How Washtenaw County, Michigan is Focused on Pavement Preservation

Washtenaw County is located in southeast Michigan. The County seat is Ann Arbor, home of
The University of Michigan Wolverines. The Washtenaw County Road Commission (“WCRC”) is responsible for maintaining 1,653 total miles of primary and local roads along with 598 lane miles of State highways under a contract arrangement with the Michigan Department of Transportation (MDOT).

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Sustainable Infrastructure Project in Gogebic County Michigan

Cold In-Place Recycling

In 2021, the Gogebic County Road Commission constructed their first recycling job.  The first phase, which was approximately 3 miles of the Lake Road Cold In-Place Recycle (CIR) project, was finished in 2021. There are approximately 2.5 miles that are projected to finish in 2022. This final section of the roadway to be completed in 2022 is to repave the stretch of road from Little Girls Point to the Wisconsin border.

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What is America’s Most Recycled Product?

Asphalt pavements are one of our greatest renewable resources! The U.S. recycles about 2 million tons of plastic each year while recycling and reusing over 60 million tons of asphalt.

In addition, plastic recycling alters the chemical structure, so many plastics become different types of products once recycled. Roads, on the other hand, are reusable and renewable infinitely. (1)

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Asphalt Materials Shines the Spotlight on Sustainability

As The Heritage Group continues to expand capabilities and investments in the sustainability space, the Asphalt Material’s team is also focused on sustainability in a number of different areas, this article is focuses on CCPR or Cold Central Plant Recycling.

CCPR is the process in which the asphalt recycling takes place at a central location using a stationary cold mix plant and an existing stockpile of RAP or reclaimed asphalt pavement.

Why is CCPR a Sustainability Initiative?

Aggregate and oil resources are not infinite and current conventional remove and replace approaches to constructions projects is unsustainable and not always budget friendly. CCPR is a modern, yet time tested approach. It has helped agencies complete more projects within the same budget, or in many cases with reduced dollars versus budget without sacrificing the structural integrity of asphalt pavements.

By reducing energy usage during the processing, CCPR is an ideal choice for road construction projects. There is a smaller carbon footprint and reduction in greenhouse gases because of the significant reduction in trucks exporting and importing materials to and from the site.

RAP is a Valuable Asset!

Agencies paid for the initial construction materials for an existing asphalt pavement. With CCPR, agencies are able to reuse those materials and stretch their budget dollars. When roads last longer, infrastructure funds go further.

CCPR Can be Less Expensive

CCPR is less expensive than conventional maintenance, reconstruction or new construction methods. Rehabilitating a road with an engineered emulsion additive is less expensive than producing virgin hot mix made from completely new materials. Typical overall project costs savings can be 25% or more.

Nate Jenkins (AMI Sales Representative) and Tim Zahrn (Specialty Products Area Manager) collaborate on a number of recycling projects around the state of Indiana. They also draw on the expertise of The Heritage Research Group, specifically team members like Jason Wielinski, Megan Yount and Zach Robinson. A few of their insights are seen below.

CCPR is a green approach that is not only environmentally friendly, but is often economically advantageous to agencies. – Tim Zahrn, Specialty Products Area Manager for Asphalt Materials, Inc.

CCPR gives an agency the ability to remove existing asphalt pavement and fix the underlying pavement issues, reusing the RAP in the new pavement structure. – Megan Yount, Heritage Research Group.

CCPR is placed at ambient temperatures and the mixing plant is typically located in close proximity to the project.  This decreases excessive hauling and utilizes a lower amount of virgin material in comparison to some other alternatives. – Jason Wielinski , Heritage Research Group.

If an agency needs to remove existing pavement structure, RAP, it makes sense to re-use the material that the agency already owns. – Nate Jenkins, Asphalt Materials Inc. Sales Representative.

RAP has value and can be used by an agency for a number of different things, but can be very valuable when used in a CCPR or other pavement recycling processes. – Zach Robinson , Heritage Research Group.

Show below are a number of different pictures taken at different stages of a CCPR project. In addition, you may be interested in watching a short video of CCPR here: Video Link.

