Cold in-place recycling (CIR) has become one of the most economical and environmentally responsible techniques for rehabilitating distressed asphalt pavements across the United States. By reusing existing materials on site without heat, CIR offers significant cost savings, reduced traffic disruption, and a smaller carbon footprint compared to traditional reconstruction. As more agencies pursue sustainable pavement solutions, understanding how CIR performs under diverse conditions is essential. This article examines four projects from California to Virginia, highlighting the methods, equipment, and outcomes that define this technology. For a closer look at how Cold in Place Asphalt Recycling in Dense Urban settings addresses unique space and traffic constraints, see the related study on Beverly Hills road repair strategies.
What Is Cold In-Place Asphalt Recycling?
CIR processes existing asphalt pavement with bituminous or chemical additives without heat to produce a restored pavement layer. All work is completed on site, making it far less disruptive than removal-and-replacement methods. The process mills the existing pavement to a specified depth, screens and sizes the material, mixes it with a binding agent, and places it back as a new base layer. Because hauling of materials is eliminated, CIR also reduces truck traffic, fuel consumption, and emissions substantially.
Key Advantages of CIR
- Cost efficiency: Savings of 20 to 40 percent versus traditional mill-and-fill operations because the same material is reused in place.
- Speed of construction: A full lane can be recycled, graded, and compacted in a single day, minimizing road closure time.
- Reduced environmental impact: No hot-mix production eliminates stack emissions and cuts fossil fuel consumption by eliminating aggregate hauling and heating.
- Traffic accommodation: Work is typically completed one lane at a time, allowing adjacent lanes to remain open throughout construction.
- Structural improvement: CIR addresses deep-seated distresses like alligator cracking and base failures that surface treatments cannot reach.
Binding Agents in CIR
CIR projects rely on one of two primary binding agents. Foamed bitumen is produced by injecting hot bitumen with cold water, causing it to expand and coat aggregate particles evenly. Asphalt emulsion uses emulsified asphalt dispersed in water. The choice depends on the existing pavement gradation, moisture conditions, and contractor preference. Foamed bitumen was used on three of the four projects profiled below.
Redmond Avenue, San Jose, California
Redmond Avenue in San Jose carries a heavy mix of cars, buses, vans, and delivery trucks. The existing pavement had deteriorated to the point where structural rehabilitation was necessary, and the city selected CIR specifically to minimize disruption. The contractor deployed a Wirtgen 3800 CR with integrated Vogele screed and a 12.5-foot recycling width. Before recycling, 1 percent cement was pre-spread over the pavement to improve moisture sensitivity and stiffness of the recycled mix.
Two-Pass Recycling Strategy
This project required a two-pass approach because the finished width of 13.5 feet exceeded the standard cutter width of 12.5 feet. The sequence proceeded as follows:
- First pass: The 3800 CR recycled the pavement to a depth of 4 inches while adding 2.2 percent foamed bitumen. The recycled material was paved directly behind the recycler using the integrated screed. Finish compaction was achieved with Hamm rollers.
- Second pass: A Wirtgen W 150 pre-milled a section ahead of the CR and windrowed the milled material between the front tracks. This additional material entered the mixing chamber alongside the material cut by the CR, providing enough volume to pave the full 13.5-foot width. The on-board mixing computer was adjusted to maintain the specified additive proportions.
| Parameter | Value |
|---|---|
| Recycling width | 12.5 ft |
| Recycling depth | 4 in |
| Cement content | 1.0% |
| Foamed bitumen | 2.2% |
| Production rate | >400 tph |
The cement pre-treatment and foamed bitumen combination produced a structurally sound base layer suited for heavy traffic. For another California application with different geographic challenges, see Cold in Place Asphalt Recycling On Californias I in the Sierra Nevada region.
Highway 15, Mason County, Illinois
Highway 15 in Mason County was over 40 years old and exhibited extensive alligator cracking, cold-mix patching from previous repairs, and transverse cracking that had degraded driving conditions. The county bid documents specified CIR as the designated rehabilitation method. The emulsion supplier carried out the mix design and pavement investigation.
Variable Depth Design
The project was divided into two sections based on pavement condition: the first 2 miles at a recycling depth of 3 inches, and the remaining 6 miles at 4 inches. Emulsion content ranged from 2.25 to 3.75 percent depending on the coarse-to-medium gradation encountered. The 3800 CR pushed the bitumen tanker while milling the existing pavement, adding emulsion proportional to its working speed and metered amounts of compaction moisture for varying in-situ conditions.
| Parameter | Value |
|---|---|
| Recycling width | 12.5 ft |
| Recycling depth | 3-4 in |
| Emulsion content | 2.25-3.75% |
| Total area | 93,646 sq m |
| Production rate | 410 tph |
The 3800 CR paved the recycled material immediately using its integrated Vogele AB425T screed. No windrowing, pick-up machine, or additional paver was required. Compaction followed directly behind the screed with a Hamm HD 120 roller. For a broader overview of recycling technologies, see Asphalt Pavement Recycling Technologies Methods and Sustainable Practices.
