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Minnesota's Cold Weather Road Research Facility

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Current Research Projects - Phase Two


The MnROAD Phase Two Research initiative is a combination of multi-state pooled fund projects, initiatives led by public and private partners, and MnDOT projects. These projects address a range of issues for the effective design, construction and maintenance of pavement systems.


In addition to pooled fund and partner projects, MnROAD will be conducting projects directed at solving local problems, for MnDOT and for the local agencies, through research sponsored by the Local Road Research Board.


Brief project descriptions, objectives and links to more information:


Aggregate Materials

Use of Taconite aggregates in pavement applications (NRRI, Partner Project)


Asphalt Pavement

Investigation of Low Temperature Cracking in Asphalt Pavements - Phase Two (Pooled Fund Project)

HMA Surface Characteristics related to Ride, Texture, Friction, Noise, Durability (Pooled Fund Project)

Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in HMA Pavements (Pooled Fund


MnROAD Field Investigation of Polyphosphoric Acid Modified Asphal (Ergon Inc, ICL Performance Products, Innophos, MTE, FHWA)

Recycled Asphalt Pavements (MnDOT Project)

Warm Mix Asphalt (MnDOT Project)


Composite Pavement

Design and Construction Guidelines for Thermally Insulated Concrete Pavements (Pooled Fund Project)

Composite Pavement Systems (SHRP 2 Project)


Concrete Pavement

PCC Surface Characteristics - Rehabilitation (Pooled Fund Project)

60 Year Design Concrete Pavement - Performance Model Development (MnDOT Project)

Concrete Pavement Optimization – Determining the Lower Threshold of Slab Thickness for High Volume Roads (MnDOT Project)

PCC Surface Characteristics - Construction (MnDOT Project)



Concrete Overlays (Whitetopping/Unbonded Overlays)

Development of Design Guide for Thin and Ultrathin Concrete Overlays of Existing Asphalt Pavements (Pooled Fund Project)

Performance of Thin Unbonded Concrete Overlays on High Volume Roads (MnDOT, American Concrete Pavement Association and Portland Cement Association Project)



Geocomposite Capillary Barrier Drain (GCBD) for Limiting Moisture Changes in Pavements: Product Application (Pooled Fund Project)


Full Depth Reclamation

Full Depth Reclamation Study (SEM Material, Partner Project)


Low Volume Roads

The Effects of Implements of Husbandry "Farm Equipment" on Pavement Performance (MnROAD Study, Pooled Fund Project)


Pervious Pavement

Pervious Concrete Mix Design for Wearing Course Applications (CTRE, Partner Project)

Permeable (HMA) Pavement Performance in Cold Regions (LRRB, MnDOT project)

Pervious Concrete Pavement Study (LRRB, MnDOT project)


Recycled Materials

Recycled Unbound Pavement Materials (Pooled Fund Project)

Recycled Asphalt Pavements (MnDOT Project)



Stabilized/Treated Layers

Field Investigation of Highway Base Material Stabilized With High Carbon Fly Ash (Bloom Consulting, Partner Project)


Use of Taconite aggregates in pavement applications (NRRI)

Expansion and maintenance of roadway infrastructure creates a demand for high quality paving aggregates. Taconite industry rock and tailings are a potential source of virgin paving aggregates. Currently there is limited information available for implementing these products in construction design specifications. The main goal of this coordinated research effort is to determine if taconite aggregates can be practically used in pavement construction projects. The issues involve both engineering/ material properties and economics/logistics of transportation. Several questions that need to be answered include:



Investigation of Low Temperature Cracking in Asphalt Pavements - Phase Two 
Low temperature cracking is the most prevalent distress found in asphalt pavements built in cold weather climates. As the temperature drops the restrained pavement tries to shrink. The tensile stresses build up to a critical point at which a crack is formed. The current Superpave specification attempts to address this issue by specifying a limiting low temperature for the asphalt binder. The specification does a reasonable job predicting performance of conventional asphalt cements, but this does not hold true for polymer-modified asphalt binders that are manufactured to reach very cold temperature grades needed in cold climates. Currently the low temperature specification considers only the asphalt binder. Specifications must be developed for the asphalt mixture as well. It is very important to understand the mechanism of crack initiation and propagation. Thermal cracks can be initiated by traffic loading or cycles of temperature changes and then propagated by a large drop in temperature. In addition, the significant effects of aging and moisture on crack formation and propagation are not fully understood and need investigation. 
A comprehensive research effort is in progress by a team led by Dr. Mihai Marasteanu at the University of Minnesota. This project is a unique partnership between MnDOT and four universities: University of Minnesota, Michigan Technological University, University of Illinois at Urbana-Champagne, and University of Wisconsin at Madison. The goal of the current project is to evaluate different laboratory procedures, material properties, and pavement features in order to develop an optimal system for selecting low temperature crack resistant materials. There is a critical need to validate the findings of this experimental work with field data. To this end, two sections will be constructed at MnROAD. MnROAD provides a unique combination of instrumentation, regular performance monitoring, controlled traffic applications, researcher expertise, and a safe work environment that makes it an ideal location for this study. More

HMA Surface Characteristics related to Ride, Texture, Friction, Noise, Durability (Pooled Fund Project)

