Although referred to as “full-depth reclamation”, this process is just an extension of the basic CIR principles to the entire HMA pavement depth plus a predetermined depth of the base material. FDR can be used to depths of 300 mm (12 inches) or more but the most typical applications involve depths of between 150 and 225 mm (6 and 9 inches) (Better Roads, 2001).
The FDR process usually consists of eight steps (Better Roads, 2001):
- Pulverization. A road reclaimer pulverizes existing pavement to a predetermined depth. Road reclaimers are usually equipped to add materials such as stabilizing agents to the newly pulverized RAP.
- Moisture conditioning. The road reclaimer or a separate truck adds water to the newly pulverized RAP to assist in achieving required density.
- Breakdown roller. A sheepsfoot or pneumatic tire roller is typically used to compact the recently pulverized RAP to a consistent density.
- Shaping. A grader is typically used to make grade and cross-slope adjustments.
- Intermediate roller. A pneumatic tire roller or a steel wheel vibratory roller is used to knead and seat any loose aggregates left from the shaping process.
- Finish roller. A 12 to 14-ton static steel wheel roller is used to seat any remaining loose aggregates and create a smooth surface.
- Sealant. A fog seal is typically applied to protect the finished reclaimed layer. After the fog seal sets the reclaimed layer can generally withstand interim traffic loading. Therefore, at this point the road is often opened to traffic until the contractor is ready to apply the surface treatment or HMA surface course.
- Surface treatment or surface course. Finally, a more durable surface treatment or surface course is applied over the new stabilized base course.
Stabilized base course.
Recycled material, asphalt emulsion or foamed asphalt, asphalt rejuvenating agent and possibly virgin aggregate.
No generally accepted mix design method, but the Asphalt Institute recommends and most agencies use a variation of the Marshall mix design method (FHWA, 2001b).
FDR is generally suitable for lower volume roads that may only require a simple surface treatment over the resulting stabilized base course, or at most a thin HMA wearing course. However, FDR has been used on major highways including interstates (Better Roads, 2001).
- Better Roads. (July 2001). Full-Depth Reclamation. Better Roads. Special insert section on full-depth reclamation in cooperation with the Asphalt Recycling and Reclaiming Association.↵
- Federal Highway Administration. (2001b). Reclaimed Asphalt Pavement User Guideline: Asphalt Concrete (Cold Recycling). Web page on the Turner-Fairbanks Highway Research Center web site. http://www.tfhrc.gov/hnr20/recycle/waste/rap133.htm. Accessed 16 October 2001.↵