Assessing binder blending level in asphalt mixtures containing recycled asphalt shingles

The recycling of asphalt shingles (RAS) in hot mix asphalt (HMA) has been the topic of much research. The asphalt binder of RAS is highly aged, oxidized, and stiffened, and the incorporation of it into HMA may alter the performance characteristics of the asphalt mixture. The first goal of this study was to determine the degree to which RAS binder blends with HMA virgin binder; the second goal was to determine the potential effects of this blending of binders on the long-term performance of RAS-containing HMA. A series of laboratory experiments were conducted, and the performance of RAS-containing HMA, which was fabricated replicating practical field conditions, was compared in two extreme scenarios-zero binder blending and total blending. The results showed that the performance of RAS-containing HMA tended to be closer to the total blending scenario. This suggests that RAS binder blends with HMA virgin binder nearly to the full extent. In addition, increasing RAS content makes HMA brittle and, therefore, more vulnerable to early-age cracking.