*3.4. FTIR Analysis*

Figure 13 shows the infrared spectra of the asphalts in the wavenumber range of 4000 cm−<sup>1</sup> to 500 cm−1. As shown from Figure 13, the infrared spectrum of the aged asphalt after the addition of the regenerating agent remained the same as that of the aged asphalt, and no apparent new absorption peaks appeared; the difference lied in the change of the transmittance size. The spectral difference between the aged asphalt and the regenerated asphalt was related to the functional group index. The functional groups that changed in the IR spectra were located at 1700 cm−<sup>1</sup> and 1032 cm<sup>−</sup>1, representing the absorption peaks of carbonyl (C=O) and sulfoxide (S=O), respectively. Figure 14 shows the carbonyl and sulfoxide group indices for each asphalt specimen. We can see from Figure 14 that the sulfoxide index did not change significantly when the regeneration agent dose increased. When the regeneration agent dose was 2%, the carbonyl index also did not change. However, when the regeneration agent dose was 6%, the carbonyl index of the regenerated asphalt decreased by 50% compared with the aged asphalt, and the carbonyl functional group transmission rate of the regenerated asphalt increased significantly. The index of the carbonyl group showed a decreasing trend, when the doses of rejuvenator were 4% and 6%; it showed that the dose of rejuvenator that was greater than the dose of 2% was beneficial to reduce the content of heavy components in asphalts, so as to achieve the purpose of reducing the viscosity of the aged asphalt.

**Figure 13.** Infrared spectra of the asphalts.

**Figure 14.** Sulfinyl and carbonyl index diagrams.
