Tag Archives: MnROAD

Research Pays Off Webinar Series: Understanding and Improving Pavement Milling Operations

The National Road Research Alliance (NRRA) is hosting “Understanding and Improving Pavement Milling Operations” on January 18 at 10 a.m. CST, presented by Eshan Dave, University of New Hampshire.

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Research Pays Off Webinar Series: Improve Material Inputs into Mechanistic Design Properties for Reclaimed HMA Roadways 

The National Road Research Alliance (NRRA) is hosting “Improve Material Inputs into Mechanistic Design Properties for Reclaimed HMA Roadways ” on December 21 at 10 a.m. CST, presented by Bora Cetin, Bora Cetin.

Continue reading Research Pays Off Webinar Series: Improve Material Inputs into Mechanistic Design Properties for Reclaimed HMA Roadways 

Research Pays Off Webinar Series: Improve Material Inputs into Mechanistic Design Properties for Reclaimed HMA Roadways

The National Road Research Alliance (NRRA) is hosting “Improve Material Inputs into Mechanistic Design Properties for Reclaimed HMA Roadways” on November 16 at 10 a.m. CST, presented by Bora Cetin, Michigan State University.

Continue reading Research Pays Off Webinar Series: Improve Material Inputs into Mechanistic Design Properties for Reclaimed HMA Roadways

Research Pays Off Webinar Series: Developing Best Practices for Rehabilitation of Concrete with Hot Mix Asphalt (HMA) Overlays Related to Density and Reflective Cracking

The National Road Research Alliance (NRRA) is hosting “Developing Best Practices for Rehabilitation of Concrete with Hot Mix Asphalt (HMA) Overlays Related to Density and Reflective Cracking” on October 19 at 10 a.m. CST, presented by by Eshan Dave and Katie Haslett, University of New Hampshire.

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Research Pays Off Webinar Series: Performance Benefits of Fiber-Reinforced Thin Concrete Pavement and Overlays

The National Road Research Alliance (NRRA) is hosting “Performance Benefits of Fiber-Reinforced Thin Concrete Pavement and Overlays” on September 21 at 10 a.m. CST, presented by Manik Barman, University of Minnesota Duluth.

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Research Pays Off Webinar Series: Determining Pavement Design Criteria for Recycled Aggregate Base and Large Stone Subbase

The National Road Research Alliance (NRRA) is hosting “Research Pays Off: Determining Pavement Design Criteria for Recycled Aggregate Base and Large Stone Subbase” on April 20 at 10 a.m. CST, presented by Bora Cetin, Ph.D., Michigan State University and Raul Velasquez, Ph.D., P.E., Minnesota Department of Transportation.

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Research Pays Off Webinar Series: FRC Jointless Roundabouts in Minnesota

The National Road Research Alliance (NRRA) is hosting “Research Pays Off: FRC Jointless Roundabouts in Minnesota” on March 16 at 10 a.m. CST, presented by Principal Investigator Peter Taylor, Ph.D., P.E., Iowa State and Technical Liaison Maria Masten, P.E., MnDOT.

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Concrete Design Software Easier-to-Use, Capabilities Expand

MnDOT has upgraded its concrete pavement design software, MnPAVE-Rigid, to make it easier to use and allow more design inputs.

“In the original software, we only allowed one aggregate base thickness and one aggregate type. MnPAVE-Rigid 2.0 allows two base thicknesses and three base types,” said Tim Andersen, Pavement Design Engineer, MnDOT Office of Materials and Road Research.

MnDOT hired American Engineering Testing to update the design software as part of a research project advised by Andersen and funded by the state research program.

Background

MnDOT developed its own pavement design software, MnPAVE-Rigid, in 2014 that incorporated the methodology of the American Association of State Highway and Transportation Officials (AASHTO) Mechanistic–Empirical Pavement Design Guide (MEPDG). Minnesota’s pavement designers use MnPAVE to apply AASHTO’s most sophisticated design principles for both rigid and flexible pavement, focusing on mechanical properties of the pavement and prevention of early cracking and other distress.

2018-17-p2-image

AASHTO’s mechanistic–empirical (M–E) design methods entail hundreds of inputs, each a mechanical parameter, a measure of site-specific characteristics or a design goal. To simplify the input selection process, AASHTO’s M–E design software offers various input levels to reduce the data gathering and input burden. The most basic level uses default values for most of the inputs based on national averages, but still requires dozens of inputs for the number of pavement layers, traffic expectations, climate and other features.

