Title
Reclaimed Asphalt Pavement (RAP) Update
Description
This report provides information to the Transportation, Infrastructure and Planning Subcommittee about the Street Transportation Department's Reclaimed Asphalt Pavement (RAP) program.
THIS ITEM IS FOR INFORMATION ONLY.
Report
Summary
The Street Transportation Department (Streets) has long utilized asphalt pavement millings for various maintenance purposes, such as repairing alleyways and roadway shoulders. Asphalt millings are a byproduct of the removal of the top layer of asphalt as part of repaving projects. Previously, the use of asphalt millings was primarily as a dust palliative to address dust control issues. Initially, there were a number of factors that gave Streets concerns about adopting its use in our paving operations including:
- Observed quality control and pavement durability issues based on prior City experience;
- Difficulty to ascertain project cost savings or other benefits through the invitation for bids (IFB/low bid) procurement process;
- Concerns with the processing and quality of reclaimed materials; and
- Long term performance testing for RAP in the Phoenix area.
However in 2017, Streets and the Public Works Department (Public Works) collaborated to find ways to incorporate RAP into the City's paving operations. Asphalt pavement is one of the most recyclable materials. When milled and processed to an engineered size gradation, it can be reutilized as aggregate fill and be reincorporated into new asphalt pavement. Additionally, the increased use of job order contracting procurements for pavement maintenance allowed the City to work more closely and collaboratively with contractors to find ways to realize cost savings to the City in the use of RAP in certain pavement applications.
To begin piloting RAP efforts in Phoenix, the City partnered with Arizona State University (ASU) to conduct a feasibility study on the use of RAP on City streets. As the study progressed, Streets began piloting the application of asphalt pavement with different proportions of RAP in the base (or lower) layers of street resurfacing projects. The pilot locations were constructed in November 2018 on 15th Avenue from Baseline to Roeser roads, as this section of 15th Avenue was already programmed for mill and overlay treatment and designated as a minor collector street. To date, the project shows no negative effects of using RAP in the pavement structure. The positive experience with this project gave Streets the confidence to incorporate using RAP as a more extensive part of its paving maintenance program.
Streets also found that in addition to adequate pavement performance with the use of RAP, industry research also showed that utilizing RAP helps reduce greenhouse gas emissions in the production of asphalt concrete pavement. By capturing millings generated by construction and day-to-day maintenance operations, it allows this potentially waste material to be diverted from City landfills and used for a better purpose.
Accelerated Pavement Maintenance Program Opportunity
In furthering its use of RAP, Streets identified the five-year $200 million Transportation 2050 Program-funded Accelerated Pavement Maintenance Program (APMP) as a prime opportunity to capture a large amount of asphalt millings at one time. The APMP provides for a 300 percent increase in the number of mill and overlay treatments being done in the City. Streets worked with its contractors and Public Works to divert these millings to a City facility for processing. This also allowed the City to continue to evaluate the use of RAP with a city-controlled millings stockpile to monitor quality of the RAP materials.
Partnerships
Street and Public Works have developed a strong partnership in this area and have been working together to facilitate the processing of asphalt millings. In 2020, the Union Hills Service Center was set up to process all asphalt millings generated north of Camelback Road. The millings were then processed by a Streets JOC contractor to the required engineered gradation as RAP. Currently, RAP from this facility is being used to replace 100 percent of the aggregate in slurry seals and microsurfacing projects in the northern parts of the City.
More recently, to expand the City's use of RAP, Streets and Public Works identified the Resource Innovation Campus located at 27th Avenue and Lower Buckeye Road as a second stockpile location, which is expected to be operational by Spring 2022, in time for the 2022 paving season. Once both stockpile sites are operational, Streets will be able to capture asphalt millings from the entire City for use as RAP.
The City has also continued to partner with ASU researchers to develop project specifications for surface treatments utilizing RAP.
Results
Streets began using RAP in slurry seals, microsurfacing, and mill and overlay treatments in fiscal year 2019, and has since utilized approximately 13,000 tons in RAP in street resurfacing projects. Streets has also added RAP pavement mix design options to its JOC contracts, where material pricing has been reduced by approximately 7.5 percent for slurry seal and microsurfacing treatments and 3.5 percent for mill and overlay treatments compared with non-RAP treatments.
Department
Responsible Department
This item is submitted by Deputy City Manager Mario Paniagua and the Street Transportation Department.