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Comparing Field and Lab CIR Mix Properties: Findings from Indiana SR 234

Any business that has been around for over 65 years should have a strong commitment to innovation. Asphalt Materials is that company. Our teams are focused on helping build longer-lasting, safer roads. To do that, we focus on big challenges as creative problem solvers. We have a unique opportunity available to us and our customers in that we are part of The Heritage Group, which includes the expertise that resides within The Heritage Research Group.

Collaboration is a hallmark of our approach as well. Working with contractors and departments of transportation, we take a collective approach that fosters long-term relationships and mutual trust. A recent project created an opportunity with Indiana State Road 234. The construction project consisted of  126,505 square yards of Cold In-place Recycling (CIR) at a depth of 4-inches. The project length was 10.37 miles with a 22 foot width. The project progression can be seen in the image below.

asphalt project progression

While comprised of similar components to conventional Hot Mix Asphalt, CIR lifts cannot be sampled in the same way to measure and confirm quality of the material. Instead, each CIR candidate pavement is sampled, with the representative materials going through a mix design process designed to closely approximate the CIR construction procedure in the lab. Once the CIR mixture meets or exceeds specified laboratory standards, construction can begin.

Per industry standard, several tests are performed during CIR operations to verify the exact material quantities are added to the mixture per the project’s mix design. In-place density testing is also performed to confirm optimal compaction is reached throughout the placed CIR lift. While this testing method is rigorous for the mixture’s components it does not directly measure mixture performance. The current testing standard reveals opportunities to test the constructed material for performance that is timely from a construction perspective and valuable for agency and contractor customers.

Heritage Research Group designed a field sampling method to sample constructed CIR materials just prior to field compaction, allowing for test specimens to be produced and performance tested, similar to mix design test specimens in the lab.

Additionally, a rare opportunity arose to sample the CIR by coring, shortly after construction and the final HMA overlay was completed. This provided field cores from the project for further analysis that is truly representative of the mixture.

Six, 6-inch cores were collected from eight locations on the project (see example below).

core testing

Based on these testing and material sampling opportunities, a research project was formed as follows:

  • Evaluate sampling procedure for field-collected samples.
  • Compare mix design results to field-collected samples.
  • Quantify impact of delayed compaction of field samples.
  • Compare mix design, field samples to field cores.

The variation in approximated versus representative processes in the three types of CIR samples provide a unique perspective to confirm accuracy of the field sampled mix tests and of the initial mix design test results. A diagram outlining the differentiations between mix design, field samples and field cores can be viewed below.

project truth scale

All of the CIR processes are approximated in the lab to produce a mix design, while field sampled materials contain more accurate versions of these processes because they are sampled from the constructed lift. Finally, cores collected from the project, several months after the CIR was completed, provide the most accurate version of the mixture, all of the CIR processes, including compaction, being true to the constructed CIR. 

After conducting testing to determine air voids in the mixtures, specimens were tested for marshall stability and indirect tensile strength in dry and wet conditions. These results are used to estimate a mixture’s resistance to water damage, rutting, and cracking in tension.

To further understand the long-term performance of the mixture, dynamic modulus testing was performed with small-scale AMPT specimens collected from the CIR pavement cores.

Several findings were determined upon analysis of the test:

  • The sampling method to collect field mix samples for lab compaction and testing could be a method to verify CIR mixture properties in the future.
  • The dynamic modulus test results provide additional data to the industry on the performance qualities of the constructed mixture, which also align with the current industry recommendations for the mastercurves which characterize CIR materials. 

This project is an excellent case study that demonstrates the outcomes that are possible when different groups are all driving to the same goal of creating longer lasting, safer roads.

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CCAP- Cold Constructed Asphalt Pavement

CCAP or Cold Constructed Asphalt Pavement is a blend of gelled asphalt and additives that is mixed with pre-approved aggregate through a mobile mixing plant. The ability to blend different aggregate during the mixing process creates a mix for application in various thicknesses. Agencies using this material are finding that pavement costs are reduced as much as 30%.

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Rebuild of County Road 151 recognized with two awards

The rebuild of County Road 151 across three townships has been honored with two awards. 

The Monroe County Road Commission received the national Asphalt Recycling & Reclaiming Association’s 2016 Award for Excellence in full-depth reclamation for the project. In addition, the road commission and Gerken Paving Inc. received an award of excellence from the Asphalt Pavement Association of Michigan. 

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