For mechanical FDR, apply granular material to the area to be reclaimed
Make a series of passes with the reclaimer to pulverize the material to the required depth
Apply water during pulverization and mixing passes to the reclaimed material as required to aid in proper compaction. Water may be added using water trucks or through the reclaimer’s on-board additive system
Compact the reclaimed material to the required percent compaction using any combination of segmented padfoot, vibratory padfoot, rubber-tired, vibratory single or double drum rollers
Shape/trim the reclaimed material to the required cross-slope and grade
Apply the wearing surface
Bituminous Stabilized FDR
Make a series of passes with the reclaimer to pulverize the material to the required depth
Lightly roll and reshape reclaimed material prior to application of dry stabilizing additives and prior to mixing passes of the reclaimer
Apply dry chemical stabilizing additives using a calibrated bulk spreader/distributor
Add bituminous stabilizing agents during the mixing pass of the reclaimer using the reclaimer’s on-board additive system
Chemical stabilizing aadditives applied as slurry can be spread ahead of mixing passes using a calibrated liquid distributor or added during the mixing pass of the reclaimer using the reclaimer’s on-board additive system
Apply water during pulverization and mixing passes to the reclaimed material as required to aid in proper compaction. Water may be added using water trucks or through the reclaimer’s on-board additive system
Compact the reclaimed material to the required percent compaction using any combination of segmented padfoot, vibratory padfoot, rubber-tired, vibratory single or double drum rollers
Shape/trim the reclaimed material to the required cross-slope and grade
Minimumize vehicular traffic on stabilized base material for 30 to 60 minutes
Allow the reclaimed mixture to properly cure
Apply the wearing surface
Chemical Stabilized FDR
Make a series of passes with the reclaimer to pulverize the material to the required depth
Lightly roll and reshape reclaimed material prior to application of dry stabilizing agents and prior to mixing passes of the reclaimer
Apply dry chemical stabilizing agents using a calibrated bulk spreader/distributor
Chemical stabilizing agents applied as slurry can be spread ahead of mixing passes using a calibrated liquid distributor or added during the mixing pass of the reclaimer using the reclaimer’s on-board additive system
Apply water during pulverization and mixing passes to the reclaimed material as required to activate chemical stabilizing agents and aid in proper compaction. Water may be added using water trucks or through the reclaimer’s on-board additive system
Compact the reclaimed material to the required percent compaction using any combination of segmented padfoot, vibratory padfoot, rubber-tired, vibratory single or double drum rollers
Shape/trim the reclaimed material to the required cross-slope and grade
Minimumize vehicular traffic on stabilized base material for 30 to 60 minutes
Allow the reclaimed mixture to properly cure
Apply the wearing surface
Pulverizing fluffs up the reclaimed material resulting in an increase in thickness, and this must be accounted for when checking treatment depths. A tolerance of 1/2 inch is usually allowed.
To prevent the risk of a thin layer of pulverized but untreated stabilized material at the bottom of the FDR layer, the final mixing pass is often made slightly deeper than the previous pulverization pass.
Application Guidelines
Control Strip
If required, a control strip should be placed at the beginning of the project to evaluate the equipment, construction methodology, workmanship and to verify that the construction process meets specification requirements
Pulverization
Overlap longitudinal joints a minimum of 6 inches and transverse joints a minimum of 2 feet
Check depth of pulverization by removing the pulverized material on each on each side of the reclaimer and checking the depth.
Check gradation of reclaimed material. Reclaimers are not crushers; therefore, it is impractical to require more than 95% of processed material to pass a 2 inch sieve. An occasional oversized chunk should be acceptable
Lightly roll and reshape reclaimed material prior to application of dry stabilizing agents and prior to mixing passes of the reclaimer
Manage speed of reclaimer and door position of cutting chamber to ensure proper blending and gradation.
