Mill and Fill Asphalt Pavement Rehabilitation: Lessons from the Wisconsin Hwy 45 Project

The mill and fill method stands as one of the most effective pavement rehabilitation techniques for restoring distressed asphalt surfaces. When Northeast Asphalt Inc. of Greenville, Wisconsin, took on the challenge of repairing a 15.25-mile stretch of US Hwy 45 from Eagle River to Land O’ Lakes in 2009, they demonstrated how proper planning, equipment selection, and safety protocols can deliver exceptional results. This project, funded through the American Recovery and Reinvestment Act, provided employment for 70 company workers and 13 subcontracting firms while rehabilitating a vital tourist corridor connecting northern Wisconsin to Michigan. For contractors and paving professionals seeking to understand the nuances of mill and fill operations, the Wisconsin Hwy 45 project offers valuable insights into every phase of the process. Before delving into the technical details, it is worth reviewing Asphalt Safety Comprehensive Guide to Hazard Management in hot mix asphalt operations, as worker protection remains paramount on any paving project.

Project Planning and Pavement Assessment for Mill and Fill Operations

Before any milling equipment mobilizes to a job site, thorough pavement assessment and project planning determine the success of a mill and fill rehabilitation. The Wisconsin Hwy 45 project began with a clear understanding of the pavement’s condition and the specific challenges that needed addressing.

Pavement Distress Evaluation

The existing surface on US Hwy 45 was suffering from two primary forms of deterioration that made mill and fill the appropriate rehabilitation choice:

• Distressed cracking caused by repeated traffic loading and environmental exposure over the pavement’s service life
• Cold temperature cracking resulting from the freeze-thaw cycles typical of northern Wisconsin winters

These conditions made the road unsafe for the high volume of tourist traffic it carried between Wisconsin and Michigan. A simple surface treatment would not suffice, as the structural integrity of the upper pavement layers had been compromised. Full-depth removal would have been excessive and cost-prohibitive, making mill and fill the optimal middle-ground solution.

Funding and Economic Impact

The American Recovery and Reinvestment Act (ARRA) provided the financial backing for this infrastructure project. The economic benefits extended well beyond road improvement:

• 70 direct jobs for Northeast Asphalt employees
• Additional employment across 13 subcontracting companies
• Local material procurement including aggregates and binder supplies
• Economic stimulus for the Eagle River and Land O’ Lakes communities through improved transportation infrastructure

John Bartoszek, regional manager with Northeast Asphalt, noted that the project provided meaningful work during a period when construction employment was under pressure. Understanding the relationship between Asphalt Plants and Pavement Construction Equipment a Complete overview of hot mix asphalt production helps contractors appreciate how material availability and plant logistics influence project scheduling.

Timeline Constraints and Seasonal Considerations

Construction began in August 2009, timed specifically after the peak tourist season had ended. This strategic scheduling minimized disruption to travelers and local businesses that depend on summer tourism. The project was completed by October 2009, working within a narrow weather window before winter conditions made asphalt paving impractical in Wisconsin.

Construction Methodology and Equipment Deployment

The execution phase of the Wisconsin Hwy 45 project showcased coordinated equipment deployment and adaptive construction methods that maximized productivity while maintaining quality standards.

Milling Operations

Northeast Asphalt employed two Wirtgen 2200 milling machines equipped with an 8-foot, 3-inch cutting width. The milling strategy involved working one lane at a time, removing 4 inches of existing asphalt pavement. Over the course of the project, crews milled more than 269,000 square yards of asphalt material.

The daily production rate reached 1.5 miles per day, demonstrating the efficiency of paired milling operations. This pace allowed the project to stay on schedule within the two-month construction window.

Paving Operations and Equipment

The paving train on US Hwy 45 consisted of several key pieces of equipment working in sequence:

The paver used automation with a dual-grade Blaw Control system featuring a 50-foot ski on the centerline and a pan-style ski reference on the outside mat. This automated grade control ensured consistent mat thickness across the entire paving width.

Mix Design and Material Specifications

The project used Superpave E3 Hot Mix Asphalt placed in two lifts:

• Lower lift: 3 inches thick at 19 millimeter nominal maximum aggregate size
• Upper lift: 2 inches thick at 12.5 millimeter nominal maximum aggregate size

The total material requirement exceeded 77,000 tons of HMA. The mix incorporated 12 percent Reclaimed Asphalt Pavement (RAP) and used a Performance Grade 58-28 binder. Virgin aggregate consisted of crushed gravel combined with natural sand. The use of RAP demonstrates how mill and fill operations support sustainable construction practices by reusing existing pavement materials in the new surface layer. For a deeper look at pavement materials and their properties, refer to Asphalt Bitumen Tar for the distinctions between these commonly confused materials.

