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

In conventional pavement replacement and mill and overlay methods, old asphalt is milled, reprocessed, and reused as recycled asphalt pavement (RAP) for new roads while unused asphalt is stockpiled and repurposed or landfilled. Full-Depth Reclamation (FDR), on the other hand, 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.

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 included an aggregate base layer sandwiched between a thinner, less costly asphalt layer and the underlying subgrade.

Aggregate base materials are becoming scarcer and more expensive, but with new technologies, roadway owners and paving contractors are not limited to exclusively using these costly materials in our pavements. 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.

With FDR, 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 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.