Temperature uniformity across the asphalt mat is one of the most critical factors determining pavement longevity and ride quality. When hot mix asphalt cools unevenly before compaction, the resulting mat develops density variations, weak spots, and premature failure points that shorten service life. Contractors facing tight specifications from state departments of transportation are increasingly turning to advanced paver technology to solve this challenge at the source. One of the most effective innovations in this area is the remix paver system, which uses in-hopper augers to reblend material moments before it reaches the screed. This article examines how remix technology helps paving crews achieve uniform mat temperatures, eliminate visible shadows, and meet performance-based incentive targets. For a broader overview of equipment options, refer to Pavement Construction and Asphalt Equipment a Complete Guide, which covers the full range of machinery used in modern road building.
The Problem of Thermal Segregation in Asphalt Paving
Thermal segregation occurs when different portions of the asphalt mat cool at different rates before compaction. The result is a mat with inconsistent density, reduced structural integrity, and a shorter service life. While visible particle segregation, often called "shadowing," is the most obvious indicator, thermal segregation is frequently invisible to the naked eye and goes undetected without proper monitoring equipment.
Root Causes of Temperature Variation
Several factors contribute to temperature differentials across the mat width:
- Long haul distances: Asphalt mix leaving the plant at 305-315 degrees Fahrenheit can arrive at the jobsite as low as 270 degrees, creating a narrow window for placement and compaction.
- Truck loading patterns: Material from the beginning and end of a truck load tends to be cooler than material from the middle, introducing temperature variations into the windrow.
- Conventional slat conveyor design: Standard paver slat conveyors pull material from the front of the hopper only, failing to blend cooler material from the sides and edges back into the mix.
- Dead flow zones: Areas in the hopper where material sits stationary can cool significantly, and when finally pulled into the auger system, these cooler pockets create cold spots in the mat.
Why Shadows Matter
When contractors begin seeing shadows from particle segregation, thermal segregation is almost certainly present as well. These visible streaks on the mat surface indicate that larger aggregates have separated from the fine mix and binder. The separated areas cool faster because the larger aggregates have less surface area coated in binder, and they create pathways for air and water infiltration in the finished pavement. Addressing these shadows requires addressing the underlying material handling practices from plant production through truck loading, hauling, and paver operation. Understanding the full equipment train is essential, so review Road Construction and Asphalt Paving Equipment Machinery for to see how pavers integrate with the broader paving spread.
MnDOT Performance-Based Temperature Incentive Program
The Minnesota Department of Transportation (MnDOT) developed a pilot program that directly links temperature uniformity to contractor compensation. The program evaluates temperature differentials across the mat width for every 150-foot segment of pavement, creating a financial incentive for contractors to minimize variation.
Bonus and Penalty Structure
The program uses three tiers to evaluate performance on each 150-foot segment:
| Temperature Differential | Compensation Level | Impact |
|---|---|---|
| Less than 25 degrees Fahrenheit | Maximum bonus | Highest pay rate for that segment |
| 25 to 50 degrees Fahrenheit | Regular pay | Standard contract rate |
| More than 50 degrees Fahrenheit | Penalty | Reduced pay or corrective action required |
For a project like the Highway 86 rehabilitation in Jackson County, Minnesota, which spans 9.4 miles with two 14-foot-wide lanes, this translates into roughly 330 evaluation segments per lane. The potential bonus or penalty adds up quickly across such a large project.
Monitoring Technology
To enforce the program, MnDOT required the use of infrared temperature monitoring systems on the paver. The MOBA PAVE-IR system was deployed on the Highway 86 project to create a continuous thermal profile of the mat. Key features of the system include:
- Infrared sensors that map surface temperatures continuously across the full mat width.
- A full-color Thin Film Transistor (TFT) touchscreen displaying real-time temperature data to the screed operator.
- Onboard data storage for post-paving review and quality documentation.
- Analysis tools that enabled MnDOT and the contractor to calculate bonus or penalty for each 150-foot segment.
Intelligent compaction technology was also deployed on the rollers. These systems log detailed compaction data to back up core testing results and help operators achieve the required 92 percent density without over-compacting. Asphalt Equipment a Comprehensive Guide to Paving Compaction provides further detail on compaction monitoring systems and how they integrate with paver operations.
How Remix Technology Redefines Material Handling
The Cedarapids CR652RX Remix paver represents a fundamental departure from conventional paver design. Instead of the traditional slat conveyor system, the Remix paver uses two sets of twin counter-rotating auger shafts that run the full length of the hopper. This design change transforms how material is handled inside the paver and directly addresses the root causes of both particle and thermal segregation.
