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Full Depth Reclamation


Full Depth Reclamation

Full depth reclamation (FDR) consists of pulverizing the asphalt-wearing layer (top) of the road into the base material and evening the sub-base material to depths of up to 300 mm. Emulsified asphalts, fillers, virgin aggregates or recycled asphalt pavements (RAP) can be added to maximize the effectiveness of the system. The process is ideal for increasing the bearing capacity of roads that utilized maintenance techniques such as pothole patching, seal coats, slurry seals and overlays, as well as increased traffic loadings.

Design Criteria

In order to design a mix to satisfy the objectives of the project the existing pavement must be investigated for structural adequacy, thickness, slope and cross-fall as well as the visual appearance. Based on these criteria a proper design can be developed. In most instances the design procedure developed by Wirtgen is the accepted method of design. This design procedure is well laid out in the Wirtgen Cold Recycling Technology Manual.

The following is a guide to the design procedure:

RAP samples: 

Representative samples should be taken. Areas where differences in type and texture of existing pavements should be noted. Proper sampling procedures should be followed and enough material taken to ensure representation.

RAP properties: 

Gradation of RAP as well as the extracted gradation should be obtained to help in deciding if new aggregate is needed. The asphalt content should be determined and the recovered asphalt properties obtained such as penetration and viscosity. Knowing these can help in deciding what recycling additive to use as well as limiting quantities.

New aggregate: 

Most CIR projects do not require new aggregates. New aggregate can be justified if the RAP is high in binder content or improved structural capacity is needed. Typically crusher run aggregate is used. In some instances straight coarse aggregate can be used to increase the coarse fraction.

Type and grade of recycling additive: 

The most common recycling additives used in CIR are asphalt emulsions and recycling agents. Polymer versions have been used as well to reduce rutting, improve early strength and aid in reducing thermal cracking.

Pre-mix moisture content: 

The use of water is very important in CIR mixes. The water has two purposes in the mixture. The first purpose is to aid in the coating the RAP by the recycling additive. The second purpose of the water is to act as a compaction aid in the field. Accurate quantities of water are required to ensure the proper coating and compaction effort of the mix in the field. The total liquids content is taken as the total of the recycling additive used, the pre-mix moisture added and the moisture present in the RAP material.

Trial mixtures: 

In order to establish the optimum recycling additive needed in the mix trial batches must be carried out in the laboratory. A number of trials are done varying the quantity of recycling agent (typically between 0.5 and 3.0% in 0.5% increments). The total liquids content is maintained so as the recycling additive varies so does the pre-mix water. The compaction of the CIR mix is typically done using the 75 blow Marshall compaction at a slightly elevated temperature of 40°C. This value seems to give density values comparable to field densities.


During the design stage the compacted mixture has to lose moisture in order to develop maximum strength. This can be accomplished in the laboratory by curing the samples at an elevated temperature for 24 to 48 hours. Typical curing temperatures are 60°C.

Strength testing:

Strength testing using Marshall stability and flow should be done to ensure adequate strength. Although it is difficult to remove all moisture the bulk specific gravity should be done . Approximate volumetrics can be determined from compacted specimens. The air voids should lie between 9 – 14 percent. The moisture susceptibility of the mix should be performed. Typically AASHTO T283 test “Resistance of Compacted Bituminous Mixture to Moisture Induced Damage” is the most common method used. Other tests involving some kind of moisture conditioning are also used.

Job mix formula (JMF):

After all testing JMF can be established. Typically it is determined by air voids, strength tests, appearance and moisture susceptibility. The JMF should specify the percent recycling additive (type and grade), the mix water content and the compacted maximum density at the optimum recycling additive content. The job mix formula is the starting point for the project and field adjustments may have to be made as conditions warrant.

Materials – Recycling Additives

Asphalt Emulsions:

A number of different types and grades of asphalt emulsions can be used in Cold In-Place Recycling. The proper emulsion to be used is based on a number of factors; environmental conditions (temperature and humidity), time of year, and the existing road conditions. All these conditions affect the emulsion to be used. Typically the most common emulsions used are High Float types, CSS-1, CMS-2 (polymer versions included) as well as proprietary products.


The rejuvenators are typically cationic emulsions combining a process oil with water. They can be used by themselves or in a combination blend with an asphalt emulsion. When using rejuvenators more detail has to be done during the mix design stage.

Recycled Asphalt Pavement (RAP):

The recycled asphalt pavement (RAP) is created by the grinding of the existing pavement. Depending on the process the RAP material may be further processed through a screening and crushing operation. Typically the maximum particle size is 37 mm. The milling machine can control the gradation of the RAP through speed, milling head direction as well as the existing pavement condition.


There are different modifiers that can be used in the CIR process. Besides the asphalt emulsion or recycling agent, aggregate may be added to improve gradation, stability or cross slope. Portland cement or lime in dry or slurry form can be added to improve early strength, cohesion and resistance to moisture damage.

Performance Guidelines

In order to construct a proper well designed CIR Mix the following guidelines should be followed:

Safety Data Sheets

DescriptionPdf File
SDS – Rapid Curing Cutback
SDS – Rejuvenite A
SDS – Rejuvenite B
SDS – Rejuvenite S

Related Resources

DescriptionPdf File
Research – The Fundamental Principles of Mechanical Stabilization
Research – The Influence of Mineral Nature and Temperature of the Aggregate in Foam Bitumen Stabilized Mixes

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