MECHANICAL RESPONSE OF SUPERPAVE RECYCLED HOT MIXTURES IN ONTARIO

The use of reclaimed asphalt pavement (RAP) for surface course layers is still conservative and even restricted in some instances. The main concern is related to the uncertainty of the long-term performance and effect of RAP in the stiffness of the mix. To counteract this effect, softer virgin asphalt is incorporated in the mix. A laboratory study was conducted on six different Superpave SP12.5 mixtures to determine the impact that RAP has on the dynamic modulus and phase angle of the mixtures, and to quantify the effect of binder bump in the mix behavior. The mixtures were designed and elaborated in the laboratory, and tested following the AASHTO TP-62 standard. Two virgin mixtures, two 20% RAP mixtures, and two 40% RAP mixtures were created with different virgin asphalt performance grades (PG). The results show that laboratory mixtures can be produced with up to 40%RAP with comparable results to the virgin mixtures, and that the use of a softer grade does not always represent a significant enhancement of the stiffness characteristics of the mixtures.