Comparison of the Relative Long-Term Field Performance among Various Warm Mix Asphalt (WMA) Pavements

The use of warm mix asphalt (WMA) has increased greatly over the past decade because it provides potential to lower energy demands, reduce emissions, and increase haul distances. However, questions remain about the long-term performance of WMA pavements, including whether different WMA technologies can provide the same field performance. In this paper, field rutting and cracking (transverse and longitudinal) performance data for chemical, organic, and foaming WMA technologies are compared pairwise. Thirty-four WMA-WMA pairs from 13 field test roads are included, which cover different pavement ages, traffic volumes, pavement structures, WMA technologies, and four climate zones across the United States. For the WMA-WMA pairs that exhibited statistically different performance, their material properties were investigated further to identify potential factors that could be used to characterize such field differences. The results indicate that, generally, no statistical performance differences are evident between the WMA-WMA pairs. However, it is worth noting that over the longer term, there are individual projects whose organic pavement sections showed statistically higher amounts of cracking than the chemical and foaming sections. Based on the laboratory testing results on field cores, it is suggested that the greater amounts of transverse cracking exhibited by organic pavements may be caused by organic’s lower mixture fracture work density and lower binder failure strain values compared with those of the chemical and foaming sections. The greater amounts of longitudinal cracking exhibited by the organic pavements may be caused by organic’s higher mixture indirect tensile strength, lower mixture fracture work density, and lower binder fracture energy values compared with those of the chemical and foaming sections.