Municipalities and other agencies are taking a closer look at hot in-place recycling (HIR) thanks to a new process by Gallagher Asphalt Corp., located in Thornton, IL. This next step for HIR can recycle 100% of the existing pavement without having to add an overlay, and it can do this for about 30% less cost. The Gallagher Recycled Hot Emulsified Asphalt Treatment — or Re-HEAT — system can also reduce the carbon footprint by 63% compared to a traditional mill-and-fill.
Re-HEAT is comprised of three pieces of equipment: two self-propelled all-wheel-drive propane-fired pre-heaters followed by a processing unit. Coming in at just over 120 feet long, the total length of the two machines, allows the Re-HEAT system to be used in municipal settings typically not feasible with other HIR systems.
How Re-HEAT works
The Re-HEAT train begins with the tandem pre-heaters gradually heating the existing asphalt pavement to 300 degrees F.
“This will be done in stages, as the preheaters develop a heating pattern — similar to a rolling pattern — to increase the pavement temperature from ambient,” explains Patrick Faster, national sales director for the Hot In-Place Recycling Division with Gallagher Asphalt.
After the preheaters, the next step is the processing machine, which is basically “a small asphalt plant going down the road,” says Faster. Paddles under the unit begin to collect the heated, softened material into a windrow, which is fed into an on-board asphalt drum mixer.
In the horizontal drum mixer, the rejuvenating oil is uniformly applied and mixed while the heating process is maintained within the drum. The recycled hot mix is then distributed out of the drum onto the pavement where it’s augered and placed through a traditional asphalt paving screed. The paving screed ensures proper slope and grade is delivered to the final surface course.
Following the processing machine is a steel-drum vibratory roller that achieves specified density. Minutes later, the road is open to traffic.
In order for a process like Re-HEAT to perform correctly, the pavement must be structurally sound with no base failures or underlying drainage problems and be at least three inches thick.
“We’re pretty particular about the roads we select,” says Faster. “We want to find the best candidate to perform work for that agency so that we’re invited back for the next season.”
Re-HEAT has been successfully performed throughout the country, including in Chicago, Pittsburgh and Cleveland. Several cities, including Chicago, Milwaukee and Marietta, GA, had the process incorporated into their resurfacing programs for 2012. Counties in Georgia, Ohio, Tennessee and Indiana are also including the process into their preservation programs — as have state DOTs in Rhode Island, Illinois and Indiana.
Lancaster, CA has a population of about 100,000 and is located in the high desert of Los Angeles County. Last summer, city officials approved the use of Re-HEAT to “get the absolute best value for every construction and maintenance dollar the city spends,” they said in a release.
The project consisted of using the Re-HEAT process on approximately 115,000 square yards of asphalt on six different roadways. The roads varied from two-lane, lightly-traveled roads on the outside of Lancaster, to six-lane, heavily-traveled roads in the heart of the city, including a section of roadway in front of city hall.
Lancaster was the first city in California to adopt the pavement preservation technique. The efficiency, cost-effectiveness and eco-friendly nature of the process were key selling points in the city’s decision to use Re-HEAT.
“With this kind of technology, residents can leave for work in the morning before we start the road work and come home to an entirely new street by the evening,” says Ray Hunt, Lancaster’s capital engineering manager.