Short-term performance and evolution of material properties of warm-and hot-mix asphalt pavements

This paper presents case studies of the short-term field performance and material property evolution of four warm-mix asphalt (WMA) projects in Iowa, Louisiana, Montana, and Tennessee, constructed in 2011 and 2012. Each project had one or several WMA overlay sections and a control hot-mix asphalt (HMA). Two rounds of performance investigations were conducted, including a survey of field distress and characterization of material properties. Field cores from the two rounds (the first immediately after construction, the second 2 to 3 years after construction) were used to evaluate the performance of the mixtures in terms of dynamic modulus, creep compliance, fracture testing at intermediate and low temperatures, and the Hamburg wheel-tracking test. The following tests were also used to evaluate the extracted asphalt binders: performance grading, multiple stress creep recovery, and monotonic fracture at two temperatures. This study showed that the material properties (rutting and cracking resistance) evolved over time for both the HMA and WMA pavements; however, pavement maintenance (e.g., chip seals) affected this evolution. In general, the material properties of WMA and HMA pavements for the second-round samples were consistent with those of the first-round samples.