Influence of Reclaimed Asphalt Pavement Temperature on Mix Design Process of Cold In-Place Recycling Using Foamed Asphalt

The temperature of the existing asphalt pavement, which is to be recycled, would change from a low morning temperature of the spring/fall season to a high afternoon temperature of summer. However, most agencies do not consider the temperature of the reclaimed asphalt pavement (RAP) materials when they design cold in-place recycling using foamed asphalt (CIR-foam) mixtures. The main objective of this research is to determine whether the temperature of RAP materials would affect the optimum foamed asphalt content (FAC), which would produce the highest wet indirect tensile strength. On the basis of the limited laboratory test results, the temperature of RAP materials would have a significant impact on the wet indirect tensile strength of CIR-foam mixtures. This research supports the field reduction of FAC up to 0.5% when the RAP temperature reaches up to 55°C. The change in the wet indirect tensile strength caused by RAP temperatures was not sufficient to warrant a design method change. Also, improved compaction is expected with RAP materials with higher temperatures. It is recommended that the CIR-foam mix design should be performed using RAP materials heated to an anticipated temperature of the existing asphalt pavement in the field.