Rumble Strips Are Becoming More Popular, But They Also Need To Be Protected
It is important to plan ahead when protecting the infrastructure investments made for our streets, roads, and highways. Reducing air voids is critical to improving pavement life. When air voids are higher, permeability is higher, and this will adversely affect pavement life.
Roadway safety is a growing concern in the United States. In 2019 alone, there were 36,096 traffic fatalities, an increase of 5.3% from the year before, according to a recent study conducted by the National Highway Safety Administration (NHTSA).1 Every year, thousands of Americans are injured or killed in preventable accidents, many of them due to distracted driving. Fortunately, the recently enacted Infrastructure Investment and Jobs Act (IIJA), includes several provisions that can make America’s roads safer.
“This research helps to confirm the direction the department has taken with recent changes to longitudinal joint specifications.”
– Project Manager Dan Kopacz, WisDOT
How to Create Better Longitudinal Joints?
The longitudinal joint is the Achilles’ heel of every paved road. Road managers know the first part of the pavement to fail is the longitudinal joint. As the road’s most permeable part, this joint is susceptible to the elements, especially with their inherently lower density. Air and water work down through this unavoidable seam in the pavement causing the joint to deteriorate, crack, and pothole. And when the longitudinal joint fails, the rest of the road soon follows — triggering the need for even more maintenance and costly repairs.
Many states are looking for methods to improve longitudinal joint performance of their pavements, since these joints often fail before the rest of the surface. With the inherently lower density at the longitudinal joints we often see pavements fail by cracking, raveling, and potholing. Lower density is synonymous with higher air voids which leads to premature failure of pavements due to the intrusion of air and water. Studies have shown that longitudinal joints in pavements are often the weakest areas of a road. (1)
Several state DOTs (Department of Transportation) are now using a materials approach to seal the longitudinal joint region by filling these air voids with asphalt content from the bottom up.
The materials approach is referred to as VRAM(2), a Void Reducing Asphalt Membrane. VRAM is a highly polymer-modified asphalt cement that is placed at the location of a longitudinal joint before paving. As mix is paved over it, the VRAM melts and migrates up into voids in the low-density mix, making the mix impermeable to moisture while sealing the longitudinal joint itself.
Illinois Department of Transportation (IDOT) test pavements were evaluated after 12 years and found to have longitudinal joints that exhibited significantly better performance than the control joint sections and were in similar or better condition than the rest of the pavement. Laboratory testing of cores showed decreased permeability and increased crack resistance of mix near joints with VRAM as compared with similar mix without VRAM. The life extension of the joint area is approximately 3–5 years, and the benefit is calculated to be three to five times the initial cost.
This project’s VRAM application began at 8:05pm with ProTack operating the 05-distributor shooting from the driver’s side. They started at address N3362 in the eastbound lane. Ambient temperature was 61F and existing pavement was 80F. ProTack applied a straight and consistent line throughout the project. VRAM width was measured with an average of 18 inches. (3)
The paving crew started at 11:40. Paving equipment consisted of a Volvo P7170B paver, Sakai SW850-II – 12-ton breakdown roller and a Volvo DD25B-5-ton finish roller. Width was 12 feet. Mix temp was 275F under the screed.
J-Band® is a VRAM product from Asphalt Materials, Inc. and was created in the labs of the Heritage Research Group.
J-Band has been helping roads last longer since 2002. VRAM has been used in 20 states and the District of Columbia.
National Air Traffic Control Day was first held on July 6, 1986, on the 50th anniversary of the establishment of the air control system in the United States. According to Senate Joint Resolution 188, which designated the day, it was created to increase public awareness about the United States National Airspace System and to give people a way to “express their gratitude and respect” to “pioneers of the technology of air traffic control” and to all air traffic control personnel.
Many might wonder how National Air Traffic Control Day relates to the work we do here at AMI. The work we do expands far beyond just county roads and highways. We also have experience working with airports because just like with roads, protecting longitudinal joints is also important for airport runways! This past June, we completed a 7,300-foot J-Band project at the Coles County Airport, located near Mattoon, Illinois. The application was scheduled to be 18” wide and 1.51 lb./ft for the 2” surface mix, P401, PG64-22, N40. This was over a recently applied and tacked level binder mix. J-Band, which is a Void Reducing Asphalt Membrane (VRAM) was measured at 280F after the distributor applied. In total, 7,124 ft and 10,330 lbs. were applied for a total yield of 1.45 lbs./ft. Images of the project can be found below. In Illinois, you may also see VRAM referred to as a Longitudinal Joint Sealant (LJS).
The air control system, created by the United States Bureau of Air Commerce, is the National Airspace System. It works to ensure adequate spacing between airplanes that are flying on routes and to prevent congestion at airports. There are more than 14,000 air traffic controllers, who together with engineers, electronics specialists, and technicians make up the National Airspace System. The system is a model for the world aviation community, is known for its safety and efficiency. Over the course of its first 50 years, the volume of air traffic in the United States expanded one hundred and eighty fold. Today, 5,000 aircraft are in the air in the country at any given moment, with millions of flights taking place each year. The country has 5.3 million square miles of domestic airspace and 24 million miles of airspace over the oceans. On National Air Traffic Control Day, we thank all those who work to keep the airways safe as part of the National Airspace System, and we work to make the system stronger. Learn more about National Air Traffic Control Day here.
“Through the course of conducting my duties for the Asphalt Institute, I have increasingly noticed the use of centerline rumble strips when traveling. I could not help but wonder what, if any, negative effect they might be having on pavement deterioration. My concern stemmed from the fact that the final longitudinal joint on many rural two-wayroadways is at their centerline. So, milling a rumble strip into what is also commonly the most problematic location of a pavement raised concerns for me. That quickly evolved into a desire to make information available on the best ways to install and maintain all rumble strips, especially at the centerline.”