MnPAVE-Rigid for concrete pavement design reduced that number of inputs to nine, operating like a module of AASHTO’s M–E software. MnPAVE-Rigid inputs work with a set of default values for jointed plain concrete selected by the MnDOT Office of Materials and Road Research in 2014, as described in the MnPAVE-Rigid 1.0 report.

“Many states ignored the challenge of adopting AASHTO M–E or they bought an AASHTO
software license. MnDOT used its accumulated knowledge of AASHTO M–E and Minnesota conditions to build MnPAVE-Rigid, and so can account for its M–E design results firsthand,” said Derek Tompkins, Principal Civil Engineer, American Engineering Testing, Inc.

Since implementing MnPAVE-Rigid 1.0, MnDOT has gathered feedback from users about their experience with the software. In the current project, MnDOT wanted to address this feedback, and expand and improve the original software by exploring additional options with some of the default parameters for concrete pavements.

What Was Our Goal?

The goal of this project was to update MnPAVE-Rigid 1.0 by expanding the range of inputs for traffic, subgrade type, base type and thickness, and to make the user interface more accessible.

What Did We Implement?

MnPAVE-Rigid 2.0 allows users to enter 11 inputs, including inputs related to specific traffic levels and aggregate base types; calculate the new design thickness; and print a project report that summarizes the inputs and the recommended thickness. The upgraded software is more user-friendly, and MnDOT can maintain or make future upgrades to the source code.

How Did We Do It?

Researchers met with the Technical Advisory Panel and reviewed the list of software improvements requested by pavement designers and the MnDOT Office of Materials and Road Research.

Because every change to an input affects a large number of default input variables, investigators ran over 21,000 simulations to analyze the impact of changes made to inputs for base type, base thickness, subgrade type and traffic level. The research team also modified the traffic input calculator to allow designers to enter traffic values from MnDOT’s weigh-in-motion and traffic counting data. The calculator runs input traffic data in software simulations and assigns the input an appropriate axle value for design.

MnPAVE-Rigid 1.0 ran designs based on Class 5 aggregate base over a subgrade like clay loam. Other aggregate types were added to simulations to determine how the software responds to these changes. Investigation also explored the addition of subgrade material options in design simulations.

The code developer modified elements of the advanced inputs tab and PDF report generation features to improve performance for software users, and rebuilt the software in JavaScript 2.0 code, including an installer for use with Windows software.

What Was the Impact?

MnPAVE-Rigid 2.0 is more user-friendly. Its tabs better match designer needs, and the software offers a design report PDF file for export. Instead of selecting from limited options for traffic volumes (default, normal and heavy), users can now input traffic data that the software will categorize. Designers can input Class 5 aggregate, Class 5Q (a higher quality aggregate with fewer fines) and open graded aggregate (no fines). Users can also choose 4-inch or 12-inch aggregate base thicknesses. An additional subgrade option was not included, as simulations indicated a sand subgrade input did not discernibly impact structural thickness outputs.

The AASHTO M–E software is expensive, and agencies that use it have to work closely with consultants to receive training and to explore or modify the code. MnDOT owns and manages the source code for MnPAVE-Rigid 2.0, can keep it secure, and can continue to change and upgrade it internally for Windows and Linux platforms.

What’s Next?

The updated MnPAVE-Rigid is now available online. Presentations about the software upgrades will be made at meetings for materials and soils engineers through the fall of 2018.

Still underway is an effort to further incorporate recycled material properties into MnPAVE Flexible, the design software for asphalt pavement.

This Implementation Summary pertains to Report 2018-17, “MnPAVE-Rigid 2.0,” published May 2018.

Recycled Asphalt Pavement Use is Increasing

MnDOT has long been a leader in the use of recycled asphalt pavement or RAP. Much of the nation’s current use of RAP in hot mix paving asphalt is based on the methods first used in a 1978 project that reconstructed the streets in what is now the 3M campus in Maplewood.

Subsequent MnDOT projects using as much as 80 percent RAP in hot mix paving revealed significant pavement performance problems, according to Curt Turgeon, state pavement engineer.

Currently, MnDOT asphalt paving specifications allow 30 percent RAP in overlay projects and 20 percent RAP when crack resistance asphalt cements are used in new or reclaimed pavements.

