The pavement preservation industry continues to evolve as contractors and state Departments of Transportation seek more efficient methods for road rehabilitation. One approach that has gained significant traction is the use of Cold In-Place Recycling equipment to perform Full-Depth Reclamation, often with Portland cement stabilization. This method combines the efficiency of modern milling technology with the structural benefits of cement treated bases, allowing crews to address the full pavement section in a single pass. For contractors looking to expand their pavement rehabilitation capabilities or DOT specifiers evaluating alternative reconstruction methods, understanding how Cold In-Place Recycling integrates with full depth reclamation is essential.
This technique has been deployed across multiple municipalities and states, demonstrating measurable savings in material costs, project timelines, and environmental impact. By utilizing 100 percent of existing pavement materials, FDR with CIR equipment eliminates the need for virgin aggregate import and reduces truck traffic on surrounding roads. Below, we examine detailed case studies where this approach delivered outstanding results for agencies and contractors alike.
Understanding the CIR-FDR Process
Cold In-Place Recycling was originally developed for recycling the upper 3 to 4 inches of existing asphalt pavement. The process involves a milling machine that cuts and sizes the pavement, mixes it with stabilizing additives, and places the material back on the roadway in a single continuous train operation. When adapted for Full-Depth Reclamation, the depth of cut increases to 8 inches or more, and the stabilizing agent shifts from asphalt emulsions to hydraulic binders such as Portland cement. Full-Depth Reclamation has gained significant momentum as agencies recognize these structural and economic advantages.
The full depth reclamation train typically consists of several equipment components working in sequence:
- A cement spreader, often truck mounted or towed, that distributes dry Portland cement at a controlled rate ahead of the milling machine
- A down cutting milling machine that cuts to the specified depth, typically 6 to 8 inches, and mixes the milled material with cement in an enclosed chamber for complete hydration
- A water tanker that meters water into the cutting head at a computer controlled rate to achieve the optimum moisture content for cement hydration
- A bituminous paver that receives the mixed material via conveyor and places it back on the roadway at the required profile and grade
- Compaction equipment including vibratory rollers and pneumatic tire rollers to achieve target density
Why Portland Cement for FDR
Portland cement is the preferred additive when the existing base course lacks structural strength. Unlike asphalt emulsion recycling, which primarily addresses the asphalt layer, cement stabilization creates a cement treated base that increases the load bearing capacity of the entire pavement section. This makes it particularly suitable for roads with failed subgrade conditions or where traffic loads have exceeded the original design capacity.
The cement reacts with water and the fine particles in the milled material to form a durable, rigid layer. Typical application rates range from 35 to 40 pounds of Portland cement per square yard, depending on the target unconfined compressive strength and the properties of the existing materials.
Case Study: Limerick Township Industrial Park
Limerick Township, Pennsylvania, faced premature pavement failure in a growing industrial park. The original pavement structure consisted of 4 inches of asphalt on a thin aggregate base. Increased construction traffic from new developments was causing soft areas and distortion. The project had initially been scheduled for Cold In-Place Asphalt Recycling at a standard 4 inch depth.
The Challenge
Shortly after starting the CIR process, crews discovered that the pavement became wavy and distorted under compaction with vibratory rollers and pneumatic tire rollers. Cold In-Place Recycling alone could not correct the underlying pavement problems because the base was too weak to support anticipated traffic loads without full depth stabilization.
The Solution
The municipality and contractor decided to pivot to Full-Depth Reclamation using the same CIR equipment train, this time adding Portland cement at 35 pounds per square yard. The milling machine had no difficulty cutting to the full 8 inch depth despite the original pavement being only 4 inches of asphalt over thin aggregate. The enclosed cutting and mixing chamber of the CIR equipment ensured complete hydration of the Portland cement, with no dry cement left behind.
| Parameter | Value |
|---|---|
| Total depth of treatment | 8 inches |
| Cement application rate | 35 lb/sq yd |
| Original pavement depth | 4 inches asphalt + thin aggregate base |
| Wearing course | 2.5 inches 19mm Super Pave HMA |
| Project outcome | No failures after 4 years of service |
The project was completed successfully despite late season weather. No mix design was performed due to the urgency of completing the work before winter. The industrial park continued to expand over subsequent years with no pavement failures reported.
