# Evaluation of the Long-Term Performances of SMA-13 Containing Different Fibers
## 4 Results and Discussion
### FTIR Test Result  
To study the effect of the aging process on the chemical composition of the SBS modified asphalt used in the asphalt mixtures, the SBS modified asphalt in the BFSMA-13 and LFSMA-13 under different aging degrees were extracted using the rotary evaporation asphalt recovery instrument to test the change of the chemical functional group of the SBS modified asphalt, and the extraction medium is trichloroethylene. The FTIR spectrum of the SBS asphalt extracted from the unaged, short term aged and long term aged BFSMA-13 and LFSMA-13 mixtures were listed in Figures 11-13. In Figures 11-13 it can be seen that the FTIR absorption peaks of the extracted SBS modified asphalt are at 2920, 2850, 1700, 1376, 1030, 966 and 698 cm\({}^{-1}\), etc. The peaks at 2920 cm\({}^{-1}\) and 2850 cm\({}^{-1}\) are caused by the antisymmetric stretching vibration and symmetric stretching vibration of methylene (CH2) separately. The peak at 1700 cm\({}^{-1}\) is caused by the carbonyl and the peak area of carbonyl or the carbonyl index (CI) can be adopted to evaluate the aging situation of asphalt [42]. The peak at 1376 cm\({}^{-1}\) is formed by a specific vibration of methyl (CH3). The peak at 1030 cm\({}^{-1}\) is the characteristic peck of the sulfoxide [43], and it can also be used to describe the aging degree of asphalt. The peaks at 966 cm\({}^{-1}\) and 698 cm\({}^{-1}\) are special peaks of the SBS modified asphalt, and are caused by the butadiene and styrene respectively [44]. The peak areas at 1700, 1376, 1030, 966 and 698 cm\({}^{-1}\) were chosen to study the property change of the SBS modified asphalt extracted from the mixtures, because these peaks can reflect the aging degree of the asphalt and the change of some special component of the SBS modified asphalt (butadiene and styrene). The peak areas are calculated using OMNIC software and are shown in Table 8.  
It can be seen from Table 8 that when the aging degree increases, the peak areas at 1700 and 1030 cm\({}^{-1}\) in the spectrum of the SBSBF (defined as the SBS modified asphalt extracted from BFSMA-13) increase, and the peak areas at 966 and 698 cm\({}^{-1}\) decreases. It shows the same change pattern in the spectrum of the SBSLF (defined as the SBS modified asphalt extracted from LFSMA-13). The peak area at 1376 cm\({}^{-1}\) is stable because there is almost no change with the increase of the aging degree at this peak. This means that the aging process increases the amount of carbonyl and sulfoxide in the asphalt and decreases the amount of the butadiene and styrene in the SBS modified asphalt. This phenomenon is worth of being paid attentions, because in further studies, the properties of the asphalt mixtures paved on the road can be estimated by conducting the FTIR test on the SBS modified asphalt extracted from the asphalt. However, this will only be reasonable when the number of testing samples is enough. Thus, this paper just analyzed the change of the chemical functional groups in the SBS modified asphalt extracted from the mixture samples. The peak areas at 1030 cm\({}^{-1}\) in the spectrum of SBSBF are bigger than that in the spectrum of SBSLF at all the aging degrees, and the peak areas at 1700 cm\({}^{-1}\) in the spectrum of SBSBF is higher than that in the spectrum of SBSLF under the unaged and the short-term aged situation. This means that overall, the aging degree of the asphalt in BFSMA-13 is bigger than that of the asphalt in LFSMA-13. This is mainly because, in the LFSMA-13, the asphalt content (6.0%) is bigger than that of the BFSMA-13 (5.8%). However, the increasing percentage of the peak areas at 1030 and 1700 cm\({}^{-1}\) in the spectrum of SBSBF is lower than those in the SBSLF. The peak area at 1030 cm\({}^{-1}\) in the spectrum of short-term aged and long-term aged SBSBF is 15.75% and 24.18% higher than that of the unaged SBSBF. The corresponding increasing percentage of the SBSLF indexes is 29.88% and 42.96%.