Application of Granular Materials and Dry Stabilizing Agents
For mechanical stabilization apply granular materials prior to pulverization using a mechanical spreader, paver or by haul trucks and then spread to a uniform thickness with a motor grader
If required, granular materials for bituminous and chemical stabilization can be placed prior to or after pulverization but before mixing passes
Dry chemical stabilizing agents can be added prior to pulverization or after pulverization and prior to the mixing pass of the reclaimer. Applying after pulverization generally results in a more uniform application
Dry chemical stabilizing agents should be applied with non-pressurized mechanical vane-feed, cyclone or screw type bulk spreaders/distributors
Check application rates either volumetrically or by using a “canvas patch” test or similar procedure
Application of Stabilizing Agents Applied as Slurry
Chemical stabilizing agents applied as slurry can be spread ahead of mixing passes using a calibrated liquid distributor or added during the mixing pass of the reclaimer using the reclaimer’s on-board additive system. Application through the reclaimer generally results in a more uniform application
Verify application of slurry stabilizing agents using the consumption of stabilizing agent (and water) obtained from the computer that controls the slurry mixing unit.
Restrict overall time from initial blending of chemical stabilizers through final rolling to no more than 2 - 3 hours, depending on weather conditions.
Application of Bituminous Stabilizing Agents
Apply bituminous stabilizing agents during the mixing pass of the reclaimer using the reclaimer’s on-board additive system.
Verify the application rate by evaluating the mass of recycled material against the volume of recycling agent used for a single tanker.
For foamed asphalt stabilization, check the temperature of the asphalt before connecting a tanker to the reclaimer.
For foamed asphalt stabilization, verify the expansion ratio and half-life using the test nozzle on the reclaimer.
Mixing Pass
Check depth of mixing by removing the pulverized material on each side of the reclaimer and checking the depth. Pulverizing fluffs up the material and should be accounted for when determining treatment depths. A tolerance of ± 1/2 inch (12.5 mm) is usually allowed.
Overlap longitudinal joints a minimum of 6 inches and transverse joints a minimum of 2 feet
Compaction
Establish a rolling pattern to achieve the required percent compaction
Compact the reclaimed material to the required percent compaction using any combination of segmented padfoot, vibratory padfoot, rubber-tired, vibratory single or double drum rollers
Compaction requirements for Pulverization, Mechanical and Bituminous stabilization are typically based on 95% of the maximum dry density determined in accordance with AASHTO T 180 or ASTM D1557, modified Proctor
The total time for mixing, placing and compacting FDR mixtures with cementitious stabilizing agents should be less than 2 hours
Compaction requirements for Cement stabilization are typically 95 to 98% of ASTM D588.
FDR stabilization with hydrated lime or LKD, the mix is usually allowed to mellow prior to compaction
For FDR stabilization with quicklime, the first and final mixing should not be performed on the same day. The mix is usually allowed to mellow for at least 12 hours prior to final mixing and compaction
Compaction requirements for Lime/LKD stabilization are typically based on standard Proctor, 95% of the maximum dry density
Check compaction with a nuclear gauge, sand cone or other approved method
Check cross-slope after final rolling
If the FDR surface must be opened to high traffic counts a curing membrane and blotter sand is recommended to protect the surface. Remove the blotter sand before appling a surface course.
Curing
Stabilized reclaimed materials need to be properly cured to achieve ultimate strength, prevent raveling and facilitate placement of the surface course
Minimize vehicular traffic on stabilized materials for 30 to 60 minutes
Limit truck traffic until the recycled material has cured sufficiently to support the anticipated traffic without damaging the reclaimed mixture
For chemical stabilizing agents either keep the surface moist or apply a curing membrane to allow proper hydration and strength gain of the materials, typically 2-7 days
Surface Course
A surface course is required over FDR materials
Prior to placing the subsequent course sweep the reclaimed mixture with a power broom. A fog or tack coat of emulsified asphalt may be required, depending on local practice.
Let's Connect
Get the latest in industry trends, research, success stories, and technical updates in a succinct e-newsletter.
PPRA Industry News Signup
Thank you!
Thank you for signing up for the PPRA mailing list!
If you created an account, you should receive an email shortly with more instructions to activate your account.