More and more attention has been paid recently to hot mix asphalt pavement surface characteristics. In addition to structural capacity and durability, it is now desirable to design pavements to meet noise, texture, friction, and ride requirements. Noise (both interior and roadside) is at the forefront of the minds of both pavement designers and the traveling public. Many studies are currently underway around the United States and in Europe to address noise and these other issues.  
The traditional way to reduce noise for nearby residents and businesses has been to build noise walls. Besides being large and undesirable to look at, noise walls can also be quite expensive. Innovative pavement surfaces have recently been developed as an alternative to building noise walls. The type of wearing course plays a major role in determining the surface characteristics of a pavement. Several options that can provide lower noise levels than conventional dense-graded pavements include stone matrix asphalt (SMA), open graded friction course (OGFC), porous HMA, 4.75-mm Superpave mixes, and NovaChip. In general pavements with smaller maximum aggregate size, open gradation, and negative macrotexture produce less noise. 
SMA and OGFC pavements have been used extensively in the southern United States with great success. However, far fewer states in cold climates have used these open-textured mixes. As a result little is know about the performance of open-textured mixes in cold climates. There is a fear that over the harsh winter the pavement will disintegrate due to sand and salt operations, freeze-thaw action, snow plowing operations, and the like. There is a need to conduct a controlled experiment in a northern state like Minnesota to determine the durability and performance of a pavement built for certain surface characteristics. MnROAD offers an experimental site where the risk can be taken to construct and monitor open-texture mixes in a cold environment.  


This research project will progress on two tracks: 

  1. Construct two new HMA pavements using SMA, 4.75-mm Superpave mix, etc. specifically for the purpose of reducing the noise while maintaining other important surface characteristics.  
  2. Monitor all of the new test cells built at MnROAD for their noise, texture, friction, and ride characteristics. 


Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in HMA Pavements (Pooled Fund Project)

One of the major tasks in any transportation agency pavement management system is to select the appropriate alternative for rehabilitation and maintenance. There is a need to understand how preventive maintenance improves the performance of the existing pavements, to develop new techniques, and to determine the optimal timing for the application of these treatments. 
Perhaps the main reason to apply a preventive maintenance treatment to an HMA pavement is to reduce the aging of the asphalt binder and therefore maintain a higher level of pavement performance. Some research has documented the aging of asphalt through traffic loadings. However, the mechanisms that cause environmental aging are not well understood. This research aims to better understand the mechanisms behind aging and therefore apply the right surface treatment at the right time.  
This research requires a mixture of fundamental analyses based on laboratory experiments and field investigations. The timing of the surface treatment is related to the aging and distresses that develop in asphalt pavements over time. Ideally, a surface treatment should be applied at the proper time to provide a balance between maximum life and minimum cost. The progression of the asphalt pavement surface condition is mostly related to the aging characteristics of the asphalt binder and to the evolution of the mechanical properties of the binder with aging. An ongoing project at the University of Minnesota is investigating some of the issues related to the application of surface treatments, including environmental (climatic) modeling and mixture and binder testing to determine when preventive maintenance activities should be done.


The goal of this study is to determine the proper timing of preventive maintenance treatments in order to optimize life cycle costs and pavement performance. This pooled fund study will perform preventive maintenance research on Phase Two test sections at MnROAD. More


MnROAD Field Investigation of Polyphosphoric Acid Modified Asphalt (ICL, Innopos, MTE, FHWA)

Polyphosphoric acid has been used for some thirty years to stiffen asphalt for paving applications. More recently it has been used to stiffen asphalts that may be marginal on the Superpave RTFOT test. This has been particularly so in the case of polymer modified binders. It was found more cost effective to add a small amount of acid, which could readily be dispersed in the binder rather than mill in additional quantities of more expensive polymer. It was then found that by adding polyphosphoric acid the amount of polymer could be reduced thereby saving cost for the contractor. The Federal Highway Administration, Office of Infrastructure, is completing a laboratory project to address the risks and benefits associated with the use of polyphosphoric acid as an asphalt modifier. To clearly identify which grades can and cannot be used and the pitfalls associated with the use of polyphosphoric acid with antistrip compounds, such as amines and lime as well as asphalt binders from differing sources. The MnROAD study will build upon the findings of this study and conduct a field trial to assess the performance of PPA mixes over a 5 year period. This study will be a joint venture between MnDOT (overall project management and administration), Ergon Inc, ICL Performance Products, and Innophos, Inc.( funding support, advice and guidance on the proper inclusion of PPA into the asphalt mixtures), Federal Highway Administration (asphalt binder/mixture performance testing and financial support for MnROAD operations), and Mathy Construction (asphalt binder supply and evaluation of stripping susceptibility).

The goal of this project is to investigate the field performance of asphalt mixtures modified with polyphosphoric acid (PPA) and compare them to similar mixtures using traditional modification techniques. Traditionally the addition of polymers (SBS, SBR, Elvaloy, etc.) have been used to enhance the properties of asphalt binders. Specifically, polymers have improved the pavement performance at high temperatures (i.e., rutting) without adversely affecting the low temperature properties (i.e., low temperature cracking). The use of PPA is seen as a lower-cost alternative to polymers in order to achieve the same increased performance. Several laboratory experiments have successfully demonstrated the effectiveness of PPA modification. What is needed now is a field validation study, which will be undertaken with this project. Development of a solid experimental plan will be part of forthcoming work agreements between the parties. Related previous or ongoing studies Federal Highway Administration, Mathy Construction, Western Research Institute, and other organizations have recently performed research on several aspects of acid modification of asphalt binders. The MnROAD study is seen as field validation of the findings from those studies. Construction of five MnROAD Low Volume Road test cells to study the performance of asphalt mixtures modified with polyphosphoric acid was completed in 2007. The cells include the following binder materials: