In-place Pavement Density
About the Program
Proper compaction of an asphalt pavement is essential for long-term pavement performance. Studies indicate a 1 percent increase in density can extend the asphalt pavement service life by at least 10 percent.
Demonstration Project and Workshops
About the Project
Twenty-six State DOTs participated in 29 demonstration projects by constructing 121 experimental pavement sections to determine if it would be possible to obtain at least 1 percent increase in in-place pavement density. This was done in three phases from 2017 through 2019.
The FHWA Mobile Asphalt Technology Center (MATC) participated in 3 of the 29 demonstration projects, supporting the initiative through testing with the Asphalt Mixture Performance Tester (AMPT). Results showed that increases in density produced enhanced index properties (which can be used in a performance-engineered mix design) and longer lasting pavements through performance prediction software.
Of the 29 demonstration projects:
- 17 achieved ≥ 1.0% Gmm increase
- 23 achieved ≥ 94.0% Gmm
- 24 achieved ≥ 1.0% Gmm increase OR 94.0% Gmm
New York State DOT has a 5 percent incentive available on density alone. For 2015, the statewide average density was 94.1 percent. The standard deviation of projects statewide was 0.83.
As a result, 24 of the 26 participating States are making or discussing these specification changes. The number of States are shown in brackets [].
- Using the primary density specification more often [3]
- Improving the quality measure (e.g., PWL, AAD, minimum lot average) [5]
- Improving method of measuring density [1]
- Changing reference density [1]
- Increasing minimum density [10]
- Increasing the maximum density [5]
- Improving consistency with standard deviation [7]
- Adjusting t/NMAS [3]
- Adjusting incentives/disincentives [7]
- Adding a quality characteristic [1]
- Improving inspection and validation [2]
- Changing mixture design requirements [14]
- Including new technologies [5]
- Changing mixture design requirements (e.g., increasing asphalt content, adding mixture performance test [14]
- Adjusting the t/NMAS [3]
- Using the primary density specification more often [3]
- Improving the quality measure (e.g., PWL, AAD, minimum lot average) [5]
- Increasing the minimum density [10]
- Increasing the maximum density [5]
- Improving the acceptance plan (e.g., lot size, sublot size) [10]
- Adjusting incentives / disincentives [7]
- Improving quality control, inspection and validation [3]
- Improving longitudinal joint density [4]
- Improving the testing methodology (e.g., gauge correlation, reference density) [2]
- Utilizing new technologies [5]
About the Workshops
Workshops about the demonstration project were delivered in 28 States to nearly 2,000 attendees in 2016 and 2017. Participants included representatives of State DOTs, Local Program Agencies, academia, and industry. Here's what one participant had to say:
"Please accept my enthusiastic THANK YOU for delivering the workshop. Everything went great, and I think it was very informative. I had several VDOT folks approach me and tell me how good they thought it was." - Robert Crandol, Assistant State Materials Engineer, Virginia DOT