Fractionating RAP

"We're literally running it around the clock, almost 24 hours a day, seven days a week," Phillips says. "We're getting very good volume out of one plant."

With that high production rate, the new RAP-processing plant needed to be able to keep pace. One element that keeps the processing plant moving is the fact that not all of the RAP has to go through the crusher.

"Before we got this system, we merely threw RAP onto a high-frequency screen — and 70 percent of the return was material that didn't really need to be crushed," says Phillips. "With the new RAP-processing plant, we have the ability to go around the crusher. We simply throw the RAP into a hopper, screen it, and separate it by size. Everything that is oversized automatically goes to the crusher. If everything went straight into the crusher, we would end up crushing all of the material and creating more fines. This system avoids that problem completely."

Phillips says that P & S Paving used more than 200,000 tons of RAP in 2004. In order to do that, the plant's Telsmith 5252 HSI horizontal-shaft impact crusher processed about 350 tph. "We crush about 1,000 tons a day," says Phillips. "It is extremely fast: It only takes about four hours to crush that amount."

In order to assure the best-quality material, P & S Paving creates RAP inventory on a just-in-time basis. In other words, they process only as much RAP as they will need and when they will need it.

"We do that for an important reason," explains Phillips. "The processed-RAP piles will actually harden if they sit there with the sun beating down on them. So we process the RAP on a day-by-day basis — typically the day before the material is to be used in the hot-mix plant. There is another advantage to that: We don't let the piles get wet — and that cuts down on drying costs."

One more safety measure that P & S Paving has put in place is their quality-control program.

"We have set up a quality-control plan in order to do daily checks on the volumetrics of the RAP, as well as the viscosity," says Phillips. "That report is turned over to the Florida DOT."

Phillips says that despite the daily checks by their technicians, P & S Paving has found that the volumetrics and viscosity tend to be very consistent. This is due in part to the care and attention to detail that is taken by the operator of the front-end loader.

"The loader operator can see color changes in the RAP piles. If the pile starts getting streaky, then he knows the AC content is not consistent," says Phillips. "So, the operator can help you or hurt you in that process — and we have trained our loader operators to feed that crusher consistently."

Since the RAP-processing facility went into operation, Phillips says it has attracted the attention of others in the industry. "We've had some of our competitors come in and look at it, and I think one of them even purchased a system like it," he says. "We're not doing anything magical here. Producers have been crushing RAP for a long time. But they have not been screening it on a high-frequency screen like we do here.

"That's the real difference in what we're doing."