Can More Reclaimed Asphalt Pavement be Added?

Abstract

Results of a study conducted by the New Hampshire Department of Transportation (NHDOT) in cooperation with three local paving contractors are presented. Plant-produced hot-mix asphalt (HMA) mixtures containing reclaimed asphalt pavement (RAP) percentages from 0% to 25% were obtained from seven different batch plants. Twenty-eight mixtures were sampled and sent to the binder testing laboratories at NHDOT and Pike Industries, Inc. The virgin binders were also sampled and sent for binder testing. Binders were extracted and recovered from all of the mixtures and were tested to determine the performance grade (PG) binder grade and critical cracking temperature. The effect of the RAP at various percentages on binder properties was evaluated. High-end PGs were found to remain the same or increase only one grade for the mixtures tested. Low-end PGs also remained the same or bumped only one grade, and the critical cracking temperatures changed by only a few degrees for the mixtures examined in this study. Results of this study led to a change in the implementation of the new NHDOT specification in regard to the use of recycled asphalt binder in HMA.