Designing Recycled Hot Mix Asphalt Mixtures Using Superpave Technology

Mix design procedures for recycled asphalt pavements require the selection of virgin asphalt binder or recycling agent. This research project was undertaken to develop a procedure for selecting the performance grade (PG) of virgin asphalt binder based on the Superpave PG grading system. Blending charts, similar to the viscosity blending charts, were constructed and evaluated based on test parameters obtained from the dynamic shear rheometer (DSR). The criteria for selection was based on Superpave performance grading (PG) specification, for example, G*/sinδ=1 kPa minimum for unconditioned asphalt binder, G*/sinδ=2.2 kPa minimum for rolling thin film oven (RTFO) residue, and G*sinδ=5 MPa maximum for RTFO and pressure aging vessel (PAV) residue. The criteria based on the fatigue parameter (G*sinδ=5 MPa maximum for RTFO+PAV residue) was determined to be too liberal and, therefore, was not recommended. An alternative criteria based on the high temperature stiffness (G*/sinδ) was recommended.