Best Practices for RAP Use Based on Field Performance

This study included a survey of practicing local engineers, field performance observations of new bituminous and bituminous overlay construction, and laboratory testing. The most common binder performance grades were identified along with the most common percentage of recycled asphalt in bituminous mixtures. Local engineers regarded cracking, rutting, and construction as the most important issues when using recycled asphalt pavement. Roughly one-third of Minnesota agencies exclude RAP from wear course mixture. Analysis of dynamic modulus curves from field cores showed that full-depth specimens were more useful for relating field and laboratory performance than were the wear or non-wear course specimens. Analysis showed stronger relationships existed to low temperature performance grade and to the percentage of new asphalt binder in the mixture than to the percentage of RAP in the mixture. Field performance related well to mixture master curves in the middle portion of the test frequency range. Recommendations include using low-temperature grades of PG-34, including RAP in the wear course, and using material control to achieve good performance. Other consideration are specifying the source material origin, screening and separating by particle size (fractionated RAP), or specifying RAP asphalt content.