Understanding the State Agency Policies toward RAP Usage in the United States: State of Practice

The usage of Reclaimed Asphalt Pavement (RAP) material is a highly resource-conservative, economical, and sustainable practice in flexible pavement construction. However, its usage in hot mix asphalt (HMA) is capped at 25% by the majority of state transportation agencies due to its aging levels, stiffness characteristics, and handling capabilities, which may result in early-age pavement distress. Though researchers suggest methodologies to increase RAP usage, higher RAP percentages in asphalt pavements require the support of state authorities. The main objective of this paper is to provide information on how different states design their mixtures with high RAP percentages. This study reviewed the current state of practice of fifty (50) state DOTs in the United States (US) with respect to RAP usage and the factors governing its regulations. It was observed that the limit of RAP content is mainly governed by traffic levels, gradation, binder content, and stiffness contributed by RAP and layer position in a pavement structure. The specifications also suggest that apart from volumetric and performance justification, blending charts, fractionation, and virgin binder grade selection would facilitate the use of higher RAP content in HMA. Controlled mixture design abiding by state specifications can increase the allowable RAP to 40-100%.