Full-Depth Reclamation: Sustainable Asset Management Reduces Costs and Saves Time

Nearly 400 million tons of asphalt pavement are replaced in the United States every year. This amounts to enough asphalt to pave a four-inch thick, two-lane highway around the world six times! The average life span of an asphalt roadway is 15 years. So, what happens to the 6 billion tons of asphalt replaced in those 15 years? In conventional pavement replacement and mill and overlay methods, old asphalt is milled, reprocessed, and reused as recycled asphalt pavement (RAP) for new roads. Unused asphalt is stockpiled and repurposed or landfilled.

The Evolution of Asphalt Pavement

Historically, asphalt pavement thickness was designed and constructed based on traffic volume and the strength of the underlying subgrade, often resulting in asphalt thicknesses of 6 to 12 inches. In the 1970s, construction techniques evolved and asphalt pavements were designed as composite sections, which include an aggregate base layer sandwiched between a thinner, less costly asphalt layer and the underlying subgrade. While aggregate base materials are becoming scarcer and more expensive, with new technologies, we are not limited to exclusively using these costly materials in our pavements.

According to the National Asphalt Pavement Association (NAPA), there are currently approximately 18 billion tons of asphalt pavement in use on roads, parking lots, and airports in the United States. Over the last decade, the paving industry has evolved to utilize an abundance of materials for new pavements, many of which involve repurposing existing asphalt.

Full-Depth Reclamation Explained

Full-Depth Reclamation (FDR) is the process of pulverizing all layers of existing asphalt pavements in place to depths of up to 20 inches. FDR has grown in popularity as equipment has evolved and recycling efforts have heightened. The pulverized layers are reclaimed to provide a homogeneous base layer to support a new, thinner surface layer section of asphalt. FDR is best for high severity distressed or failed pavements, where rehabilitation methods including maintenance or mill and overlay, are not enough to rejuvenate the pavement. For added stability, the reclaimed base layer can be chemically or mechanically stabilized. Chemical stabilization introduces cement, lime, kiln dust, or emulsified asphalt to improve binding of the materials. Mechanical stabilization adds other aggregates or RAP to strengthen the reclaimed base.

Full-Depth Reclamation Benefits

Roadway owners and paving contractors are realizing the benefits of FDR as this eco-friendly technology grows in practice:

• Cost Savings: Recent bid analysis has shown FDR to be 20 to 30 percent less expensive than traditional removal and replacement methods. FDR without added stabilization typically ranges in cost from $17 to $20 per square yard. As more robust and improved reclaimers and pulverizing equipment become available, prices will likely decrease, making FDR more viable than traditional reconstruction practices. Additional cost savings are realized through less equipment and materials used, fewer construction personnel, and more pavement service life.
• Time Savings: Construction time is shorter with less disruption to the end user. FDR’s single process of reclaiming existing materials in place typically takes one-third of the time of traditional methods, which require multiple processes including removal, hauling, re-preparing the subgrade, and replacing with new aggregate base.
• Reduced Impact: FDR has fewer construction obstacles than traditional pavement rehabilitation methods. With less equipment and fewer haul trucks confined to a reduced construction footprint, traffic impacts are lessened during construction on a roadway and downtime for parking lots is minimized.
• Stronger Structures: FDR increases flexibility and strength, while decreasing susceptibility to moisture and rutting potential. Deeper subgrade and base failures can be repaired through FDR.
• Reduced Waste: Since all the site’s material is recycled, unnecessary waste is prevented, resulting in less waste in our landfills. Fewer trucks leads to a reduction in fuel consumption and emissions.

Considerations for Full-Depth Reclamation

While implementing the FDR process, these practices should be considered: