# Effect of Chemical Composition of Bio- and Petroleum-Based Modifiers on Asphalt Binder Rheology
## 3 Results
### Chemical Characterization of Modifiers
#### 3.1.2 Fourier Transform Infrared Spectroscopy (FTIR)  
Figure 2a shows the full FTIR spectra for all modifiers, from which chemical functional groups present in the modifiers can be identified. The majority of the absorbance peaks were observed in wavenumbers ranging from 1000 to 1800 cm\({}^{-1}\) (Figure 2b) and 2700 to 3200 cm\({}^{-1}\) (Figure 2c).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **C (\%)** & **H (\%)** & **N (\%)** & **O (\%)** & **S (\%)** \\ \hline A & 77.3 & 11.9 & 0.4 & 10.4 & 0.001 \\ C & 70.1 & 11.5 & 3.5 & 14.9 & 0.004 \\ D & 76.1 & 11.8 & 0.8 & 11.3 & 0.03 \\ E & 77.1 & 11.5 & 0.6 & 9.9 & 0.33 \\ G & 47.9 & 10.0 & 9.0 & 33.1 & 0.00 \\ K & 79.7 & 12.7 & 0.9 & 5.7 & 0.98 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Elemental analysis of modifiers.  
Following are the observations from the FTIR spectra shown in Figure 2:  
* All modifiers show characteristic peaks in the range of 2800-3000 cm\({}^{-1}\) and 1300-1460 cm\({}^{-1}\) which correspond to C-H stretching and C-H bending, respectively (Figure 2a).
* Peaks at 2850, 2920, 2955, and 3008 cm\({}^{-1}\) correspond to C-H stretching and are observed in modifiers A, C, D, E, and K (Figure 2c). These peaks are absent in G. Instead, a distinct broad peak at 2860 cm\({}^{-1}\) in G was observed (Figure 2c). This peak is representative of N-H stretching specific to amine salt.
* The common peak at 1460 cm\({}^{-1}\) in all the modifiers shows the presence of C-H bending for alkanes (Figure 2b). It is the most common functional group present in hydrocarbons.
* Series of peaks were observed from 1000-1300 cm\({}^{-1}\) in all modifiers (Figure 2a). This may reflect the presence of either alkoxy (-C-O-), phenyl (=C-O-), or C-N stretching.
* Peaks for modifiers A, C, D, and E at 1165 cm\({}^{-1}\) show the presence of a common functional group which can be either of alkoxy (-C-O-), phenyl (=C-O-), or C-N (Figure 2b). Because a negligible amount of nitrogen was observed in these modifiers, the probability of alkoxy (-C-O-) or phenyl (=C-O-) groups presence is higher.
* An accentuated peak at 1120 cm\({}^{-1}\) for G and a smaller peak around 1050 cm\({}^{-1}\) for C might correspond to C-N stretching (Figure 2b). This is characteristic of amine stretching (1000-1250 cm\({}^{-1}\)).  
Figure 2: FTIR spectra for modifiers from (**a**) 600–4000 cm\({}^{-1}\); (**b**) 1000–1800 cm\({}^{-1}\); and (**c**) 2700–3200 cm\({}^{-1}\).  
* Smaller peaks at 1350 and 1375 cm\({}^{-1}\) for modifier K correspond to stretching of sulfoxide (-S=O) group (Figure 2b).
* Strong peaks of carbonyl (-C=O) stretching were observed in modifiers A, C, D, and E between 1650-1800 cm\({}^{-1}\). The peaks are close to wavenumber 1742 cm\({}^{-1}\) which may reflect the presence of aldehydes, ketones, esters, or carboxylic groups (-C=O). However, a very small peak for modifier G was also observed closer to wavenumber 1650 cm\({}^{-1}\) which is characteristic of amides (-NC=O) (Figure 2b). There is no peak for modifier K in this region.
* Modifier G and C have a single broad peak in range of 3100-3500 cm\({}^{-1}\) (Figure 2a). This peak is usually due to the stretching in alcohols (O-H) or secondary amines (-R\({}_{1}\)R\({}_{2}\)N-H). Based on elemental analysis, G and C have higher nitrogen content compared to other modifiers. Therefore, presence of secondary amines is highly likely in these modifiers.
* The spectral analysis results of modifiers confirm the type as provided by the suppliers (Table 1). No information on modifier A's composition was provided; however, the FTIR results suggest that modifier A has characteristics similar to the bio-oil blend (modifier D).