Listed below are examples of success stories, best practices, and/or innovative tools/approaches. This section will grow as entries are submitted or links to other sites with useful examples are provided. If you believe your agency has utilized a best practice/approach that others could learn from, please submit a short description to AASHTO (including any pertinent links) on the Share Info with AASHTO form. Please note that currently submissions are only being accepted from governmental entities.
The Missouri Department of Transportation has been a pioneer in the use of recycled asphalt pavement in its asphalt mixes, allowing the agency to save money and protect the environment.
When a contractor approached MoDOT in 2003 with the proposal to try recycled tear-off shingles in an asphalt mix, MoDOT stood to save millions of dollars while simultaneously keeping waste out of landfills. MoDOT used an average of 4,170,300 tons of asphalt each year between 2004 and 2014 to build and maintain its state roadways.
“It’s not often that you come across a product that can be used in pavement that is inexpensive, produces a good viable product, saves taxpayers money, and helps the environment, said Sarah Kleinschmit, Field Materials Engineer at MoDOT. “Using recycled shingles is more than win-win!” she said.
Post-consumer RAS was not being used by any other state DOT at the time MoDOT and the contractor began their investigation into the viability of using RAS-containing asphalt mixes. Today, about 20 state DOTs allow or are making efforts to allow using post-consumer RAS in their asphalt mixes. Integrating shingles in asphalt was not a new concept when MoDOT and their contractor used a pilot shingle mix—based on favorable test results—on Route 61/67 in St. Louis County in 2005; manufacture waste recycled asphalt shingles (RAS) were being used at various state DOTs. However, using post-consumer RAS represented an innovative step towards continuing to reduce waste and increase cost-savings for roadway projects.
When MoDOT began investigating the potential for using post-consumer RAS in asphalt mixtures, it began with a literature review and then participated in a demonstration project with the contractor in 2004. MoDOT found results from testing the demonstration mixture favorable enough to launch the pilot project on Route 61/67 in St. Louis County. Though some reflective cracking was visible on the roadway after six years, the pavement’s performance was still deemed favorable by MoDOT.
Another project using manufacture-waste RAS was constructed in Joplin, MO, around the same time and produced similar results. With the initial positive performance of these two text mixtures, a provisional MoDOT specification allowing RAS in asphalt mixes was developed in 2006. In 2008 MoDOT’s added specifications to include different types of asphalt products (surface levels, bituminous mixes, and asphaltic concrete). In 2010, MoDOT added “Roofs to Roads” to its Tracker performance reporting accountability tool.
Key takeaways from MoDOT’s Roofs to Roads efforts:
Other State DOTs Using Roofs to Roads
Texas DOT was one of the first states to allow RAS in asphalt mixes and has developed stringent deleterious materials requirements for RAS. Its first RAS testing began in 1990, and Texas DOT developed its RAS program after the Asphalt Shingle Recycling Forum in Chicago, IL, in 2007.
Many examples from various state DOTs can serve as a starting point for other state DOTs interested in RAS. MoDOT recommends keeping any RAS program outcome-based, staying focused on the end result that meets its state’s particular needs (e.g., cheaper mixes, longer lasting pavement, pavement that does not crack, diverting waste from landfills, or all the above). State DOTs can reference other DOTs specifications to help develop their own specifications to include RAS.
The following state DOTs have effectively used RAS in projects:
Today, every contractor working for MoDOT has mixtures that incorporate manufacture waste or post-consumer RAS in their asphalt mixes. MoDOT continues to lead the way in using RAS in asphalt mixes by serving as the lead state of the Transportation Pooled Fund Study TPF-5(213), Performance of Recycled Asphalt Shingles in Hot Mix Asphalt.
With the help of partner agencies and other states—including Federal Highway Administration, Minnesota, Iowa, Indiana, California, Colorado, Illinois Tollway, and Wisconsin—this TPF study includes demonstration projects aimed at understanding how RAS affects both the binder and mixture properties of asphalt mixes. The study focuses on quality control practices, grind size of the shingles, and both post-consumer and manufacture waste shingles.
Study results showed that RAS can be successfully used in asphalt mixes; field performance showed no rutting, thermal cracking, or fatigue cracking after two years. Reflective cracking was noted on five of the projects.
Moving forward, MoDOT will continue to use RAS in asphalt mixes, monitoring mix performance and making adjustments as needed. Contractors are excited about the possibilities of using even more shingles in their asphalt mixes and are experimenting with how different grades of virgin binder are affected by the increase in shingles. MoDOT prides itself on encouraging innovation in collaboration with its contractors.
