What is Full Depth Reclamation (FDR)

Full Depth Reclamation 

Full-depth reclamation (FDR) is a pavement rehabilitation technique used to restore the structural integrity and functionality of deteriorated roads or pavements. It is a cost-effective and sustainable approach that involves recycling the existing pavement materials to create a new base layer for the road.

FDR can be performed in place of traditional remove and replace reconstruction. FDR is done  by grinding up the old pavement and using it as a stronger foundation for the new roadway. This is beneficial in cases where reconstruction is necessary in order to increase the structural capacity of the roadway due to increased vehicle traffic.

In FDR a new base is produced by pulverizing the existing asphalt pavement and mixing it with some of the underlying granular materials. The FDR process allows complete reconstruction using 100 percent of the existing pavement materials, while correcting grade, cross slope, and underlying pavement problems.

The process of full-depth reclamation typically includes the following steps:

Pulverization:

 The existing pavement is pulverized using specialized equipment such as a reclaimer or a milling machine. This machine grinds the old pavement into small pieces, including the underlying layers of asphalt, base course, and sometimes the subgrade.

 

 Reclaimer or a milling machine

Mixing:

 Once the pavement is pulverized, additional materials are often added to improve the properties of the reclaimed material. These materials may include cement, lime, or fly ash. These additives help stabilize the recycled pavement and enhance its strength and durability.

Moisture control: 

Controlling the moisture content of the reclaimed material is crucial for proper compaction and achieving the desired strength. Water is added to the mix as needed to optimize the moisture content for compaction.

Compaction:

 The recycled pavement mixture is thoroughly mixed and compacted using heavy rollers or compactors. This compaction process ensures that the recycled materials bond together and form a solid and stable base layer.

Surface treatment: 

Once the reclaimed material is properly compacted, a new wearing course, such as hot mix asphalt (HMA), is often applied on top of the reclaimed base layer to provide a smooth and durable driving surface.

Full-depth reclamation offers several advantages over traditional pavement rehabilitation methods:

Cost-effectiveness: FDR reduces the need for extensive excavation, disposal of old materials, and importation of new materials, resulting in significant cost savings compared to complete reconstruction.

Environmental sustainability: By recycling the existing pavement materials, FDR reduces the demand for new aggregate and preserves natural resources. It also minimizes the generation of construction waste and the associated environmental impacts.

Time efficiency: FDR can be completed relatively quickly compared to traditional reconstruction methods since it eliminates the need for extensive removal and replacement of pavement layers.

Improved pavement performance: The recycled base layer created through FDR is often stronger and more uniform than the original pavement. It can enhance the structural integrity of the road, reduce cracking and rutting, and increase the overall lifespan of the pavement.

Full-depth reclamation is a versatile technique that can be applied to various types of pavements, including asphalt roads, concrete roads, and even low-volume gravel roads. It is commonly used in both rural and urban settings to rehabilitate deteriorated pavements, extend their service life, and improve the overall quality of road infrastructure.