For economic and environmental reasons, Turgeon said MnDOT has renewed interest in increasing the use of RAP. Work includes trials of varying percentages in hot mix, trials at MnROAD of cold central plant recycling, and continued use of cold in-place recycling and full depth reclamation.

Increase in hot mix percentages

In District 6, a 13-mile section of the 30-mile Hwy 52 resurfacing project contains 40 percent RAP on the wide outside shoulders. The mixture contains proprietary additives to potentially assist in the rejuvenation of the RAP.

Tom Meath, District 6 materials engineer, said the higher percentage is being used because of the abundance of RAP available.

“This project allows the contractor to use up stockpiles of pavement from this and other projects and reduces the amount of new material needed, while not diminishing the quality of what’s used in the traveling lanes,” he said.

Meath said there are counties and cities in District 6 already using 40 percent RAP, but this is the first time MnDOT is trying it.

“We’re trying to figure out ways to use more RAP,” he said. “That’s a lot of money sitting there when we remove an asphalt pavement.”

Cold central plant recycling

This year’s MnROAD reconstruction, funded by the National Road Research Alliance, contains test sections of cold central plant recycling. This process uses 100 percent RAP mixed in a standard plant at ambient temperatures using an emulsified or foamed asphalt cement. The result is a product that is not resilient enough be used as a top surfacing so the test sections will receive either a standard hot mix overlay or a double chip seal.

Cold in-place recycling

The resurfacing portion of the Hwy 110 project east of I-35E and I-494 in Mendota Heights and Inver Grove Heights will use 100 percent recycled asphalt as the base layer of pavement.

Tim Clyne, Metro pavement and materials engineer, said using 100 percent saves on rock and asphalt costs, trucking costs and time. Since the material is reused with the cold in-place recycling process, the result is a more variable product than the material produced at the plant. Hot mix will be used as the top surface.

“It’s not a new technology, but this is the first time Metro has used the 100 percent RAP in at least 30 years,” he said. “It provides a long-term pavement solution for an extended pavement life.”

See a video of cold in-place recycling, which shows a milling machine, a machine that screens and crushes oversize materials and then mixes in an asphalt emulsion, an asphalt tank and an asphalt paver and roller.

Full depth reclamation

Full depth reclamation uses equipment often described as a rototiller for pavements. The asphalt pavement and some of the existing base is ground together in place. Multiple passes of the reclaimer are often used. The final pass may include the addition of a binder such as asphalt emulsion, foamed asphalt, cement or lime. The result is an aggregate base with the old crack pattern completely erased.

“Hot mix overlays on full depth reclamation base have shown excellent performance compared to a typical mill and overlay project,” said Turgeon.

Economic and performance benefits of these techniques are well understood.  Until recently, the environmental benefits of using materials in place instead of hauling off to a plant haven’t been well documented. MnDOT participates in the Recycled Materials Resource Center pooled fund project now housed at the University of Wisconsin – Madison.

In June 2017, the RMRC completed an analysis of nine paving projects that documented an average of 22 percent overall savings and 20 percent savings in water usage.


This post was written by Sue Roe and was originally published on MnDOT’s Newsline on  Aug. 23, 2017. 

MnROAD Breaks New Ground

In June, MnROAD, the only cold-weather accelerated pavement testing facility of its kind in North America, begins construction on its third phase of research since 1994, the first time MnDOT has rebuilt in partnership with other states.

Dozens of new experiments are planned along MnROAD’s test tracks in rural Albertville: the high-volume original Interstate-94 westbound (built in 1973), the mainline I-94 westbound (originally opened in 1994) and an adjacent low-volume road closed track.

Six states and numerous  industry partners recently formed the National Road Research Alliance (NRRA) to co-sponsor  the reconstruction.

NRRA-prioritized research will support state and local needs, including effective use of fiber-reinforced concrete, asphalt overlays of concrete pavements, cold central plant recycling and concrete partial depth repairs to name a few.

MnROAD has two 3.5 mile test segments on Interstate 94 and one closed 2.5-mile low-volume road.
MnROAD has two 3.5 mile test segments on Interstate 94 and one closed 2.5-mile low-volume road.

“The advantage of having these test  sections at MnROAD is we can take  bigger risks and push the envelope in terms of mix designs and layer thicknesses for both asphalt and concrete  layers that could not be done on a public roadway,” MnDOT Research Operations Engineer,   Dave Van Deusen said.