Case Study: Delaware DOT on Wilgus Cemetery Road
In 2008, the Delaware Department of Transportation in Sussex County demonstrated how FDR with CIR equipment can create significant cost savings through operational efficiency. The department was already Cold In-Place Recycling several roadways under contract. An adjacent roadway, Wilgus Cemetery Road, was scheduled for Full Depth Reclamation under a separate contract with E.J. Breneman.
Because the CIR equipment was already on site with no additional mobilization required, the department decided to use the existing CIR train to perform the FDR work as a pilot project. The roadway served residential and agricultural traffic with several layers of oil and chip seal on top of a thin hot mix asphalt layer, underlain by a sand subbase.
The equipment configuration included a tractor pulling a Stolfus spreader that laid Portland cement at approximately 40 pounds per square yard ahead of the CIR train. The train consisted of a water tanker pushed by a Caterpillar 750C milling machine with a down cutting mandrel, which produced consistent material sizing by chipping the surface with pressure applied from above. The enclosed mixing chamber ensured complete hydration with no dry cement remaining.
A Caterpillar 1050B bituminous paver received the material via a two stage conveyor and placed it at the required grade. The down cutting configuration was essential for controlling material sizing; an up cut mill would have produced oversized material requiring a secondary crusher. After placement and compaction, a 2 inch overlay of 12.5mm Super Pave asphalt was applied as the wearing surface.
Case Study: West Norriton Township Industrial Corridor
West Norriton Township in Montgomery County, Pennsylvania, had two major industrial parks that had received little maintenance over the preceding 25 years. The pavement was severely deteriorated with 2 to 3 inches of oxidized, cracked, and potholed hot mix asphalt on top of a failed pozzolan base course. The sites served heavy truck traffic, multiple shift operations, and a large child care facility, creating complex logistical constraints.
The in-line FDR train operation was the only viable approach given the traffic volume and the need to keep employee access open. The contractor used a Wirtgen WR 2500S to excavate along curb lines at a distance of 4 feet from the curb face to maintain curb reveal. The Boulevard of the Generals had only one entrance and exit, making daytime construction impossible, so night operations were scheduled.
A working mix design was developed and verified through field sampling. Samples were tested for moisture content and density after compaction, and laboratory plugs confirmed unconfined compressive strength. After a prime coat was applied to control the cure rate and minimize airborne dust from the cement treated base, Glasgow Inc. placed a 3 inch 19mm Super Pave wearing course.
Best Practices for Contractors
Based on the lessons learned from these case studies, contractors considering FDR with CIR equipment should follow several critical guidelines to ensure project success and maximize return on their pavement preservation equipment investment.
Preliminary Testing and Design
A certified geotechnical engineering company, independent from the construction contractor, should complete the mix design and conduct all on site testing. Preliminary testing establishes design criteria for:
- Gradation of the reclaimed material after milling
- Residual asphalt content in the existing pavement
- Optimum moisture content for cement hydration
- Target cement application rate
- Required unconfined compressive strength
Equipment and Depth Considerations
Not every CIR train is suitable for FDR work. Contractors must verify that their milling equipment can handle the increased depth of cut, typically 8 inches or more. Key equipment considerations include:
- Down cutting mills generally produce better material sizing than up cut mills for FDR applications
- On board computer controls for water metering are essential to achieve proper cement hydration
- The paver screed must be adjustable to handle the full depth reclaimed material profile
- Beyond 8 inches compacted depth, the paver has difficulty handling material in the hopper and through the screed
Utility Conflicts and Metropolitan Constraints
The 8 inch cut creates challenges around utilities. Manholes, valve boxes, and other utility monuments must be raised or lowered before the FDR pass, with steel plates placed over open holes before the train passes. In metropolitan areas with dense utility networks, the standard CIR equipment recycling only 3 to 4 inches may be more appropriate than deeper FDR passes. Contractors should evaluate utility density during the preliminary site assessment.
Conclusion
The use of Cold In-Place Recycling equipment trains for Full-Depth Reclamation represents a powerful option in the pavement preservation toolkit. As demonstrated by the projects in Limerick Township, Delaware DOT Sussex County, and West Norriton Township, this method can address failing pavement sections, utilize 100 percent of existing materials, and deliver cost effective rehabilitation that meets structural demands. As modern pavement rehabilitation equipment trains continue to evolve, contractors who invest in understanding the equipment requirements, mix design protocols, and operational constraints of FDR with CIR equipment will be well positioned to serve the growing market for sustainable pavement reconstruction.