition evolution with ageing, we performed an FTIR semi-quantitative study according to the French MLPC Method No. 69 for binders \"Identification et dosage des fonctions oxygenees presentes dans les liants bitumineux--analyse par spectrometrie infraruoge a transformee de Fourier\" [32]. This method calculates the carbonyl index (I\({}_{\text{CO}}\)) and the sulfoxide index (I\({}_{\text{SO}}\)) based on the  
Figure 11: FTIR spectra for BP + RT at all ageing stages. peak areas of the FTIR spectrum as given in Equations (12) and (13), respectively; thus, an accurate idea of the change in oxidation level could be derived by comparing those indices. \[\text{I}_{\text{CO}}=\text{A}_{\text{CO}}/\text{A}_{\text{r}} \tag{12}\]  
\[\text{I}_{\text{SO}}=\text{A}_{\text{SO}}/\text{A}_{\text{r}} \tag{13}\]  
where A\({}_{\text{CO}}\) is the area centered around 1700 cm\({}^{-1}\), A\({}_{\text{SO}}\) is the area centered around 1030 cm\({}^{-1}\), and A\({}_{\text{r}}\) is the area centered around 1460 cm\({}^{-1}\) plus the area centered around 1375 cm\({}^{-1}\). We integrated the peaks using OriginPro software. Figure 12a,b present a comparison, at every ageing stage, of the neat bitumen's carbonyl index (curve) and sulfoxide index (grouped histogram) values with those of the thermally cycled sample (BP + TC) and the sample stored at room temperature (BP + RT), respectively. Figure 12a shows that, at the unaged stage, BP + TC exhibited higher carbonyl index (0.019) and a lower sulfoxide index (0.034) values compared to BP (I\({}_{\text{CO}}\) = 0.010 and I\({}_{\text{SO}}\) = 0.053), which means that the thermal fluctuation storage favored carbonyl formation at the expense of sulfoxide. After short-term ageing, the carbonyl index of BP + TC is much higher (0.047) than that of BP (0.014), whereas the value of its sulfoxide index doubled from 0.034 to 0.069, which is much lower than BP's I\({}_{\text{SO}}\) (0.118). We can see from the unaged stage results in Figure 12b that room temperature storage did not affect the carbonyl amount because BP and BP + RT had the same I\({}_{\text{CO}}\) (0.010), although it led to an increase in sulfoxide formation (from 0.053 to 0.072). After short-term ageing, the I\({}_{\text{CO}}\) results confirm those of the unaged stage; the carbonyl index values of BP and BP + RT are very close (0.014 and 0.017). BP + RT kept its initial I\({}_{\text{SO}}\) (0.073) after short-term ageing, whereas the value of I\({}_{\text{SO}}\) for BP doubled from 0.053 to 0.118.