Louisiana\u27s experience with WMA technologies: Mechanistic, environmental, and economic analysis

Warm mix asphalt (WMA) describes various technologies that allow asphalt mixtures to be produced at lower temperatures as compared to hot mix asphalt (HMA). WMA technologies also offer improvements in workability, cost, and environmental sustainability such as reduced fuel usage, greenhouse gas emissions, and wear and tear at plants, while enhancing worker health and safety conditions. These benefits, as well as the mechanical properties of WMA mixtures, need to be quantified and compared to that of HMA. The primary objective of this study was to evaluate the laboratory performance of plant-produced lab-compacted mixtures utilizing various WMA technologies. The secondary objective of this study was to compare WMA energy consumption cost and emission data to conventional HMA mixtures in terms of fuel/energy savings at the plant and in terms of CO and CO2 emissions. Three projects in Louisiana utilizing four different WMA technologies were considered in this study, yielding 11 mixtures total. Each project included a companion HMA mixture section to allow for direct comparison. Loose mixtures were obtained from trucks at the plant and compacted on-site in a mobile asphalt laboratory. Laboratory tests included dynamic modulus (|E*|), flow number (FN), loaded wheel tracking (LWT) test, indirect tensile (IDT) test, semicircular bend (SCB) test, thermal stress restrained specimen test (TSRST), and the Lottman moisture susceptibility test. Results indicated that WMA mixtures exhibit similar high and intermediate temperature performances in the laboratory as compared to HMA. On average, $1.61 of energy savings per ton of produced asphalt mixture was observed, along with a considerable reduction in air pollutants at the plant. However, the cost of additives and royalty fees would reduce the total cost savings from using WMA. These benefits were observed without reduction in the mechanistic performance of the mix