Associated Asphalt has completed a case study documenting PennDOT’s 5-year work plan to investigate the use of void-reducing asphalt membrane (VRAM) for longitudinal joints and extending the life of asphalt pavement. PennDOT’s program led to the introduction of a VRAM Standard Special Provision that can be used on projects let on or after April 14, 2023. PennDOT’s selection of VRAM to extend the life of Pennsylvania’s roads joins other agencies, most in America’s Mid-West, who have been using VRAM successfully since 2002 and are conscientious stewards of taxpayers’ money.
Continue reading the high-level summary, or download the study in its entirety: Extending the Life of Asphalt Pavement with Void-Reducing Asphalt Membrane: PennDOT Case Study.
VRAM is an innovative material-based solution for improving longitudinal joint performance and involves the application of a thick layer of hot-applied, polymer-modified asphalt (rather than an emulsion). It is applied beneath the future centerline of the longitudinal joint, and, as the asphalt is laid and subjected to heat and compaction by rollers, the VRAM gradually migrates from the bottom up, rendering the joint nearly impermeable to water and air.
Based on the knowledge gained by similar trials in other states, beginning as early as 2002 by the Illinois Department of Transportation (IDOT), it was determined that VRAM treatment could extend the joint life by approximately three to five years. The pavement life extension translated to a cost savings, over the life of the pavement, of three to five times the initial cost to apply the VRAM. These findings were published in a Transportation Research Board paper, A Materials Approach to Improving Asphalt Pavement Longitudinal Joint Performance, at their 2021 Annual Meeting.
First PennDOT Trial
In October 2018, PennDOT District 56 began its first trial on a 2.1-mile stretch of I-81. Annual visual assessments were conducted to examine the state of the VRAM longitudinal joint and the control joint. In April 2023, a fifth-year evaluation was completed. After more than four years, the VRAM section had minor cracks present in a few areas; however, the cracks did not penetrate into the paving mat. On the other hand, the control sections had obvious cracking.
Second PennDOT Trial
PennDOT’s second VRAM trial was applied on October 17, 2018, on a 1.1-mile section of I-380 in Monroe County. This experimental section would be compared over time to approximately 0.5 miles of control sections.
A team visually reviewed the joints annually, and in 2021, cores were pulled from the three-year-old joints in the control and VRAM sections. These cores were sent to Rutgers University Center for Advanced Infrastructure & Transportation (CAIT) for complete testing.
The chart below shows the impact of the J-Band migrating upward into the joint area, sealing off some of the interconnected voids of the constructed joint in the surface layer. The average permeability measured in the 9.5mm SMA Control surface course cores was 927.1 cm/sec x 10-5 (26.3 ft/day). Meanwhile, the average permeability for the 9.5mm SMA VRAM surface course cores was 14.0 cm/sec x 10-5 (0.40 ft/day).
PennDOT Continues the VRAM Work Plan
Through the end of 2022, thirteen trials had been constructed and six separate core tests were conducted. The following summarizes all of the data collected from the PennDOT test projects by Rutgers University CAIT.
Average Permeability Results: The permeability of the field cores was measured using the Florida Department of Transportation (FDOT) test method, FM 5-565, Florida Method of Test for Measurement of Water Permeability of Compacted Asphalt Pavement Mixtures.
Average Air Voids Results: The air voids of the recovered field cores were determined in accordance to AASHTO T269, Standard Method of Test for Percent Air Voids in Compacted Dense and Open Asphalt Mixtures.
Average Ideal-CT Index Results: The IDEAL-CT is similar to the traditional indirect tensile strength test, and it is run at room temperature with cylindrical specimens at a loading rate of 50 mm/min in terms of cross-head displacement. For mix design and laboratory QC/QA, the same specimen size as the Hamburg wheel track test was used: 150 mm diameter an 62 mm height, and the post-peak segment was chosen to extract cracking resistance.
VRAM SSP in 2023 and Beyond
In March 2023, PennDOT issued a new Standard Special Provision for Void Reducing Asphalt Membrane (VRAM). This SSP, which can be used on projects let on or after April 14, 2023, is recommended for use on limited access and expressway-type pavements where exceptional longitudinal joint performance is difficult to achieve.
As of August 2023, there have been six VRAM projects completed or scheduled to be completed in 2023, and seven confirmed from 2024.
To get more information about the PennDOT Case Study or learn how you can benefit from using VRAM, complete our contact form, and we will be in touch with you.