A novel double-drum mixing technique for plant hot mix asphalt recycling with high reclaimed asphalt pavement content and rejuvenator

- A novel double-drum mixing technique is proposed and evaluated.
- This mixing technique can reduce the air voids of hot recycled asphalt mixtures.
- This mixing technique can improve the performance of hot recycled asphalt mixtures.

Hot mix asphalt (HMA) recycling has been widely used in pavement engineering. When the content of reclaimed asphalt pavement (RAP) is high, asphalt rejuvenator is often used to improve the performance of asphalt mixtures. The existing mixing technique of HMA recycling with rejuvenator is adopted from the traditional hot mix asphalt plant with one mixing drum. The drawbacks of this mixing technique are that the rejuvenator cannot fully interact with RAP and some aggregates may not be well coated with virgin asphalt binder. In recognition of these, a novel mixing technique, namely double-drum mixing, is proposed and evaluated. A comparative study was carried out to investigate the effect of double-drum mixing on the performance of hot recycled asphalt mixtures. In detail, the volumetric properties, tensile strength, moisture damage resistance, rutting resistance, and low temperature cracking resistance were evaluated. Two asphalt mixtures (AC-13 and AC-25) with three RAP contents (40%, 50% and 60%) were investigated. The results showed that the proposed new mixing technique can improve the performance of hot recycled asphalt mixtures in several aspects. The double-drum mixing process can reduce the air voids if all other mix design parameters are the same. Additionally, the tensile strength, moisture damage resistance, rutting resistance, and low temperature cracking resistance were improved to a certain extent.