This article discusses the results of a study that expanded upon NationalCooperative Highway Research Program (NCHRP) Project 9-12, Incorporation of Reclaimed Asphalt Pavement in the Superpave System, by investigating materials common to the North Central region, as well as studying the use ofa higher reclaimed asphalt pavement (RAP) content. The study results showed that acceptable Superpave mixtures could be designed with as much as 40% to 50% RAP, although the gradation and aggregate quality may limit the amount of RAP that can be used. States in the North Central region reportthat, in general, RAP use is returning to the levels common before Superpave. As a sponsoring state, Indiana conducted a cost benefit analysis of the research project as part of an independent review of the cost effectiveness of the U.S. Department of Transportation's research program. A conservative estimate indicates that the Indiana Department of Transportation has saved nearly $330,000 per year when adding only 5% RAP to more than 5 million tons of base and intermediate mixes--although RAP contents of 15% to 20% are more typical.
Abstract