Characterization of Reclaimed Asphalt Pavement in Indiana: Changing INDOT Specifications for RAP

Interest has been growing to increase reclaimed asphalt pavement (RAP) usage by increasing the allowable percentage that can be used in Hot Mix Asphalt. This paper characterizes RAP used in recycled HMA in Indiana. It focuses on the properties of the asphalt binder. The Indiana Department of Transportation (INDOT) undertook a detailed evaluation of asphalt binder properties in RAP and the properties of new asphalt binders being supplied to INDOT. Asphalt binder was recovered from 33 RAP samples taken across the state and characterized for low temperature and high temperature grade. New asphalt binder properties were obtained from more than 200 Quality Acceptance samples that covered three -22 grades and three -28 grades. The data was analyzed to determine the maximum amount of RAP that could be added. Up to 22% RAP could be added without changing the original grade of binder. By shifting to a -28 grade, the allowable RAP increased to 38%. These findings supported the findings of a North Central Superpave Center study on five asphalt plants. On the basis of this information INDOT changed the specification for RAP to allow up to 25% binder substitution without changing the normal binder grade of -22 and up to 40% if the binder was changed to a -28 grade.