Cold in-place asphalt recycling (CIR) has emerged as one of the most efficient and cost-effective methods for rehabilitating deteriorated asphalt pavements in urban environments. Unlike traditional mill-and-fill approaches that require hauling old material to a plant and bringing new mix back to the site, CIR processes the existing pavement right on the job, turning the milled asphalt into a structurally sound base course for the new surface. Municipalities and contractors alike are increasingly turning to this method to reduce project costs, shorten construction timelines, and minimize disruption to the traveling public. The 2010 Beverly Hills CIR project, which rehabilitated 1.3 million square feet of roadway in just eight days, stands as a compelling example of what this technology can achieve in a dense urban setting. For additional context on how CIR has been applied in different regions, see Cold in Place Asphalt Recycling Around the U.
Understanding Cold In-Place Asphalt Recycling Equipment and the CIR Train
Cold in-place asphalt recycling relies on a carefully coordinated sequence of specialized equipment operating as a single processing train. This train moves forward in a continuous operation, milling the existing pavement, processing the reclaimed material, adding binding agents, and placing the recycled mix as a new base course. Understanding each component of this train is essential for contractors and agencies evaluating CIR for their pavement preservation programs.
The Cold Planing Milling Machine
The first and most visible element of the CIR train is the cold planing milling machine. On the Beverly Hills project, Pavement Recycling Systems used a 12.5-foot-wide milling machine that cut a 6-foot-wide pattern at a depth of 1.25 inches. The milling machine is responsible for removing the deteriorated surface layer and sizing the reclaimed asphalt pavement (RAP) into particles suitable for reprocessing. Key specifications to consider when selecting a milling machine for CIR include:
- Cutting drum width and pattern configuration, which determines production rate and surface texture
- Depth control accuracy, typically within one-quarter inch tolerance
- Conveyor system capacity for transferring millings to the recycling unit
- Ability to tow or push the downstream recycle plant as part of the train
The Portable Recycle Plant and Pug Mill
Behind the milling machine, a 100 percent closed-circuit portable recycle plant processes the milled material. The plant screens and crushes the RAP until it reaches the target maximum particle size, typically one inch. A weigh bridge on the plant measures the processed material before it enters the pug mill, ensuring accurate proportioning of the recycling agent. In the pug mill, the RAP is blended with an engineered emulsion that serves two critical functions:
- As a binder, the emulsion provides polymers that hold the recycled aggregate together, creating a cohesive base course
- As a rejuvenator, the emulsion softens the aged asphalt binder, restoring its flexibility and adhesion properties
On the Beverly Hills project, Pavement Recycling Systems used Western Emulsion’s engineered Pass-R emulsion. The precise formulation of the emulsion is tailored to the characteristics of the existing pavement, including the age and condition of the asphalt binder and the gradation of the aggregate.
Material Transfer and Paving
After the emulsion is thoroughly mixed in the pug mill, the recycled material is discharged below the unit and picked up by a material transfer vehicle. This vehicle delivers the blended RAP to the hopper of the paving unit, which forms the final element of the CIR train. The paver then places the recycled material as the new base course using standard asphalt paving techniques. This base course can be left as a riding surface for low-volume roads or, more commonly, overlaid with a hot mix asphalt wearing course to provide a durable, smooth driving surface. For more on how this equipment is configured in dense urban settings, refer to Cold in Place Asphalt Recycling in Dense Urban.
Project Logistics and Traffic Management for Urban CIR Operations
One of the greatest challenges in urban pavement rehabilitation is maintaining traffic flow during construction. The Beverly Hills CIR project demonstrates how careful planning can allow contractors to complete large-scale recycling operations with minimal disruption to motorists and businesses. The city required that one lane of traffic remain open in both directions at all times, and the project team developed a phased approach to meet this constraint.
Traffic Phasing and Lane Management
The roads scheduled for rehabilitation were between 50 and 60 feet wide, providing sufficient space for a lane-shifting strategy. The contractor opened the outside lanes to traffic while working on the inside lanes, then reversed the pattern to complete the outside lanes. This method allowed continuous two-way traffic throughout the project duration. Key traffic management considerations for urban CIR projects include:
- Coordination with local traffic authorities to establish lane closure schedules and detour routes
- Placement of signage and channelizing devices to guide motorists safely through the work zone
- Scheduling of the CIR train movements to minimize gaps between passes
- Maintenance of access to driveways and side streets for residents and businesses
- Communication with emergency services to ensure access is never blocked
Crew Size and Production Rates
Pavement Recycling Systems deployed a crew of 20 employees for the Beverly Hills project, handling both the milling and paving operations. The entire 1.3 million square foot project was completed in eight days, representing an average daily production rate of approximately 162,500 square feet. This production rate highlights the efficiency of the CIR process compared to conventional reconstruction methods, which would have required separate crews for demolition, hauling, base installation, and paving over a much longer period. For a broader look at how CIR production rates compare across different environments, see Cold in Place Asphalt Recycling On Californias I.
