Cold In Place Recycling On Interstate Highways Lessons From The Nevada Golconda I 80 Project

Cold in-place recycling (CIR) has emerged as one of the most cost-effective methods for rehabilitating asphalt pavement. While many state departments of transportation have used CIR on lower-volume roads, applying the technique to high-traffic interstate highways presents different challenges. The Nevada Department of Transportation (NDOT) crossed this threshold when it executed its first interstate CIR project on Interstate 80 near Golconda Summit in Humboldt County. Understanding how NDOT planned and delivered this landmark project offers insights for construction professionals considering similar approaches. For a broader understanding of how projects progress from inception to completion, reviewing the Key Facts About Construction Project Life Cycle Phases In Life Cycle Of A Construction Project provides useful context for the stages involved in a rehabilitation effort of this scale.

Project Scope And Engineering Assessment

The Golconda I-80 CIR project represented a significant milestone for NDOT. The agency had been performing cold in-place recycling since the mid-1990s but exclusively on low-volume roads. The decision to apply CIR on an active interstate corridor was a deliberate step toward expanding the method’s application. The original article Nevada Golconda Cir Project A First explains how the project involved recycling three inches of the existing asphalt surface, then placing four inches of NDOT-specified plant-mix bituminous surface overlay followed by a three-quarter-inch open-graded wearing course.

Traffic Volume And Load Considerations

One of the primary concerns was the traffic volume on I-80. The Annual Average Daily Traffic (AADT) was 6,620 vehicles, with approximately 50 percent being heavy truck traffic. This combination created specific engineering requirements for the recycled pavement structure. Engineers calculated the 20-year Equivalent Single Axle Loads (ESALs) at 14,988,198. To protect the recycled mat under heavy truck traffic, NDOT imposed strict access restrictions.

• Public traffic was not allowed on the recycled surface for a minimum of three days after placement
• Once the first two-inch lift of dense-graded hot mix was placed, traffic could travel on the surface for a maximum of 14 days before the second lift had to be placed
• The recycled mat had to be covered with new hot mix overlays before winter weather could cause damage

Topographical And Logistical Challenges

The project between mile posts 29.38 and 42.19 west of Elko presented a steep six percent grade over Golconda Summit. This gradient posed a challenge for the CIR train, a collection of heavy equipment that mills, screens, mixes, and places recycled material in a single pass. Normally, the recycling train operates downhill due to equipment weight. However, safety concerns led NDOT to require construction activities move with traffic flow, meaning uphill. As a contingency, a Caterpillar 988 front-end loader was attached to the front of the train and used multiple times to assist in pulling the equipment up the steepest portions of the grade.

Equipment Configuration

Execution Strategy And Construction Management

Effective project management was essential to completing the Golconda project within the tight weather window imposed by northern Nevada’s winter conditions. The strategy relied on careful coordination between the recycling subcontractor and the general paving contractor. The principles behind this approach align with Construction Project Scheduling Methods Tools And Best Practices For On Time Project Delivery, which outlines how phased scheduling drives successful outcomes.

Segment Phasing For Traffic Management

To minimize disruptions, the 13-mile project was divided into approximately six-mile segments in both eastbound and westbound directions. This allowed milling and paving to proceed simultaneously. Valentine Surfacing from Vancouver, Washington, performed the CIR work, milling 563,000 square yards at a depth of three inches across the entire project length.

The recycling process followed a specific sequence for each lane:

1. The inside 12-foot-wide travel lane and the inside 4-foot-wide shoulder were milled using the CMI Roto-Mill
2. Millings were conveyed to a screen and crusher that reduced all material to minus 1-1/4 inches
3. Processed millings were transferred to a pugmill where CMS-2S emulsion was added
4. The recycled asphalt was deposited in a windrow for laydown and compaction
5. The same process was repeated on the outside 12-foot travel lane and the 10-foot-wide outside shoulder

Lime Slurry Integration

NDOT specified the addition of lime slurry during the milling process. Chuck Valentine noted this requirement was unique to this project. The lime slurry acted as an anti-stripping agent to improve the bond between recycled asphalt and the new overlay, helped cure and strengthen the recycled material, and accelerated the emulsion setting process. Each CIR project has different requirements based on existing pavement composition, and the lime slurry addition was tailored to the material properties of the I-80 pavement.