Route 17, Hampton, Virginia
Route 17 in Hampton carries approximately 15,000 vehicles per day with 3 percent truck traffic. The pavement surface had developed extensive patching along with transverse and longitudinal cracks throughout the structure. The rehabilitation method chosen was CIR with foamed bitumen as the binding agent. A Wirtgen WLB 10 S foam laboratory delivered the mix design and pavement investigation.
Three-Machine Train for Maximum Flexibility
This project used a three-machine configuration that separated milling and paving functions:
- A Wirtgen W 2000 milling machine pre-milled the existing asphalt pavement to a depth of 2 inches, removing the most distressed surface layer.
- The 3800 CR Rear Load then recycled the remaining pavement to a depth of 5 inches in a single pass. Preceding tanker trucks delivered hot bitumen and water via hose connections. The milling and mixing rotor simultaneously incorporated foamed bitumen and water into the granulated material.
- A Vogele Super 2100-2 paver placed the recycled material to the specified grade. Hamm HD 120 and HD 130 rollers completed compaction immediately behind the paver.
The separate paver gave the crew superior control over ride quality and grade compared to an integrated screed. Down-cutting recycling produced a high-quality bituminous base layer without needing a crushing or screening plant.
| Parameter | Value |
|---|---|
| Recycling width | 12.5 ft |
| Recycling depth | 5 in |
| Cement content | 1.0% |
| Foamed bitumen | 2.2% |
| Working speed | 28 ft/min |
| Production rate | 520 tph |
The Route 17 project achieved the highest production rate among the four case studies, demonstrating that CIR with a separate paver can deliver both quality and throughput on high-traffic arterial roads.
Baileysville Road, Freeport, Illinois
Baileysville Road in Freeport is a highly trafficked business road serving local commerce. The pavement showed extensive alligator cracking, longitudinal cracking, and unstable shoulder widths that made maintenance difficult using conventional patching. CIR with foamed bitumen was selected to address the structural deficiencies.
The 3800 CR stabilized the pavement to a depth of 4 inches in a single pass across the full traffic lane width, adding 2.5 percent foamed bitumen and 1.5 percent water. The recycler then loaded the recycled material into the receiving hopper of a Vogele paver working behind it. Final compaction was achieved with Hamm rollers. Traffic was guided past the construction site on the adjacent lane, maintaining business access throughout.
| Parameter | Value |
|---|---|
| Recycling width | 12.5 ft |
| Recycling depth | 4 in |
| Foamed bitumen | 2.5% |
| Added water | 1.5% |
| Working speed | 22 ft/min |
Practical Lessons from the Project
- Shoulder condition matters: Unstable shoulders complicate lane transitions. Stabilization should be addressed before or during CIR work to avoid edge failures.
- Water control is critical: The 1.5 percent added water combined with existing pavement moisture must be carefully managed to achieve optimal compaction density.
- Separate paver advantage: Using a dedicated paver behind the CR gave the crew more control over grade and smoothness on a road with uneven cross-slopes.
- Traffic management: Guiding traffic on the adjacent lane requires clear signage and reduced speed zones, but the shorter duration of CIR work reduces the overall disruption period.
For safety guidance on working with hot bitumen and recycling equipment, see Asphalt Safety Comprehensive Guide to Hazard Management in Hot Mix Asphalt Operations.
Key Takeaways and Comparative Analysis
| Location | Agent | Depth | Rate | Notable Feature |
|---|---|---|---|---|
| San Jose, CA | Foamed bit. | 4 in | >400 tph | Two-pass width extension |
| Mason Cty, IL | Emulsion | 3-4 in | 410 tph | Variable depth, 8 miles |
| Hampton, VA | Foamed bit. | 5 in | 520 tph | Three-machine train |
| Freeport, IL | Foamed bit. | 4 in | N/A | Single-pass, separate paver |
Best Practices Summary
- Invest in thorough mix design before any work begins. Every project profiled here began with a detailed investigation. Skipping this step is the most common cause of CIR failures.
- Match the equipment train to the project. Integrated screeds offer simplicity and speed while separate pavers provide superior smoothness and grade control.
- Plan for width transitions. The San Jose project demonstrated that wider sections can be accommodated with pre-milling and controlled windrowing.
- Account for pavement variability. Real-time adjustment of depth, additive content, and moisture is essential on aged, heterogeneous pavements.
- Compact immediately after placement. Delayed compaction reduces density and compromises long-term pavement performance.
Cold in-place recycling has proven effective across diverse traffic levels, pavement conditions, and geographic settings in the United States. The common thread across these four projects is the combination of specialized equipment, rigorous mix design, and experienced crews working in close coordination. As more transportation agencies adopt sustainability goals and seek cost-effective alternatives to reconstruction, CIR is positioned to play an expanding role in the national pavement rehabilitation toolkit.