[Abstract]Abundant studies are using Attenuated Total Reflection (ATR) Fourier Transform infrared spectroscopy to quantitatively evaluate the aging extent of Styrene–Butadiene–Styrene (SBS)-modified asphalt (SBSMA). However, most currently employed SBS characteristic indexes merely represent the SBS concentration within SBSMA and may fluctuate during aging because of the poor compatibility between SBS and bitumen. In this study, a new index IB/S calculated by dividing polybutadiene infrared peak intensity by polystyrene infrared peak intensity was proposed to show the aging extent of SBS/SBSMA. And the application feasibility under various aging conditions was examined via ATR observation and rheology master curves. Results indicated that traditional SBS characteristic indexes could be influenced by possible SBS particle size variation during aging while IB/S was independent of SBS concentration change and accurately represented the SBS/SBSMA aging severity. Besides, the feasibility was not affected by different SBS dosages, SBS modifier types or aging procedures.