The following additional resource offer more information on recycled asphalt shingles in road construction:
For more information on MoDOT’s Roofs to Roads efforts, contact Sarah Kleinschmit, Field Materials Engineer, MoDOT, at Sarah.Kleinschmit@modot.mo.gov.
The Virginia Department of Transportation has realized cost and energy savings using recycled asphalt paving processes for a repaving project along a portion of Interstate 81, prompting the agency to consider broader use of the technique across the state.
The VDOT project repaved a 3.7 mile southbound section of the I-81 using pavement processes that reuse existing material from the road surface in the new pavement structure, reducing construction time by about two-thirds and saving millions of dollars, according to an announcement from the office of Governor Bob McDonnell.
|Asphalt pavement recycling on I-81. Source: Virginia DOT|
The paving processes are known as cold in-place recycling, cold central-plant recycling, and full-depth reclamation. The project was the first time that the three processes were used together in a single interstate project in the country, according to VDOT.
“Cold” refers to processing at ambient temperatures rather than using heat, according to VDOT’s project description. The recycling was done both within the roadbed and next to the highway.
Due to differences in the level of deterioration, different processes were used for the right and left lanes. After the top 10 inches of pavement were removed from the right lane, the aggregate between 10 inches and 22 inches below the surface was recycled in-place using the full-depth reclamation process. A stabilizing agent called Calciment was added. In the meantime, the pavement from the top 10 inches of the right lane was milled and processed next to the highway using the cold central-plant recycling process. The layer was then reapplied using traditional paving equipment. Finally, the right lane received a surfacing of four inches of hot-mix asphalt.
The left lane, having less deterioration, was recycled in-place to a depth of 5 inches using the cold in-place recycling method. With this process, the front of the machine mills the existing pavement, moving the milled material to the middle of the machine where the asphalt is stabilized and a binding agent is added. The reconstituted asphalt is then applied back to the roadbed. The three stages of the process occur in one pass. The left lane was also topped off with hot-mix asphalt.
Savings on the I-81 in-place pavement recycling project go beyond time, money, and materials," according to VDOT Commissioner Greg Whirley. He cited fuel savings, reduced work-zone congestion, and reduced maintenance as additional benefits.
Using conventional methods, the project would have taken two years or more to complete, requiring lanes to be added to accommodate traffic during construction, according to Mal Kerley, chief engineer at VDOT. These methods would have cost around $40 million, Kerley said.
VDOT looked at six different options for this project and considered the benefits of doing major reconstruction rather than short-term “band aid” fixes, which would require additional ongoing maintenance.
The announced contract award amount for the option VDOT chose was $7.64 million and was completed in about seven months using the new processes. Kerley said the agency anticipates that the processes will be as adequate, in terms of durability, as traditional processes.
Traffic Management Techniques
The project also employed a new traffic management plan to handle vehicle traffic during construction. Truck traffic was routed to the right or left lane when the adjoining lane was being repaired, while passenger vehicle traffic was detoured off of the interstate. Use of a detour at all was unprecedented for such a busy travel corridor, Kerley explained.
VDOT made an effort to get the word out of the dates and routes of the detours along the corridor, Kerley said. VDOT also used changeable message signs, traffic cameras linked to the internet, and warnings of traffic backups using an advance warning vehicle and notices to trucks over CB radio.
VDOT recognizes that the trend in highway project management is to help the public make informed decisions and “minimize the impact to the traveling public,” Kerley said.
Governor McDonnell also highlighted plans to use pavement recycling processes in future projects to save time and money. "Using these pavement recycling methods has the potential to revolutionize how we rehabilitate our aging roads, both in Virginia and nationally," the governor said in a statement.
VDOT will be working with district offices and the Virginia Center for Transportation Innovation and Research to develop standard specifications for this kind of rehabilitation work in the future, Kerley said. He noted that there are one or two more projects planned for 2012 that will use the pavement recycling methods.
VDOT is “trying to standardize this [type of project] so it is another tool in our toolbox,” Kerley said.
The Asphalt Recycling & Reclamation Association presented VDOT with its 2012 Recycling Award in the "Cold In-Place" category for the project at its annual meeting Feb. 21-24 in Bonita Springs, Fla.
More information about the project, including photos and a link to a VDOT study on full-depth reclamation, is available at http://www.transportation.virginia.gov/News/viewRelease.cfm?id=1108.
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