Environmental and Economic Benefits of Cold In-Place Asphalt Recycling
The decision to use CIR on the Beverly Hills project was based on a clear evaluation of its advantages over conventional mill-and-fill reconstruction. The project demonstrated measurable benefits in four key areas that are directly transferable to similar urban rehabilitation projects.
| Benefit Category | Measured Impact on Beverly Hills Project | How It Is Achieved |
|---|---|---|
| Carbon footprint reduction | 2,800 truck trips eliminated from roadways | Materials processed and placed on-site without hauling to plant |
| Construction time reduction | 33 percent faster than conventional methods | Simultaneous milling, recycling, and paving in single train operation |
| Surface quality improvement | Less loose gravel on roadway surface | CIR base is tighter and more stable than milled-only surface |
| Total project cost savings | 42 percent cost savings | Eliminated material transport, reduced equipment mobilization, shorter duration |
Sustainability and Carbon Footprint
By processing and placing the recycled pavement entirely on site, the CIR process eliminates the need to truck milled material to an off-site plant and bring virgin mix back to the project. On the Beverly Hills project alone, this eliminated an estimated 2,800 truck trips from local roadways. The reduction in heavy truck traffic not only lowered fuel consumption and emissions but also reduced wear and tear on the surrounding street network and improved safety for other road users. For agencies with sustainability goals, CIR offers a direct path to reducing the carbon footprint of pavement maintenance programs.
Cost Efficiency and Budget Predictability
James Emerson of Pavement Recycling Systems estimated the CIR process delivered a 42 percent cost savings for the Beverly Hills project compared to conventional mill and fill. The savings came from multiple sources:
- Elimination of material hauling costs, including trucking, fuel, and driver labor
- Reduced equipment mobilization, since the CIR train is a single integrated operation
- Shorter project duration, lowering traffic control, supervision, and overhead costs
- Elimination of virgin aggregate and asphalt binder for the base course layer
- Reduced landfilling or stockpiling costs for removed pavement material
These savings are particularly significant for municipalities with tight pavement maintenance budgets, as they allow agencies to rehabilitate more lane miles within the same annual funding allocation. For a detailed exploration of how CIR compares with other pavement recycling approaches, see Asphalt Pavement Recycling Technologies Methods and Sustainable Practices.
Quality Control, Testing, and Long-Term Performance of CIR Pavements
Ensuring that a cold in-place recycled pavement meets structural and performance specifications requires a robust quality control program. The Beverly Hills project incorporated third-party testing and verification throughout the construction process, establishing a model for quality assurance on future CIR projects.
Mix Design and Material Testing
Before production begins, a CIR mix design is developed based on samples of the existing pavement. The mix design determines the optimal emulsion type and content, the target gradation after processing, and the expected strength development of the recycled base. During production, quality control testing includes:
- Daily sampling of the recycled mix for gradation analysis to confirm the crushing and screening operation is producing the specified particle size distribution
- Emulsion content verification through extraction testing or flow meter calibration
- Moisture content testing to ensure the recycled material is within the optimal range for compaction
- In-place density testing using nuclear gauges or core sampling to verify compaction meets specifications
Third-Party Verification and Core Sampling
For the Beverly Hills project, Pavement Recycling Systems engaged an independent engineering firm to take core samples throughout the project. Core sampling serves several important functions in a CIR quality assurance program:
- It provides a direct measurement of the in-place thickness of the recycled layer
- It allows laboratory testing of the cured recycled material for strength and stiffness properties
- It documents the uniformity of the recycled layer across the project area
- It creates a permanent record of construction quality for the agency’s pavement management system
Performance Lifecycle and Future Recycling Potential
One of the most compelling features of the CIR process is that it preserves the ability to recycle the pavement again in the future. Unlike conventional reconstruction, which consumes the existing pavement material and replaces it with virgin materials, CIR maintains the pavement structure in a condition that can be recycled again at the end of its service life. Emerson noted that the ability to recycle asphalt every 20 years means a single pavement system does not have to have only one lifespan. This multicycle recycling potential makes CIR an investment in long-term pavement sustainability rather than a one-time repair.
Following the success of the initial project, the City of Beverly Hills indicated it was considering using the same CIR process to reconstruct an additional 28 streets. This follow-on work validates that CIR can deliver the structural performance, cost savings, and public acceptance that municipalities need for their long-term pavement programs. For contractors and agencies evaluating the method, the Beverly Hills project provides a well-documented reference point that demonstrates both the practical logistics of urban CIR and the measurable benefits that make it an attractive alternative to conventional mill-and-fill reconstruction.
Cold in-place asphalt recycling continues to gain adoption across the United States as agencies seek cost-effective, sustainable solutions for their pavement preservation needs. The combination of significant cost savings, reduced construction time, lower environmental impact, and the ability to recycle pavements repeatedly makes CIR a valuable tool in the pavement maintenance arsenal. As more projects demonstrate the reliability and performance of the process, CIR is positioned to become an increasingly standard approach for urban road rehabilitation.