Cracking Cold: Solving the Riddle of RAP and Thermal Cracking
Reclaimed asphalt pavement (RAP) increasingly is being used in asphalt mixes. However, there are some concerns that higher quantities of RAP may compromise mix performance in cold-weather regions and contribute to low-temperature (thermal) cracking. This article discusses the causes of low-temperature cracking, and describes some of the research being conducted to ensure that RAP does not add to the problem. Some research suggests that the use of RAP in the amount of 15% or less should not present a problem. However, higher amounts of RAP can increase the stiffness properties of the mixture. In cold climates, this may contribute to the occurrence of low-temperature cracking. One solution might be to use RAP in warm-mix asphalt, which could allow for less premature aging, less thermal cracking and the ability to use a cheaper binder that does not require a polymer modifier. Cold in-place recycling may also result in better low-temperature cracking performance. New test procedures and testing devices also are being developed to evaluate low-temperature cracking.