Paving Operations And Quality Control

Frehner Construction, a Las Vegas-based paving contractor, managed the placement of both recycled cold mix and new hot mix overlays. The company established two dedicated paving crews to maintain the aggressive schedule. Understanding how these operations fit within the broader Construction Project Life Cycle Phases In Life Cycle Of A Construction Project helps illustrate where recycling and overlay work falls within the overall project timeline.

Cold Mix Placement And Compaction

According to Gary Isaman, Frehner’s Elko area manager, the main difference between placing cold mix and hot mix was the lag time between placement and compaction. The crew waited 30 to 45 minutes after the paver laid the cold mat before beginning the rolling pattern, allowing time for the lime to set the emulsion. Once compaction began, the team achieved 90 to 92 percent density using pneumatic rollers followed by a steel-drum roller.

Curing Time And Hot Mix Overlay

Project specifications required moisture content in the recycled mat to drop to 2 percent before placing the hot mix overlay. NDOT allowed up to 10 days for curing, but favorable weather meant the target was achieved in only three to five days. The hot mix crew then placed the first of two 2-1/2-inch mats of dense-graded asphalt. The new 5-inch overlay was covered with the three-quarter-inch open-graded wearing course.

Quality control was maintained through strict density and smoothness requirements:

• 92 percent density was required on the hot mix (Type 2C)
• Vibratory rolling was used only during re-roll of the cold mat before hot mix placement
• NDOT required a re-roll pass for additional compaction density
• The project achieved NDOT’s Type A smoothness specification, allowing no more than 5 inches of quarter-inch deviations per lane mile
• No grinding was needed to correct surface deviations

Performance Outcomes And Comparative Benefits

The Golconda project was completed in 140 working days against the 220 days allowed by NDOT. The project demonstrated that CIR could be successfully applied to high-traffic interstate corridors. The success has broader implications for infrastructure rehabilitation programs nationwide. Similar innovative approaches are emerging in other regions, as seen with the Cumulus Unveils First Major Tourism Project In South Australia, where new construction methods are being deployed on large-scale projects.

Cost Comparison With Conventional Rehabilitation

The CIR process delivered significant savings compared to Nevada’s conventional Road Bed Modification (RBM) method, which involved pulverizing 8 to 10 inches of road surface, adding 2 percent cement slurry for stabilization, and placing a 4-inch hot mix overlay. Once NDOT began using CIR, the agency realized substantial cost benefits through the number of lane miles it could rehabilitate with the same budget.

System-Wide Quality Improvements

The impact of adopting CIR extended beyond individual project savings. Nevada’s road quality rating improved from 30th in the nation to 4th during the period the state has been using CIR as a standard method. Most states using CIR report a service life of 7 to 8 years up to 12 to 15 years. Nevada’s pavement management analysis indicated that CIR delivers 10 to 12 years of additional service life. Valentine noted that as emulsion technology improves, CIR is producing performance characteristics increasingly similar to traditional hot mix asphalt.

Evolution Of Traffic Restrictions

An important outcome was the evolution of NDOT’s approach to traffic management. Initially, the agency imposed strict restrictions to protect the recycled mat. However, as the project progressed, Valentine Surfacing demonstrated that the recycled mat could handle traffic without damage before the new asphalt was placed. This finding has implications for future interstate CIR projects, potentially reducing traffic disruption duration and making the method more attractive for busy corridors.

Summary And Key Takeaways

The Nevada Golconda I-80 project established that cold in-place recycling can be successfully applied to interstate highways carrying heavy truck traffic across challenging terrain. The project’s completion 80 working days ahead of schedule, combined with demonstrated cost savings and improved statewide road quality ratings, makes a strong case for wider adoption of CIR in highway rehabilitation. For construction professionals looking to replicate this success, the core principles include thorough traffic analysis, appropriate equipment configuration, careful coordination between recycling and paving crews, and understanding that initial conservative restrictions can often be relaxed as experience accumulates. The practices demonstrated on this project align with what 5 Habits Of Successful Construction Project Managers Essential Practices For Project Delivery identifies as key factors in delivering complex infrastructure projects on time and within budget.