By Dr. Grover Allen, Ph.D., P.E.

If you’re reading this article, you probably already know that RAP stands for “reclaimed asphalt pavement” and is valued by users and producers alike because it can be recycled as a component of a new asphalt mixture. In addition to being resource-responsible, the use of RAP in an asphalt mixture means that at least some portion of the reclaimed asphalt binder can be used to offset the amount of new asphalt binder used in the mix. But how much of that reclaimed asphalt binder is actually available to act as a binder and how much is too hard to serve that role – acting more like a black rock?