While rejuvenator manufacturers have abided by the traditional performance guidelines of roadway authorities, it is important to recognize that these historically formulaic approaches are not always applicable to high RAP mixes.
Some Departments of Transportation, which do not have a long history with high RAP mixes, are becoming increasingly aware of, and adopting different approaches to mixes designed with RAP. For example, specifying that the binder shall be of a certain viscosity, or Pen/SP or PG Grade, does not work. Instead, using a “Balanced Mix” design for high RAP mixes is taking precedence. With a balanced mix design, the goal is to balance contrasting properties and optimize them for roadway performance.
Take rutting and fracture testing (i.e. resistance to cracking failure and fatigue). If a mix is too stiff, the rutting resistance is excellent but the crack resistance is poor. If the mix is too soft, then cracking failure is prevented at the expense of early onset rutting. Aging tests, as well as moisture susceptibility (hot-wet strength tests), are other properties that are key to roadway performance and should be checked before use. Sripath has extensive data and performance testing results for all of these properties on mixes that have been dosed with ReLIXER and utilize high RAP content.