Field Evaluation of Warm-Mix Asphalt Technologies

Warm mix asphalt (WMA) has received considerable attention in the past few years to reduce energy consumption and pollutant emissions during hot mix asphalt (HMA) production and placement. However, many concerns and questions are still unanswered regarding the field performance and environmental benefits of WMA. In this study, WMA mixtures containing reclaimed asphalt pavement (RAP) were evaluated in a field project in Ohio. The project included using Aspha-min, Sasobit, and Evotherm in three test sections. Furthermore, a control section was also produced so that a side-by-side comparison could be made between WMA and HMA mixtures. Temperature and emissions were monitored during the production and placement of the considered WMA and HMA mixtures. In addition, core samples were obtained from the evaluated sections and tested in the laboratory. Roughness and rutting measurements were also conducted during the first 46 months of service. The results of this study showed that the emissions were significantly reduced during the production and placement of WMA mixtures as compared to the control HMA mixture. In addition, although WMA mixtures were compacted at much lower temperatures, they achieved higher in-place density than the control HMA mixture. The results of the laboratory tests conducted on core samples showed that the WMA mixtures had higher indirect tensile strength (ITS) than the HMA mixture after 3 months of service. However, the HMA ITS value increased more rapidly with time than that of the WMA. The moisture susceptibility test results demonstrated that the Sasobit and Evotherm mixtures exhibited acceptable resistance to moisture-induced damage. Finally, the collected performance data indicated that the WMA and HMA sections had similar International Roughness Index (IRI) values after 46 months of service. In addition, no measurable rutting was observed in any of the test sections.