If you're not convinced how a high RAP mix design can work for you and your road agency customers, you need to take a look at what Daytona Beach, FL-based P & S Paving has been able to do with its aggressive RAP content proposals, and do so to the delight of its Florida Department of Transportation (FDOT) customer.
P & S recently completed the third segment of the State Road 15A reconstruction project north of DeLand, FL this past fall, placing 14,099 tons of Superpave Traffic Level C base and binder course mix designs containing 45 percent fractionated RAP. This two-mile segment was the third of a four-phase projectto convert the two-lane truck route into a four-lane divided highway.
P & S was awarded and completed the first two phases of the project in 2004 and 2005.
As the general contractor on the project, P & S performed all grading to expand the two-lane road into a divided four-lane highway, placing all the crushed rock subbase and then paving the approximate eight lane miles of new road surface. Bechtol Engineering and Testing Inc. of DeLand was hired by P & S to perform the quality control and quality assurance (QC/QA) requirements of the project.
The 45 percent fractionated RAP base and binder courses, which were composed of 12.5 mm and 9.5 mm recycled and virgin aggregate material respectively, were QC designed by Bechtol and produced at P & S's Daytona Beach HMA production facility. Following placement of the recycled base and binder courses, P & S then produced and placed 8,261 tons of virgin friction course (FC12.5mm TLC) to complete the project.
P & S has been fractionating (separating by size) RAP since 2002. In late 2004, the asphalt producer/contractor installed a completely self-operating, closed-loop RAP processing facility. When the system is operating, the manpower required is for a loader operator to deposit RAP into a 42-inch by 16-foot Telsmith vibrating grizzly feeder. Once the material enters the Astec system, it passes over two screens — one a ¼-inch by 6-inch slotted screen for fine product, and one a 5/8-inch by 6-inch slotted screen for coarse product. Any oversized material is transferred back to the crusher until it is sized correctly and can be deposited into one of two piles — ¼-inch minus fines and ¼- to ½-inch coarse material. The system allows the asphalt producer to separate road millings back to the specific dimensional size of virgin aggregate without excess crushing, which would only create additional problematic fines that have to be controlled in producing a quality mix design.
For P & S, the fractionating system allows the producer to process recycled pavement and incorporate it into new mix as it would with virgin material. Mix content can be quantified since the processed fractionated RAP is aggregate with a black coating. The ability to quantify the contents of a mix design not only satisfies FDOT's Producers Quality Control Plan, which requires a high-frequency screen deck capable of maintaining 3,600 rpm in order to qualify as fractionated RAP, but also reduces the material, both aggregate and liquid asphalt cement binder, costs for the P & S.
"We produced 400,000 tons of mix this year (2006) and the fractionating process gives us a lot of flexibility in maintaining control over the mix content during production," says P & S President Tim Phillips.
In order to control the quality of the fractionated RAP used in its mix production, P & S processes RAP on a just-in-time basis. Having only enough processed FRAP (fractionated reclaimed asphalt pavement) on hand for a day's production prevents the stockpiles of FRAP from excess exposure to the hot Florida sun, which can actually harden the material, as well as preventing the piles from getting wet, which cuts down on drying costs. P & S conducts daily quality-control tests on its FRAP to verify volumetrics and viscosity, with reports sent to FDOT.