As state transportation budgets tighten and aging roadway networks demand ever more attention, pavement preservation techniques that stretch every dollar have become essential. Among the most effective methods is cold in-place recycling (CIR), a rehabilitation strategy that reuses existing pavement materials directly on site. West Virginia recently became the latest state to deploy this approach, completing its first CIR roadway on Monogalia CR 53/Fort Martin Road near Morgantown. The project demonstrates how Crushed Concrete Aggregates Properties and Uses of Recycled aggregates and recycling technologies can extend road life while reducing material costs and environmental impact.
West Virginia’s Division of Highways (WVDOH) maintains over 36,000 center-line miles of roadway, the sixth largest state-maintained system in the country. With reduced gas tax revenue and other funding sources falling short, the state has had to make its roads last longer with fewer maintenance repairs. This article examines the CIR process as applied on Fort Martin Road, the equipment and techniques involved, the quality control measures employed, and the broader implications for roadway preservation programs nationwide.
Understanding Cold In-Place Recycling: Process and Principles
What Is Cold In-Place Recycling?
Cold in-place recycling is an asphalt pavement rehabilitation technique that reuses existing pavement materials without the application of heat. The process involves milling the existing asphalt surface, sizing the material, mixing it with bituminous and chemical additives, and placing it as a restored pavement layer. All work is completed in-line and directly on the pavement being processed.
Unlike traditional hot mix asphalt rehabilitation, which requires hauling old material away and bringing new material in, CIR processes everything on site. This eliminates multiple truck trips, reduces fuel consumption, and preserves the existing aggregate base that has already proven its performance over years of service.
Why West Virginia Chose CIR
The WVDOH consulted with professional associations, highway industry groups, Pavement Preservation experts, and academia before adopting CIR. The state visited ongoing projects in other states and consulted with experienced practitioners. According to Thomas J. Medvick, PE, pavement engineer with WVDOH, the state’s system includes a very large mileage of two-lane secondary roads where money is stretched thin. These roads exhibit pavement distress patterns well suited to CIR treatment.
Project Site: Fort Martin Road
The project was constructed on Monogalia CR 53, a two-lane, 22-foot-wide coal haul roadway just north of Morgantown. The road carries average daily traffic of 2,200 vehicles with 35 percent truck traffic from multiple coal breakers along the route. The roadway sits wedged between the Monongahela River and the Norfolk-Southern Railroad, a constrained corridor that made traditional reconstruction challenging.
The existing pavement was oxidized and suffered from years of heavy loadings. Large cracks, potholes, and delaminating of the asphalt layers were evident throughout the section. A new pavement section was designed with an 18-year service life based on approximately 9 million equivalent single axle loads, calling for recycling of 6 inches of asphalt with a dual additive system of asphalt emulsion and Portland cement.
Equipment and Materials in the CIR Train
The Single-Unit Train Configuration
The CIR operation used a single-unit train with three main components working in sequence:
- Asphalt emulsion tanker: A 5,000-gallon tank built by E.D. Etnyer and Company to E.J. Breneman’s specifications. The emulsified asphalt used was CSS-1h.
- Milling machine: Connected to the tanker with a cutting mandrill available in 10.5-, 11.0-, or 12.0-foot widths. The mill uses a down-cutting action to size material to 1.5 inches minus.
- Bituminous paver: Fitted with a 40-foot leveling ski with no contact with the roadway surface. The ski is controlled by sonic pulses from four units attached to the beam.
Dual Additive System
The mix design specified a dual additive approach combining emulsified asphalt and Portland cement, developed by Ergon Asphalt and Emulsions Inc. Portland cement was laid dry onto the roadway surface ahead of the train at a distance of approximately 100 feet using a Stoltz Manufacturing dry additive spreader with full-length skirting to prevent the lightweight cement from becoming airborne. Operators may need to stop if wind speeds exceed 10 mph. The cement is applied at a rate of 12 to 15 pounds (1.5 percent) per square yard.
Key project parameters included:
| Parameter | Value | Notes |
|---|---|---|
| Portland cement rate | 12-15 lb/sq yd | Approximately 1.5% by weight |
| Emulsified asphalt type | CSS-1h | Slow-setting grade |
| Milled material size | 1.5 inches minus | Controlled by forward speed |
| Cutting head widths | 10.5, 11.0, 12.0 ft | Selected by roadway width |
| CIR design depth | 6 inches | Full depth recycling |
| Design life | 18 years | Based on 9 million ESALs |
Material Processing Flow
The material processing follows a specific sequence:
- The milling machine picks up existing pavement and dry Portland cement spread ahead.
