Use of Polymer Fiber to Improve Mechanical Properties of HMA Containing Recycled Asphalt Pavement (RAP)

A great percentage of highways and roads in California are constructed with Hot Mix Asphalt (HMA), and, as California infrastructure ages, these highways and roads must be maintained and rehabilitated. Reclaimed Asphalt Pavement (RAP) is considered an excellent alternative to virgin (raw, unprocessed) materials because it reduces the use of virgin aggregate and binder. Also, the use of RAP decreases the amount of construction waste placed into landfills. This laboratory study investigated the effect of two different commercial polymer fibers on the mechanical properties of HMA with RAP. Three different HMA with RAP mixes were used in the study. One mix that is commonly utilized on the Central Coast contained 15% RAP while the second and third mixes contained 25% and 40% RAP, respectively. Three different fiber dosages (0.05%, 0.10%, and 0.15% of the total mix) were investigated. Specimens were prepared and tested for rutting and moisture sensitivity in a Hamburg Wheel Tracker (HWT) and for Cracking Tolerance Index (CTI). Test results showed that adding fibers improved resistance to rutting for mixes with RAP content higher than 25%. The use of fiber improved resistance to cracking at intermediate temperatures for all mixes with RAP contents. Also, adding fibers improved mixes’ resistance to moisture damage. In addition, one of the two fibers used in the study outperformed the other. Overall, results indicate that adding polymer fibers to HMA mixes containing RAP has the potential to improve mixes’ resistance to rutting, moisture damage and cracking, depending on fiber dosage and type. This study offers information valuable to the maintenance and rehabilitation of roads and highways in California and beyond.