Safety Innovations and Traffic Management During Construction

Safety was a paramount concern on the Wisconsin Hwy 45 project, both for the traveling public and for construction crews working in an active traffic zone. The project team implemented several innovative approaches that made the work zone safer than the original design would have allowed.

Revised Construction Sequence for Safety

The original project plan called for milling 4 inches of asphalt across the full width and then placing traffic barrels at the centerline to keep vehicles confined to each lane. This approach would have created a 4-inch elevation difference between northbound and southbound lanes, making safe passing impossible along the entire 15.25-mile work zone.

Northeast Asphalt proposed a safer alternative: pave directly behind the milling operation in the same lane. This method provided several advantages:

• Reduced the centerline elevation difference between adjacent lanes
• Eliminated the need for thousands of traffic barrels along the corridor
• Maintained better traffic flow with minimal disruption to travelers
• Generated cost savings by removing barrel rental and handling expenses
• Allowed safe passing opportunities within the construction zone when possible

This adaptive approach required close coordination with the Wisconsin Department of Transportation to revise the traffic control plan mid-project.

Intersection Safety Enhancements

Beyond the pavement rehabilitation itself, the project included permanent safety upgrades at five intersections along the highway. Each intersection received a dedicated acceleration lane and deceleration lane. These improvements addressed a long-standing safety concern for a road that carries high tourist traffic volumes but was originally designed to a lower standard.

Work Zone Safety Record

The project was completed without any reported safety incidents in the work zone. This achievement reflects the effectiveness of the revised traffic management plan and the professionalism of the crews. Understanding the fundamentals of safe asphalt operations is essential for any paving contractor, and reviewing Asphalt Pavements Types helps operators understand how different pavement structures respond to traffic loads and environmental conditions.

Quality Control, Incentive Achievement, and Best Practices

The Wisconsin Hwy 45 project stands out not only for its efficient execution but also for the quality metrics achieved. Northeast Asphalt earned both ride incentives and density incentives, demonstrating that proper technique and attention to detail pay measurable dividends.

Ride Quality: International Roughness Index Performance

The International Roughness Index (IRI) measures pavement smoothness in inches per mile, with lower values indicating a smoother ride. Northeast Asphalt achieved an IRI of 32.0 in the northbound lane and 31.2 in the southbound lane, both of which qualified for ride incentives. Several factors contributed to these results:

1. Uniform milling: Crews paid close attention to ensuring the existing asphalt was milled evenly and uniformly across the entire 15.25-mile stretch. An uneven milled surface cannot produce a smooth final pavement regardless of paving technique.
2. RAP size control: A nugget cruncher was used to control oversized RAP material before it entered the plant. Oversized RAP particles in the mix can create surface imperfections and compromise ride quality.
3. Continuous paving: The RoadTec 2500 Shuttle Buggy delivered mix to the paver continuously, eliminating the starts and stops that would occur with truck-only delivery. Each stop and start creates a potential joint or density variation in the mat.
4. Experienced roller operators: Skilled operators avoided creating roller bumps, which are localized surface deformations caused by improper rolling patterns or stopping on the mat.

Density Achievement

The project specification required 91.5 percent density for both the lower and upper lifts. Northeast Asphalt averaged above 93 percent density across the project, exceeding the requirement and earning density incentives. Achieving high density is critical for pavement durability because it reduces permeability to water and air, extends fatigue life, and resists rutting under traffic loads.

Key Takeaways for Paving Professionals

The Wisconsin Hwy 45 project offers several lessons that apply to mill and fill operations of any scale:

• Milling quality determines paving quality. Invest in well-maintained milling equipment and experienced milling operators. An uneven milled surface cannot be corrected during paving.
• Continuous paver movement improves ride quality. Use material transfer vehicles to keep the paver moving steadily rather than cycling between stops and starts as trucks exchange.
• Consider safety alternatives to standard traffic control. Revising the construction sequence to pave behind the mill reduced hazards and costs simultaneously.
• RAP management matters at every stage. From milling to crushing to plant blending, controlling RAP particle size directly affects mix quality and final pavement performance.
• Roller training is worth the investment. Experienced operators who understand rolling patterns, vibration settings, and temperature windows produce smoother, denser pavement.

The successful completion of this project without safety incidents, on schedule, and with both ride and density incentives demonstrates that mill and fill rehabilitation, when executed with proper planning and skilled crews, delivers excellent value for both contractors and the traveling public.