Fractionating RAP

When you get a good idea from someone you respect, the next logical step is to follow through and put that idea into practice. About three years ago, Tim Phillips, president, P & S Paving Inc. of Daytona Beach, FL, attended a seminar at the Astec headquarters in Chattanooga, TN. Fractionating RAP was one topic discussed that resonated for Phillips.

Fast forward three years. Now you will find that P & S Paving is having continued success with fractionating RAP, but they have added a new twist — a completely self-operating, closed-loop RAP-processing facility. And this cutting-edge technology has helped propel P & S Paving to the top of their market.

"Today we're running 50 percent RAP, whenever state specifications allow," says Phillips. "And we've perfected it. In the old days, we were out there, like most other contractors, taking up asphalt on jobs that we had paved because we got out of specification. Today, since we added this machine, we haven't taken up a single ton of asphalt."

A new stage in fractionating RAP

For most people, fractionating or processing RAP is not an entirely new concept — sizing RAP and separating it into specific piles — a producer gains more control over the size and amount of the reclaimed aggregate that goes into new mixes, as well as the amount of liquid AC that is being used during production.

This is the concept that captured Phillips' attention at the seminar back in 2001. But early in 2004, Phillips and Astec Industries began talking about a slightly different concept: a RAP-processing facility that would crush, size, separate, and store RAP — all within one automated, closed-loop system.

"We wanted to make sure that it did not have an operator," says Phillips. "We wanted to merely turn it on, and then the only manpower needed would be the loader operator."

Once material enters this system, oversized material is screened and then fed back to the crusher until it is sized correctly and can be deposited into one of two piles: 1/4-inch minus and 1/4- to 1/2-inch.

Phillips avoids using the word crushing. "Even though the oversized material is passed through a crusher," he says, "we don't like to call it crushing. Instead, we like to think of it as separating. We are actually separating the millings and returning them back to their virgin state. We don't want a true crushing operation because crushing creates fines — and fines create problems."

Phillips says once the RAP is separated, the material is handled just like any virgin aggregate. "The only difference is that this material is coated black. And that one fact makes the material extremely valuable to us."

At its Florida facility, P & S Paving has limited resources for virgin aggregate, relying on shipments by rail from either Georgia or south Florida. This, of course, drives up the cost of the aggregate to about $20 per ton. Plus, Phillips points out, the costs of liquid-AC has continued to rise.

Meanwhile, P & S Paving seems to have an endless supply of RAP from milling operations.

"Before this RAP-processing system came in, our milling piles were becoming enormous," says Phillips. "We were looking for more land where we could put all the millings we were accumulating. We realized that we needed to do something —we actually needed to be using the same amount of millings that we were bringing in.

"Now, we've solved that problem. Since we installed this system, our RAP piles have remained at a constant size rather than growing. That's because of the increase in the percentage of RAP that we're able to use in new mixes: Instead of running 30 percent RAP, we're now running 50 percent."

Unique equipment equals serious production

P & S Paving knows how to use state-of-the-art equipment to promote company growth, and to turn out serious production rates. Several years ago, they upgraded from a 1956 batch plant to a brand new Astec Turbo 400 Double Barrel drum-mix plant. With three paving crews out in the field, that HMA plant is now producing close to 450,000 tons per year.

"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."