Testing of Moderate and High Reclaimed Asphalt Pavement Content Mixes

This paper describes the performance of test sections containing moderate and high levels of reclaimed asphalt pavement (RAP) at the National Center for Asphalt Technology test track. The test sections included two with 20% RAP, four with 45% RAP, and a control with no RAP. Each mixture contained the same component aggregates and RAP. One of the 20% RAP mixes contained PG 67-22 binder, and the other contained PG 76-22 binder. Different binders in the 45% RAP mixes included PG 52-28, PG 67-22, PG 76-22, and PG 76-22 plus 1.5% Sasobit. All sections performed well for rutting and raveling. Low-severity longitudinal wheelpath cracking was documented in two sections. The 45% RAP section with PG 76-22 plus Sasobit had moderate cracking, which appears to reflect cracking from the underlying pavement. The 20% RAP section with PG 76-22 had less cracking. Other sections had no cracking. Laboratory tests included asphalt pavement analyzer (APA) rutting tests, dynamic modulus, bending beam fatigue, and energy ratio. The APA results corresponded to the effective stiffness of the binder in the mixes. Master curves of dynamic moduli showed the effects of the virgin binder grade on the stiffness of the mixtures. Beam fatigue tests indicated that the 45% RAP mixes have lower fatigue lives compared with those of the other mixes, but this is because of a lower effective volume of asphalt in these mixes.