Full Depth Reclamation (FDR)
What is Full Depth Reclamation?
Full depth reclamation, or FDR for short, is a pavement recycling technique that produces a stabilized base by beneficially reusing multiple layers and materials of a pavement. This technique saves time, money, materials and resources. FDR has been used successfully nationwide primarily for failures associated with base or subgrade degradation leading to premature failure of the pavement structure, but also for many types of pavement cracking, deep rutting and maintenance patches. Check out our case studies to learn how Mintek Resources was able to help in an Ohio FDR project as well as the first Highway FDR Job.
What is the Full Depth Reclamation Process?
- The full depth reclamation process starts by pulverizing the distressed pavement to the required depth using a specialized machine called a soil reclaimer. The depth is determined during pre-project planning to be sure the final surface meets desired targets.
- Next, a portion of the material often needs to be removed in order to be sure the final elevation is correct. Since sewers and utility access covers are fixed in place, a smooth ride often depends on the elimination of this material.
- Depending on the project, different additives, such as lime or Calciment® LKD, can be combined to provide strength and help bind the layer together. When incorporating clay subgrade, lime will hold the mix together through pozzolanic bonds providing long-term strength gains that will minimize the possibility of shrink/ swell during freeze/ thaw cycles. Calciment LKD is another additive option that should be considered when subgrade soils with coarser grained soils and lower plasticity would be incorporated.
- Shaping and compaction occur before the final surface course of asphalt is placed on top of the FDR base. Once these steps are complete, the rehabilitated road will provide a smooth ride for many years.
Benefits of Full Depth Reclamation
Compared to traditional rehabilitation techniques, FDR can be completed in a fraction of the time. For example, a rehabilitation project requiring all of the asphalt to be removed and hauled away before new material can be brought to the site could take weeks. In contrast, a FDR project can be completed in a matter of days.
Minimize Traffic Disruption
Since FDR is faster than other rehabilitation strategies, traffic disruption is minimized. A road resurfaced with FDR can handle traffic loads hours after completion.
Costs associated with removing and disposing of old, failing asphalt are expensive and those costs are only going up. Similarly, the cost of new materials is also high and increasing. By using the materials on site, those costs are all but eliminated.
Full depth reclamation is a more environmentally sound solution to a failing asphalt. Importing and exporting of materials is practically eliminated and 100% of the materials can be reused, giving them new life.
Many asphalt failures occur because the strength of one or multiple underlying layers are weak or poor, not the actual asphalt surface. Full depth reclamation creates a new, stronger base, which will extend the life of the pavement. The surface course, not the FDR mixture itself, usually reaches the end of its service life before the FDR layer.
Structural Layer Coefficients
A structural layer coefficient of 0.14 to 0.30 has been associated with FDR treated pavements. This number can be incorporated into designs to minimize the thickness of other layers, further reducing costs and materials.