Full Depth Reclamation: What It Is & Best Practices

What is Full Depth Reclamation (FDR)?

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 an asphalt 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.

Importance of FDR

Full depth reclamation is important for a number of reasons; it’s cheaper and faster than traditional techniques, extends pavement performance, has an increased structural layer coefficient, minimizes traffic disruptions and who can forget that it’s environmentally friendly!

The cost savings go further than just the speed of construction that allows projects to be completed faster. Costs associated with removing and disposing of old, failing asphalt are expensive and increasing. At the same time, the cost of new materials is also high and growing as well. This is where FDR reaps the most benefit, by reusing materials already on the site, all but eliminating those costs. From a time perspective, a traditional rehabilitation project requiring all the asphalt to be removed and hauled away before new material can be brought to the site could take weeks. In contrast, an FDR project can be completed in a matter of days. Since FDR is faster than other rehabilitation strategies, traffic disruption is minimized. A road resurfaced with FDR can handle traffic loads hours after completion.

The increased strength of an FDR layer can be incorporated into the design of the new pavement. This minimizes the required thickness of subsequent layers, further reducing cost and time to import materials.

As for the performance and environmental impacts, 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. Future pavement preservation techniques = more environmentally sound pavement.

Description of Process, Equipment & Materials

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 may need to be removed 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.

Historically, cement has been used as the primary stabilizing agent. However, depending on the project, quicklime or Calciment® LKD can be used to bind the layer together. When incorporated with the subgrade, Mintek’s lime-based products hold the mix together through pozzolanic bonds, providing long-term strength gains that will minimize the possibility of shrink/swell during freeze/thaw cycles.

Finally, 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 to come.

Considerations for Full Depth Reclamation

Full depth reclamation with lime products can work especially well on low volume roads with thin asphalt overlays that have little to no aggregate base when little to no aggregate base overlying a moderate to high PI soil. As coarser grained soils and/or lower plasticity soils are incorporated, Calciment® LKD can work well.

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