Quantification of Aging Compounds in Evotherm-Modified Warm-Mix Asphalt Binder Using Fourier Transform Infrared Spectroscopy

Warm-mix asphalt (WMA) additives are widely used to reduce the mixing and compaction temperatures of the bituminous mixes. Due to lower aging temperature, one can expect a reduction in aging compounds in a WMA mix in comparison with the hot-mix asphalt (HMA) mix. In this study, an attempt is made to address the influence of the production process and the presence of WMA additive on the aging compounds formed in WMA binders. For this purpose, two binders, one unmodified (VG20 grade), and a crumb rubber modified, were used. A chemical WMA additive, Evotherm, was used. All the binders were subjected to short-term and long-term aging in the laboratory. The carbonyl and sulfoxide functionalities in all the binders were quantified using Fourier transform infrared spectroscopy. From the analysis, it was seen that the carbonyl index for WMA-modified VG20 binder and crumb rubber-modified binder (CRMB) are higher by 25 and 33% compared to the base VG20 binder and CRMB, respectively. Also, Evotherm-modified binders resulted in lower carbonyl compounds (about one-half) when compared with the HMA binders, aged at identical conditions. The magnitude and the rate of formation of sulfoxide compounds, however, varied with different binders owing to the overlapping effects of the formation and decomposition of sulfoxides.