Effects of Warm-mix Asphalt Additives on Asphalt Mixture Characteristics and Pavement Performance

The primary objective of this research is to evaluate the feasibility of several WMA mixtures as potential asphalt paving mixtures for Nebraska pavements. To that end, three well-known WMA additives (i.e., Sasobit, Evotherm, and Advera synthetic zeolite) were evaluated. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their HMA counterparts were implemented in Antelope County, Nebraska. More than one ton of field-mixed loose mixtures were collected at the time of paving and were transported to the NDOR and UNL laboratories to conduct comprehensive laboratory evaluations and pavement performance predictions of the individual mixtures involved. Various key laboratory tests were conducted to identify mixture properties and performance characteristics. These laboratory test results were then incorporated into other available data and the MEPDG software to predict the long-term field performance of the WMA and HMA trial sections. Pavement performance predictions from the MEPDG were also compared to two-year actual field performance data that have annually been monitored by the NDOR pavement management team. The WMA additives evaluated in this study did not significantly affect the viscoelastic stiffness characteristics of the asphalt mixtures. WMA mixtures generally presented better rut resistance than their HMA counterparts, and the WMA with Sasobit increased the rut resistance significantly, which is in good agreement with other similar studies. However, two laboratory tests—the AASHTO T283 test and semi-circular bend fracture test with moisture conditioning—to assess moisture damage susceptibility demonstrated identical results indicating greater moisture damage potential of WMA mixtures. MEPDG results simulating 20-year field performance presented insignificant pavement distresses with no major performance difference between WMA and HMA, which has been confirmed by actual field performance data. Although only two-year field performance is available to date, both the WMA and HMA have performed well. No cracking or other failure modes have been observed in the trial sections. The rut depth and the roughness of WMA and HMA sections were similar