Asbestos has not yet posed a problem. “An Illinois Department of Public Health certified inspector examines inbound loads and takes representative samples. Those samples are sent to a lab before the shingles are incorporated into our feed material. We have not had one detection of asbestos,” he says.
Shingles also need to be cleaned prior to processing and there is income potential in this process. “The nails are almost more valuable than the oil,” says Vondra. “A special magnet is required to pull them out, and those nails are recycled for several hundred dollars a ton.”
Not all contaminants can be removed as easily. Sorting shingles is a laborious process. “An employee must stand next to a conveyor belt removing plastic, wood and anything that is not roofing,” says Vondra.
There is the expense of grinding the shingles. The company’s RG-I Rotochopper shingle grinders, powered by Caterpillar engines, are custom-made for grinding shingles. This keeps the RAS in spec and ensures a consistent gradation. The abrasive nature of the shingles creates a lot of wear on the grinder, and maintenance is something that must be performed regularly.
In addition, the stockpiles of material must be worked over (Southwind RAS uses Caterpillar loaders) prior to loading in the grinders to prevent clumping of the shingles.
As the state begins to use the new mix spec, the future for RAS mix in Illinois looks bright. One high-profile project already on the board is the “Green Mile” in the city of Chicago. “In addition, the state plans to use RAS on the resurfacing of Michigan Avenue,” says Vondra.
The mix is called Stone Matrix Asphalt (SMA) which is an 80% course and 20% fine mix. This will be mixed with the RAS. “It is a technology used frequently in Europe,” he explains. “It’s quieter, more stable and very durable. It has many good properties to it, including being high friction and high loading.”
The prospects for other paving projects also look promising. “Now that we are a little past the learning curve, people are becoming more interested in using RAS mix as opposed to a pilot project,” he notes. “The day-to-day use has really started to pick up.”
One of the keys to success hinges on training the paving companies about RAS. “Contractors need to understand what they are working with,” concludes Vondra. “Paving companies are already experts at paving; they just need to understand the unique characteristics of RAS material.”