Performance of hot in-place recycled Superpave mixtures in Florida

It has been nearly two decades since the advent of flexible pavements designed following the Superpave process. This study focused on determining whether a Superpave mixture can be hot in-place recycled to meet the Superpave requirements. Recycling in-place can salvage existing asphalt pavements to incorporate them as part of a rejuvenated structure and represents a more sustainable rehabilitation practice. In this study, the key properties of the hot in-place recycled pavement were compared to the original performance criteria of an equivalent section of new asphalt pavement. Four mixes were obtained from existing Superpave pavements and the in-place (i.e., the properties of the existing asphalt before recycling) properties of the mixes were determined. The optimum amount of rejuvenator and aggregate screenings were evaluated. In addition, a volumetric analysis was performed to ensure compliance with Superpave requirements. The four mixes were tested and evaluated for rutting, moisture damage, and cracking performance. In general, there was an observed correlation between the aggregate gradation of the sample and the average quality control data obtained during construction. The recycled mix met the Superpave Performance Grade (PG) and the amount of rejuvenator was adjusted to achieve the binder PG requirements. The addition of finer aggregates was effective in increasing the air voids in all four mixes and all mixes had air voids near or at the 4% Superpave requirement. Performance testing using the Hamburg Wheel Tracking Device and Indirect Tension Testing (IDT) indicated that all of the mixes exhibited good cracking, rutting, and moisture damage performance in the laboratory. The results of the experiments showed that a hot in-place recycled pavement can effectively meet the Superpave requirements. In order to improve the process, it is recommended that pavement designers refine the design method to optimize the air voids and binder grade for improving the performance of these mixtures.