Forensic analysis of failed cells
Many old test cells will be dug up.  Before any reconstruction starts, however, each test section that is being reconstructed will receive a final forensic study. This allows researchers a look at each layer to see the distress that has occurred over the years—and make the final analysis of why it failed. There are always a lot of theories on the causes of what actually failed, but until the forensic is performed, there isn’t proof on what happened. These findings will help build longer-lasting pavements in the future.

The bid letting date for this year’s construction is April 28, but plans were made available for contractors on March 31. This should give the projects more exposure and generate more interest. Construction begins June 5 and continues until November 2017.

Focus Areas

  • HMA overlay and rehab of concrete and methods of enhancing compaction – States are looking for longer lasting HMA overlays of concrete. New mix designs were developed to promote long-term performance, including how reflective cracking effects can be minimized through design or other joint treatment.
  • Cold central plant recycling – Other states have used reclaimed asphalt pavement stockpiles into plant mix base course mixes (layers below the wear surface) to effectively recycle these materials in a controlled mix design. How can these layers best be used and what type of surface mix or chip seal can be placed on top?
  • Fiber reinforced concrete pavements – Nationally, states want to get a better understanding of the beneficial use of fibers in concrete pavement layers. Is it worth the cost? How can it be best used in both thin city streets and higher volume roadways? Can it be used in new construction and in concrete overlays? The research will provide the answers.
  • Long-term effects of diamond grinding – Each state has aggregates that have been used in concrete pavements that are considered reactive aggregates. Questions arise as to whether diamond grinding might accelerate deterioration in these pavements. What types of topical sealers can be used to treat the surface after the diamond grinding will also be tested.
  • Early opening strength to traffic – What effect does heavy traffic loading have on the long-term performance of full-depth concrete pavement, as well as fast–setting repairs? Test sections will be loaded by a pickup truck in one lane early enough to produce shallow ruts in the surface. In the other lane, a loaded 18-wheeler will travel over the new concrete immediately after it sets, and then sequentially every six hours up to 30 hours. The long-term effects of these early loadings will then be evaluated.
  • Optimizing the mix components for contractors – What effect do low-cementitious content mixes have on long-term performance and constructability of concrete pavements?  Two low cementitious content mixes will be studied to give agencies a better understanding of cost savings. Can these savings be achieved without significantly affecting long-term performance?
  • Compacted concrete pavement for local streets – Compacted concrete pavement is a form of roller compacted concrete that has a standard concrete pavement surface texture. The RCC industry has been successful in Michigan and Kansas constructing CCP pavement on local streets.  This research will determine if the texture that is accomplished is durable in harsh freeze-thaw climates.
  • Recycled aggregates in aggregate base and larger sub-base materials – States continue to look for effective ways to recycle materials into unbound bases. This research will add to MnROAD’s understanding of recycled bases and what seasonal strength values can be used for advanced mechanistic designs–and how they are affected by size/gradation.
  • Maintaining poor pavements– Road owners continually have less funding to maintain their roadway systems. What practices should be used for stabilizing both hot mix asphalt and Portland cement concrete roadways when longer-term repairs cannot be done due to funding levels?
  • Partial depth repair of concrete pavements – Agencies continually seek improved materials and methods for the repair of concrete pavements. In this study, up to 15 innovative concrete pavement repair materials will be evaluated on the concrete panels of the westbound I-94 bypass parallel to the MnROAD mainline.
  • Thin overlays-Experimenting with very thin overlays could provide a real benefit for a lot the roads currently out there. The premise is that with thin overlays, the ride can be smoother and the life of older roads can be extended.

“We don’t often get to reconstruct random roads these days, and when we do, we have much better specifications for low temperature cracking. By the same token, we have to maintain all those older roads built before we had performance grade binders,” said Dave Van Deusen, Materials and Road Research Lab principal engineer. “We will be doing this makeover on an original section of MnROAD built back in the 90’s.”

In one experiment, there is a head-to-head comparison of thin overlays on two sections of road. One section has a thick base and subbase under the asphalt. The other has a heavy asphalt top with very little base.

Van Deusen says if they can get an extra five years of life out of road using thin overlays, he would be pleased. Often, he admits, he is surprised by how long these “short-term” fixes actually last.

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