In-Hopper Remixing Augers vs. Slat Conveyors
The difference between the two systems is significant:
- Slat conveyor systems pull material from the front of the hopper directly back to the spreading augers. Material sitting at the sides and rear edges of the hopper remains undisturbed and can cool significantly before it eventually enters the feed tunnel. This creates layered temperature variation that appears as cold spots in the finished mat.
- Remix auger systems use large-diameter, variable-pitch augers that pull material from all areas of the hopper simultaneously. The twin counter-rotating shafts create a figure-eight motion that aggressively reblends 100 percent of the asphalt, diffusing segregated material over an area five times greater than traditional slat pavers.
- Hopper inserts can be added to the Remix paver to provide additional surge capacity and eliminate dead flow zones where material would otherwise sit and cool. This helps maintain continuous paving and further stabilizes mat temperatures.
Outboard Spread Auger Drive
Beyond the in-hopper remixing, the CR652RX features outboard spread auger drives that allow the augers in front of the screed to back up directly to each other. This eliminates the center drive gearbox present on conventional pavers. The benefit is twofold: it removes the source of centerline segregation where material tends to separate around the gearbox housing, and it reduces the potential for top-down cracking that originates at the center joint. The cost of ownership between a Remix paver and a conventional slat paver is essentially the same, making the upgrade a practical choice for contractors who regularly work on projects with tight specifications.
Continuous Paving Strategy
The Highway 86 project used a windrow paving approach with a Cedarapids pick-up machine that conveyed material from the windrow to the paver hopper without direct truck contact. This non-contact paving method, combined with the Remix paver hopper insert for surge capacity, allowed the crew to maintain continuous paving as consistently as possible. Finding the correct paving speed that does not outpace plant production is the critical element in making continuous paving work effectively.
Real-World Results from the Highway 86 Project
Duininck Inc. of Prinsburg, Minnesota, used the CR652RX Remix paver to pave one lane the full length of the Highway 86 project in late September 2014. After the demonstration, the crew returned to its traditional 10-foot mainline slat paver to complete the remaining lanes. This created a rare opportunity to compare both paver types on the same job with the same mix design, the same crew, and closely matched environmental conditions.
Comparative Temperature Data
MOBA Mobile Automation analyzed five random segments from each paver type. The results showed a dramatic difference in temperature uniformity:
| Temperature Range per 150-ft Segment | Remix Paver (CR652RX) | Conventional Slat Paver |
|---|---|---|
| 0-25 degrees F (maximum bonus) | 63.0 percent | 5.0 percent |
| 25-50 degrees F (regular pay) | 36.0 percent | 69.2 percent |
| Over 50 degrees F (penalty) | 1.2 percent | 25.8 percent |
The Remix paver placed nearly 63 percent of its mat segments in the maximum bonus category compared to just 5 percent for the conventional slat paver. Meanwhile, more than 25 percent of the slat paver segments fell into the penalty zone, while the Remix paver recorded penalty-level variation on only 1.2 percent of segments.
Field Observations
Crew members immediately noticed the difference in mat quality behind the Remix paver. The shadows that had been visible behind the conventional paver were completely absent. The remixing augers produced a homogeneous mat with no visible streaks or aggregate separation, and early temperature readings from the MOBA PAVE-IR system showed three test shots with ranges of 15, 18, and 20 degrees Fahrenheit, all well within the maximum bonus threshold.
Cost-Effectiveness Considerations
Material transfer vehicles (MTVs) can also help with segregation and temperature uniformity, but they add approximately $1.50 per ton to paving costs and are expensive to transport between jobsites. The Remix paver achieves comparable reblending results without the additional equipment cost, making it a more economical choice for contractors who encounter challenging mix designs, long haul distances, or performance-based specifications. For safety considerations when working with hot mix asphalt and paving equipment, see Asphalt Safety Comprehensive Guide to Hazard Management in.
Key Takeaways for Contractors
- Performance-based specifications are becoming more common. States like Minnesota are leading the way with pilot programs that tie compensation directly to mat temperature uniformity and compaction density.
- Thermal segregation often goes undetected without infrared monitoring. Investing in thermal profiling technology provides the data needed to make real-time adjustments and document quality for owners.
- Remix paver technology offers a cost-effective solution for contractors who regularly face challenging paving conditions including long hauls, modified binders, and high aggregate content mixes.
- The outboard spread auger drive design eliminates centerline segregation and the associated top-down cracking that can shorten pavement service life.
- Continuous paving supported by windrow pick-up machines and hopper inserts helps maintain stable temperatures through the entire paving operation.
The Highway 86 project demonstrated that remixing during asphalt paving delivers measurable improvements in mat temperature uniformity. Contractors who adopt this technology position themselves to meet increasingly stringent specifications, earn performance bonuses, and deliver longer-lasting pavement to their customers.