- Emulsified asphalt is metered into the mixing chamber with cement and milled material.
- Water is added, and components are mixed into a homogeneous blend.
- Mixed material moves to the throw area and onto a first-stage conveyor.
- The conveyor transfers material to a second-stage conveyor feeding the paver.
- The paver’s insert bin distributes material to augers and screed for placement.
Quality Control and Construction Practices
Daily Equipment Calibration
Each day before work begins, equipment is calibrated to ensure accurate application rates. A one-square-yard tarp is placed on the roadway surface. The application truck drives over the tarp at a specific gear and speed, depositing cement onto it. The tarp is then lifted and weighed. Based on the weight, gear and speed adjustments are made until the correct pounds per square yard are achieved.
Compaction Procedures
Once the CIR material is laid, compaction begins under a nuclear gauge operator’s guidance using two roller types:
- Steel wheel vibratory roller: An 11- to 13-ton unit used as the initial breakdown roller. Most density requirements are obtained during this first pass.
- Pneumatic-tired roller: A 22.5-ton unit that rolls the entire mat from shoulder edge to pavement edge, leaving no area untouched.
After compaction, the roadway received a prime coat of 50/50 emulsified asphalt and water sprayed through a distributor truck. The prime coat dries in approximately 15 minutes, and traffic was maintained in one lane while the adjacent lane was sprayed.
Traffic Management
Throughout construction, traffic traveled along Fort Martin Road under traffic control direction. A pilot car was used where the road narrowed to 18 feet. At no time were motorists kept waiting more than three or four minutes. This minimal disruption is a significant advantage of CIR compared to full reconstruction, which typically requires extended road closures.
Drainage Preparations
Mountaineer Construction placed dozens of new catch basins with pipes under the roadway to channel stormwater away from the shoulders. Trenches were backfilled with concrete two feet thick and 24 inches wide. Because of the number of drainage trenches, a decision was made to cut through them at the same depth as the CIR operation rather than constructing separate transitions. The down-cutting mill sliced through the concrete-filled trenches with ease.
Performance, Outcomes, and Future Applications
Overlay and Wearing Surface Design
After the CIR base was compacted, a new 3-inch Marshall hot mix asphalt (HMA) binder base course was placed, followed by a Marshall HMA wearing surface with PG 76-22 binder compacted to 2 inches. The heavy hot mix asphalt lift was specified because of the volume of loaded coal trailers and tri-axle trucks hauling along Fort Martin Road.
Project Results
WVDOH considers the project a resounding success. More than 12 months after completion, the road performed outstandingly with no signs of premature distress. District Four in Clarksburg was very pleased, and three more CIR contracts were let or advertised in that district. One was completed within weeks of the Fort Martin project, with two additional CIR projects planned for 2014 elsewhere in the state.
Ongoing Research and Benefits
The Fort Martin Road project has been selected for NCHRP Project 9-51, a study to develop pavement design inputs for CIR conducted by the University of Maryland, VDOT, Colas Solutions, and Wirtgen. Cores from CR 53 were obtained for developing standard design methodologies that will help agencies nationwide adopt CIR with greater confidence.
The environmental and economic benefits are substantial. Reusing existing aggregates conserves natural resources and reduces dependency on virgin materials. Eliminating heating reduces fuel consumption and greenhouse gas emissions. Fewer truck trips mean less traffic disruption and reduced wear on adjacent roads. For agencies maintaining vast networks on limited budgets, every mile treated with CIR instead of traditional reconstruction represents significant savings.
As more states incorporate CIR into their pavement preservation toolboxes, the performance data grows, making it easier for engineers to specify the technique with predictable results. For states facing the same challenges that prompted West Virginia to pursue Concrete Sustainability and Green Building Practices Low Carbon approaches in roadway construction, CIR offers a proven path. The engineering expertise applied on projects like Fort Martin Road depends on qualified professionals; those pursuing careers in this field can learn about How to Become a Professional Engineer in Virginia 2 or explore How to Become a Licensed Land Surveyor in Virginia State 2 for related career paths in transportation infrastructure.