Studies have shown that longitudinal joints in pavements are often the weakest areas of a road. Typically the joints are low in density, high in voids and thus are highly permeable. These areas become conduits to air and water infiltration which leads to damage and premature pavement failure.(1)
During the 2016 construction season a new method of longitudinal joint construction was specified in Illinois. This new method is a materials approach and is referred to as VRAM(2), a Void Reducing Asphalt Membrane. Applying VRAM at the time of construction helps fill the pavement voids, thus reducing the permeability in this most critical area. As part of their evaluation, DuPage County ensured that test cores were taken on different joint constructions, such as VRAM and joint heater. DCT, I-FIT, density, and asphalt binder grading tests were performed to compare the different joint construction methods. The report summarized that the addition of the VRAM contributes to a more durable joint by partially filling the joint and adjacent mat air voids. The joint will be much less permeable and less likely to allow water infiltration.
How VRAM Works?
Prior to paving, VRAM material is sprayed on an 18” wide location directly under the area where the longitudinal joint will be located. When the HMA is placed and compacted over VRAM, the material migrates upward into the fresh pavement. It fills voids to help ensure the joint is less permeable.(3)
Asphalt Materials, a midwestern based company that has been involved in the asphalt business since 1956, supplies an industry leading VRAM named J-Band®.
Recently Chris Snyder, Director of Transportation/County Engineer for DuPage County, Illinois noted that, “DuPage County tried J-Band in 2016 and was very pleased with the performance and test results. We began adding J-Band to our pavement preservation program in 2018 and continue to do so.”
Snyder continues, “We currently specify that VRAM be placed at all center line, lane line, turn lane, and shoulder joints, also including the EOP joint across side streets. Since 2018 we have placed nearly 700,000 feet of VRAM on over 200 lane miles of resurfacing with our pavement maintenance projects.”
Since 2002, J-Band has a proven track record of extending the life of roads by protecting longitudinal joints and improving the performance of the entire pavement in over 20 states.
Picture of a Centerline Joint that did use VRAM
Picture of a Centerline Joint that did NOT use VRAM
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Editor’s Notes:
(1) The density and air void content of asphalt mixtures affect the durability and performance of asphalt pavements. Pavement longitudinal joints typically have a lower density than the mat because they receive less compaction than the center section of the mat for various reasons. The higher air void percentages resulting from lower densities can lead to high permeability and allow water infiltration, which in turn can cause moisture-induced damage and decrease base and subbase support to the pavement, reducing pavement life. Void-reducing asphalt membrane (VRAM) has been used at the longitudinal joints of asphalt pavements to achieve higher densities and prevent moisture infiltration, thereby reducing deterioration at the longitudinal joints. VRAM is applied before the hot-mix asphalt (HMA) layer is placed and migrates into the HMA to fill 50% to 70% of the air voids.
(Iowa State University Study for Minnesota Department of Transportation, DEC. 2020)
(2) VRAM, Void Reducing Asphalt Membrane is referred to in Illinois as LJS, Longitudinal Joint Sealant.
(3) Depending on the situation VRAM can be sprayed at different width’s. This article notes 18” which is a typical application width for centerline applications.
J-Band® is a product of Asphalt Materials, Inc. and created in the labs of Heritage Research Group.
